VFD Basics: How Does the VFD Control

VFD Basics: How Does the VFD Control

VFD Basics: How Does the VFD Control the Motor’s Operation? In order to control the motor, the surrounding control circuit must be connected to the relevant terminals and the starting mode parameters of the VFD must be set to the external operation mode when the main circuit of the VFD is connected to the power line. Switch control and relay control are the two most common ways a VFD controls the motor’s operation. 1. Switch-controlled circuit for forward rotation The diagram that follows depicts the forward-rotation circuit that is controlled by the switch. The motor’s forward rotation is controlled by manually operating the external switch SA at the VFD’s STF terminal. The following is a description of the circuit’s working principle: 1.1 Get Preparing The contactor km coil is activated when the button SB2 is pressed. The KM coil is electrified and self-locking, and the normally open auxiliary contact and main contact are closed. The KM coil’s normally open auxiliary contact is also closed and locked. In order to connect the VFD’s primary power supply, the main contact of KM is closed. 1.2 Control for Forward Rotation When you press the external switch on the STF terminal of the VFD, the SA, STF, and SD terminals are connected, which is the same as sending a forward control signal to the STF terminal. The forward power supply voltage is sent out by the VFD’s U, V, and W terminals to cause the motor to move forward. The VFD output power and motor speed will change if you adjust the potentiometer r outside the terminal. 1.3 Protection against VFD errors In the event that there is any unusual activity or mistakes during the activity of the VFD, the inside identical switches between the B and C terminals of the VFD which are regularly shut will be disengaged, and the KM loop of the contactor will lose power, and the KM primary contact will be detached to remove the information power supply of the VFD and safeguard it.