Chapter 6 The Fundamental Theory of AC Machines

AC machine windings AC rotating machine is composed in synchronous or asynchronous machines. Generally, the single AC machine and 3-phase AC machine are very popular. Principle 1. Waveforms of EMF and MMF in a machine air-gap should be typically sinusoidal, the harmonic waves are as smaller as possible; 2. In a three phase machine, there are three voltage phases, separated by 120 electrical degrees.

Machine Angle --- Space angle in geometry, 360 degrees Electric Angle & Machine Angle Machine Angle --- Space angle in geometry, 360 degrees Electric Angle --- Defined as 360 degrees divided by the number of mechanic phases Number of pole is 2p Electric Angle = p×360 degree=p× Machine Angle

Number of Slot (per pole & per phase) Slot angle Number of Slot (per pole & per phase) Phase band The zone covered by the slots which belongs to each phase.

Composed by homocentric coils with different coil pitch. Single layer windings homocentric winding chains winding cross winding Homocentric winding Composed by homocentric coils with different coil pitch.

Eg: An two poles, 3-phase AC machine with 24 slots

The pitch of chains winding coils is same and is an odd.

Cross windings

Double layer windings