# Difference Between 3 Phase and Single Phase

## Main Difference – 3 Phase vs. Single Phase

3 Phase and single phase are both types of power distribution systems. The main difference between 3 phase and single phase is that, in single phase, an alternating current is transmitted along a single wire whereas, in 3 phase, three wires carrying currents with a phase difference of 120o between them is used to provide current.

## What is Single Phase

Single phase power refers to situations where power is supplied by one wire containing an alternating current — i.e. a current which is constantly switching direction. The voltage of a single phase supply varies periodically, as shown below. The y-axis gives the relative voltage, while the x-axis is given here in terms of the “phase angle” of voltage. However, you can take the x-axis to represent time:

Difference Between 3 Phase and Single Phase – Waveform of Single Phase

In single phase supplies, as the voltage varies the power supplied also varies continuously. Homes are usually provided with sngle phase power.

## What is 3 Phase

3 Phase power refers to cases where power is supplied using 3 wires carrying current. The alternating currents in every cable has the same frequency and the same peak voltage. However, they maintain a phase differrence of 1/3 the period (or 120o) with respect to each other. The diagram below illustrates this concept:

Difference Between 3 Phase and Single Phase – 3 phase waveform

The sum of currents in the three wires is always 0. As a result, 3 phase supplies can provide constant power to a connected load which helps reduce vibrations in the case of a motor. The power supplied never has to drop to 0 as with single phase supplies. In addition, the three wires produce a rotating magnetic field that allow 3 phase motors to be self-started. Consequently, motors work much more efficiently under a 3 phase supply. Most large motors with industrial applications require 3 phase suplies.

3 phase supplies also do not require a neutral wire (although sometimes neutral wires are also used, depending on the usage). The three wires in the 3 phase supply can provide 3 times the power as the two wires (live and neutral) do in single phase. This means that it is much more cost-efficient to use a 3 phase system to deliver power, especially over long distances. Electrical power stations use 3 phase supplies to transmit current.

Difference Between 3 Phase and Single Phase – These high tension lines use 3 phase to transmit electricity.

## Difference Between 3 Phase and Single Phase

### Current Conduction

Single phase uses only one wire with an alternating current.

3 Phase uses 3 wires, carrying current with same frequency and peak voltage, but out of phase with each other by 120o.

### Power Variation

In single phase systems, the power delivered varies constantly.

3 phase systems deliver constant power to the load.

### Usage

Single phase is typically used for domestic purposes.

3 phase is used to operate industrial machinery and to transmit power from power stations.

### Requirement of a Neutral wire

Single phase requires a neutral wire.

3 phase does not necessarily require a neutral wire.