Causes and treatment methods for vibration and noise generated by the inverter

There are also some problems in the process of the inverter. For example, vibration and noise are the problems that often occur when the inverter is working. What is the cause of vibration and noise in the inverter? What are the problems? The solution is to introduce the causes and treatment methods of vibration and noise generated by the inverter.

The reason for vibration and noise is that when the inverter is working, the magnetic field caused by the higher harmonics in the output waveform generates electromagnetic force for many mechanical components. The frequency of the power can always be close to or coincide with the natural frequency of some mechanical components. Causes resonance.

The higher harmonics that have a large influence on the vibration are mainly lower harmonic components, and have a greater influence in the PAM (Pulse Amplitude Modulation), the pulse amplitude modulation method and the square wave PWM mode. However, when the sinusoidal PWM method is used, the low-order harmonic components are small and the influence is small. When the inverter is used to drive the motor, since the output voltage and current contain higher harmonic components, the higher harmonic flux of the air gap increases, so the noise increases. The electromagnetic noise instrumentation world network gives the following characteristics: Since the low-order harmonic component in the inverter output resonates with the rotor’s inherent mechanical frequency, the noise near the natural frequency of the rotor increases. The higher harmonic components in the inverter output resonate with the core housing and the like, and the noise near the respective natural frequencies of these components increases. The noise generated by the drive motor of the inverter, especially the harsh noise, is related to the switching frequency of the PWM control, especially in the low frequency region. Using frequency converter speed regulation will generate noise and vibration, which is the influence of high harmonic components in the output waveform of the inverter. As the operating frequency changes, the fundamental component and the higher harmonic components all vary over a wide range, which is likely to cause resonance with various parts of the motor.

Vibration and noise processing methods to reduce or eliminate vibration, you can connect the AC reactor on the output side of the inverter to absorb the higher harmonic current components in the inverter output current.

When using the PAM mode or the square wave PWM mode inverter, the sine wave PWM mode inverter can be used instead to reduce the ripple torque. In order to prevent the vibration of the mechanical system connected to the motor and the load, the entire system must not resonate with the electromagnetic force generated by the motor. The following measures are generally used to suppress and reduce noise: an AC reactor is connected to the output side of the inverter. If the electromagnetic torque has a margin, the U/f can be made smaller. When using a special motor, such as when the noise level of the lower frequency is more serious, check the resonance with the natural frequency of the shaft system (including the load).

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.
One

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.
two

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
three

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;

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.

How does the inverter control the motor speed?

The frequency converter is mainly composed of rectification (AC to DC), filtering, re-rectification (DC to AC), braking unit, drive unit, and detection unit micro-processing unit.


1. Why is the rotational speed of the motor freely changeable?
Motor rotation speed unit: r / min rotations per minute, can also be 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 rotational speed of an inductive AC motor (hereinafter simply referred to 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, such as a pole number of 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/p
n: synchronization speed
f: power frequency
p: motor pole pairs
Conclusion: Changing frequency and voltage is the optimal motor control method

If the frequency is changed only 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, the output frequency of the inverter is changed from 50 Hz to 25 Hz, and 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?
The starting torque and maximum torque when the inverter is driven are less than that of the direct-frequency power supply. When the motor is powered by the commercial 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 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 in 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, for a particular motor, its rated voltage and current rating 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. At this time, 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 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 unchanged, E does not change.

And 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, the magnetic flux (X) is constant when U/f=E/f is constant. The torque T is proportional to the current. This is why the overcurrent capability of the frequency converter is often used to describe its overload (torque) capability. Also known as constant torque speed regulation (rated current is not changed -> maximum torque is unchanged)

Conclusion: When the inverter output frequency increases from above 50 Hz, 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 is not like increasing the protection current value of the inverter because it detects that the ambient temperature is low.

Altitude: Increased altitude, which has an impact on heat dissipation and insulation performance. Generally less than 1000m can be ignored. It is enough to derate 5% per 1000 meters above.

Causes of inverter overvoltage

(1) The overvoltage of the breaking transformer is based on the theory of intercepting overvoltage. When the transformer is disconnected, the current in the transformer inductance cannot be abrupt, and the magnetic field energy stored therein oscillates between the transformer magnetizing inductance and the ground capacitance. An overvoltage has occurred.

(2) Overvoltage generated by transformer with load closing In the actual test, the combined no-load transformer has detected several times the overvoltage of the power supply voltage. The physical principle is that the no-load transformer can still be equivalent to a magnetizing inductance and Parallel connection of the equivalent capacitance of the transformer itself. If the neutral point of the transformer is not grounded, the switch is aperiodic closing (one phase or two phase first), due to the inductance of the feeder, the capacitance of the transformer to the ground, the longitudinal capacitance and the inductance of the transformer. As a result, a higher overvoltage is generated, especially in the transformer neutral point overvoltage. Although the transformer is basically loaded with a load, the transformer will also generate an overvoltage when it is loaded with a load, but it is smaller when it is relatively empty. There is a relatively large capacitance in the real load, because the storage of the capacitor does not suddenly increase, and the transmission cable has a distributed capacitance to the ground when transmitting a high frequency oscillating voltage, and these capacitors have an absorption effect on the overvoltage. The combination of the two causes the overvoltage of the transformer during the closing process to be suppressed, but sometimes the value is still high and may even be higher than the withstand voltage of the component, which is very dangerous.

(3) The commutation overvoltage rectifying element of the rectifying element is high in steering, and therefore the steering overvoltage is also high. This not only damages components, but also creates electromagnetic interference.

Frequency converter overvoltage processing method

(1) For the breaking overvoltage of the phase shifting transformer of the frequency converter, the overvoltage absorption circuit is formed by the RC absorption network and the zinc oxide arrester, and good results are obtained.

(2) For the overvoltage generated by the transformer with load closing, a switch with good cycle performance can be selected (the switch will have different periods after long-term operation); a good resistance-capacitance absorption circuit or active suppressor technical solution is adopted; The shielded transformer can also effectively suppress the closing overvoltage. However, the difficulty of making a high-power transformer in the formation of an electrostatic shielding layer will be considerable.

(3) For the overvoltage generated by the commutation of the rectifying element, the point of attention is: the reverse withstand voltage of the rectifying element is sufficient, and the second is that the absorption circuit and the freewheeling circuit must be properly controlled. Otherwise, the rectifier device may be broken down by an overvoltage. (4) Since the overvoltage during the operation of the inverter is basically generated when the transformer is opened, it is necessary to start from the transformer to find a way to suppress the overvoltage of the inverter. Can be used:

1 Increase the magnetizing inductance of the transformer and the capacitance to the ground, increase the excitation inductance to reduce the no-load current, which will increase the cost of the transformer.

2 increase the capacitance of the transformer to the ground: in principle, it is easy to analyze, but in fact, due to the structure and material limitations of the transformer itself, it is impossible to make a transformer with any insulation method or high insulation level, so it is necessary to increase it greatly. The capacitance to ground C of the transformer is also quite difficult.

VFD Inverter Frequency converter single phase 220v input 3phase 380v output for motor

  • Brand Name: ECOGOO
  • Type: DC/AC Inverters
  • Power :0.75kw ~22kw
  • is_customized: Yes
  • Output Type: Triple
  • Output Frequency: 0~650hz
  • Output Power: 1 – 200KW
  • color: black
  • Communication: RS 485
  • Output Voltage: 3 phase 380v
  • Input Voltage: single phase 220V

Specification:

Product name: General 220V to 380V AC motor frequency inverter VFD

Output frequency:0-400HZ

Input voltage:1 phase 220V

Output voltage:3 phase 380v

Adapter motor:  AC motor

 

+Advantages of  Frequency inverters

We have sophisticated engineers, scientific producing workmanship and management team with rigorous quality control systems , frequency inverter are equipped with advanced features as below:
01 V/F control, vector control  and output torque control;
02 Built-in RS-485 communication interface
03 Compact size, easy to install;
04 With a speed potentiometer and external panel;
05 Built-in synchronous control and proportional synchronization control;
06 16 speed control modest,Can run automatically;
07 Can choice multiple running commands or frequency channel;
08 Can be achieve Part or all of the keys locked(Analog potentiometer unlock);
09 Relay normally open or closed and two high configuration output have 100 kinds of ways optional;
10 6 digital opto-isolated inputs, 100 kinds of ways optional;
11 3 analog input, 1 analog output channel;
12 Having textile pendulum frequency function, It can be widely applications for many kinds of textile
equipment;
13 Built-in user timer / counter;
14 Built-in PID regulation function to facilitate the realization of closed loop control of the temperature,
pressure and tension.
15 At zero speed time,can be achieve output 0-100% of Adjustable torque,With zero speed brake
function,instead foreign inverter application on freight elevator and crane.

 

How to make the inverter “live” longer

The frequency converter is often used in electrical systems, but the service life of the frequency converter will also be shortened due to overvoltage and overcurrent, and once the inverter fails, it will cause serious failures in the entire electrical system. Therefore, the electrician is gradually paying attention to and paying attention to the maintenance and repair skills of the inverter. After all, anyone who wants to buy the inverter can live longer, so how should the inverter “longevity”?

1, the correct wiring and parameter settings. Be sure to read the manual carefully before installing the inverter, master its usage, precautions and wiring; after installation, set the parameters correctly according to the use.

2. The ambient temperature has a great influence on the service life of the inverter. When the ambient temperature is 10 °C per liter, the life of the inverter is halved, so the problem of ambient temperature and heat dissipation of the inverter must be solved.

3. V/F control is a constant torque adjustment. The vector control increases the output torque of the motor in proportion to the square of the voltage, thereby improving the output torque of the motor at low speeds.

4. If the system is operated by the power frequency/frequency conversion mode, the interlock of the power frequency output and the frequency conversion output should be reliable. Moreover, the pump should be stopped, the power frequency/frequency conversion should be stopped, and then the contactor should be operated. Since the contact sticking and the extinguishing of the large-capacity contactor arc take a certain time, the order and time of the above switching should be considered comprehensively.

5. The problem of external control signal failure. Generally, there are several cases: the signal mode is incorrect, the terminal wiring is incorrect, the parameter setting is incorrect, or the external signal itself has a problem.

6, pay attention to the relationship between speed and head. The choice of the motor and its optimal working segment are important issues. If the inverter runs below 5HZ for a long time, the motor heating becomes a serious problem.

7. The difference between overcurrent trip and overload trip. Overcurrent is mainly used to protect the inverter, and overload is mainly used to protect the motor. Because the capacity of the inverter sometimes needs to be increased by one or two gears than the capacity of the motor. In this case, the inverter does not have to overcurrent when the motor is overloaded. The overload protection is carried out by the electronic thermal protection function inside the inverter. When preset electronic thermal protection, the “current take-up ratio”, that is, the ratio of the rated current of the motor to the rated current of the inverter should be accurately preset.

How to eliminate inverter interference? Inverter interference solution?

The inverter includes a rectifier circuit and an inverter circuit. The input AC power is converted into a DC voltage through the rectifier circuit and the flat circuit, and then the DC voltage is converted into pulses of different widths through the inverter. Voltage (called pulse width modulation voltage, PWM). By using this PWM voltage to drive the motor, the motor torque and speed can be adjusted.
This working principle leads to the following three kinds of electromagnetic interference:

1, harmonic interference:
Rectifier circuits generate harmonic currents that produce a voltage drop across the impedance of the power supply system, causing distortion of the voltage waveform. This distorted voltage interferes with many electronic devices (because most electronic devices only work. In the case of a sinusoidal voltage, the common voltage distortion is that the top of the sine wave flattens. When the harmonic current is constant, the voltage distortion is more serious in the case of a weak power supply. The characteristic of this type of interference is that it will interfere with the equipment that uses the same power grid, and has nothing to do with the distance between the equipment and the frequency converter;

2, RF conducted emission interference:
Since the load voltage is pulsed, the frequency converter draws current from the power grid also in the form of a pulse. This type of pulsed current contains a large number of high-frequency components that form radio frequency interference. This type of interference is characteristic of devices that use the same power grid. Interference, independent of the distance between the equipment and the frequency converter;

3, radio frequency radiation interference:
RF emissions interfere with the input and output cables from the frequency converter. In the above-mentioned case of radio frequency conducted emission interference, when there is radio frequency interference current on the input and output cables of the frequency converter, since the cable is equivalent to the antenna, electromagnetic wave radiation will inevitably occur and radiation interference will occur. The PWM voltage transmitted on the output cable of the inverter also contains rich high-frequency components, which will generate electromagnetic wave radiation and form radiated interference. The characteristic of radiated interference is that the interference phenomenon becomes serious when other electronic devices are close to the inverter.

Need help? Email Us Here! Chat With Us Now!

← Prev Step

Thanks for contacting us. We'll get back to you as soon as we can.

Please provide a valid name, email, and question.

Powered by LivelyChat
Powered by LivelyChat Delete History