Protective Device for Crane

1. Distribution protection

The main circuit of crane distribution is equipped with automatic air switch for general power, main contactor and other protection components.

2. Short circuit protection

The general power circuit is equipped with automatic switch as a short circuit protection for the crane. The control circuit is provided with small-capacity automatic air switch as a short protection.

3. Phase sequence protection

The equipment adopt phase sequence protector to monitor the quality of power supply in real time. The control system will cut off the main circuit to protect effectively the safety of equipment and personnel when power supply cause the over voltage, under voltage, phase lack and phase dislocation due to external reasons.

4. Lifting limit protection

The lifting mechanism is equipped with fire stopper for the upper and lower limit, limit switch to ensure that they can automatically cut off the power of lifting mechanism when the hook rises or falls to the limit position.

The counter weight limit switch is also provided for the user to choose, the limit of lifting mechanism is equipped with double protection.

5. Lifting overload protection

Lifting mechanism is equipped with overload protective device and alarm, the overload limiter will send suggestive alarm signal when the load reaches 90% of rated capacity. When the load reaches 110% of rated capacity, it will cut off the power of lifting mechanism at once and send the prohibitive alarm signal. The sensor of overload limiter has the damp proof and anti-seismic function.

6. Limit protection for crane travel

Crane traveling mechanism is equipped with limit switch to ensure that it can automatically cut off the power of travel mechanism when mechanism is horizontally moved to limit position. When several cranes are running on the same track, the photoelectric anti-collision switch is also provided to prevent the collision of two cranes on the same track, which is more reliable and safer.

7. Emergency power-off protection

Control circuit of the crane is equipped with emergency switch. It can cut off the power of control circuit at any time to make the main circuit power off, ensuring the safe operation of the crane when the accident happens.

8. Voltage loss protection

The control circuit of the crane is equipped with voltage loss protective device. When the power suddenly fails or the voltage is too low, main contactor will lock automatically and break, the crane must be restarted after the power is restored.

9. Zero interlock protection in the cab (when there’s cab cam controller and master control)

The crane operated by cab has zero protective device. The zero protective device eliminate the motor running automatically when the power is failure, which can prevent accidents. The power supply of crane is restored after the controller set to zero position.

10. Switch protection safety door of the cab

The switch interlock device of door avoids the personnel or goods dropping from the door because safety door is not closed and the crane is operated suddenly.

11. Ground protection

There are reliable grounding device on the metal structure of the crane, metal enclosures of all electrical equipment, pipe chases and low-voltage side of transformer. The total grounding resistance is not more than 4Ω, insulation resistance to ground at normal temperature is not less than 1MΩ.

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