Do Cranes Have To Be Equipped With Overspeed Protection?

Do cranes have to be equipped with overspeed protection?

The overspeed protection device is a very important safety protection device on hoisting machinery. It is a protective measure taken to prevent the crane from falling too fast and exceeding the rated speed when it is descending with a load.

The overspeed protection device can eliminate the dangerous situation of crane overspeeding, avoid damage to motors, gearboxes, brakes and other components caused by crane overspeeding, reduce the work fatigue intensity of crane operators, ensure the safety of lifting heavy objects, and protect crane operators, Personal safety of lifting personnel.

This control device is widely used in bridge cranes, gantry cranes, tower cranes, metallurgical cranes, crane loading and unloading bridges for lifting molten metal (non-metallic), mine hoists and other lifting mechanisms, and can fully meet the needs of various lifting mechanisms. Various tonnages and various occasions are needed.

What are the crane overspeed protection devices?

There are three types of overspeed protection currently used in cranes: overspeed protection switch, speed feedback (tachometer generator, rotary encoder, etc.), and undercurrent relay.

The overspeed switch is a mechanical control switch that electrically limits the maximum speed of the motor and can quickly Disconnect the circuit to ensure safe operation. It is mainly used in the overspeed protection circuit for the lowering of the crane lifting mechanism, and can also be used in situations where overspeed protection is required under similar conditions.

The speed feedback link is used to measure the speed during closed-loop speed regulation so that the motor's running speed follows the set value. It is a part of the speed regulation device. The speed control device should be capable of sending out a fault signal when overspeeding, and the crane's electrical control system uses this signal to cut off the power supply and cause the brake to power off.

When the undercurrent relay adopts thyristor stator voltage regulation, thyristor power supply, or DC unit power supply, the speed regulating torque on the motor shaft is determined by the controllable power supply.

How to check crane overspeed protection?

In addition, for the inspection of overspeed protection, the main inspection is the setting and setting of the overspeed protection, and generally no overspeed test is performed. To check the interlocking protection function, the overspeed protection switch should be manually triggered or the interlocking contact of the overspeed protection relay should be disconnected. At this time, the mechanism motor should not start.