The most familiar electric equipment for electrical workers should be the electric motor. There are many ways to start the motor, including direct start, auto-decompression start, Y-Δ step-down start, soft starter start, drive start, etc. the way. So what is the difference between them?
1, full pressure direct start
In the case of full-voltage direct start in both grid capacity and load, full-voltage direct start can be considered.
The advantages are convenient operation control, simple maintenance and economical. It is mainly used for the starting of small power motors. From the perspective of saving electric energy, this method should not be used for motors larger than 11kw.
2, auto-decompression start
The multi-tap decompression of the autotransformer can not only meet the needs of different load starting, but also obtain a larger starting torque. It is a decompression starting method that is often used to start a large capacity motor.
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 starting. And the starting torque can be adjusted by tapping. It is still widely used today.
3, Y-Δ start
For a squirrel-cage asynchronous motor in which the normal running stator winding is a delta connection, if the stator winding is connected to a star at the start, and then connected to the triangle after the start, the starting current can be reduced and the grid can be reduced. The impact. Such a starting method is called a star-delta decompression starting, or simply a star-delta starting (Y-Δ starting).
When starting with the star-delta, the starting current is only 1/3 of the original starting directly by the delta connection. If the starting current at the time of direct start is 6 to 7 Ie, the starting current is only 2 to 2.3 times when the star-delta is started. This means that when starting with the star-delta, the starting torque is also reduced to 1/3 of the original direct start by the delta connection.
Suitable for applications with no load or light load start. And compared to any other decompression starter, the structure is the simplest and the cheapest. In addition, the star-delta starting method has the advantage that when the load is light, the motor can be operated in star connection. At this time, the rated torque can be matched with the load, which can improve the efficiency of the motor and save power consumption.
4, soft starter
This is the use of the phase shift voltage regulation principle of the thyristor to achieve the voltage regulation start of the motor, mainly used for the start control of the motor, the starting effect is good but the cost is high. Due to the use of thyristor components, the thyristor has a large harmonic interference during operation and has a certain impact on the power grid. In addition, fluctuations in the grid can also affect the conduction of the thyristor components, especially when there are multiple thyristors in the same grid. Therefore, the failure rate of the thyristor component is high, and since the power electronics technology is involved, the requirements for the maintenance technician are also high.
5, the frequency converter
The frequency converter is the motor control device with the highest technical content, the most complete control function and the best control effect in the field of modern motor control. It adjusts the speed and torque of the motor by changing the frequency of the power grid. Because it involves power electronics technology and microcomputer technology, it is costly and has high requirements for maintenance technicians. Therefore, it is mainly used in areas where speed regulation is required and speed control is required.