3 PHASE CONVERTER
What is a phase converter?
A phase converter is simply a rotating machine, much like a motor, that converts single-phase utility power into 3-phase electricity to operate 3-phase equipment. Phase converters are typically applied where utility 3-phase is unavailable or too expensive to install. A properly sized and selected converter will operate any load just as well as utility 3-phase and will provide years of trouble-free service.
How does a rotary phase converter work?
A rotary 3 phase converter is actually a rotating transformer. Through transformer action a phase converter splits off and phase shifts a portion of the single-phase supply from the utility creating true 3-phase power. When energized, the rotary phase converter uses the single-phase 2-line supply from the utility and creates a manufactured third line of power. The 3 lines (or phases) look identical to utility 3-phase with all three lines shifted 120°. The output of a rotary phase converter is true 3-phase. Each of the three output voltages will be shifted 120 electrical degrees. If the converter is properly sized, these voltages will remain in a balanced state over the entire range of connected loads.
Why would I use a phase converter?
The principle advantage of a phase converter is a matter of economics. Electric utility companies typically charge substantial fees to extend 3-phase service to areas not currently served. Charges vary by terrain, but it is widely accepted that line extension costs range from $30,000 to $90,000 per mile with a common average being $50,000. In addition to those utility costs, there is the added expense of a 3-phase service panel and associated internal distribution wiring.
The rotary phase converter is virtually always a less expensive alternative to this approach because it completely eliminates utility installation charges and does not require a new 3-phase service panel. It can usually be installed right off an existing 1-phase circuit at the main service. In addition to those savings, a phase converter may afford substantial savings on utility bills by eliminating the typical demand charges that accompany most 3-phase services.
In some situations, a machine owner may choose to replace 3-phase motors with 1-phase motors to operate on the existing 1-phase service. This may be a viable alternative on small horserpower loads but generally 1-phase motors above 3 HP are extremely expensive and very difficult to locate. As a further consideration whether to change equipment to 1-phase, it should be noted that most of the time you would be economically ahead to choose 3-phase motors and a 3 phase converter for several reasons:
- 3-phase motors run more efficiently than single-phase motors.
- 3-phase motors are less expensive to purchase than single-phase motors.
- 3-phase motors are more readily available than single-phase motors.
- 3-phase motors are more reliable than single-phase motors.
- 3-phase motors will last 6-8 years longer than single-phase motors.
- Immediate power availability. A phase converter can be installed in a few hours compared to several weeks or even months for utility line extensions.
Is Rotary or Static for You?
Rotary 3 phase converter are the most flexible and reliable type of phase converter. They produce true 3-phase power to run any type of load or combination of motors. For this reason, Kay Industries recommends rotary phase converters for most applications requiring a phase converter.
Static 3 phase converter do not produce true 3-phase power. In fact, static phase converters are little more than electric rope starters. Unlike a rotary phase converter, static phase converters cannot balance the load between the three legs after the motor has started. As a result, static 3-phase converters never allow your motor to develop full horsepower. Static phase converters are thus suited only for small-horsepower, single-motor applications. In addtion, they cannot be used for heaters or rectifier loads.