The electrical control system of Tower crane hoist should be equipped with the necessary electrical protection measures.

31-08-2019

The good operation of tower crane electrical control system can effectively protect the safety of tower crane equipment and operators. In order to protect the safety of the electrical equipment and staff of the tower crane, the electrical control system of the tower crane must be equipped with necessary electrical protection measures.
1. Main isolation switch.
Maintenance inspections of electrical equipment should generally be carried out in the event of a power failure. Therefore, there should be isolation switches or other isolation measures between electrical equipment and the power supply grid. When the isolation switch is disconnected, the disconnect distance and visible disconnect point must be hurriedly parked so that the maintenance staff can intuitively confirm that the total power supply circuit has been disconnected. In particular, it should be pointed out that when the air switch and the iron shell switch are disconnected, there is no obvious disconnection point and can not be used as a isolation switch.

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2. Short circuit protection of total power supply.
When the electrical equipment is damaged by the insulation of the tower lifting, the short-circuit protection device of the total power supply should move quickly to cut off the faulty power supply. The total power supply short circuit protection device shall be completed by the fuse breaker circuit breaker.
3. Pressure loss protection of total power supply.
The loss of voltage protection of the total power supply means that the total power supply loop can be automatically disconnected after the power supply is interrupted; When power supply is restored, the total power loop can not be connected by itself without manual operation. In general, the automatically reset button is connected to the total power contactor coil or the unbuckling coil loop of the automatic circuit breaker to achieve the total power loss protection.
4. Zero protection.
The mechanism motor is controlled by a controller that can not be automatically reset. In order to prevent the controller handle from being at zero, the power supply of the tower crane is restored after the power supply is lost, causing the motor to start incorrectly. The tower crane is provided with zero-position protection. Zero bit protection check method:
4.1 The mechanism motor is directly controlled by the cam controller; Turn off the total power supply, and pull the handle of the controller out of the zero position, turn on the total power supply, the total power supply should not be connected, put all controller handles in zero position, the total power supply can be connected.
4.2 The mechanism motor is controlled by the main controller and the contactor, turning off the total power supply, pulling the main controller away from the zero position, and turning on the total power supply. When the total power supply is switched on, the mechanism motor can not start at the same time.

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5. Overloading protection of electric motors.
If the rated power of the motor on the tower is greater than 1 KW, overload protection should be set up separately. Overcurrent protection is the general use of motor overload protection for tower hoists.
6. Emergency power off switch.
The tower crane must be equipped with an emergency power outage switch that can quickly disconnect the total power supply in case of emergency and be located where the driver can operate easily. Emergency power outages should not be automatically reset. There are two ways to determine whether the emergency power outage switch is qualified:
6.1 Check the tower for total power contactors. The tower crane must be equipped with a total power contactor, and the power source lines of all mechanisms must all be connected from the outlet end of the power contactor.
6.2 The operation of the emergency power outage switch, the total power contactor or circuit breaker with a voltage release coil, is switched off from the total power supply to all units, and the operation of all units is stopped. At the same time, meeting the death condition can be judged to be qualified for emergency power outage switches.
7. Safety interlock protection at access points.

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The tower crane shall be equipped with a passageway interlock switch for disconnecting the total power supply when the passageway is turned on. The small car of the bridge tower is powered by a bare sliding line, which can prevent the staff members who boarded the platform from being accidentally electrocuted, and it can also prevent the sudden start of the mechanism from causing congestion and falling accidents.
8. Limit protection.
In order to prevent the accidental failure of work, which causes the ceiling to the top support structure of the suspension, the cable is broken, and the suspension is crashed. The position limiter of the limit position of the dagger should be installed. Common types are hammer type and screw(or worm worm) type. In addition, electrical protection also includes stroke protection and ground protection.

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