For variable frequency motors, starting is a very easy task, but for asynchronous motors, starting is always a very critical operating performance indicator. Among the performance parameters of asynchronous motors, the starting torque and starting current are important indicators reflecting the starting performance of the motor. They are usually expressed by the multiple of the starting torque relative to the rated torque and the multiple of the starting current relative to the rated current.
From the perspective of motor application, we hope to have a larger starting torque to ensure that the motor can be easily started in a short period of time, especially for motors that start and stop frequently, the size of the starting torque directly affects the overall performance of the equipment. Operating efficiency; as for the starting current, it is hoped that it should be as small as possible to avoid adverse effects of large current on the motor body and the grid.
The effective way to solve this contradiction is to increase the rotor resistance, which is very beneficial to improve the starting performance, but it is not conducive to the satisfaction or improvement of other performance indicators of the motor. How to take into account the starting and running indicators and make a fuss about the rotor part of the motor It is effective and necessary.
In the wound rotor asynchronous motor, as long as the external resistance is connected in series in the rotor circuit, the rotor resistance can be increased. This is very effective and easy to do. When the motor starts and turns into normal operation, the series connection The external resistance cut off can realize the double guarantee effect of starting performance and running performance.
According to the idea of improving the starting performance of the wound rotor asynchronous motor, for the cage rotor asynchronous motor, the deep groove rotor and the double cage rotor are used, and the “skin effect” is used to dynamically realize the effect of starting performance and running performance guarantee.
For special working conditions that require high starting performance, there is a high-slip motor. The guide bars of the cage rotor are made of materials with high resistivity, and the starting torque of the motor is improved by increasing the rotor resistance.
In order to solve the contradiction between starting torque and starting current of asynchronous motors, and take into account the relationship between starting performance and other operating indicators, auxiliary starting measures such as reduced voltage starting and variable frequency starting are derived.
Post time: Mar-09-2023