Phase Converters & Power Factor
Phase Converter Efficiency
Installing a Phase Converter
Rotary Phase Converters
Static Phase Converters
VFDs as Phase Converters
     • Harmonic Distortion
Three-Phase Motors
Phase Converters & Voltage Balance
Phase Converter Applications
     • Submersible Pumps
     • Woodworking Equipment
     • Dual Lift Stations
     • Phase Converters & Welders
     • Phase Converters & CNC Machines
     • Phase Converters & Air Compressors
     • Phase Converters & Elevators
     • Phase Converters & Wire EDM
     Phase Converters & HVAC
Phase Converters & Transformers
     • Step-up Transformers
     • Buck-Boost Transformers
     • Isolation Transformers
Phase Converter Experts
Digital Phase Converters
Regenerative Power
Three-Phase Power
     • Delta vs. Wye Configured Power
Motor Starting Currents

Phase Converters and Three-Phase Power


Electric  Power Distribution

The backbone of every modern electric power distribution system is a three-phase alternating current (AC) transmission line.  It consists of three primary current-carrying wires sometimes referred to as L1, L2, and L3 and in some cases a fourth wire called the neutral conductor. Single-phase distribution systems are also common because single-phase transmission lines costs significantly less than three-phase lines.  They consist of one high-voltage line and a neutral.  Most residential and rural areas are supplied with single-phase service.

Three-phase power cannot be supplied from single-phase service unless a phase converter is used.

Single-phase power is a single voltage that alternates between a positive voltage and a negative voltage for a specific number of times per second (in the U.S., 60 times per second or 60 Hz).  Three-phase power is three distinct AC voltages, each shifted in time 120 degrees relative to one another as depicted in figure 1.

The wave forms shown in figure 1 can be calculated using the sine function in trigonometry and are called sine waves.  Notice that the voltage between L2 and neutral (L2-N) is delayed by 1/3 of a cycle from the L1-N voltage, and that the L3-N voltage is displaced 1/3 of a cycle from the L2-N voltage.  A complete cycle of the one of the wave forms corresponds to one complete rotation around a

circle or 360 degrees.  The phase delay in the L2 and L3 voltages is often referred to as 1/3 times 360 degrees or 120 degrees for L2 and 240 degrees for the L3 voltage.

Customers are supplied with electricity from the distribution system by placing transformers on the high voltage distribution system to reduce voltage to a level compatible with electric devices, for example, 240 volts.  Three-phase service requires three transformers compared to one for single-phase service, and requires different metering equipment as well.  Because of this, three-phase service costs more to install, so utilities usually prefer to install single-phase service unless there is a specific demand for three-phase power at the site.