The majority of residential buildings in Australia rely on single-phase power from the mains connection to run things like TVs, fridges and computers. The supply is delivered as 230V of alternating current and is more than enough to power all appliances and lighting. For industrial and commercial use, however, there is three-phase electricity that runs at 415 Volts, and is used to run more power-hungry machinery and equipment. The wiring and connections are different in each type.
Single-phase electricity consists of one active wire and one neutral wire that is connected to the earth in the switchboard. Three-phase power consists of three active wires (or phases) and a neutral wire. The three wires deliver electricity in three different alternating currents, meaning three times the available amount of power over single-phase wiring at any given time. The benefit of three-phase wiring is greater consistency, meaning an uninterrupted power supply and higher efficiency. If there is a fault in a single-phase wire, then the whole supply needs to be cut off for maintenance, whereas in three-phase wiring the remaining two wires supply power to other single-phase loads connected to them. The only time you’d need a three-phase connection to your home is when you’re running hundreds of bigger appliances simultaneously and there is the possibility of an overload.
3-phase Plugs and Sockets
If appliances, machinery and equipment are not directly connected to the mains switchboard, in what is known as hardwiring, then they are supplied with power with plugs that connect into sockets. Larger machines use more power, so are connected with a 3 phase plug and socket. Since these are mostly used in industrial settings with big power needs, they are also known as industrial plugs and sockets.
3 phase plugs and sockets differ from the ones you’ll find at home. With more wires come more pins. And these are round instead of flat. Also, to handle the harsh conditions and the fact they are often used outdoors, they have a much better build. Lastly, sockets and plugs used in a 3-phase power supply need to cope with higher electrical loads.
Build quality is substantially better in any industrial plug over standard plugs used at home. Hard-wearing yet lightweight polymers, typically nylon compose the outer shells. They can endure particularly harsh conditions, like extreme temperatures found in food processing plants or fridge rooms, exposure to chemicals and liquids in a variety of industries, and impact from machinery, equipment or vehicles. The purpose is to provide a consistent power supply, no matter the conditions. To this end, rotating collars are locked into place with the corresponding socket so there’s a constant electrical supply. In addition, cables are set in reinforced clamps to avoid cable twisting as plugs and the equipment they connect are often moved around.
In terms of shapes, 3 phase plugs can be straight or angled to suit different connection angles. To run higher-powered equipment, there are a range of current ratings in amps for plugs as well as the choice between 4 or 5 pins if additional earthing is needed. These alternate the position and size of the neutral pin, which is bigger, so you won’t mistakenly connect equipment to the wrong socket.
3-phase sockets are built to the same high standard as plugs, and include inner and outer seals for an IP66 rating or above for water ingress protection. Most also have protective outer flaps that are spring-loaded and collars to enable a secure fit with the plug. There are sockets with 4 or 5 pins to connect the right plug, and a different neutral position. Sockets can be flush mounted or surface mounted depending on the application.
For greater safety, and to avoid an unintentional operation, 3 phase sockets can have a switchable on and off knob that locks into place once turned. Surface switches can be connected separately where there is the need to maintain and disconnect power to very high loadings.
3-phase Plugs and Sockets Operating Ranges
Prices climb proportionately with the voltage and amps in a 3-phase plug and socket. Current ratings start at 10A at 250V for light machinery and equipment, all the way up to 200A and 500V for heavy machinery like conveyor belts or cranes.
Benefits of 3-phase Plugs and Sockets
3 phase power supply has obvious benefits over a single-phase supply in that it provides for more consistent power at higher loads to run big pieces of equipment efficiently. The plugs and sockets used here are made to ensure safety, as well as act as circuit breakers if anything goes wrong. Additional safety features are the integrated switches in sockets, which can also be used to restrict operation at certain times or by unqualified staff. A 3 phase plug and socket is built to high standards. They show high levels of impact, chemical and environmental resistance meaning they can be used in places exposed to water, liquids, high or low temperatures, dust and in any weather. This means they’ll also last much longer than standard plugs and sockets at home. The only downside is that all this comes at a higher price.