Five specialised elements are used, which together constitute the motor's INSULATION SYSTEM. The following are typical in an AC motor:

1. TURN-TO-TURN INSULATION between separate wires in each coil. (Usually enamel on random wound coils of smaller motors - tape on "form wound" coils of larger motors.

2. PHASE-TO-PHASE INSULATION between adjacent coils in different phase groups. (A separate sheet material on smaller motors - not required on form wound coils because the tape also performs this function.

3. PHASE-TO-GROUND INSULATION between windings as a whole and the "ground" or metal part of the motor. (A sheet material, such as the liner used in stator slots, provides both di-electric and mechanical protection.

4. SLOT WEDGE to hold conductors firmly in the slot.

5. IMPREGNATION to bind all the other components together and fill in the air spaces. (A total impregnation, applied in a fluid form and hardened, provides protection against contaminants.