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. 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; then the next highest; and so on.
Three-phase power is used in large industrial motors because it is efficient for high speeds and heavy loads. It is also used in air conditioners, refrigerators, and dishwashers because they use large amounts of electricity during start-up and when heating or cooling is required immediately. These appliances need circuits that will carry enough current to run them smoothly and safely when they are turned on and off repeatedly by a timer. In houses, three-phase power can be supplied by an extension cord made for outdoor use, or by a special transformer located in a panel inside the house. This article focuses on three-phase breakers used in commercial buildings but many other types of breakers are available.
Four-wire branch circuits provide power to several outlets on a single switch. Each outlet has its own pair of conductors to connect it to the branch circuit, with the third conductor connected to the fourth.
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 One way to think about a three-pole breaker is that it has three separate paths that you can take. The paths are called "poles" because they lead to each phase of the circuit. A pole can be thought of as a possible route through which current might travel. Current will always take the path of least resistance, so if there are multiple paths, current will choose one path and follow it. A third path would then become available if current was following the first path; therefore, a three-path, or "pole," breaker provides three ways for current to flow.
When current flows through a conductor, it creates magnetic fields around the conductor. These fields interact with other magnets placed near the conductor, causing them to also deflect toward the source of the current. Induction coils built into electric circuits measure the amount of deflection caused by these interactions, indicating the presence of current flowing through the conductor. A magnetic induction sensor uses the same principle as a transformer, but instead of changing voltage, it changes current through an inductor.
Three-phase electric power is a form of alternating current that is often used in power generation, transmission, and distribution. It is a sort of polyphase system that uses three wires (or four, plus an optional neutral return wire) to transport power and is the most popular way used by electrical grids globally. Three-phase power can be produced by any device capable of creating multiple simultaneous currents of unequal strength; for example, this can be done with three separate circuits each fed from a single line-voltage source or with one circuit using 3-wire delta connection. Delta is the name given to the third set of lines not involved in either a hot or neutral conductor.
In order to use three-phase power effectively, it is necessary to have some method of identifying which phase is being supplied through any given conductor. This is usually done by means of color coding on the wiring itself or by other physical means such as printed labels. The term "three-wire system" refers to an electrical installation using at least three conductors to transmit alternating current (AC), where the presence of a fourth conductor, called the neutral, is optional. A three-wire system will carry three-phase current, meaning that each conductor carries a different phase of sine wave voltage. In fact, any number of phases between 1 and 3 may be used in a three-wire system provided they are evenly spaced and non-zero.