Forward and reverse control circuit to prevent phase-to-phase short circuits
When the forward rotation starts, press the forward rotation start button SB2, and a set of normally closed contacts (13-15) of the SB2 are disconnected. Cut off the reverse handover.
Flow contactor KM1 coil loop, play the role of interlocking;Another set of normally open contacts (3-5) of SB2 is closed and turns AC forward.
The contactor KM coil is energically engaged, and the KM1 auxiliary normally open contact (3-7) is closed and self-locking, and the KM1 three-phase main contact is closed, and the motor is energized and starts to run.
At the same time as the motor is energized, the intermediate relay KA coil is energized and engaged, and the KA is connected in series in the forward rotation to start back.
The disconnection of two sets of normally closed contacts (5-7, 11-13) in the circuit or reverse start circuit will restrict the forward turn of the start button SB2 or reverse.
Turn the start button SB3 to start the operation, but do not affect the stop work of the circuit.
After the motor is in forward rotation, if you want to reverse the operation, press the reverse start button SB3, a group of normally closed contacts of SB3.
Point (7-9) is disconnected, cut off the power supply of the forward AC contactor KM1 coil circuit, and the forward AC contactor KM1 coil is disconnected.
The power must be cut off and released first, the KM1 three-phase main contact is disconnected, and the motor stops running when the power is lost.
At the same time, the intermediate relay KA coil is also de-energized and released, and the two sets of normally closed contacts (5-7, 11-13) of the KA are also restored.
The normally closed state provides a pathway for reversal.
In this way, after the conversion of the intermediate relay KA is avoided, the AC contactor is likely to be damaged by the motor when the forward and reverse conversion is avoided.
Arc short circuit caused by a large starting current.
When the KA normally closed contacts returned to the normally closed state, another set of normally open contacts (3-11) of SB3 (already closed, waiting to be connected with the KA
The normally closed contacts are connected to the reversing AC contactor KM2 together, and the coil circuit power supply) is connected to the reversing AC contactor KM line.
Loop power supply. km2。The coil is electrically engaged, and the km2 auxiliary normally open contact (3-13) is closed and self-locking, and the km2 three-phase main.
The contact is closed, and the motor is energized and reversed to start operation.
Regardless of whether the motor is in forward or reverse operation, to stop the operation, just press the stop button SB2 (1-3), then the forward AC contactor KM1 or the reverse AC contactor KM2 coil is de-energized and released, KM2 or KM1 respective three.
The phase main contact is disconnected, and the motor stops running due to power failure.