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.
The purpose of a triple pole breaker is to cut off all power to an entire section of a building in case of an emergency such as a fire alarm or earthquake. These are necessary in areas that are served by multiple power sources like electricity from several different companies on separate cables to prevent a situation called "earthing up". If two of the cables were to suffer damage at the same time, the third would still be able to supply power because each cable has its own independent wiring within the facility. A triple pole breaker can be used instead of using many individual breakers to protect against this kind of incident.
Individual conductors within each phase of a multi-wire branch circuit are referred to as "hot wires". Hot wires of equal voltage must be separated by enough distance along their common path to allow current to flow without interference from one hot wire to another. This is usually done by crossing over each other at right angles (90 degrees) within the enclosure or cabinet where they are joined together by a splice or junction.
The three-pole breaker works in the same way as the single-pole breaker. A three-pole breaker can also be used in a two-wire branch circuit if one conductor is defined as a ground. This type of circuit is called a grounded neutral circuit. The third conductor on a three-pole breaker must be defined as a hot wire because they will all need to carry current to the motor.
A three-pole breaker is different from a three-way switch in that a three-way switch connects three circuits, each between a pair of terminals. On a three-pole breaker, each pole connects one circuit to the engine, one circuit to the floor panel, and one ground connection.
Since all motor vehicles have four-pole power outlets, it is not necessary to use a five- or six-pole breaker for automotive applications. However, some industrial motors require six-pole breakers for proper operation. These motors are run from 115-volt power sources and include air compressors, conveyors, and welders among others. A motor technician should always check the load being driven by the motor before installing a six-pole breaker because some loads may require more than three phases of power.
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 can each carry current. The paths include the hot wires to the load, the neutral wires to the load, and the ground wire to the load. Each path through the breaker must meet the same electrical requirements as any other path, but because there are more possibilities with three paths, some methods for selecting which paths will carry current at any given time are available. For example, one path may be used at a time, or multiple paths might be forced on simultaneously if there's enough power in the circuit.
A common arrangement is to have one pole open the circuit while the remaining two poles close it. This arrangement is useful when you want to allow some parts of the circuit to remain energized while others not. For example, you could leave the third pole open in a three-pole breaker used for lighting circuits. This would allow lights to stay on even if someone forgot to shut off the main power switch.
Another common arrangement is to have all three poles open the circuit at once.