Common line faults and troubleshooting methods of electric hoist overhead crane power supply

(1) Push the three-phase knife switch of the protection cabinet, press the start button, and the fuse of the control circuit fuse will blow. It is usually caused by a short circuit of the fused phase to ground. Use electrical instruments to find the grounding location and eliminate it.

(2) Push the switch of the protective cabinet knife and press the start button, the main contactor of the crane will not be closed (commonly known as the switch cannot be closed and cannot be started). In any of the following situations, it cannot be started.

①The circuit has no voltage;

②The fuse of the control circuit fuse 1FU or 2FU is blown;

③Some controller handles are not set to the zero position;

④Emergency switch SE, the safety interlock switches SQ1 and SQ2 are not closed;

⑤Normal closed contacts KC1, KC2...KC4 of each overcurrent relay are not closed;

⑥ The KM coil of the main contactor is broken or its wiring is broken. Check the connection line step by step to find the reason why the crane can't start and eliminate it.

(3) After the crane starts, the button SB cannot be self-locked after the button is released, and the contactor is released (commonly known as tripping). It is usually caused by poor contact of the contactor interlocking contacts KM1 or KM2, failing to connect circuit ② to the control loop to replace circuit ①.

Adjust the spring pressure of the interlock contact KM1 or KM2 to keep it in good contact.

(4) The main contactor is often released during the operation of the crane (commonly known as the phenomenon of "brake-off" of the cart), and one of the following conditions can cause the crane to "bron-off".

1) The setting value of the over-current relay of the large vehicle is adjusted to be too small, which is caused by the over-current relay often operating greatly when the large vehicle is working.

2) Poor installation of the trolley trolley wire, too much dust or rust-skin insulation, causing the current collector of the crane to frequently disconnect from the power supply slip wire.

3) The crane track is installed poorly, the gap between the track joints is too large, and the crane generates vibration during operation, which causes the collector support to slip away from the crane slip line instantaneously.

4) The hatch door or the driver's door is not closed tightly, and vibration occurs during the operation of the crane, which causes the normally closed contacts of these door switches to be disconnected momentarily.

5) The normally closed contacts of various mechanisms and total overcurrent relays are caused by instantaneous tripping due to vibration.

6) The self-locking contact KM1 or KM2 of the main contactor is not in firm contact, and sometimes it is disconnected instantly due to vibration.

(5) When a certain mechanism is started, the crane will "off".

1) The setting value of the overcurrent relay that protects the motor of the mechanism is too small. When the motor is turned on, the relay will act and the control circuit will be de-energized, causing the crane to "off".

2) There is a phase-to-phase short-circuit or a relative-to-ground short-circuit in the motor power cord of the mechanism, and the short-circuit current causes the relay to operate and short-circuit.

3) The mechanism has a jam phenomenon, which leads to an increase in resistance, which increases the motor current and causes the relay to operate.

(6) After the terminal limiter of a certain mechanism operates, the crane is powered off and the mechanism continues to run.

1) A short circuit in the terminal limiter circuit causes the limiter to fail. Check the circuit, eliminate the short contact, and connect the normally closed contact of the limiter into the control loop to solve the problem.

2) The limiter wiring is disordered and the control direction is wrong. The wiring should be reconnected correctly.

(7) After the crane is started, only the trolley running mechanism can operate, and the hoisting mechanism and the trolley running motor do not operate.

It is usually caused by the poor contact between the collector support of the trolley current introducer and the trolley sliding contact line or the broken wiring, resulting in the lack of phase of the motors of the two mechanisms.

Check the poor contact between the collector support and the sliding wire or connect the wiring to eliminate the phase failure.

(8) When the cart is driven centrally, the motor of the cart does not work, and other mechanisms work normally.

1) The overcurrent relay coil of the cart or its wiring is disconnected, resulting in the lack of phase of the cart motor.

2) There is an open circuit in the motor stator winding or its wiring.

3) Poor contact of the stator contact of the cart controller causes a lack of phase in the motor.

After checking the cause of the motor not working, take corresponding measures to solve it.

(9) When the trolley is driven separately, the trolley motor does not work, and other mechanisms work normally. It is usually caused by a disconnection in the wiring from the main contact of the contactor of the protection cabinet to the stator contact of the controller.

The open circuit of the circuit should be carefully checked and connected.

(10) The motor of a certain mechanism does not work (other mechanisms are normal), or the motor torque is very small, and it is difficult to start under light load. After checking that the stator circuit is normal, the fault generally occurs in the rotor circuit.

1) The lead wire of the rotor winding is grounded, or the copper sheet connected to the slip ring is broken at a 90° bend, resulting in a disconnection in the rotor loop. Check the point of failure and eliminate it.

2) The slip ring and the brush are in poor contact, and the carbon brush is seriously burned; the spring pressure of the carbon brush holder is not enough; the wire of the carbon brush is broken or the wiring bolt is loose.

Check the poor contact or replace the brush, adjust the spring pressure, and tighten the wiring bolts to solve the problem.

3) Poor contact between the collector slider (collector support) and the sliding contact line.

4) The wiring of the collector slider is broken.

5) There is a break in the resistance element or the resistance wire is broken.

6) The contact of the cam controller rotor circuit is burned and caused by bad contact. Check separately, find out the fault point and solve it.