Method for expanding constant-torque variable-frequency speed control range of AC motor by Y/YY conversion

Abstract

The invention relates to a method for expanding the constant-torque variable-frequency speed control range of an AC motor by Y / YY conversion. The method is characterized by when the motor voltage rises to a rated value with the frequency, performing Y / YY conversion on the stator winding of the AC motor to reduce the number of series turns of each phase winding to a half, and reducing the supply voltage of winding to a half so that the winding obtains a lifting space equivalent to a doubled voltage, and the system constant-torque speed control range is doubled in the new winding connection mode. The method realizes a purpose of expanding the constant-torque speed control range of the motor without increasing the power supply voltage or increasing the number of semiconductor switching devices of an inverter circuit, and makes the winding voltage phase unchanged before and after the Y / YY conversion, and provides convenience for control.

Description

technical field [0001] The invention relates to the fields of power electronics, DSP technology, motors and electrical appliances, in particular to a method for enlarging the constant-torque frequency conversion speed regulation range of an AC motor by using Y / YY conversion. Background technique [0002] The constant torque speed regulation range of the existing AC motor frequency conversion speed regulation system below the base frequency (50HZ) is strongly restricted by the rated voltage of the motor. When the voltage increases with the speed (or frequency) to the rated voltage U N At this time, the constant torque speed regulation reaches the limit. Although the output frequency can be continued to increase to increase the speed, the excitation must be reduced so that the torque decreases with the increase of the speed. (above the fundamental frequency) still maintains the driving requirement of constant torque output. For example, the air resistance suffered by electric...

AI Technical Summary

Problems solved by technology

Although this technology has many advantages such as low cost and simple control, its constant torque frequency conversion speed regulation expansion range is limited to times, and the phase shift of the winding phase voltage π / 6 must be considered before and after the Y / △ conversion, thus adding a corresponding processing link

Otherwise, a large transient current will be caused, threatening the safety of power semiconductor devices

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