Phase Converter vs. VFDs: Which to Use?

Performing a voltage conversion will allow your business to take a single-phase system and convert it into a three-phase system. You can facilitate this conversion in one of two main ways — with a phase converter or with a variable frequency drive (VFD). While both options can help you achieve the same result, they each work differently and have distinct advantages and disadvantages. Let’s take a look at each type to help your business decide which one is best for your applications.

Phase Converter

static phase converter

A phase converter facilitates the conversion by adding another leg to the two single-phase lines.


Phase converters can rely on any of three main control methods:

Static phase conversion: Static conversions work best with low-powered motors. With this method, the motor is not running at full efficiency. Instead, it’s mainly running on just two of the legs.

rotary phase converter

Rotary phase conversion: A rotary phase converter works well with large machines that have heavy starting loads. This solution uses two motors and is made from a three-phase electric motor.

Digital phase conversion: A digital phase converter provides excellent voltage balance between the phases. A digital signal processor (DSP) is able to produce the third-phase power.


Phase converters require less wiring, making them easy to install. They can also be used to run multiple machines simultaneously. Other advantages of a phase converter include the generation of three-phase power as well as its ability to operate with resistive and inductive loads.


A phase converter won’t deliver the same complicated settings that a VFD would or the same control over power distribution and regulation.


A VFD, also referred to as an adjustable-frequency drive, AC drive or variable-speed drive, allows variable speed control when it converts frequency.

single phase to three phase vfd


The VFD controls the torque and AC motor speed of a system. The control of this system takes place on a VFD interface, and it relies on an adjustable-speed drive, which can be a vector drive or sensorless vector.


VFDs will help your business save energy. They also offer a precise control system with a motor speed controller. Other benefits include experiencing a performance improvement on everything from mixers to pumps.


While you will get more control, a VFD does not work well for lighter loads or running more than one three-phase machine from one single line. Usually, just one connected machine is run at a time.

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