A Variable Frequency Drive (VFD) is an electronic device that is also known as variable voltage and frequency drive and is also used to control AC induction motor speed. It is due to the inception of VFD that the AC Motors have become prominent again and are now efficiently used in electric motor systems across industrial processes.
How VFD Works?
A VFD can be used with a single phase as well as with a three phase electric motor. Consisting of an AC motor, an operator interface and a controller, a VFD works by changing the frequency of the voltage used to power the induction motor. Meaning the VFD can change the supplied voltage which subsequently changes the speed of the induction motor. A VFD implementation is only successful when it works without affecting the torque, magnetic flux, impedance, and electrical consumption of the motor.
Reason to Use VFDs in Induction Motors
An AC motor’s speed is directly proportional to the frequency of the supply voltage. In industrial applications, when the peak time requirement is high, an AC motor working at its optimum or rated speed is suitable to meet the required output. However, when the application requirement is not of high degree, a motor running at its rated or top speed means wastage of electricity and inefficiency of the system.
This is where the need for a device arises which can efficiently control the speed of the motor, which can be done only by controlling the frequency of the supplied voltage. A VFD changes the magnitude of the input voltage at a constant ratio, along with the frequency as well, which results in a constant torque whether the speed of the motor is low.
A key process during the application of VFD is ensuring that the supplied voltage is proportionately lowered with the frequency of the specified fixed ratio; otherwise it would lead to the saturation of the magnetic flux, which eventually causes the motor to get damaged. When you are looking to implement VFDs for your industrial application, ensure to go through all the related information, device details, your specific requirements to find the best output.