ABSTRACT
In the industrial and agricultural manufacture, alternating current asynchronous motor is one of the most important driving equipments. It has got vast application for a simple framework and well maintain ability. But when asynchronous motor is started directly, the motor and the driving equipments’ longevity will be badly affected by huge starting-current and mechanical collision, and big voltage decrease would influence the power-supply network, even other equipments’ operation. So it is necessary to undertake the asynchronous motor’s soft start technology.
The paper analyzes the working principle of asynchronous motor soft-starter, and realizes software and hardware expansion based on single-chip microcomputer Intel-89C51.A interface between human and soft-starter, where the operation data of the motor could be modified has also been added. The power factor measure circuit and the soft-starter’s thyristor voltage modualtor form a close circuit feedback system, by which the single-chip microcomputer can change the motor’s terminal voltage according to the load, and make the motor runs under the set power factor. In this way, the asynchronous motor’s constant power factor control system is realized, and the energy saving operation is achieved.
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Keywords：Asynchronous motor；Power factor；Single-chip microcomputer ；Soft start；
Energy-saving operation
