Analysis of self-locking control circuits common to main protection system components in explosion-proof distribution boxes
There are two common forms of use in explosion-proof power distribution boxes: 1. power mixing, 2. maintenance and mixing. In these two common power distribution box devices, there must be safe components to protect electrical equipment. Contactors, thermal relays, circuit breakers.
The editor of this article mainly analyzes the most common self-locking protection circuits in most explosion-proof distribution boxes, as follows:
Contactor self-locking forward rotation control circuit
在要求电动机起动后能连续运行时，采用上述点动控制线路就不行了。 When the power distribution device of the explosion-proof distribution box requires continuous operation after the motor is started, the above-mentioned jog control circuit is not enough. Because the motor M needs to run continuously, the start button SB cannot be turned off, which is not in line with the actual production requirements. To achieve continuous operation of the motor, the contactor self-locking forward rotation control circuit shown in Figure 2.6 can be used.
The circuit works as follows: Close the power switch Q first.
Start: Press the start button SB1 →
When the normally open contact of SB1 is released and disconnected, because the normally open auxiliary contact of contactor KM is closed, SB1 is shorted, and the control circuit is still connected, so contactor KM continues to be energized and motor M achieves continuous operation. . When the start button SB1 is released like this, the effect of the contactor KM holding the coil through its normally open contact is called self-locking (or self-protection). The normally open contact that acts as a self-locking function in parallel with the start button SB1 is called a self-locking contact (also called a self-protecting contact). Stop: Press the stop button SB2
When the normally closed contact of SB2 is released and closed, the self-locking contactor of the contactor KM is disconnected when the control circuit is disconnected, and the self-locking is released. SB1 is also disconnected, so the contactor KM cannot be powered, and the motor M It will not turn.
中 电路的保护环节： Circuit protection in explosion-proof distribution box :
(1) Short circuit protection
(2) Overload protection
(3) Loss of voltage and under voltage protection
3.Continuous and jog mixed control forward rotation control circuit
When the machine tool equipment is in normal operation, the general motor is in continuous operation. However, when testing or adjusting the relative position of the tool and the workpiece, the motor can be jogged. The line required to achieve this control is a forward control circuit with continuous and jog control.
(1) Continuous control
(2) Jog control
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