Large equipment often requires what is known as “3 phase” power, and this can present issues if one is forced to move one’s shop from a facility that has three-phase power to a facility that does not. If you find yourself in such a situation, don’t panic; there are ways to convert machinery so that it can transition from common single-phase to three-phase power and vice versa.
What is 3 Phase Power?
Three-phase power is a type of alternating current which provides a stream of three alternating currents—representing, in essence, three separate electric services—uniformly separated in phase angle. As such, the points in time at which each stream of alternating current reach a maximum voltage wind up separated by 1/3 of the time in a full cycle. In simpler terms, the total amount of power supplied by all three alternating currents remains constant; see http://www.emiter.co.uk/product-category/3-phase-meter-boxes/ for more information.
For those who work with powerful equipment requiring large loads of electricity, this consistency in power delivery is a major boon. Large pieces of equipment are therefore frequently designed with 3 phase in mind, leaving many home hobbyists and small shop owners faced with the problem of having three-phase equipment with no three-phase service.
Four Viable Alternatives to Three-Phase Power
Replace three phase motors with single-phase motors: While this option is not practical if you have many motors, if you have just one or two machines with accessible, configurable motors, it may well be ideal. Be aware, however, that an equivalent single phase motor will draw far more current than the three phase motor. It will also cost more upfront, and be larger in size.
Static Phase Converters: A static phase converter will allow you to start a three phase motor on single phase power, which in some cases is all you will need, as a three phase motor can actually run on single phase power once you get it started. Be prepared, however, for a 2/3 reduction in the motor’s rated horsepower and a shorter overall life expectancy.
Rotary Phase Converters: A rotary converter will produce more balanced three-phase electricity than a static phase converter will, but of course, they also cost significantly more. This type of converter can actually supply a form of three-phase power to your shop, making it ideal if you need to power multiple pieces of three-phase machinery (just keep in mind that typically more than one load cannot be started at one time, and certain loads are harder to start than others—air compressors, for example, are notoriously hard to start).
Variable Frequency Drives: These useful tools are based on the same technology that is found in the inverters that generate 110V power from automobile cigarette lighters: Variable frequency drives use inverters to synthesize three-phase power, using transistors to switch current flow. This system results in a cleaner, more balanced, more variable form of three-phase power; using a VFD, one can actually control the speed of a motor by varying the frequency, while still providing full power. VFDs are also quite expensive, however.