# Is a 3-pole breaker the same as a 3-phase breaker?

The three-pole breaker works in the same way as the single-pole breaker. A three-pole breaker links three distinct wires, as required by heavy-duty industrial motors, and is most commonly found in a three-phase electrical system. A three-pole breaker can also be used in a two-wire branch circuit if one conductor is designated as a "ground" conductor and all three conductors are separated at both ends of the panel. The third conductor is then always available to supply power to devices that need three-wire operation such as heaters, air conditioners, and dishwashers.

A three-phase generator uses three pairs of coils, each pair being connected together in opposition to each other around the coil. This means that if one side of the generator is excited by an external source, such as an electric motor, the other sides will be driven in opposition to this first side. Thus, the entire machine will function as a single-coil generator with three phases. Three-phase power is necessary for many appliances that use electricity for their motive force; examples include large motors and generators as well as industrial lasers and welders.

Three-phase power is readily available from public utilities on almost every street corner in North America. However, it is also possible to generate three-phase power directly from two-phase power sources.

## How does a 3-phase breaker work?

When there is a surge anyplace in the system, it trips the breaker, the power bridge falls, and the circuit opens. The wire with the highest voltage gets through first, followed by the next highest, and so on. If a wire gets damaged at some point along its route to the motor, it can no longer conduct current and will not trigger the breaker. This is called a "hot" wire. The remaining wire can still conduct current and be used to supply power to other parts of the system. This is called a "neutral" wire.

Three-phase power is made up of three separate conductors or lines. These are named "line" 1, "line" 2, and "line" 3. They are also referred to as "the hot wires", since they carry the highest voltage during normal operation of the motor. Neutral is the third conductor that stays constant no matter which phase is activated. It always carries a zero voltage signal. Line 1 is connected to one side of the power bridge, line 2 is connected to another, and line 3 is connected to the other side. The order in which these lines connect to the bridge determines how the bridge will operate when it receives a pulse from a magnetic sensor or relay.

## Is 3-phase and 3-pole the same?

The number of conductors connected or bridged by the three-pole conductor is the difference. A three-phase system uses three separate two-wire circuits to provide power to five lamps or appliances. The fifth lamp or appliance is powered by a second set of three poles on a third wire. Thus, each phase has two pairs of conductors, one pair for positive voltage and the other for negative voltage.

A three-phase system requires six breakers in all, three for each phase. Each time a circuit is opened or closed, a different breaker is used. Three-phase power is available at many locations where single-phase power is provided, but it must be included on all utility meters used with that electricity. Most residential electric circuits are designed to handle only single-phase power, so they cannot receive three-phase power directly from the meter. Instead, a special transformer called a delta-wye transformer steps down the voltage from the utility company's transmission line to the household distribution center, where it can be used by single- or three-phase appliances. The term "three-way" plug fits into such a receptacle, allowing it to be used with three-way appliances such as vacuum cleaners and floor polishers.

## What is a 3-pole circuit breaker used for?

Breakers for Multiple Poles The most typical multi-pole use is to safeguard and break both sides of a circuit: the wire to the load and the wire back from it. Both poles of a two-pole breaker are identical in this application. A three-pole breaker, for example, can be used to break all three wires in a three-phase circuit.

Poles of a Three-Pole Breaker In addition to the load wire and the return wire, each pole has an associated neutral wire. Neutral wires do not carry current when the switch is open, but they do when the switch is closed. Because neutrals are always connected to ground or another neutral, there can be only two ways to connect them to the power source: either directly from the line conductor or through another terminal on the breaker.

When all three wires are connected to one pole, that pole is called the "hot" pole. If two of the wires are connected to one pole and the third wire is connected to another pole, those two poles are also hot. If all three wires are not connected to any pole, then none of the poles are hot. A third option is for one side of the circuit to be hot and the other side to be neutral. This is appropriate if there is a single appliance that needs to be turned on/off without affecting the other parts of the circuit.

## Can I use the three-phase circuit breaker in a single-phase power supply?

A 3p breaker can be used on a three-phase system with two or three poles. As shown below, a 3p breaker may only be used on a 14-phase system if the indications suggest it. Some manufacturers indicate that certain parts of their products are for use on single-phase systems only; others indicate that all parts of their products can be used on both three- and single-phase systems. For example, the manufacturer's label may specify that the breaker is for use on 3- or 4-wire systems but not on 2-wire systems.

The reason for this limitation is that some parts of the product will not work properly if installed on a single-phase system. For example, the handle may not be repositioned as needed to select the correct phase. The main purpose of using a 3p breaker on a single-phase system is so that you can replace broken phases without turning off the power.

## Can you use 2 phases of a 3 phase breaker?

The term "3P" means that the breaker controls all three phases and each phase is split into two or more branches, called "poles". A 4P breaker would have four separate branches or poles. The same thing applies to double pole breakers - they can be used on a three-phase system with two or three poles. Double pole breakers are also called "6P" because they control six different phases of electricity.

A 5P or 7P breaker would have five or seven separate branches or poles. There are no 5P or 7P breakers available in consumer markets; they are used mainly by electric utilities for large projects.

It is important to remember that even though these breakers are labeled as "three-phase", they can be used on a four-or-more-wire system as long as there are not too many circuits being fed off of one branch. For example, if there are four wires coming into a single junction box and only three circuits are being served from this box, then a three-phase breaker could be used here as well. The fourth wire can be used for ground fault detection or some other purpose.

##### Brian Alvarez

Brian Alvarez has an eye for the classic. He loves to find hidden gems, and knows how to spot a good deal. Brian has an impressive collection of antique clocks, typewriters, and even an antique automobile!

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