System and method for expanding the constant torque frequency conversion speed regulation range of AC motors based on y-△ transformation

Abstract

The invention relates to a star-delta transform based system and method for expanding a constant-torque frequency control range of an alternating-current motor. The system comprises a three-phase rectifier module, a three-phase inversion module, a star-delta transform control circuit module, a three-phase alternating-current motor, a speed sensor and a DSP (digital signal processor) control system, wherein an input end of the three-phase rectifier module is connected with a UVW three-phase alternating-current power supply; an output end of the three-phase rectifier module is connected in parallel with a first capacitor C1; an input end of the three-phase inversion module is connected in parallel to two ends of the first capacitor C1; an output end of the three-phase inversion module is connected to a three-phase alternating-current input end of the star-delta transform control circuit module; the star-delta transform control circuit module is connected with the three-phase alternating-current motor. The purpose of expanding the constant-torque frequency control range of the motor can be achieved under the conditions that power voltage is not increased and the number of semiconductor switch elements of an inverter circuit is not increased.

Description

technical field [0001] The invention relates to the field of constant torque speed regulation range of AC motors, in particular to a system and method for expanding the constant torque frequency conversion speed regulation range of AC motors based on Y-△ transformation. 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 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 drive requirements are still maintained. For example, the air resistance suffered by electric vehicles and high-speed trains increases with the square of...

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Problems solved by technology

In terms of control, two sets of inverter power supplies must be used to supply power to two sets of three-phase windings of the motor, that is, six-phase windings, so that the number of power semiconductor devices is doubled. In addition, the current of the two sets of windings is in a good balance. Control is also more complex

[0007] To sum up, the main disadvantage of the existing method of increasing the rated voltage of the motor is that it increases the pressure on the semiconductor power devices, which must be solved by increasing the number of devices, but this increases the complexity of the system cost and control. Extremely detrimental to operational reliability

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