How to Wire a Three Phase Motor

A three phase motor has three magnetic poles, rather than just two. The three poles advance in 1/3 steps around the rotor when each Line reaches its full voltage. This rotation occurs due to the sequence of magnetization of each pole, which is consistent and predictable. As a result, a three phase motor does not need a starting circuit.

When wiring a three phase motor, it is important to understand that the currents must pass from Phase A to Phase B to Phase C in the same order. In the reverse order, this current will flow through the same circuit but in the opposite direction. These currents combine to form a magnetic field within the motor, which is visible on the graphs of the current in each phase. In addition, the magnetic poles are color coded to match the background color of the graphs, and large letters next to them indicate a peak magnetic field, while small letters denote weaker fields.

The second most common type of three phase motor is the wound rotor motor. This is a little more expensive than the first type, as the construction is much more complicated. It involves connecting three sets of coils in a star pattern. The similar ends of each winding are connected to a common point, and the other ends are connected to slip rings containing brushes. The ends of the windings are routed to the outside, making it possible to achieve a soft start and stop.