Both the AC and DC generators that we have discussed produce a pulsating supply of current that continually increases and decreases as the armature rotates. We can reduce the impact of these fluctuations by attaching more than one coil to the armature. With two coils, the flow of current from one coil will always be 90° ahead or behind the other. This is called a two-phase system. With three coils we would have a three-phase system where the current in one coil will always be equal to the opposite of the current in the other two coils combined. For instance, if one coil is producing a current of two amps in one direction, the other two will each be producing a current of one amp in the other. If one coil is at the zero line the other two will be at equal amplitudes but in opposite directions.
This is why electric utilities distribute three-phase electrical power for use in large industrial motors that operate off the three synchronized 60 Hz current cycles. Most homes use single-phase 60 Hz service.
| Three-Phase Power | = | (1.732) x (Line Volts) x |
| (Line Amps) x (Power Factor), in Watts |
| Wye Systems
Delta Systems Three-Phase Systems |
When To Use Medium & Low Voltages
Comparison Of Four-Wire Wye Systems Choosing Between 240 Volts & 480 Volts |
