Electricity has come a long way since its humble beginnings in the late 19th century — the mind boggles at the sheer scale of things in our world which it is responsible for. It’s one thing to imagine a world without smartphones, let alone light circuits.

If you ever were curious about what kind of power supply it takes for your home, this guide explores how levels of power are achieved through what are called different phases.

As XP Power explains, “although single-phase is more prevalent, three-phase supplies are the power of choice for many applications. Three-phase electricity is a smoother form of power than single or two-phase systems since it allows machines to run more efficiently and extending their lifetime”.

Let’s break down what these ‘phases’ mean, and how they are able to create different capabilities for electrical power.

What is a phase in electricity?

Voltage and current

In electricity, power is carried in waves. These fluctuating waves are otherwise known as alternating current (AC). The key detail with a phase is the difference between this current and the voltage (V), which measures the potential energy difference for every unit of charge between two points in an electric circuit. If the charge is the movement of electrons, the current is the flow of said movement. The energy difference (pressure) of this movement — its electromotive force — is voltage. In a nutshell, you need the voltage to produce the current, as it provides the energy for the electrons movement, forming the current.

Distribution

A phase, then, refers to what happens during the cyclical process of electrical supply from an AC. Here electrical energy fluctuates between zero and its peak values, repeatedly changing directions, unlike direct current (DC) which only flows in one linear direction. A phase is the distribution of this total flow of current and voltage — also known as its load.

Single-phase supply

In the field of electrical engineering, power supplies are divided into single and triple phases. In a single phase, power is supplied through two wires. The AC circuit uses a phase wire and a neutral wire. Current flows between the phase wire, powering an appliance, and a neutral wire carrying the circuit back to the power source. AC power fluctuates at an even rate, and the voltages of each wire change simultaneously.

This means that, during one phase cycle, the delivery of electrical power alternates in waves, with peaks and troughs. The waves peak at 90⁰ and 270⁰, with the two intervals of this alternating cycle marking when the amount of power being conveyed is at its height. During the other periods of the AC cycle, there is a deficiency, and this means that power is not being supplied at a constant rate.

Three-phase supply

For a three-phase system of power supply, the load is instead distributed across three wires which are built to be out of sync (or phase) with one another: specifically, they supply their maximum power 120 degrees apart.

As a result, a dip in the voltage of one wire’s current will occur simultaneously with a peak in the other current. The total load is distributed between these different currents. Since the three alternative currents are provided in these varying phases, the delivery of electrical power is maintained, and does not ever drop below the maximum level.

Single-phase versus three-phase supply

Single-phase supplies are what are found in home supplies and residences. Your toaster, television and food processor all require small loads of energy to function. Even though the alternating current is less consistent than three phase, the reduced power means that the electrical output from the single-phase connection works effectively.

However, the difference between these two systems also hinges on their varying capacity. Three-phase systems are desirable not just for their efficiency, but because they can accommodate higher loads of energy, and can transmit maximum amounts of power. The higher the number of phases that increases in the supply system, the smoother the voltage.