The three-phase asynchronous AC motor has the characteristics of simple structure, convenient maintenance and reliable operation, and is widely used compared with other motors of the same capacity, such as light weight, low cost and low price.
In the forward and reverse control circuit of the three-phase cage asynchronous motor, two contactors KM1 and KM2 can be used to change the phase sequence of the three-phase power supply of the motor to change the rotation direction of the motor. However, the two contactors cannot be sucked at the same time. If they are simultaneously attracted, the power supply will be short-circuited, as shown in the figure below.
Figure 1 Motor is reversing
When the motor is running forward, KM1 is energized and pulled, and the phase sequence of the motor at this time is L1, L2, L3, that is, forward operation.
Contactor interlocking positive and negative control line
When the motor is reversed, KM2 is energized and pulled, and the KM2 main contact is closed to replace the three-phase power phase sequence of the motor. At this time, the phase sequence of the motor is L3, L2, L1, that is, reverse operation.
Figure 2 Three-phase cage asynchronous motor forward and reverse control circuit
a) no interlock circuit b) with electrical interlock circuit c) with double interlock circuit
Double interlocking positive and negative control line
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