The Study Of Energy Saving Control Of VVVF Induction Motor Base On Double CPU Technique

In China, asynchronous motors are widely used in many aspects and they play an essential role in modern society. Now there is a great shortage of electrical power in most areas of China. References of electrical power department show that the load caused by the use of asynchronous motors takes eighty percent of the whole. So, it is both necessary and beneficial to study how to reduce the loss and improve the efficiency of asynchronous motors.The VVVF asynchronous motors studied in this paper often run under the circumstances of low load or no load. Under these conditions, they can be nearly considered as a pure inductance that cause the increase of reactive power and more unnecessary losses of active power. And all of these will result in the decrease of their efficiency. So what this paper is going to achieve is, to those asynchronous motors with low load or no load, to seek for a proper ratio of voltage to frequency and when the motors run with it, their active power loss will be decreased as much as possible while they can burden their load safely. That is to say, this paper is going to find the way to improve the efficiency of VVVF asynchronous motors with low load or no load.To achieve the goal, this paper analyses the VVVF asynchronous motors' characteristics which run with low load or no load. Firstly we find that the active power losses in motors can be lowered when both the input voltage and the frequency is adgusted and then we get the optimal principle about the value of the ratio of the voltage to frequency relative to various loads. Then we realize that the optimal principle doesn't fit the disturbed motors in real operation very well. So another adaptive method is put forward in this paper and we conclude a principle of adaptive by means of adjuestion of parameter of motor. To eliminate the harmonic comes out when both the voltage ang frequency is adjusted by the PWM modulation, we apply the SVPWM wave that is able to efface specific harmonic which should disappear.To make these theory realizations, we design a device which can supervise the running of motors and adjust ratio of the voltage to frequency offered to them. The Computer is the DSP that is used to control motor. In addition, we design a circuit whose main components are IPM. It is this circuit that is used to adjust ratio of the voltage to frequency by using the SVPWM wave.