What is the difference between a motor cast copper rotor and a cast aluminum rotor?

Update:15 Nov 2019
Summary:

One of the main differences between the motor cast copp […]

One of the main differences between the motor cast copper rotor and the cast aluminum rotor is that the resistance of the cast copper rotor is smaller than that of the cast aluminum rotor. Because copper has a resistivity that is 40% lower than aluminum. Therefore, the use of cast copper instead of aluminum, in addition to the motor rotor resistance difference, the performance and characteristics of the motor will change.

(1) Changes in motor performance:

The only affected parameter when we replace the aluminum rotor with a copper rotor is the rotor resistance r2 of the motor, which is reduced by about 40%, which is equivalent to the change in resistivity of copper/aluminum. Since the electromagnetic torque is directly dependent on r2, the slip will decrease with the same torque. And because the rotor copper consumption is also dependent on r2, it will also be reduced by 40%. This means increased motor efficiency and reduced motor losses.

(2) Changes in mechanical properties of the motor:

If copper is used instead of aluminum, the motor rotor resistance r2 will be reduced, which will increase the gradient of the curve. This means that in the case of the same torque, the slip will decrease and the efficiency will increase. Example: If a 5.5KW copper rotor squirrel cage motor is used, the torque will increase by 13% for the same slip.

(3) Changes in motor efficiency characteristics:

Because the slip is reduced, the rotor heat loss is also reduced, which increases the efficiency of the motor by about 1.3 percentage points. Many experiments on other motors have shown that if copper is used instead of aluminum, the total loss of the motor is reduced by more than 15%, and the motor efficiency is increased by 2%-5%;

(4) Increased motor life

The operating temperature of the machine has a great influence on the service life of the motor. If the overall heat generation of the motor is reduced, if we think that the motor life is halved for every 10 ℃ increase in the motor temperature, then reducing the heat of the motor will increase the motor. Life expectancy. Therefore, the use of a cast copper rotor motor can greatly increase the service life of the motor. Of course, it also helps the motor designer to reduce the size of the motor and increase the power density of the motor.