Construction of DC Motor (Parts & Images)

A DC motor is built from a stator field system and a rotor armature with a commutator and brushes. Those parts convert DC into rotation (learn about a DC motor’s working principle).

A DC motor is constructed with:

• A Stator
• A Rotor
• A Yoke
• Poles
• Field windings
• Armature windings
• Commutator
• Brushes

The stator is the stationary part. It holds the field windings and takes the supply. The rotor is the rotating armature that delivers the mechanical output.

Together they are the construction of a DC motor.

This video walks through the same DC machine construction:

Yoke of DC Motor

The magnetic frame or yoke of DC motor is a stator part, usually of cast iron or steel.

It forms a protective covering and mechanical support. It also houses the magnetic poles and field winding of the DC motor.

Poles of DC Motor

The magnetic poles of a DC motor are screwed to the inner wall of the yoke. Each pole has a core and a shoe. The core has a smaller section and holds the shoe to the yoke. The larger shoe spreads magnetic flux across the air gap and lowers reluctance. The shoe also has slots for the field windings that produce the field flux.

Field Winding of DC Motor

The field winding of a DC motor is copper coils in the pole-shoe slots. When current flows, adjacent poles have opposite polarity. That electromagnet produces the field in which the armature rotates and cuts flux. Permanent-magnet DC motors omit this winding.

Armature Winding of DC Motor

The armature winding of a DC motor sits on the rotor, which sees a changing magnetic fields as it turns, so iron loss appears. The armature core is laminated silicon-steel sheets. Those laminations cut hysteresis and eddy current loss and form the cylindrical core.

The core has slots of the same steel. Copper-wire armature winding is distributed around the periphery. Fibrous wedges typically close the slot mouths so the conductor cannot fly out under centrifugal force when supply current and field are present.

The armature winding of DC motor is usually one of two simplex types:

Lap Winding

In simplex lap winding the number of parallel paths A equals the number of poles P.
i.e A = P
***An easy way of remembering it is by remembering the word LAP—–→ L A = P

Wave Winding

In simplex wave winding the number of parallel paths between conductors A is 2, whatever the pole count. Multiplex windings use other path counts, so the rest of the design follows the winding chosen.

Commutator of DC Motor

The commutator of a DC motor is a cylinder of copper segments insulated by mica. It carries supply current from the stationary brushes to the rotating armature winding. In a motor it also reverses coil current so torque stays in one direction.

Brushes of DC Motor

The brushes of DC motor are carbon or graphite blocks that slide on the rotating commutator. They pass current from the external circuit into the commutator and then into the armature winding. The commutator and brush unit of the DC motor therefore couples the static electrical circuit to the rotating rotor.