As illustrated below, these coils are connected to form a three phase winding. Each phase is able to produce a specified number of magnetic poles (in the diagram below, four magnetic poles are generated by a phase winding). The windings of the three phase are arranged uniformly around the stator periphery and are labeled in the sequence that phase a is 120o (electrical) ahead of phase b and 240o (electrical) ahead of phase c. It is noted that in the diagrams above, two coil sides are laid in each slot. This type of winding is known as the double layer winding. In the case that there is only one coil side in each slot, the winding is known as the single layer winding.