VSD 220v to 380v Spindle Inverters VFD AC drive frequency converter

Due to national policies and regional restrictions, many regions will now withdraw three-phase 380V industrial power. The cumbersome procedures for applying for three-phase electricity in areas without three-phase electricity, various labor costs, and various hidden costs have caused some Regions cannot use industrial 380V electricity, and general industrial equipment, such as motors, are mostly three-phase 380V, which cannot be operated without three-phase electricity, and can only find ways to convert single-phase 220V to three-phase 380V, but Many single-phase 220V electric liters and three-phase 380V equipment on the market are ridiculously expensive, and many users in need are discouraged. The original machine can only be placed temporarily or used in other places with industrial electricity.

Now our company has introduced a single-phase 220V input to three-phase 380V output boost converter, which can drive the three-phase asynchronous motor to start softly and perform stepless speed regulation. The input power only needs single-phase 220V and output three-phase 380V, and most users can accept the price. It is about 1/10 of the price of the booster on the market. It is small in size and powerful in function. Solve the embarrassing situation that industrial equipment does not have three-phase electricity.

2. Introduction of the principle and characteristics of 220V to 380V inverter

The principle of the frequency converter is the principle of applying frequency conversion technology and microelectronic technology. The power control equipment of the AC motor is controlled by changing the frequency of the working power of the motor, and the power frequency AC with a fixed voltage and frequency is converted into a variable voltage or frequency. The device for alternating current is called “frequency converter”.

The output waveform of the frequency converter is an analog sine wave, which is mainly used for the speed regulation of three-phase asynchronous motor, also known as frequency converter. The frequency converter is mainly composed of rectification (AC to DC), filtering, inverter (DC to AC), braking unit, drive unit, detection unit micro-processing unit, etc. The frequency converter mainly adopts the AC-DC-AC method (VVVF frequency conversion or vector control frequency conversion). First, the power frequency AC power is converted into a DC power through a rectifier, and then the DC power is converted into an AC power that can be controlled by frequency and voltage to supply electric motor.

The 220V to 380V frequency converter converts the power frequency AC 220V power supply to a DC power supply through a rectifier (voltage doubler rectification), and then converts the DC power supply into a three-phase 380V AC power supply that can be controlled by frequency and voltage to supply the motor.

2.1 Inverter function

1. Can reduce the impact on the power grid, it will not cause the problem of excessive peak-valley difference.

2. The acceleration function can be controlled, so as to smoothly accelerate according to the needs of users;

3. The stopping mode of the motor and equipment can be controlled, making the entire equipment and system safer, and the life will be increased accordingly;

4. Control the starting current of the motor, fully reduce the starting current, and reduce the maintenance cost of the motor;

5. Can reduce the wear of mechanical transmission components, thereby reducing procurement costs, while improving system stability.

6. Reduced motor starting current and provide more reliable variable voltage and frequency.

7. Effectively reduce the reactive power loss and increase the active power of the power grid

8. Optimize the technological process, and can change rapidly according to the technological process, but also realize the speed change through remote control PLC or other controllers.

Input single phase 220V to output 3 phase 380V VFD/ frequency inverter

Introduction to the principle and characteristics of 220V to 380V inverter
The principle of the frequency converter is to apply the principle of frequency conversion technology and microelectronic technology. The power control equipment of the AC motor is controlled by changing the frequency of the working power of the motor, and the power frequency alternating current with constant voltage and frequency is converted into voltage or frequency. The device of alternating current is called “inverter”.
The waveform outputted by the inverter is an analog sine wave, which is mainly used for three-phase asynchronous motor speed regulation, also called frequency converter. The frequency converter is mainly composed of rectification (AC to DC), filtering, inverter (DC to AC), braking unit, drive unit, and detection unit micro processing unit. The frequency converter mainly adopts the AC-DC-AC mode (VVVF frequency conversion or vector control frequency conversion). First, the power frequency AC power supply is converted into a DC power source through a rectifier, and then the DC power source is converted into an AC power source whose frequency and voltage can be controlled to supply. electric motor.
The 220V to 380V inverter converts the power frequency AC 220V power supply into a DC power supply through a rectifier (double voltage rectification), and then converts the DC power into a three-phase 380V AC power source whose frequency and voltage can be controlled to supply the motor.

2.1 inverter function
1. It can reduce the impact on the power grid, and it will not cause the problem of excessive peak-to-valley difference.
2. The acceleration function can be controlled to smoothly accelerate according to the needs of the user;
3. The motor and equipment stop mode can be controlled, making the whole equipment and system more secure and the life expectancy will increase accordingly;
4. Control the starting current of the motor, fully reduce the starting current, and reduce the maintenance cost of the motor;
5. It can reduce the wear of mechanical transmission components, thereby reducing procurement costs and improving system stability.
6. Reduced motor starting current, providing a more reliable variable voltage and frequency.
7. Effectively reduce reactive power loss and increase the active power of the grid
8. Optimize the process and change rapidly according to the process. It can also realize the speed change through remote control PLC or other controllers.
Third, product features
The single-phase 220V variable three-phase 380V inverter adopts the AC-DC-AC circuit structure, and uses the SPWM modulation control technology to convert the ordinary single-phase 220V electric power into the industrial three-phase 380V electric power. Applicable to three-phase asynchronous motor, the output phase angle is 120°, fully meets the motor use standard, and is suitable for various types of motor loads. The single-phase electric-to-three-phase electric inverter solves the inconvenience caused by three-phase electric power limitation in some areas, and also solves some users’ demands that cannot be applied for three-phase electric power due to site restrictions.

3.1 Technical characteristics:
· Ordinary mains 220V input, eliminating the cumbersome procedures for applying for three-phase electricity and various labor costs and various hidden costs
·The output uses industrial three-phase electricity, but it is economical according to civil single-phase electricity billing.
·The core components are imported devices with stable performance and long service life.
·Safe and reliable, the input single-phase electricity is completely electrically isolated from the output three-phase electricity
·Input wide pressure range design, adapt to the working environment of low commons voltage in all regions
·The output protection function is perfect, and there are various protections such as overvoltage, overload, over temperature, short circuit and over current.

Regular maintenance and inspection of the inverter

1. Inverter maintenance check precautions

When performing maintenance inspection, be sure to cut off the power input to the inverter (R.S.T);
After confirming that the inverter power is cut off and the display disappears, wait until the internal high voltage indicator is off before performing maintenance and inspection.
During the inspection process, the internal power supply and wire, cable should not be pulled up and mismatched, otherwise the inverter will not work or be damaged.
Accessories such as screws should not be left inside the inverter during installation to avoid short circuit on the board.
Keep the inverter clean after installation to avoid dust, oil mist and moisture intrusion.

2, the inverter regularly check the project

The power supply voltage is confirmed to meet the voltage required by the inverter; (pay special attention to whether the power cord and motor are damaged.) Is the wiring terminal and connector loose? (Whether there is a broken wire in the power cord and terminal)
Whether there is dust inside the inverter, output current, output frequency (the difference between the measurement results is not too large)
Check if the surrounding temperature is between -5 °C and 40 °C, and whether the installation environment is well ventilated;
Humidity: maintained below 90%; (no phenomenon of water droplets)
Whether there is abnormal sound or abnormal vibration during operation; (The inverter cannot be placed in a place with high vibration)
Please do the cleaning work regularly.

3. Replacement of spare parts

The frequency converter is composed of various components, some of which will gradually reduce and age after long-term operation. This is also the main reason for the failure of the inverter. In order to ensure the long-term normal operation of the equipment, the following components should be replaced regularly:

(1) Cooling fan

The power module of the frequency converter is the most heat-generating device, and the heat generated by its continuous operation must be discharged in time. The life of the general fan is about 10kh~40kh. According to the continuous operation of the inverter, it is necessary to replace the fan for 2~3 years. The direct cooling fan has two lines and three lines. One of the two-line fans is positive and the other line is negative. Do not connect incorrectly when replacing. The three-wire fan is not only connected. There is also a detection line outside the negative pole. Please pay attention when replacing it, otherwise it will cause the inverter to overheat alarm. The AC fan is generally 220V, 380V, and the voltage level should not be mistaken when replacing.

(2) Filter capacitor

Intermediate DC loop filter capacitor: also known as electrolytic capacitor, its main function is to smooth the DC voltage, absorb the low frequency harmonics in DC, and the heat generated by its continuous operation plus the heat generated by the inverter itself will accelerate the drying of the electrolyte. Directly affect the size of its capacity. Under normal circumstances, the life of the capacitor is about 5 years. It is recommended to check the capacitance capacity once a year regularly. Generally, if the capacity is reduced by more than 20%, a new filter capacitor should be replaced.

4 regular maintenance

Regular dust removal check whether the fan air inlet is blocked, and clean the air filter cooling air duct and internal dust every month.

Regular inspections should be carried out once a year: check whether the screws, bolts and plug-ins are loose, whether the grounding and phase-to-phase resistance of the input and output reactors are short-circuited, and should be greater than several tens of megaohms. Whether the conductor and the insulator are corroded, if necessary, wipe it with alcohol in time. Measure the smoothness of the voltage of each circuit output of the switching power supply, such as: 5V, 12V, 15V, 24V and other voltages. Whether the contact of the contactor has a fire mark, it is necessary to replace the new contactor of the same model or larger than the original capacity; confirm the correctness of the control voltage, perform the sequence protection action test; confirm that the protection display circuit is not abnormal; confirm that the inverter is The balance of the output voltage when operating alone.

Carefully do the daily maintenance and repair of the inverter, the main contents include:

(1) Regularly dedusting the inverter, focusing on the rectifier cabinet, the inverter cabinet and the control cabinet. If necessary, the rectifier module, the inverter module and the circuit board in the control cabinet can be removed for dust removal. Whether the air inlet and upper air outlet of the inverter are dusty or blocked due to excessive dust accumulation. The frequency converter has a large amount of ventilation due to its own heat dissipation. Therefore, after a certain period of operation, the surface area dust is very serious and must be cleaned regularly.

(2) Open the front door of the inverter, disassemble the rear door, carefully check whether the AC and DC busbars are deformed, corroded, oxidized, whether the screws at the joints of the busbars are loose, and whether the screws at the fixed points are loose or not. Whether the insulating sheet or the insulating column for fixing has aging cracking or deformation, if it should be replaced in time, re-tighten, and the busbar that has been deformed must be corrected and reinstalled.

(3) After dust removal of circuit boards and busbars, carry out the necessary anti-corrosion treatment, apply insulating varnish, and remove the burrs of the busbars that have appeared partial discharge and arcing before processing. For insulation boards that have been insulated and penetrated, the damaged parts shall be removed, and the insulation boards of the corresponding insulation grade shall be insulated in the vicinity of their damage, and the insulation shall be tightened and tested and deemed to be qualified before being put into use.

(4) Whether the fan running and rotating in the rectifier cabinet and the inverter cabinet are normal. When the machine is stopped, turn it by hand to observe whether the bearing has stuck or noise, and replace the bearing or repair if necessary.

(5) Thoroughly inspect the input, rectification and inverter, and DC input fast-melting, and find that the burning is replaced in time.

(6) Whether the capacitor in the intermediate DC circuit has leakage, whether the casing is expanded, bubbling or deformed, whether the safety valve is broken, and the capacitor capacity, leakage current, and withstand voltage can be tested under conditions, which does not meet the requirements. The capacitors are replaced. For new capacitors or unused capacitors that have been unused for a long time, they must be passivated before replacement. The usage period of the filter capacitor is generally 5 years. If the usage time is more than 5 years, the capacitance capacity, leakage current, and withstand voltage are obviously deviated from the detection standard, and should be replaced partially or completely as appropriate.

(7) Conduct electrical inspection on the rectifier and inverter part diodes and GTO multimeter, measure the forward and reverse resistance values, and carefully record in the prepared form to see if the resistance between the poles is normal. , the same type of device is consistent, and replace if necessary.

(8) Check the main contactor and other auxiliary contactors in the A1 and A2 incoming cabinets, and carefully observe whether the contactors of the contactors have arcing, burrs or surface oxidation, unevenness, and find such problems. The corresponding moving and static contacts are replaced to ensure that the contact is safe and reliable.

(9) Carefully check whether the terminal block is aging or loose, whether there is a hidden fault in the short circuit, whether the connection of each cable is firm, whether the wire is damaged or not, and whether the plugs of each circuit board are firmly connected. Whether the connection to and from the main power line is reliable, whether there is heat generation and oxidation at the connection, and whether the grounding is good.

(10) Whether the reactor has abnormal squeaking, vibration or odor.

Four common faults and incentives of the inverter

As a very popular control device in the field of electronic control, the frequency converter almost penetrates into every corner of industrial production activities. However, for some newcomers or newcomers who are just beginning to contact the inverter, they are still relatively unfamiliar and mysterious, especially if the inverter fails, it is easy to get started. Today, based on years of experience in using and overhauling inverters, I have summarized the four major faults common to inverters and given the relevant incentives for causing them.

First, over current (short circuit)
Overcurrent faults are most common among various faults in the frequency converter. This fault is mostly caused by the following problems: First, as long as the inverter speeds up, it reports a fault, indicating that the overcurrent is very serious, mostly the load short circuit, mechanical parts are stuck, the inverter module is soft breakdown damage and the acceleration time is over. Shortly caused; secondly, the inverter reports a fault when it is powered, and it cannot be “reset” to be eliminated. Most of it is caused by damage to the internal drive circuit of the inverter and damage to the current detection circuit. The last phenomenon is the most extreme. When the power is turned on instantaneously or after a short delay, it directly causes the upper air to trip and the internal fuselage is blown out or sparks. The inverter rectifier unit and the power inverter component directly cause breakdown failure. Second, overvoltage
This type of fault phenomenon is also often found in inverter faults. In addition to eliminating the supply voltage is too high, there is also a case of such a fault – when the inverter is stopped. The main reason for this may be caused by a slow deceleration time or a problem with the braking resistor and the brake unit.
Third, under voltage
The above overvoltage fault corresponds to the undervoltage fault of the inverter. Generally, the power supply voltage is too low. It may also be caused by the following reasons: the power supply phase loss, the open circuit fault of one bridge arm of the rectifier circuit, and the main circuit If the capacity of the filter electrolytic capacitor becomes small or a problem occurs in the voltage detection circuit, the inverter may experience an undervoltage fault. In addition, if the internal snubber resistance of the inverter is not cut off by short circuit, an undervoltage fault will occur as long as the inverter is loaded.
Fourth, over temperature
Over-temperature is also a common fault of the inverter. This fault is mostly caused by the temperature of the inverter working environment is too high, the cooling holes are blocked, the cooling fan is damaged, the temperature sensor and the temperature detection circuit are damaged.
Through the above analysis of the four common faults of the inverter (of course, faults such as overload and output imbalance), it is not difficult for the peers to see that the inverter needs to work harder in daily maintenance, and more needs to be done in daily maintenance. We will use it flexibly according to the situation on the spot, and try our best to prevent it before it happens!

The influence of the carrier frequency of the inverter and the setting standard

  Most of the inverters are in the form of PWM modulation for the inverter. That is to say, the voltage output from the inverter is actually a series of pulses, and the width and interval of the pulses are not equal. Its size depends on the intersection of the modulated wave and the carrier, which is the switching frequency. The higher the switching frequency, the greater the number of pulses in a cycle, the better the smoothness of the current waveform, but the greater the interference to other devices. The lower the carrier frequency or the poor setting, the motor will make an unpleasant noise. By adjusting the switching frequency, the noise of the system can be minimized, the smoothness of the waveform is best, and interference can be minimized. 1. Overview of low frequency inverter carrier frequency

For inverters with voltage ≤500V, almost all of the main circuits of AC-DC-AC are used today. The control mode is sinusoidal pulse width modulation (SPWM). Its carrier frequency is adjustable, generally from 1~15kHz, which is convenient. Make artificial choices. However, in actual use, many users only follow the original set value of the inverter manufacturing unit, and do not adjust according to the actual situation on site. As a result, the carrier frequency value is improperly selected, which affects the correct effective working state. How to correctly select the carrier frequency value of the inverter during the use of the inverter is also important. This article provides considerations for the following aspects and as a basis for the correct selection of carrier frequency values.

2, carrier frequency and inverter power consumption

The power loss of the power module IGBT is related to the carrier frequency, and the carrier frequency is increased, the power loss is increased, such that the efficiency is reduced, and the second is that the power module generates heat, which is disadvantageous for long-term operation, of course, the inverter The higher the operating voltage, the greater the impact on power loss.

The larger the carrier frequency, the greater the loss of the inverter and the smaller the output power. If the ambient temperature is high, the dead zone of the upper and lower inverter tubes of the inverter bridge will become smaller during the alternate conduction process. In severe cases, the bridge arm may be short-circuited and damage the inverter.

3, carrier frequency and ambient temperature

When the frequency converter requires high carrier frequency and the ambient temperature is high, it is very unfavorable for the power module. At this time, the frequency of the carrier frequency of the different power inverters and the ambient temperature are used. The size and the allowable constant output current of the inverter should be appropriately reduced to ensure safe, reliable and long-term operation of the power module IGBT.

4, carrier frequency and motor power

If the motor power is large, the relative carrier frequency is lower. The purpose is to reduce the interference (the influence on the use of other devices) and reduce the power consumption and heat generation. Generally, this principle is followed, but the specific values ​​of different manufacturers are different.

5. The relationship between the carrier frequency and the length of the secondary output (U, V, W) of the inverter.

Generally, as the output line grows, the leakage current of the inverter will increase. Therefore, if the output line is long, the carrier frequency should be appropriately reduced.

Carrier frequency: 15kHz 10kHz 5kHz 1kHz

Line length: <50m>50~100m>100~150m>150~200m

The difference between inverter and soft start

Soft starters and frequency converters are two completely different applications. The frequency converter is used for speed regulation. The output not only changes the voltage but also changes the frequency. The soft starter is actually a voltage regulator. When the motor starts, the output only changes the voltage and does not change the frequency. The frequency converter has all the soft starter functions, but it is much more expensive than the soft starter and the structure is much more complicated.

The main difference between the two is:

1, soft start is to try to cut and destroy the sinusoidal waveform, it is easy, just as water flows down to the bottom;

2, the frequency converter is to do everything possible to obtain a sinusoidal waveform with adjustable frequency, it is difficult! Just as water is going to flow as high as it is difficult.

The characteristics of the inverter are:

1. About the inverter, it is a device that changes the frequency of three-phase sinusoidal alternating current;

2. It is an irreversible process, or impossible, because it is necessary to change the direct current into a sinusoidal AC waveform. Only the PWM widened carrier whose average voltage waveform is a sine wave can realize the frequency conversion purpose of the sinusoidal waveform;

3. The average voltage waveform is a sinusoidal PWM widened carrier, which is realized by the switching action of the full control device IGBT. The actual output of the inverter is a periodically varying rectangular wave with different widths;

4. The asynchronous motor filters out the sinusoidal waveform from the PWM widened carrier and generates a constant rotating magnetic field required for electric power;

5, and change the synchronous speed of the asynchronous motor by changing the frequency to achieve the purpose of frequency control of the AC motor

Differences in technical indicators:

1. The thyristor AC voltage regulating circuit is a circuit for adjusting the thyristor alternating current waveform by adjusting the conduction angle of the thyristor to obtain an alternating current with an adjustable average voltage;

2. The AC voltage regulating circuit is applied to an automatic heating temperature control circuit, a stage dimming circuit, and the like, and the load circuit related to the average voltage is independent of the AC waveform;

3, but some people and even so-called experts put this thyristor AC voltage regulator circuit for the start of asynchronous AC motor, and its name is soft start;

4. Because the asynchronous AC motor works under the three-phase symmetrical sinusoidal AC waveform, there is a constant rotating magnetic field;

5. If the alternating current of the waveform of the sinusoidal alternating current is adjusted for the conduction angle of the thyristor by using the conduction angle of the thyristor, a constant rotating magnetic field cannot be generated;

6. This AC waveform is used for the asynchronous motor to completely destroy the starting performance of the asynchronous motor. The starting torque is low and the starting current is large. There is no soft start function that everyone imagines;

7. All soft-start motors are started when they are close to full pressure. The start-up time is long, the starting current is large, and the impact on the power grid is greater;

8, asynchronous motor self-twisting step-down start, star-delta start, water resistance step-down start, etc., step-down does not change the sinusoidal waveform, are good effective starting devices, are better than soft start;

Key points for judging the quality of inverter products

The technical grade of the frequency converter is gradually developed and formed. With the improvement of the use requirements and the development of technology, the quality of the device, the expansion of functions, and the advancement of automation technology are gradually advanced. Generally, the following ten points are generally considered in determining the quality of the product, as follows:
1, the control mode of the inverter
The control method is the first to determine the performance of the inverter, it depends on the software programming technology. With the advancement of the times and technological development, the inverter control methods are:

(1) V/f=C is an open loop control;
(2) SVPWM space voltage vector control, which is open loop control;
(3) Vector control VC, which is closed-loop control, with current I, magnetic flux φ, torque T, and rotational speed n; generally inner ring is φ, T, I, and outer ring is n (or w) .
(4) Direct Torque Control DTC is a closed-loop control. It can have 400% Te at n=0, the above four commonly used.

After 2000, there are inverters without feedback devices in foreign countries, that is, there is no need to install additional sensors or encoders, and the current, voltage, magnetic flux, and rotational speed changes of the inverter during operation are passed, and device devices such as detection and decoupling are fed back. See Figure 1, Table 1, and Table 2 for the input. Since its inception, it has been well received and favored by users. It is mainly convenient to use and functions as a frequency converter with speed sensor feedback device. At present, the control mode of high-voltage inverters is mostly A and B. No feedback device is in trial production, C is in development.

2. Unique control methods for several inverters
(1) Optimized PWM vector control
The sinusoidal pulse width modulation SPWM has the advantages of simple circuit and good linearity, but the output voltage is not high. The maximum linear output voltage amplitude is only /2=0.866 of the input voltage, which is essentially the phase voltage control method. The optimized PWM vector control mode adopts a dual modulation process, that is, the amplitude of the triangular wave phase and the modulation signal (0 to 50 Hz) are adjusted together to control the switching operation state of the IGBT by the switching angle α (30° to 60°) and modulation. Depth α = sine wave amplitude / triangle wave amplitude < 0.95. The characteristic is that the total harmonic current loss is small and the pulsation torque is small. When α=0.92~0.95, the harmonic loss is the smallest, especially when the carrier frequency is low, it can fully show its superiority, which shows that the output voltage is increased by about 20%, the harmonic is reduced, but the signal wave modulation depth is The linearity between the switch angle and the switch angle is affected. As the α increased voltage control becomes smaller, the total harmonic current distortion THD value is still small, so it is often used.
(2) PWM modulation method control
1 synchronous modulation
The number of triangular waves included in one modulation signal period is constant, and the carrier period is changed proportionally while changing the signal period, so that ≥3 and must be an odd number. When the switching frequency is low, the symmetry of the output waveform can be guaranteed, but at a lower frequency, the number of carriers appears sparse, resulting in an increase in the ripple of the current waveform, so it is only applicable to the frequency range of f>20Hz, the current This is the case with the V/F method.
2 asynchronous modulation
The carrier period remains unchanged while the modulation signal changes periodically. That is, the modulation characteristic is that the harmonic loss and the torque ripple are greatly improved during low frequency operation, and the f<20Hz low frequency working segment is applicable.
3 random modulation
According to the period of the modulation signal and the voltage value of the output, the modulation mode, the modulation depth a and the switching angle α can be automatically selected to adapt to the closed-loop system with large operating frequency variation amplitude, large load torque or power variation and impact. This modulation method fundamentally solves the shortcomings of SPWM in the low-frequency working segment, that is, the shortcomings of torque, torque ripple and harmonics. However, there are certain difficulties in software technology, and there is no such modulation method at home and abroad. The product. near
(3) Control according to the U-shaped characteristic curve of the motor and the V/f matching mode
According to the control method of the U characteristic curve of the motor and V/f, it is known that the V/f control is static voltage regulation, that is, when f is constant, the voltage is also fixed, and it is not according to the motor load factor β. For optimal control. Japan’s AREX company won the world-recognized super energy-saving controller 10 years ago. It has an additional link, which can automatically search (through ASIC) according to the actual load rate β, and output the minimum working voltage and minimum working current (U). Shape characteristic curve), therefore it is the most energy-saving, it can save 8%~10% more power than the general frequency converter under the same working conditions, and cos is a dynamic power adjustment controller, especially suitable for fans and pumps. . In the energy-saving operation, the effect is very good, the early products are SMX series. In recent years, in order to expand the scope of use, it is suitable for speed regulation, and the new variety is VMX series. Later, Hitachi J300 series inverters also have this function during energy-saving operation. The U-shaped characteristic curve of the motor is shown in Figure 2.
(4) Fuzzy control mode
Fuzzy control (FUZZY)
This method is controlled by the fuzzy control method according to the motor parameters and operating state, and is especially suitable for the application of the general-purpose single-chip microcomputer such as 8031 ​​as the CPU. The fuzzy control software simplifies the mathematical model, and can control the multi-variable real-time. The random variable can reach a certain precision. It is required to be widely used in household appliances such as refrigerators, air conditioners, washing machines, and microwave ovens. Of course, fuzzy control is also applicable to the control of the frequency converter. For example, the Vacon inverter uses fuzzy current vector control (see Figure 3).
(5) Self-tuning (motor parameter online measurement control)
(6) Recently, green harmonics have come out

Inverter maintenance knowledge

A frequency converter for motor control that changes both voltage and frequency. However, the inverter used for fluorescent lamps is mainly used to adjust the frequency of power supply. Equipment used in automobiles to generate AC power from batteries (DC) is also sold under the name “inverter”. The working principle of the frequency converter is widely used in various fields. For example, the power supply of a computer power supply, in this application, the frequency converter is used to suppress reverse voltage, frequency fluctuations and instantaneous power failure of the power supply.

1. Why is the rotational speed of the motor freely changeable?
*1: r/min Motor rotation speed unit: The number of rotations per minute, also expressed as rpm.
For example: 2-pole motor 50Hz 3000 [r/min] 4-pole motor 50Hz 1500 [r/min]

Conclusion: The rotational speed of the motor is proportional to the frequency

The motor referred to in this article is an inductive AC motor, and most of the motors used in the industry are motors of this type. The rotational speed of an inductive AC motor (hereinafter referred to simply as a motor) is approximately determined by the number of poles and frequency of the motor. The number of poles of the motor is fixed by the working principle of the motor. Since the pole value is not a continuous value (a multiple of 2, for example, the number of poles is 2, 4, 6), it is generally uncomfortable and the speed of the motor is adjusted by changing the value.

In addition, the frequency can be supplied to the motor after being adjusted outside the motor, so that the rotational speed of the motor can be freely controlled.

Therefore, the inverter for the purpose of controlling the frequency is the preferred device for the motor speed control device.

n = 60f/pn: Synchronous speed f: Power supply frequency p: Motor pole pairs

Conclusion: Changing frequency and voltage is the optimal motor control method

If only the frequency is changed without changing the voltage, the frequency will decrease and the motor will be over-voltage (overexcitation), causing the motor to be burned out. Therefore, the inverter must change the voltage at the same time while changing the frequency. When the output frequency is above the rated frequency, the voltage cannot continue to increase, and the maximum can only be equal to the rated voltage of the motor.

For example, in order to reduce the rotational speed of the motor by half, change the output frequency of the inverter from 50Hz to 25Hz, then the output voltage of the inverter needs to be changed from 400V to about 200V.

2. What is the output torque when the motor’s rotational speed (frequency) changes?
*1: Power frequency power supply Power supply from the power grid (commercial power supply)
*2: Starting current The output current of the inverter when the motor starts running

The starting torque and maximum torque when the inverter is driven are smaller than those driven by the commercial power supply.

When the motor is powered by the commercial frequency power supply, the starting and acceleration shocks are large, and when the inverter is used for power supply, these impacts are weaker. A direct start of the power frequency produces a large starting and starting current. When the inverter is used, the output voltage and frequency of the inverter are gradually added to the motor, so the starting current and impact of the motor are smaller. Generally, the torque produced by the motor is reduced as the frequency decreases (the speed decreases). The reduced actual data is given in some of the drive manuals. By using a flux vector controlled inverter, the torque of the motor at low speeds is improved, and even in the low speed range, the motor can output sufficient torque.

3. When the inverter is adjusted to a frequency greater than 50Hz, the output torque of the motor will decrease.
The usual motor is designed and manufactured at a voltage of 50 Hz, and its rated torque is also given within this voltage range. Therefore, the speed regulation below the rated frequency is called constant torque speed regulation. (T=Te, P<=Pe). When the output frequency of the inverter is greater than 50Hz, the torque generated by the motor should decrease in a linear relationship inversely proportional to the frequency. When the motor is running at a frequency greater than 50 Hz, the size of the motor load must be considered to prevent the motor from outputting insufficient torque. For example, the torque generated by the motor at 100 Hz is reduced to approximately 1/2 of the torque at 50 Hz. Therefore, the speed regulation above the rated frequency is called constant power speed regulation. (P=Ue*Ie).

4. Application of inverter above 50Hz
As you know, the rated voltage and current rating of a particular motor are constant. If the inverter and motor are rated: 15kW/380V/30A, the motor can work above 50Hz. When the speed is 50Hz, the output voltage of the inverter is 380V, and the current is 30A. If the output frequency is increased to 60Hz, the maximum output voltage of the inverter can only be 380V/30A. Obviously, the output power is unchanged. So we call it constant power speed regulation. What is the torque situation at this time? Because P=wT (w: angular velocity, T: torque). Since P does not change, w increases, so the torque will decrease accordingly. We can also look at another angle:

The stator voltage of the motor is U = E + I*R (I is the current, R is the electronic resistance, and E is the induced potential). It can be seen that when U, I are constant, E is also unchanged. E = k*f* X, (k: constant, f: frequency, X: flux), so when f is from 50–>60Hz, X will decrease accordingly. For the motor, T=“K”*I*X, ( K: constant, I: current, X: flux), so the torque T will decrease as the flux X decreases. Meanwhile, when it is less than 50 Hz, since I*R is small, U/f=E/f When constant, the flux (X) is constant. The torque T is proportional to the current. This is why the overcurrent capability of the inverter is usually used to describe its overload (torque) capability. (The rated current does not change -> the maximum torque does not change). Conclusion: When the inverter output frequency increases from above 50Hz, the output torque of the motor will decrease.

5. Other factors related to output torque
The heat and heat dissipation capacity determine the output current capability of the inverter, which affects the output torque capability of the inverter. Carrier frequency: Generally, the rated current of the inverter is the highest carrier frequency, and the value of continuous output can be guaranteed at the highest ambient temperature. When the carrier frequency is reduced, the current of the motor will not be affected. However, the heat of the components will decrease. Ambient temperature: It does not increase the protection current value of the inverter because it detects that the ambient temperature is low. Altitude: The altitude increases, which has an effect on heat dissipation and insulation performance. Generally, it can be ignored below 1000m. 5% of the rice can be reduced.

6. How does vector control improve the output torque capability of the motor?
*1: Torque boost
This function increases the output voltage of the inverter (mainly at low frequencies) to compensate for the output torque loss caused by the voltage drop across the stator resistance, thereby improving the output torque of the motor. The technique of improving the low output torque of the motor at low speed, using “vector control”, can make the output torque of the motor at low speed, such as (without speed sensor) 1Hz (for a 4-pole motor, its speed is about 30r/min) The torque of the motor at 50 Hz output is reached (maximum approximately 150% of rated torque). For conventional V/F control, the voltage drop of the motor increases relatively as the motor speed decreases, which results in the motor not being able to obtain sufficient rotational force due to insufficient excitation. In order to compensate for this deficiency, the inverter needs to increase the voltage to compensate for the voltage drop caused by the motor speed reduction. This function of the inverter is called “torque boost” (*1). The torque boost function is to increase the output voltage of the inverter. However, even if a lot of output voltage is increased, the motor torque cannot be increased corresponding to its current. Because the motor current contains the torque component produced by the motor and other components (such as the excitation component). The “vector control” distributes the current value of the motor to determine the value of the motor current component and other current components (such as the excitation component) that produce the torque. The “vector control” can be optimally compensated by responding to the voltage drop at the motor end, allowing the motor to produce large torque without increasing the current. This function is also effective for improving the temperature rise of the motor at low speeds.

7. Inverter braking situation
*1: Braking concept: means that the electric energy flows from the motor side to the inverter side (or the power supply side). At this time, the motor speed is higher than the synchronous speed. The energy of the load is divided into kinetic energy and potential energy. Kinetic energy (by speed and weight) Determine its size) as the object moves. When the kinetic energy is reduced to zero, the thing is in a stopped state. The method of mechanically holding the brake device is to use the brake device to convert the kinetic energy of the object into friction and energy consumption. For the frequency converter, if the output frequency is reduced, the motor speed will also decrease with the following frequency. This will generate a braking process. The power generated by the brake will return to the inverter side. These powers can be dissipated with resistance heating. When used to lift the load, when it is falling, the energy (potential energy) is also returned to the inverter (or power supply) side for braking. This method of operation is called “regenerative braking” and the method can be applied. The inverter brakes. During deceleration, the power generated is not consumed by the method of heat consumption, but the method of returning energy to the power supply side of the inverter is called “power return regeneration method”. In practice, this application requires an “energy feedback unit” option. How to improve braking ability? In order to dissipate the regenerative power with heat dissipation, it is necessary to install a braking resistor on the inverter side. In order to improve the braking capacity, it is not expected to solve the problem by increasing the capacity of the frequency converter. Please use options such as “brake resistance”, “brake unit” or “power regeneration converter” to improve the braking capacity of the inverter.

Look at the motor nameplate to know the motor

The motor is an important part of the transmission and control system. With the development of modern science and technology, the focus of the motor in practical applications has begun to shift from the simple transmission to the complicated control; especially the speed, position and rotation of the motor. Precise control of the moment. However, the motor has different design and driving methods depending on the application. At first glance, it seems that the selection is very complicated, so in order to make a basic classification according to the use of the rotating electric machine. Below we will gradually introduce the most representative, most commonly used and most basic motors in the motor – control motor and power motor and signal motor. One: control motor

The control motor is mainly used in precise speed and position control, and is used as an “actuator” in the control system. Can be divided into servo motor, stepper motor, torque motor, switched reluctance motor, DC brushless motor and so on.

Servo motor

Servo motors are widely used in various control systems to convert the input voltage signal into mechanical output on the motor shaft and drag the controlled components to achieve control purposes. Generally, the servo motor requires the speed of the motor to be controlled by the applied voltage signal; the speed can be continuously changed as the applied voltage signal changes; the torque can be controlled by the current output by the controller; the motor is reflected quickly, The volume should be small and the control power should be small. Servo motors are mainly used in various motion control systems, especially in servo systems.

The servo motor has DC and AC. The earliest servo motor is a general DC motor. When the control accuracy is not high, the general DC motor is used as the servo motor. With the rapid development of permanent magnet synchronous motor technology, most servo motors refer to AC permanent magnet synchronous servo motors or DC brushless motors.

2. Stepper motor

The so-called stepper motor is an actuator that converts electrical pulses into angular displacement; more generally, when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction. We can control the angular displacement of the motor by controlling the number of pulses to achieve precise positioning. At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency to achieve the purpose of speed regulation. At present, the more commonly used stepping motors include reactive stepping motors (VR), permanent magnet stepping motors (PM), hybrid stepping motors (HB), and single-phase stepping motors.

The difference between a stepper motor and a normal motor is mainly in the form of its pulse drive. It is this feature that the stepper motor can be combined with modern digital control technology. However, the stepping motor is not as good as the traditional closed-loop controlled DC servo motor in terms of control accuracy, speed variation range and low-speed performance; therefore, it is mainly used in applications where the accuracy requirements are not particularly high. Stepper motors are widely used in various fields of production practice because of their simple structure, high reliability and low cost. Especially in the field of CNC machine tools, because stepper motors do not require A/D conversion, The digital pulse signal is directly converted into an angular displacement, so it has been considered as the most ideal CNC machine tool actuator.

In addition to its application on CNC machines, stepper motors can also be used on other machines, such as motors in automatic feeders, as general-purpose floppy disk drives, as well as in printers and plotters.

In addition, stepper motors also have many drawbacks; stepper motors can run normally at low speeds due to the no-load start-up frequency of stepper motors, but they cannot start at higher speeds than with a certain speed, accompanied by sharp howling sounds; The accuracy of the subdivision driver of the manufacturer may vary greatly. The larger the subdivision number, the more difficult it is to control the accuracy; and the stepper motor has large vibration and noise when rotating at low speed.

3. Torque motor

The so-called torque motor is a flat multi-pole permanent magnet DC motor. The armature has more slots, commutator segments and series conductors to reduce torque ripple and speed pulsation. The torque motor has two kinds of DC torque motor and AC torque motor.

Among them, the DC torque motor has a small self-inductance reactance, so the responsiveness is very good; its output torque is proportional to the input current, independent of the speed and position of the rotor; it can be directly connected to the load at a low speed when it is close to the locked state. Without gear reduction, a high torque-to-inertia ratio can be generated on the shaft of the load, and system errors due to the use of the reduction gear can be eliminated.

AC torque motors can be divided into synchronous and asynchronous. Currently, squirrel-cage asynchronous torque motors are used, which have the characteristics of low speed and large torque. Generally, an AC torque motor is often used in the textile industry, and its working principle and structure are the same as those of a single-phase asynchronous motor. However, since the squirrel-cage rotor has a large electrical resistance, its mechanical characteristics are soft.

4. Switched reluctance motor

Switched reluctance motor is a new type of speed-regulating motor. Its structure is extremely simple and sturdy, its cost is low, and its speed regulation performance is excellent. It is a strong competitor of traditional control motors and has strong market potential. However, there are also problems such as torque ripple, running noise and vibration, and it takes time to optimize and adapt to the actual market application.

5. Brushless DC motor

Brushless DC motor (BLDCM) is developed on the basis of brushed DC motor, but its driving current is uncompromising AC; brushless DC motor can be divided into brushless speed motor and brushless torque motor. . Generally, there are two kinds of driving currents of a brushless motor, one is a trapezoidal wave (generally “square wave”), and the other is a sine wave. Sometimes the former is called DC brushless motor, the latter is called AC servo motor, and it is also a kind of AC servo motor.

In order to reduce the moment of inertia, brushless DC motors usually adopt a “slender” structure. Brushless DC motors are much smaller in weight and volume than brushed DC motors, and the corresponding moment of inertia can be reduced by 40% to 50%. Due to the processing of permanent magnet materials, the general capacity of brushless DC motors is below 100 kW.

The motor has good linearity of mechanical characteristics and adjustment characteristics, wide speed range, long life, easy maintenance and low noise, and there is no series of problems caused by brushes. Therefore, this kind of motor has great control system. Application potential.
Two: Motor model parameters: Motor model is a code that is easy to use, design, manufacturing and other departments to carry out business contacts and simplify the description of product names, specifications, types and other technical documents. The following is a description of the meaning of the motor model.

A, motor model composition and meaning

It consists of four sub-sections: motor type code, motor characteristic code, design serial number and excitation mode code.

1. The type code is a Chinese phonetic alphabet used to characterize various types of motors. such as:

Asynchronous motor Y synchronous motor T

Synchronous generator TF DC motor Z

DC generator ZF

2. The feature code is to characterize the performance, structure or use of the motor, and is also represented by the Chinese phonetic alphabet. such as:

Flameproof type B means YT for YB axis flow fan

Electromagnetic Brake YEJ Variable Frequency Speed ​​Control YVP

YZD, etc. for variable-speed multi-speed YD cranes.

3. Design serial number refers to the order of motor product design, expressed in Arabic numerals. For the first design of the product, the design serial number is not marked, and the products derived from the series product are marked in the order of design.

For example: Y2 YB2

4. The excitation mode codes are respectively represented by letters, S represents the third harmonic, J represents the thyristor, and X represents the complex excitation.

Such as: Y2– 160 M1 – 8

Y: model, indicating asynchronous motor;

2: design serial number, “2” indicates the product of the improved design on the first basis;

160: the center height is the height from the center of the shaft to the plane of the base;

M1: frame length specification, M is medium, wherein footnote “2” is the second specification of M-type core, and “2” type is longer than “1” type core;

8: The number of poles, “8” refers to the 8-pole motor.

Such as: Y 630-10 / 1180

Y represents an asynchronous motor;

630 represents power 630KW;

10 pole, stator core outer diameter 1180MM.

B. The specification code is mainly expressed by the center height, the length of the base, the length of the core, and the number of poles.

1. The center height refers to the height from the motor shaft center to the bottom angle of the base; according to the height of the center, the motor can be divided into four types: large, medium, small and miniature.

H is a micromotor in the range of 45mm~71mm;

H is a small motor from 80mm to 315mm;

H is a medium-sized motor at 355mm~630mm;

H is a large motor at 630 mm or more.

2. The length of the base is indicated by international common letters:

S—short frame

M-center stand

L—long stand

3. The length of the core is expressed by the Arabic numerals 1, 2, 3, 4, and , respectively, from long to short.

4, the pole number is divided into 2 poles, 4 poles, 6 poles, 8 poles and so on.

C. The special environment code has the following provisions:

Special environment code

“High” original G

Ship (“sea”) with H

Household “outside” with W

Chemical anti-corruption F

Tropical T

Wet tropical TH

Dry tropical TA

D. The supplementary code is only applicable to motors with supplementary requirements.

for example:

The meanings of the motor codes of the model number YB2-132S-4 H are:

Y: product type code, indicating asynchronous motor;

B: Product feature code, indicating explosion-proof type;

2: Product design serial number, indicating the second design;

132: The center of the motor is high, indicating that the distance from the axis to the ground is 132 mm;

S: the length of the motor base, expressed as a short base;

4: pole number, indicating 4-pole motor;

H: Special environmental code, indicating the marine motor.

Through the above detailed description of the motor model, I believe that the product type, the type, characteristics, design number, motor specifications and the environment it uses can be known.

Ten benefits of using a frequency converter

Variable frequency speed control can be applied to most motor drag applications. Because it provides accurate speed control, it can easily control the rise, fall and shift speed of mechanical transmission. Variable frequency applications can greatly improve the efficiency of the process (shifting does not depend on the mechanical part), and it can be more energy efficient than the original fixed speed running motor. The following are ten reasons to use variable frequency speed regulation to illustrate the basic understanding of the increasing popularity of frequency converter applications:

1. Control the starting current of the motor When the motor is directly started by the power frequency, it will generate 7 to 8 times the rated current of the motor. This current value will greatly increase the electrical stress of the motor winding and generate heat, thus reducing the life of the motor. The frequency conversion speed regulation can be started at zero speed zero voltage (it can also be appropriately increased torque boost). Once the relationship between frequency and voltage is established, the inverter can drive the load to work according to V/F or vector control. The use of variable frequency speed regulation can fully reduce the starting current and improve the bearing capacity of the winding. The most direct benefit of the user is that the maintenance cost of the motor will be further reduced and the life of the motor will increase accordingly.

2. Reducing the voltage fluctuation of the power line When the motor power frequency starts, the current will increase sharply while the voltage will fluctuate greatly. The magnitude of the voltage drop will depend on the power of the starting motor and the capacity of the distribution network. A voltage drop will cause a voltage-sensitive device in the same power supply network to trip or operate abnormally, such as PCs, sensors, proximity switches, and contactors. After the frequency conversion speed regulation is adopted, since the voltage can be gradually started at the zero frequency zero voltage, the voltage drop can be eliminated to the greatest extent.

3. The power required at startup is lower. The motor power is proportional to the product of current and voltage. The power consumed by the motor directly driven by the power frequency will be much higher than the power required for the inverter startup. In some working conditions, its power distribution system has reached the highest limit, and the surge generated by its direct power frequency starter motor will have a serious impact on other users on the same network. If the inverter is used to start and stop the motor, no similar problem will occur.

4. Controllable acceleration function The frequency conversion speed regulation can be started at zero speed and uniformly accelerated according to the user’s needs, and its acceleration curve can also be selected (linear acceleration, S-shaped acceleration or automatic acceleration). When the power frequency is started, the motor or the connected mechanical part shaft or gear will generate severe vibration. This vibration will further exacerbate mechanical wear and tear and reduce the life of mechanical components and motors. In addition, variable frequency start-up can also be applied to similar filling lines to prevent the bottle from falling over or being damaged.

5, adjustable operating speed Using variable frequency speed control can optimize the process, and can be quickly changed according to the process, but also through remote control PLC or other controllers to achieve speed changes.

6. Adjustable torque limit After frequency conversion and speed regulation, the corresponding torque limit can be set to protect the machine from damage, thus ensuring the continuity of the process and the reliability of the product. The current frequency conversion technology makes not only the torque limit adjustable, but even the torque control accuracy can reach 3% to 5%. In the power frequency state, the motor can only be controlled by detecting the current value or thermal protection, and it is not possible to set an accurate torque value to operate as in the variable frequency control.

7. The controlled stop mode is the same as the controllable acceleration. In the variable frequency speed regulation, the stop mode can be controlled, and there are different stop modes to choose (deceleration stop, free stop, deceleration stop + DC brake), also It reduces the impact on mechanical components and motors, making the entire system more reliable and with a correspondingly longer life.

8. Energy-saving centrifugal fans or pumps can greatly reduce energy consumption after using inverters, which has been reflected in more than ten years of engineering experience. Since the final energy consumption is proportional to the speed of the motor, the return on investment is faster with the use of frequency conversion.

9. Reversible operation control In the inverter control, no reversible control device is required to realize reversible operation control. Only the phase sequence of the output voltage needs to be changed, which can reduce maintenance cost and save installation space.

10. Reducing mechanical transmission components Due to the current vector control inverter plus synchronous motor, high-efficiency torque output can be realized, thereby saving mechanical transmission components such as gear boxes, and finally forming a direct conversion transmission system. This reduces costs and space and improves stability.

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