How do Phase Convertors Work?

A Phase Convertor is a device that converts the power from a singe phase source into 3 phase power.

Phase convertors were invented in the later part of the 1900s. They are also known as 3 phase convertors. The first phase convertors were static phase convertors. Later development gave rise to the rotary phase convertors and recently we see digital phase convertors in use.

Why are Phase Convertors Used

Phase convertors find their applications in places where there is only a single phase power source for running various applications which require 3 phase power. Normally, 3 phase power is very costly, and it is often not supplied in all the areas. Therefore, these phase convertors are quite useful for converting the power in such areas.

Types of Phase Convertors

The types of Phase Convertors are:

Static Phase Convertors

These are the simplest type of phase convertors. Static phase convertors contain one or more capacitors and a relay. The relay switches between the capacitors once the motor comes to speed.

Static phase convertors run under the principle that a 3 phase motor can be started by using the capacitors in a series via the third terminal of the motor.

Static phase convertors however can run for only short periods of time or they end up delivering only half output, else they become damaged with overheating. Thus, they can only operate single load motors for a short period of time.

Rotary Phase Convertors

A rotary phase convertor contains a bank of capacitors wired together to act as one big capacitor and a 3 phase motor. 2 leads to the motor are connected to the single phase power source. The third lead is connected to the capacitor in series. Normally the motor used is larger than the load it supplies.

For loads that need more balanced voltage in the output, the size of the frame of the convertor motor is normally increased.

Rotary phase convertors can provide resistive, capacitive and inductive loads and they can power several loads at one time. They have a simple design and are reliable and low on cost. However, the only problem is in maintaining a voltage balance. To combat that problem, motors of a larger size are used only for a single machine each.

Thus, rotary phase convertors are an effective solution for simple load motors.