JDB-LQ-TQ/2 motor full voltage starting circuit

This circuit uses JDB-LQ-TQ/2 with 380V contactor for full voltage start wiring. As shown in the figure below.

1. Working principle

The power supply of the circuit protector is 220V, and the coil voltage of the contactor KM is 380V. When the button SB2 is pressed, the coil of the AC contactor KM is energized, the contactor is attracted, and its auxiliary normally open contact KM1 is closed and self-locked, and its main contact KM212 is closed, the three-phase power supply is connected, and the motor M runs. When it is necessary to stop, press the stop button SBI. The motor stops running.

When the motor fails to operate, is overloaded, or fails to operate, the protector trips and its normally closed protection contacts ((3), (4)) are disconnected, cutting off the power supply to the control circuit. The motor M stops running and the fault indicator lights HI, R light up.

2. Electrical appliance selection

The circuit breaker QF uses three-pole 10A, model D247-63; the AC contactor uses CDC10-10, coil voltage 380V; the protector uses JDB-LQ-TQ/2; the three-phase asynchronous motor uses model Y90S-6, rated power 0.75kW, rated current 2.3A, speed 910r/min.

3. Common troubleshooting

(1) Press button SB2. Contactor KM does not close. Possible reasons are: fuse FU is blown; button SB1 or SB2 contacts are in poor contact; contactor coil KM is open circuit; protector normally closed protection contacts ((3), (4)) are damaged. If button SB1 or SB2 contacts are in poor contact and cannot conduct electricity to connect coil KM power, you can rub the contact surface to make its contact resistance less than 1Ω. If contactor KM coil is open circuit, the multimeter measures its resistance value to be infinite, and you can replace a new contactor. If the above treatment still cannot eliminate the fault, and the protector is not operating, you should check the protector protection contacts ((3), (4)). If they are not conducting, replace the protector.

(2) Press SB2. The protector trips and the fault indicator lights up. This situation should be caused by a phase failure in the main circuit. Check the main circuit separately and the circuit breaker. If the neon tube of the test pen of one output contact of the circuit breaker is not lit, it is determined that the circuit breaker is internally broken. Replace the circuit breaker, press the reset button of the protector to reset it, and restart the motor to resume normal operation.