When the main circuit of the inverter is connected to the power line, in order to control the operation of the motor, it is also necessary to connect the relevant terminals to the peripheral control circuit, and set the parameters of the inverter's starting method to the external operation form.
The inverter controls the motor to operate, and there are two common methods, namely the switch control method and the relay control method.
1. Forward and rotary control circuit controlled by switch
The switch control circuit relies on the manual operation of the inverter STF terminal external switch SA to control the motor forward.
The operating principle of the circuit is described as follows:
1. Start preparation: press the button SB2, the contactor KM coil is energized, the KM normally open auxiliary contact and the main contact are closed, the normally open auxiliary contact is closed to determine that the KM coil is energized and self-locked, and the KM main contact is closed for the inverter to turn on the main power supply.
2. Forward rotation control: press the STF terminal external switch SA of the inverter, and the STF and SD terminals are turned on, which is equivalent to the STF terminal transmission and input forward rotation control signal, and the U, V, and W terminals of the inverter output the forward power supply voltage to drive the motor to run in the forward direction. When the potentiometer R is conditioned on the external terminal of the inverter, the output power supply frequency of the inverter will change, and the speed of the motor will also change.
3. Abnormal maintenance of the inverter: If there is an abnormality or problem during the operation of the inverter, the equivalent normally closed switch between the terminals B and C of the inverter is disconnected, the KM coil of the contactor loses power, the KM main contact is disconnected, the input power supply of the inverter is blocked, and the inverter is maintained.
4. Stop control: When the inverter is operating normally, the switch SA is disconnected, the STF and SD terminals are disconnected, the inverter stops the output power supply, and the motor stops.
If you want to block the input main power supply of the inverter, you can press the button SB1, the KM coil of the contactor loses power, the KM main contact is disconnected, and the input power supply of the inverter is blocked.
Second, the forward rotation control circuit controlled by the relay
The operating principle of the circuit is described as follows:
1. Preparation for starting: press the button SB2, the KM coil of the contactor is energized, the KM main contact and the two normally open auxiliary contacts are closed, the KM main contact is closed for the inverter to turn on the main power supply, a KM normally open auxiliary contact is closed, and the KM coil is energized, and the other KM normally open auxiliary contact is closed, so as to prepare for the energization of the relay K center A coil.
2. Forward rotation control: press the button SB4, the relay KA coil is energized, the 3 KA normally open contacts are closed, a normally open contact is closed to determine the KA coil is energized, a normally open contact is closed to short the button SB1, and there is a normally open contact closed to turn on the STF and SD terminals, which is equivalent to the STF terminal input forward rotation control signal, and the transformer U, V, W terminals output the positive power supply voltage to drive the motor to run in the forward direction. When the potentiometer R is connected to the conditioning terminal, the output power frequency of the inverter will change, and the speed of the motor will also change.
3. Abnormal maintenance of the inverter: If there is a problem during the abnormal period of the inverter, the internal equivalent normally closed switch between the terminals B and C of the inverter is disconnected, the KM coil of the contactor loses power, the KM main contact is disconnected, the input power supply of the inverter is blocked, and the inverter is maintained, and the relay KA coil is also lost power, and the three KA normally open contacts are disconnected.
4. Stop control: when the inverter is in normal operation, press the button SB3, the KA coil loses power, and the KA3 normally open contacts are disconnected, during which a KA normally open contact is disconnected to make the STF, SI) terminals connect and intercept, the inverter stops the output power supply, and the motor stops.
When the inverter is running, if you want to block the inverter input main power supply, you must first stop the inverter control, and then press the button SB1, the contactor KM coil loses power, the KM main contact is disconnected, and the input power supply of the inverter is blocked.
This is because the KA normally open contact has shorted SB1 during the normal operation of the inverter, and it is invalid to disconnect SB1, which can avoid misoperation of SB1 to block the main power supply during the operation of the inverter.
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