When the contactor for forward rotation and the contactor for reverse rotation operate at the same time
What happens if the electromagnetic contactor for forward rotation and the electromagnetic contactor for reverse rotation are mistakenly operated at the same time to form a closed circuit? The interline voltage between the L1 and L3 phases of the three-phase power supply is completely short-circuited by reversing the main contact of the electromagnetic contactor, so there will be a large short-circuit current flowing through and burning out the circuit. Therefore, in order to prevent the short circuit accident of the two-phase power supply, the main contacts of the contactors KM1 and KM2 are never allowed to be closed at the same time.
Forward and reverse control line of three-phase contactor interlocking
As shown in the above figure, the electrical schematic diagram of the forward and reverse rotation control of the three-phase asynchronous motor contactor interlock, in order to ensure that when one contactor is energized, the other contactor cannot be energized, so as to avoid the interphase short circuit of the power supply, the normally closed auxiliary contact of the reverse contactor KM2 is connected in series in the forward rotation control circuit, and the normally closed auxiliary contact of the forward contactor KM1 is connected in series in the reverse control circuit. When the contactor KM1 is energized, the normally closed contact of KM1 stringed in the reversal control circuit is broken, the reversal control circuit is cut off, and the main contact of KM2 cannot be closed when the main contact of KM1 is closed. Similarly, when the contactor KM2 is energized, the normally closed contact of KM2 is broken, cutting off the forward rotation control circuit, and reliably avoiding the occurrence of two-phase power supply short circuit accidents.
Interlock (or interlock): When one contactor is energized, the function of making another contactor unable to be energized through its normally closed auxiliary contact is called interlocking (or interlocking). The normally closed contacts that achieve the interlocking effect are called interlocking contacts (or interlocking contacts).
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