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Wuxi Lanhai Electric Motor Co.,Ltd

Add: 4#, Tianshi Road Shitangwan Town, Wuxi, Jiangsu, China


TEL: 0086-0510-83269982

FAX: 0086-0510-83269953

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Operation requirements and automatic control of three phase asynchronous AC motor
Aug 24, 2018

The three-phase asynchronous AC motor starts to run from the power supply, and its rotational speed rises gradually until it runs stably. This process is called start-up. According to the starting mode, it can be divided into direct start and decompression start. Starting current of direct startup is large, which has great influence on power supply transformer. Squirrel cage asynchronous motor with large capacity is usually started by step-down. 


The step-down startup of three-phase asynchronous motor is to reduce the power supply voltage properly, and then start it on the stator winding of the motor when operating, and then restore the voltage of the motor to the rated value when the motor starts up or will be finished. The main purpose of this is to reduce the starting current, but because of the step-down, the starting torque of the motor will also be reduced. Therefore, the buck start-up is only applicable to no-load or light load start-up.


The direct starting of three-phase asynchronous motor mainly uses switch to start directly. The circuit which uses switch to start directly is only suitable for small-capacity motor which is not frequently started. It can not realize long-distance control and automatic control, nor can it realize zero-voltage, under-voltage and overload protection.