The method of forward and reverse control circuit for three-phase asynchronous motor

Release time：2020-05-08 16:39Number of views：Originate：

1、 Several methods of forward and reverse control circuit

 

There are three main forward and reverse control circuits for three-phase asynchronous motor. One is relatively simple interlocking circuit of inching contactor

 

This circuit only has contactor interlock, no button interlock, it is forward and backward inching control. As long as the control line is connected to the normally open contacts of the two buttons, press and hold the forward inching button, and the motor will rotate forward. Press and hold the reverse jog button, and the motor will run in reverse. Release the manual motor to stop.

 

The second control circuit is contactor interlock and motor self-locking operation control circuit

 

When the SB2 button is pressed, the forward contactor KM1 is attracted by electricity through the interlocking km2 normally closed auxiliary contact. At this time, the km2 reverse contactor cannot operate because the KM1 normally closed contact is open.

 

third is the double interlock control circuit of contactor and button

 

In addition to the addition of button interlock, the principle is the same as above. Press the SB2 button, and the contactor km2 will be electrically connected. At the same time, the normally closed contacts of SB2 button and km2 will be disconnected, so that KM1 contactor cannot be connected. The advantage of this control mode is that the forward and reverse switching operations can be reversed without pressing the stop button SB1. Next, follow the three-phase asynchronous motor manufacturers to see the common fault analysis of the three-phase asynchronous motor.

 

First, forward or reverse contactors do not close

 

Since the two contactors are interlocked, when the first control line has such a fault, it may be that one of the contactor contacts is stuck, causing the normally closed contact to open. In addition, the button may be disconnected.

 

2、 The two contactors are not working, which may be the open circuit of the common power control circuit (the open circuit of the normally closed contact of the thermal relay protection) or the damage of the main switch phase failure.

 

3、 The double interlock control circuit is relatively complex, but the fault is similar to the above two points. Only the button interlock is added, and one point of closing does not work, which may cause other circuit components unable to connect and work. Therefore, when finding the fault, it is necessary to check the electrical drawing, understand the principle of forward and reverse control, carefully analyze and gradually check the fault.

Next：What causes three-phase asynchronous motor failure?
Last：How can three-phase asynchronous motor improve efficiency?