Phase converters are electric devices that are used to convert electric power supplied as single phase to multi-phase or vice versa. Most phase converters are used to generate three phase power from a single phase source. They are essential for running electric equipment or devices which require a three phase supply in locations where only a single phase electric supply is available.
Usually, utility companies provide both single phase as well as three phase power. However, the price of three phase supply service is comparatively very high, and it is not provided in many rural areas. In all these cases, one has to use a single phase to three phase converter. It is a much cheaper option than getting the utility company to install a three phase supply system at a required site.
A three phase converter, also simply known as a phase converter, has three wires that carry the same current, thereby offering a balanced load. It provides a smoother and more efficient service, and the equipment that run on it last longer than those that run on single phase power. In the following section, we shall look at the important types of phase converters.
Rotary Phase Converter
The rotary phase converter is the most common converter. Some of these convert single phase power into unbalanced three phase power. However, quality converters provide true, balanced three phase power, which can be used for gadgets like ovens, computers, and motors.
Variable Frequency Drive
The other most common three phase converter is the variable frequency drive, which controls the rotational speed of the AC power by controlling its frequency. These are commonly used in variable frequency motors that are generally used in fans to save electricity. Frequency drives are also used in conveyors and pumps. The three main types of frequency drives are constant voltage, cycloconverters, and constant current, among which constant voltage drives are the most popular ones.
Digital Phase Converter
In power systems, a digital phase converter uses a rectifier and inverter. A microprocessor-based system is used to control the switching process and for monitoring the phase conversion. The output of the digital phase converter is a pure sine wave, which gives a balanced voltage as compared to other three phase converters.
The oldest three phase converter is the static converter. These use two capacitors and a relay switch to convert the power from a single phase to a three phase. However, owing to the fact that they have a poor performance, and their tendency to overheat the equipment that they drive, the use of static converters has largely been discontinued.
Three phase motors are preferred over single phase motors. There is a switch in single phase motors that connects and disconnects the secondary winding to the capacitor. Frequent switching of the secondary transformer causes overheating, and the switch contacts get corroded. A three phase motor, on the other hand, does not have a switch to connect and disconnect the secondary winding, which leads to a long motor life.
Thus, a three phase converter is an essential device in those applications where the single phase power supplied by utility companies needs to be converted to three phase supply for driving heavy-duty machinery. It is widely used in many large- and small-scale industries, and in rural areas for running farming equipment.