In order to enable the motor to rotate forward and reverse, two contactors KM1 and KM2 can be used to change the phase sequence of the three-phase power supply of the motor, but the two contactors cannot be sucked. If the suction is simultaneously, the short-circuit accident of the power supply will occur. To prevent such accidents, reliable interlocking should be adopted in the circuit. The above figure shows the control circuit running in the forward and reverse directions of the motor with double interlocking of the button and the contactor.
The line analysis is as follows:
First, the positive start:
1. Close the air switch QS to connect the three-phase power supply.
2. Press the forward start button SB3, KM1 energizes and absorbs the self-locking, and the main contact closes to turn on the motor. The phase sequence of the motor at this time is L1, L2, L3, that is, forward running.
Second, reverse start:
1. Close the air switch QS to connect the three-phase power supply.
2. Press the reverse start button SB2, KM2 energizes and absorbs and self-locks through the auxiliary contact. The normally open main contact closes and replaces the three-phase power phase sequence of the motor. At this time, the phase sequence of the motor is L3, L2, L1. , that is, running in reverse.
Third, the interlocking link: has a prohibition function to play a security role in the line
1. Contactor interlock: KM1 coil circuit is connected to the normally closed auxiliary contact of KM2, and KM2 coil circuit is connected to the normally closed contact of KM1. When the coil of the forward contactor KM1 is energized, the auxiliary normally closed contact of KM1 is disconnected from the KM2 coil circuit. If the KM1 is electrically connected, the KM2 must be powered off first, and the auxiliary normally closed contact is reset. This prevents the KM1 and KM2 from simultaneously attracting and causing phase-to-phase short circuit. This line is called the interlocking link.
2, button interlock: in the circuit using the control button operation of the forward and reverse transmission control circuit, buttons SB2, SB3 have a pair of normally open contacts, a pair of normally closed contacts, these two touch The points are respectively connected to the KM1 and KM2 coil circuits. For example, the normally open contact of button SB2 is in series with the contactor KM2 coil, while the normally closed contact is in series with the contactor KM1 coil loop. The normally open contact of button SB3 is in series with the contactor KM1 coil, while the normally closed contact pressure KM2 coil circuit is connected in series. Thus, when SB2 is pressed, only the coil of contactor KM2 can be energized and KM1 can be powered off. When SB3 is pressed, only the coil of contactor KM1 can be energized and KM2 can be powered off. If SB2 and SB3 are simultaneously pressed, then two None of the contactor coils can be energized. This plays the role of interlocking.
4. After the motor is running in the forward (or reverse) direction, you do not need to press the stop button to stop the motor. You can directly press the reverse (or forward) start button to make the motor run in the opposite direction.
5. The overload protection of the motor is completed by the thermal relay FR.
Motor reversible operation control wiring diagram motor reversible control circuit debugging
1. Check whether the wiring of the main circuit is correct. In order to ensure that the phase sequence of the motor can be reliably replaced when the two contactors are in operation, the upper port of the contactor should be kept consistent during wiring, and the phase of the contactor should be phased.
2. After checking the wiring is correct, the power-on test, in order to prevent accidents during the power-on test, the motor wiring should be disconnected first.
Pre-processing of fault phenomena;
1. Do not start; one of the reasons is to check whether the control insurance FU is open circuit, whether the thermal relay FR contact is wrong or bad contact, and whether the normally closed contact of the SB1 button is bad. The reason for the second button interlock is incorrect.
2. When the device is activated, the contactor “Do not suck†is not sucked; this is because the interlocking connection of the normally closed contact of the contactor is wrong, the interlocking contact is connected to lock itself, and the closed contact is the contact when starting. The electric coil of the coil is closed, the normally closed contact is disconnected after the contactor is sucked, the contactor coil is discharged again, the normally closed contact is released, the contactor is turned on and the contact is closed again, and the contact is disconnected, so哒†The contactor does not attract.
3, can not be self-locking and lift the hand contactor to disconnect, this is because the self-locking contact wiring is wrong.
Use connection method 1: The general three-phase contactor has a total of 8 points, three inputs, three outputs, and two control points. The output and input are corresponding and can be easily seen. If you want to add a lock, you need to connect the line from the terminal of the output point to the control point.
Second: First of all, you should know the principle of the AC contactor. He uses an external power source to apply to the coil to generate an electromagnetic field. After the power is applied, the contact point is disconnected after the power is turned off. Knowing the principle, you should figure out the contact point of the external power supply, that is, the two contacts of the coil, generally in the lower part of the contactor, and on each side. The other few inputs and outputs are generally in the upper part and are known at a glance. Also pay attention to the voltage of the external power supply (220V or 380V), which is generally marked. Also note that the contact point is normally closed or normally open. If there is self-locking control, the line can be based on the principle.
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