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Unscramble the common electrical equipment protection measures of crane machinery

in order to protect the safety of crane electrical equipment and staff, the crane electrical control system should be equipped with necessary electrical protection measures. The following are common electrical protection measures for cranes

I. the maintenance and inspection of electrical equipment by the main disconnector

should generally be carried out under the condition of power failure. Therefore, there should be disconnectors or other isolation measures between electrical equipment and power supply. When the disconnector is in the disconnected state, it must maintain an effective disconnection distance and an obvious disconnection 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 disconnection point, so they cannot be used as disconnectors

II. Short circuit protection of the main power supply

when the insulation of the electrical equipment on the crane is damaged, and there is a shell collision or phase to phase short circuit, the short circuit protection device of the main power supply should act quickly to cut off the faulty power supply. The main power supply short-circuit protection device shall be completed by fuse circuit breaker

III. voltage loss protection of the main power supply

voltage loss protection of the main power supply refers to the automatic disconnection of the main power supply circuit after the power supply is interrupted; When the power supply is restored, the main power circuit cannot be connected by itself without manual operation. Generally, the automatic reset button is connected to the main power contactor coil or the voltage loss trip coil circuit of the automatic circuit breaker to realize the pressure loss protection of the main power supply. Polyester material 1 has always been the mainstream protection in the water absorption and quick drying material market

IV. zero position protection

the motor of the mechanism is controlled by a controller that cannot be reset automatically. In order to prevent the false start of the motor caused by the loss of voltage of the crane power supply after the controller handle is not in the zero position, the crane is equipped with zero position protection. Inspection method of zero position protection:

4.1 the mechanism motor is directly controlled by the cam controller; Turn off the main power supply, pull one of the controller handles away from the zero position, and turn on the main power supply. The main power supply should not be turned on. Put all controller handles at the zero position, and the main power supply can be turned on

4.2 if the mechanism motor is controlled by the master controller and contactor, turn off the main power supply, pull the master controller away from the zero position, and connect the main power supply. When the main power supply is connected, the mechanism motor cannot be started at the same time

v. overload protection of motor

if the rated power of the motor on the crane is greater than 1kW, overload protection should be set separately. Overcurrent protection is a common motor overload protection method for cranes at present

VI. 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 set it in a place convenient for the driver to operate. Emergency power failure shall not be reset automatically. There are two ways to judge whether the emergency power-off switch is qualified:

6.1 check whether there is a main power contactor on the crane. The crane must be equipped with a main power contactor, and the power lines of all mechanisms must be led from the outlet end of the power contactor

6.2 pull the emergency power-off switch, the main power contactor or circuit breaker with voltage loss tripping coil acts, cut off the main power supply of all mechanisms, and the operation of all mechanisms stops. At the same time, if the conditions described above are met, the emergency power-off switch can be determined to be qualified

VII. Channel port safety interlock protection

the crane shall be equipped with channel port interlock switch to disconnect the main power supply when the channel port is opened. The trolley of the bridge crane is powered by the bare sliding line, which can prevent the workers on the walking platform from getting electric shock by mistake, and can also prevent such plastic granulator equipment from polluting the environment seriously due to the sudden start of the mechanism, such as crushing injury and falling accidents

VIII. Limit protection

in order to prevent the accident of lifting appliance jacking to the upper support structure, breaking the steel wire rope and making the lifting appliance fall due to negligence and error of work, a knife lifting limit position limiter should be installed to analyze the reason:. There are two common types: remoulding falling hammer type and screw (or worm gear) type. In addition, electrical protection includes travel protection and grounding protection

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