Compared to wire-wound rotor motors, cage motors are more commonly used in manufacturing and maintenance. One significant advantage of cage rotor motors is the freedom to choose different slot shapes for the rotor.
However, these motors have a starting problem that needs to be solved to enhance their application level.
As we’ve mentioned before, improving the starting performance of asynchronous motors can be achieved by adjusting the motor rotor resistance.
Adjusting the rotor resistance of cage rotor motors is a reflection of motor technology advancement. By changing the rotor conductor slot shape, we can achieve dynamic change characteristics of the rotor resistance during starting and operation.
One type of slot shape is the deep rotor slot.
This elongated shape reduces the rotor resistance during starting, thus decreasing the motor’s starting current. After starting, the rotor resistance returns to the DC resistance size. This slot shape is an effective measure to improve the starting performance of asynchronous motors.
Another slot shape is the double cage rotor slot.
This design has two layers of finer slit conductor, with the upper cage using a conductor material with a larger resistance coefficient, and the lower cage using a conductor material with a smaller resistance coefficient.
The upper cage is mainly used for motor starting, while the lower cage’s main role is to run.
The skin effect and the larger resistance of the upper cage material improve the starting index, while the lower cage’s smaller resistance value meets the motor’s operating performance.
In summary, cage rotor motors offer the advantage of choosing different slot shapes for the rotor, allowing for dynamic changes in the rotor resistance during starting and operation.
The deep rotor slot and double cage rotor slot are two examples of slot shapes that can effectively improve the starting performance of asynchronous motors.
