6 easy-to-understand electrical control schematics

1. Inching start circuit diagram

Figure 1

The inching control is realized only by a button switch. When the button switch SB1 is pressed, the coil of the contactor is attracted and the motor runs. When the button switch SB1 is released, the motor stops. This is the working principle of the inching control.

2. Start, protection and stop control circuit

Figure 2

The start, protection and stop control circuit is widely used. When the button switch SB2 is pressed, the contactor coil is energized and the contact is closed, and the auxiliary contact of the contactor is also closed, thereby realizing the self-locking function. When the button switch SB1 is pressed, the contactor is de-energized and the coil is disconnected.

3. Forward and reverse interlock control circuit

Figure 3

This kind of control circuit is still widely used. For example, motors that move up and down, left and right all use this kind of circuit.

When the button switch SB2 is pressed, the KM1 coil is energized, the contactor contacts are closed, and the motor runs forward. When the button switch SB2 is pressed, the normally closed contact of the button switch SB2 is disconnected, which can ensure that the other control line will not be operated by mistake.

When the button switch SB3 is pressed, the KM2 coil is energized, the contactor contacts are closed, and the motor runs in the reverse direction. The operating principle is the same as the forward operation. The only difference is that the control circuit controls the two contactors to change the phase sequence of the three-phase electricity to achieve the forward and reverse operation of the motor.

4. Control circuit for controlling one motor from two locations

Figure 4

Controlling a device circuit from two locations means that a motor can be controlled from multiple locations, which greatly improves efficiency.

The circuits that control a motor at two locations can be understood as two independent start, protection and stop control circuits, and the working principles are the same.

5. Automatic round trip control circuit

Figure 5

The automatic round-trip control circuit is based on the forward and reverse control circuit, and two travel switches are added to realize the round-trip operation. Therefore, it is not difficult to understand this round-trip control circuit. According to the picture, you can see that the normally open contacts of the two travel switches are connected to the button switches SB1 and SB2 respectively, and then the normally closed contacts of the travel switches are connected in series to the coil circuit to realize the double interlocking effect, which greatly increases the safety of the circuit during operation.

6. Star-angle step-down starting control circuit

Figure 6

The star-delta step-down starting control circuit is widely used in many heavy-load motors. How to interpret this circuit diagram?

We can divide the circuit diagram into three parts: KM1, KM2, and KM3. The circuit controlling KM1 is a start, protection, and stop control circuit; KM2 is similar to a jog control circuit; and KM3 is also equivalent to a start, protection, and stop control circuit. It is much easier to understand if we separate them. A time relay is used in this circuit to realize automatic star-angle conversion without manual operation.