What Are The Electrical Protection Measures For Cranes

What are the Electrical Protection Measures for cranes？

 

1. Electrical wiring specification:

 

Before installing the electrical equipment of the 10 ton overhead crane, the size of the equipment should be checked;

 

The location, direction and pipeline location of its equipment installation shall meet the requirements of design and equipment technical conditions.

 

The installation of distribution panels and cabinets shall meet the following requirements:

 

A. The installation of power distribution panels and cabinets should comply with the relevant provisions of the current national standard "Code for Construction and Acceptance of Panels, Cabinets and Secondary Circuit Wiring of Electrical Installation Engineering".

 

B. The installation of distribution panels and cabinets should not be fixed by welding, and the fastening bolts should have anti-loosening measures.

 

C. The rainproof device of the power distribution panel and cabinet of the outdoor crane should be installed correctly and firmly.

 

2. Short circuit protection of the main power supply.

 

When the insulation of the electrical equipment on the crane is damaged, and when there is a shell collision or a short circuit between phases, the short-circuit protection device of the main power supply should act quickly to cut off the faulty power supply.

 

The main power short-circuit protection device should be completed by a fuse circuit breaker.

 

 

3. Loss of voltage protection for the total power supply.

 

The loss of voltage protection of the main power supply refers to the ability to automatically disconnect the main power supply circuit after the power supply is interrupted;

 

When the power supply is restored, the main power circuit cannot be connected without manual operation.

 

Generally, the automatic reset button is connected to the main power contactor coil or the voltage-loss tripping coil circuit of the automatic circuit breaker to realize the loss-of-voltage protection of the main power supply.

 

4. Main disconnect switch.

 

The maintenance and inspection of electrical equipment should generally be carried out under the condition of power failure.

 

Therefore, there should be an isolating switch or other isolation measures between the electrical equipment and the power supply grid.

 

When the isolating switch is in the disconnected state, there must be an effective disconnecting distance and a clearly visible disconnecting point, so that the maintenance personnel can visually confirm that the main power circuit has been disconnected.

 

In particular, it should be pointed out that when the air switch and iron shell switch are in the off position, there is no obvious break point, so they cannot be used as isolating switches.

 

 

5. Zero position protection.

 

The motor of the mechanism is controlled by a controller that cannot be automatically reset. In order to prevent that when the controller handle is not at the zero position, the power supply of the crane will be restored after losing voltage, causing the motor to start by mistake, and the crane is equipped with zero position protection.

 

Inspection method of zero position protection:

 

A. The motor of the mechanism is directly controlled by the cam controller; turn off the main power supply, and pull one of the controller handles away from the zero position, and then turn on the main power supply. The main power supply should not be connected, and set all the controller handles to zero. position, the main power supply can be connected.

 

B. If the motor of the mechanism is controlled by the master controller and contactor, turn off the main power supply, pull the master controller away from the zero position, and turn on the main power supply. When the main power supply is turned on, the motors of the mechanism cannot be started at the same time.

 

6. Limit protection.

 

In order to prevent accidents where the sling is lifted to the upper support structure due to negligent mistakes in work, the steel wire rope is broken and the sling falls, a stopper for the limit position of the dagger lift should be installed.

 

There are two common types: hammer type and screw (or worm gear) type.

 

In addition, electrical protection includes stroke protection and grounding protection.

 

7. Motor overload protection.

 

If the rated power of the motor on the crane is greater than 1KW, overload protection should be set separately. Overcurrent protection is the motor overload protection method commonly used in cranes at present.

 

 

8. Emergency power off switch.

 

The crane must be equipped with an emergency power-off switch that can quickly disconnect the main power supply in an emergency, and it should be located at a place where the driver can easily operate.

 

Emergency power-off shall not be automatically reset. There are two ways to judge whether the emergency power off switch is qualified:

 

8.1 Check whether there is a main power contactor on the crane.

 

The crane must be equipped with a main power contactor, and the power supply lines of all mechanisms must be led from the outlet end of the power contactor.

 

8.2 Pull the emergency power-off switch, the main power contactor or the circuit breaker with undervoltage tripping coil will act, cut off the main power supply of all institutions, and stop the operation of all institutions.

 

At the same time, meeting the above conditions can determine that the emergency power-off switch is qualified.

 

9. Passage port safety interlock protection.

 

The 10 ton bridge crane should be equipped with an interlock switch of the passage opening, which is used to cut off the main power supply when the passage opening is opened.

 

The trolley of the bridge crane is powered by bare wires, which can prevent accidental electric shocks to the staff on the walking platform, and also prevent crushing and falling accidents caused by the sudden start of the mechanism.