Development Of Intelligent Three-Phase Asynchronous AC Motor Power Saver

Three-phase asynchronous AC motors cost more than 40 percent of China’s total electricity consumption, there are 60 percent of motors running in a low efficiency situation which will cause a lot of energy wasting. Due to motors own structure, when three-phase asynchronous motors are running in a light load situation, the loss of power will occupy a large part of the total energy. By using some effectively methods to reducing the voltage, power saver can cut down power losses and improve the motors’ running efficiency, besides, the output power will still stay in the same. In the current context of increasingly tense energy, the power saver of motors has broad application prospects and practical significance. This paper puts forward a practical method to make a power saver of three-phase asynchronous AC motors, including:First of all, this paper analyzes the asynchronous motor’s running mode and gets the T-equivalent circuit of the motor. From analyzing the equivalent circuit model, it can be drew that the stator terminal voltage is proportional to the losses of motors. Through the relationship of motor efficiency and power factor of the motors’no-load and full-load conditions, the relationship can be inferred to normal load conditions. Thereby we can infer that cutting down voltage can reduce motor losses and improve the efficiency of motors.Second, the motor stater’s voltage has a coupling relationship with the current power factor of motor and the thyristor’s cut-off angles, any of them changes will influence the other two variables. By using power factor and its changing rate to fuzzy control method, we can get a cut-off angle to determine the value of stator’s voltage.Third, in order to verify the feasibility of the control method, this paper builds a MATLAB\SIMULINK model which is based on the losses analysis and the control methods. This paper confirms the power saver of motor is effective and practical.Fourth, based on the method of Chapter 3, this paper presents a practical hardware and software implementation. The hardware system includes a minimum system which is based on a 32-bit ARM processor, zero crossing detection and A\D detection of voltage as well as current, triggering circuit of thyristor, serial transceiver circuit and other hardware circuits. On software level, the processor need calculating the A\D converter voltage and current values accurately, the power factor and power factor’s change rate can be obtained from voltage and current values, then I write a fuzzy control function to get obtain the cut-off angle, by using cut-off angle to control thyristor, the voltage will decrease and the motor will run efficiently.Finally, this paper operates an experiment to manipulate the motor, and verifies the feasibility of proposed scheme.