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The most common two ways to analyze the operation of the inverter to control the motor

The most common two ways to analyze the operation of the inverter to control the motor

Classification:
Question and answer
Author:
2018/10/08 03:10

The two most common ways for the inverter to control the motor operation

After the main circuit of the inverter is connected to the power line, to control the operation of the motor, it is necessary to connect the peripheral terminal to the relevant terminal control circuit, and set the startup mode parameter of the inverter to the external operation mode.

The inverter controls the motor operation. There are two common methods, namely the switch control mode and the relay control mode:

1. Switching control forward rotation control circuit

The switch control circuit is shown in the figure below. It relies on manual operation of the inverter STF terminal external switch SA to control the forward rotation of the motor.

Switch control method

The working principle of the circuit is as follows:

1. Start preparation: Press button SB2, the contactor KM coil is energized, KM normally open auxiliary contact and main contact are closed, normally open auxiliary contact closure lock KM coil is electrically self-locking, KM main contact is closed The inverter is connected to the mains

2. Forward rotation control: press the external switch SA of the STF terminal of the inverter, the STF and SD terminals are connected, which is equivalent to the STF terminal input and input forward rotation control signals. The inverter U, V and W terminals output the forward rotation power supply voltage and drive. The motor is running forward. Adjusting the potentiometer R outside the terminal, the inverter output power frequency will change, and the motor speed will also change.

3. Inverter abnormal protection: If abnormal or fault occurs during the running of the inverter, the internal equivalent 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. Input power to protect the inverter.

4. Stop control: When the inverter is working normally, the switch SA is disconnected, the STF and SD terminals are disconnected, the inverter stops outputting power, and the motor stops.

To cut off the main input power of the inverter, press button SB1, the contactor KM coil is de-energized, the KM main contact is disconnected, and the inverter input power is cut off.

 

Second, the forward control circuit of the relay control

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.

 

When the inverter is running, if you want to cut off the main input power of the inverter, you must first stop the inverter control, then press button SB1, the contactor KM coil loses power, KM main contact is disconnected, the inverter input power is Cut off, if the inverter is not controlled to stop, and directly press SB1, it is impossible to cut off the input power of the inverter.

This is because the KA normally open contact has shorted SB1 and the SB1 is disabled when the inverter is working normally. This can prevent the SB1 from being disconnected from the main power supply when the inverter is working.