Split-phase power is a low-voltage distribution method where a single-phase transformer secondary is tapped at its exact center. The center tap is grounded to create a neutral, leaving two live legs that are 180 degrees out of phase with each other. This allows a building to draw a lower voltage between one leg and neutral for small appliances, and double that voltage across both legs for heavy loads like ovens and air conditioners.
The house is wired for split-phase power, giving us 120 volts at the wall outlets and 240 volts for the dryer.
A lost neutral in a split-phase system is highly dangerous, as it causes the voltage on the lightly loaded leg to spike, destroying appliances.
Also heard as
- single-phase three-wire system
- Edison system
Do not mix it up with
- Polyphase: Split-phase is derived from a single phase and its two legs peak at opposite times, whereas polyphase systems use multiple independent phases generated 120 degrees apart.
Related terms
Neutral conductor
The wire in an alternating current system that provides the return path for load current.
Polyphase circuit
An electrical network that carries multiple alternating currents with staggered phase angles.
Phase
A single distinct oscillating voltage or current in a multi-conductor electrical system.