Vfd

A variable frequency drive, or VFD, helps to change the fixed voltage and frequency of the motor's input power to a variable voltage and frequency. The electric motor replaces the permanent magnet alternator with one or more electric motors. Businesses can use VFD motor control to adjust the speed of motor-driven equipment for different loads. Smoothing the rise and fall in motor rpm can also reduce electrical and mechanical stress on the system. Less stress means more efficient equipment and fewer unplanned outages.

Operating principles of a VFD

The variable speed drive only provides the motor with the power needed in real-time to meet the system's demands. It converts ac electricity to direct current, which is then sent through a dc bus to further filter the voltage. The electricity goes through an inverter, making dc pulses that spin the motor's rotor via induction processes.

Categories of VFD

Adapting the output frequency using pulse width modulation alters the output voltage waveform. The second one is the current source inverter which changes a constant dc input current into a variable output ac current. Rather than relying on voltage, it depends on current for smooth output. Another type of VFD controller is a voltage source inverter, which converts constant dc voltage into variable ac voltage. It uses a simple diode circuit to separate the ac signal into a dc signal and a capacitor to store energy. Inverters use the power in the capacitor to send it to the output.

Commercial uses of the VFD

A VFD drive can also transform natural and renewable energy and make it available to the power grid or locally. Hybrid technology combines energy storage and traditional energy sources with an AC drive to produce an energy management package. Businesses use single-phase VFD mainly for low-power applications such as airflow controls that require less than one horsepower. Meanwhile, air compressors, centrifugal pumps, HVAC systems, and other high-power commercial machinery and systems use three-phase VFDs. There are also several uses for a VFD motor, like home furnishings. In VFD pumps, dc electricity drives the motor shaft directly instead of through a gearbox.