Understanding the Operational Principle of VFD Electric Motor and its Speed Control

What is VFD electric motor?

VFD electric motor refers to a motor equipment with high degree of mechanical automation composed of a special frequency conversion induction motor and a frequency converter AC speed control method. At present, this combination has completely replaced the traditional mechanical speed regulation and DC speed regulation solutions. With the astonishing development of power electronics technology and microelectronics technology, the AC speed control method with special frequency conversion induction motor and frequency converter is guiding a new generation of replacement of traditional speed regulation methods in the field of speed regulation with its outstanding performance and economy.

Due to the unparalleled superiority of vfd electric motor in speed regulation and control, it greatly improves the degree of mechanical automation and production efficiency. EPS power supply has its uniqueness as a trend in the development of future frequency converter technology. However, due to the demanding requirements of VFD electric motor system for high-speed or low-speed operation, dynamic response of speed, etc., to the power body motor, it will bring innovation in electromagnetic, structural, insulation and other aspects to the VFD electric motor. It can be said that due to the superiority of VFD electric motor in frequency conversion control, wherever vfd frequency converter is used, we can see the figure of VFD electric motor.

What is the speed control principle of VFD electric motor?

From the essence of speed control, different speed control methods are nothing more than changing the synchronous speed of AC motor or not changing the synchronous speed. Widely used speed control methods that do not change the synchronous speed of the production machinery include rotor series resistance speed regulation, pulse width modulation speed regulation, inter-stage speed regulation, and application of electromagnetic differential clutches, hydraulic couplings, oil film clutches, etc. to speed regulation. Changing the synchronous speed includes multi-speed motor with changing stator pole pairs, variable frequency speed regulation that changes stator voltage and frequency, and reversible motor speed regulation without replacing direction.

From the perspective of energy consumption during speed control, there are two types of efficient and inefficient speed control methods: efficient speed control refers to the constant slip rate, which does not cause slip loss, such as multi-speed motor, variable frequency speed regulation and speed control method that can recover the slip loss (such as inter-stage speed regulation). Speed control methods with slip loss belong to inefficient speed control, such as rotor series resistance speed regulation method, energy is lost in the rotor circuit; speed control method of electromagnetic clutch, energy is lost in the clutch coil; speed regulation of hydraulic coupling, energy is lost in the oil of the hydraulic coupling. Generally speaking, the slip loss increases with the expansion of speed control range. If the speed control range is not large, the energy loss is very small.