Vector control asynchronous motor speed adjusting method combining pole changing with frequency changing

Abstract

The invention aims to provide a vector control asynchronous motor speed adjusting method combining pole changing with frequency changing and provides a pole-changing asynchronous motor speed adjusting system which comprises a pole-changing asynchronous motor, a frequency-changing power source, a pole-changing control circuit and a control system. The frequency-changing power source powers the pole-changing asynchronous motor through the pole-changing control circuit which is controlled by the control system, the control system actually measures rotating speed of the pole-changing asynchronous motor, and a connecting mode of stator windings of the pole-changing asynchronous motor is YY/Y connection. When voltage of the motor increases to a rated value along with frequency (the rated value corresponds to rotating speed (i)n(/i)>/=(i)n(/i)1N), a pole-changing operation is performed on the pole-changing asynchronous motor, and reconstruction (i)U(/i)/(i)f(/i) is performed according to new motor parameters after pole changing and current rotating speed to enable a constant-torque speed adjusting range of a system to be expanded under new parameter conditions, so that the objective of expanding a constant-torque speed adjusting range of the motor without increasing voltage of the power source and number of inversion circuit semiconductor switch devices is achieved.

Description

technical field [0001] The invention relates to an asynchronous motor speed regulation method, in particular to a vector control asynchronous motor speed regulation method combining pole change and frequency conversion. Background technique [0002] The constant torque speed regulation range of the existing asynchronous motor frequency conversion speed regulation system below the base frequency (50HZ) is strongly restricted by the rated voltage of the motor. When the voltage rises to the rated voltage with the speed (or frequency) U N At this time, the constant torque speed regulation reaches the limit. Although the output frequency can continue to be increased to increase the speed, the torque will decrease with the increase of the speed. ) In the case of constant torque output driving requirements are still maintained. For example, the air resistance suffered by electric vehicles and high-speed trains increases with the square of the running speed. When the running speed...

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Problems solved by technology

The more inverter units used in series, the greater the output voltage, but the number of power semiconductor devices used and the complexity of control also increase, and each inverter unit must be equipped with an independent additional transformer with phases staggered by a certain angle. Secondary winding power supply, the number of required secondary windings is equal to the number of series units, and the internal connection of the winding is complicated, so that the additional transformer takes up a lot of cost and space

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