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.