3 Phase Power Supplies

3 Phase Power Supplies

3 Phase AC power supplies designed to meet the needs of high power applications

Our 3 phase input power supplies are designed to operate from a variety of global 3 phase sources, including 208VAC, 380/400/415VAC and 480VAC. The product range includes DIN Rail mounting supplies rated at 120, 240, 480 & 960W, chassis mount supplies to 5kW and configurable power supplies from 1500W to 3kW with output voltages from 3.3VDC to 400VDC.

These base products are also used in combination to provide bespoke, high power, stand alone and rack mounting 3 phase power systems up to 30kW.

3 Phase example 1
3 Phase example 2
3 Phase example 3

3 Phase Reference Guide

Three-phase AC

The power delivered by a single-phase system pulsates and falls to zero during each cycle, whereas the power delivered by a three-phase circuit also pulsates, but never to zero. In a balanced three-phase system, the conductors need be only about 75% the size of the conductors for a single-phase two-wire system of the same kVA rating.

If three separate coils are spaced 120° apart, the three voltages are produced 120° out of phase with each other, when the magnetic field cuts through the coil.

There are two basic three-phase connections used:

Star or Wye Connection

Connecting one end of each of the coils together, as shown on the right, makes a star or wye connection. The phase voltage (or phase to neutral voltage) is the voltage measured across a single coil. The line voltage (phase to phase voltage) is measured across two coils.

graph 2a

In a star or wye-connected system, the line voltage is higher than the phase voltage by a factor of the square root of 3 (1.732).


This is a 4-wire plus earth system.

Delta Connection

The three separate coils are connected to form a triangle in a delta-connected system, which derives its name from the fact that a schematic diagram of this connection resembles the Greek letter delta (∆).

graph 2b

In this configuration the line voltage and phase voltages are the same.


However, the line current is higher than the phase current by a factor of the square root of 3 (1.732). The reason for this difference in current is that current flows through different windings at different times in a three-phase circuit.

At times, current will flow between two lines only, at other times current will flow from two lines to the third.

Three-Phase Voltage and Frequency

Although single-phase power is more prevalent, three phase supplies are the power of choice for many applications. As previously discussed, power stations supply three-phase electricity and it is often used in industrial applications to drive motors and other devices. Three-phase electricity is a smoother form of power than single or two-phase systems allowing machines to run more efficiently and extending their lifetime.

220 – 240 VAC single phase supplies are derived from 400 VAC three phase systems and 100-127 VAC single phase supplies from 200 VAC three phase systems. In the USA there is also a 480 VAC three phase system used for some high power applications which results in a nominal 277 VAC single phase supply often used for applications such as street furniture & street lighting.

graph 3