When we use cranes, we often encounter power failures due to some reasons. At this time, due to inertia, the equipment cannot stop operation immediately, which can easily cause it to crash the work piece or the machine tool. In severe cases, it can also cause other accidents. The vibration generated by the crane during operation makes the sliding iron and the guide rail not firmly integrated, and the power supply has problems, which causes the main contact and the normally open auxiliary contact of the main contractor to be disconnected at the same time, and the main contractor coil fails to lock and causes the power to be cut off.
The partial contact of the sliding iron is poor, causing the crane to lose phase instantaneously when it reaches a certain section of the sliding rail. If the missing phase happens to be connected to the control circuit, the coil of the main contractor will be de-energized and self-locking will fail. The device is re-energized after slipping through the poor contact due to inertia, and the main contractor coil cannot be closed by itself. Press the start button again. The vibration generated when the crane lifts heavy objects makes the main contractor not close tightly, the main contact and the normally open auxiliary contact are disconnected due to vibration at the same time, and the main contractor coil fails to lock and loses power. So how should we deal with it:
Crane handling measures:
The crane control circuit is connected from the three-phase 380V power supply through the switch QS, and the two-phase power supply is taken from the three-phase power supply as the power supply of the control circuit, to supply power to the main contractor coil KM, and the overcurrent relay normally closed contact KI is serially connected to the control circuit. , KI1, KI2, KI3, overload protection for each motor.
Connect 3 limit switches SQ1, SQ2, SQ3 in series for chain protection.
The button SB is used to start, and the two normally open auxiliary contacts KM of the main contactor complete the self-locking of the main contractor.
The following groups of position limit switches and the corresponding two pairs of contacts of each cam controller work together to complete the limit of the crane.
