The Way The Motor Starts

Motor starting methods include: full-voltage direct start, self-coupling decompression start, Y-δ start, soft starter, frequency converter.
Full pressure direct start:
In cases where both grid capacity and load allow full-voltage direct starting, full-voltage direct starting can be considered. The advantages are convenient operation and control, simple maintenance, and relatively economical. It is mainly used for the starting of low-power motors, and from the perspective of saving electric energy, motors larger than 11kW should not use this method.
Autocoupling decompression start:
The use of autotransformer multi-tap decompression, which can not only adapt to the needs of different load starting, but also obtain larger starting torque, is a decompression starting method that is often used to start larger capacity motors. Its biggest advantage is that the starting torque is large, when its winding tap is at 80%, the starting torque can reach 64% of the direct start. And the starting torque can be adjusted by the tap. It is still widely used today.
Y-δ start:
For the squirrel cage asynchronous motor with the stator winding of the normal operation is triangular connection, if the stator winding is connected into a star shape when starting, and then connected into a triangle after starting, the starting current can be reduced and its impact on the power grid can be reduced. Such a starting method is called star-delta decompression start, or simply star-delta starting (y-δ start). When starting with the star-delta method, the starting current is only 1/3 of the original direct start according to the delta connection method. If the starting current at direct start is calculated as 6~7ie, the starting current is only 2~2.3 times when starting the star-delta. This means that when starting with the star triangle, the starting torque is also reduced to 1/3 of the original direct start according to the triangle connection method. It is suitable for no-load or light-load starting. And compared with any other decompression starter, its structure is the simplest and the cheapest price. In addition, the star-delta starting method has another advantage, that is, when the load is light, the motor can be allowed to run under the star connection. At this time, the rated torque can be matched to the load, which can improve the efficiency of the motor and thus save power consumption.