In the previous topic we talked about motor starting, efficiency and other performance parameters of the relationship between the fish and the bear's paw is a very desirable effect, but how to try to achieve, is indeed a topic of motor research.

We have talked about, the starting process we expect a large starting torque and small starting current, this time the need for motor rotor resistance, but the motor running process, in order to meet the motor's efficiency targets, and hope that the rotor resistance is smaller. For this requirement, the winding rotor motor can be started through the process of series resistance, the operation process to cut off the resistance of the way to solve, but for the cast aluminum rotor motor, how to achieve, which is our topic today.

In the previous topic we talked about motor starting, efficiency and other performance parameters of the relationship between the fish and the bear's paw is a very desirable effect, but how to try to achieve, is indeed a topic of motor research.

We have talked about, the starting process we expect a large starting torque and small starting current, this time the need for motor rotor resistance, but the motor running process, in order to meet the motor's efficiency targets, and hope that the rotor resistance is smaller. For this requirement, the winding rotor motor can be started through the process of series resistance, the operation process to cut off the resistance of the way to solve, but for the cast aluminum rotor motor, how to achieve, which is our topic today.

When the motor starts, the current in the rotor guide bars will be evenly distributed. The change of resistance before and after starting is mainly due to the change of rotor current frequency, the deep groove rotor makes full use of the skin effect of the conductor, which effectively improves the starting performance of the motor without affecting the operating efficiency.

When the skin effect squeezes the current in the guide bar to the slot, the slot leakage flux generated by the same current is reduced, so the slot leakage reactance is reduced. Therefore, the skin effect increases the rotor resistance and decreases the rotor leakage reactance.

The strength of the skin effect depends on the frequency and slot size of the rotor current. The higher the frequency, the deeper the slot shape, and the skin effect is significant. For rotors with the same slot size, the effect of skin effect is different with different frequencies. When the motor is running normally and starting, the difference of rotor equivalent resistance is large. At the same frequency, the skin effect of the deep groove rotor is very strong, but the skin effect of the ordinary cage rotor also has a certain degree of influence. Therefore, even for the squirrel cage rotor with ordinary structure, the rotor parameters during startup and operation shall be calculated separately.

The rotor leakage reactance of deep-slot asynchronous motor, due to the deep rotor groove shape, although reduced by the influence of skin effect, but ultimately still larger than the ordinary squirrel cage rotor leakage reactance. Therefore, the power factor and maximum torque of the deep slot motor are slightly lower than those of the ordinary squirrel cage motor.

For motor products, should be combined with the specific conditions of use, the performance advantages associated with appropriate trade-offs. But with the progress of frequency conversion technology, squirrel cage motor starting may not be too big a problem, how to combine the traditional motor control and new control technology, is the irreversible trend of future motor development.