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Relay controlled forward control circuit

Relay controlled forward control circuit

Question and answer
2018/10/08 03:18

The forward control circuit of the relay control is shown below.

Relay control method

The working principle of the circuit is as follows:

1. Start preparation: press button SB2, contactor KM coil is energized, KM main contact and two normally open auxiliary contacts are closed, KM main contact is closed for inverter to turn on main power, one KM normally open auxiliary When the contact is closed, the KM coil is locked to be energized, and the other KM normally open auxiliary contact is closed to prepare for the relay K intermediate A coil.

2. Forward rotation control: press button SB4, the relay KA coil is energized, 3 KA normally open contacts are closed, one normally open contact closure locks the KA coil to be energized, and a normally open contact closure shorts button SB1 There is also a normally open contact closure to turn the STF and SD terminals on, which is equivalent to the STF terminal input forward rotation control signal, and the U, V, and W terminals of the inverter output the forward rotation power supply voltage, and the drive motor is running forward. Adjusting the potentiometer R connected to the terminal, the frequency of the output power of the inverter will change, and the motor speed will also change.

3. Inverter abnormal protection: If there is a fault during the abnormality of the inverter, the internal equivalent normally closed switch between the B and C terminals of the inverter is disconnected, the KM coil of the contactor is de-energized, the KM main contact is disconnected, and the inverter is cut off. The input power is input to protect the inverter. and the relay KA coil is also de-energized, and the three KA normally open contacts are disconnected.

4. Stop control: When the inverter is working normally, press the button SB3, the KA coil loses power, and the KA 3 normally open contacts are disconnected. One of the KA normally open contacts is disconnected to connect the STF and SI terminals. When it is cut off, the inverter stops outputting power and the motor stops.