Why are motor armatures laminated?

Motor armatures have to be made of thin laminations of iron to work efficiently.

A plain solid iron armature would waste a lot of energy in at least two ways:

• the magnetic field that is produced by the motor's stator would induce strong eddy currents in the solid armature and as a result the armature would get unnecessarily hot
• those same eddy currents would counteract the magnetic field of the stator so that extra energy would have to be supplied to the motor to make it drive its intended load.

By using an armature made of very thin iron laminations, the eddy currents can be reduced to an acceptable minimum level, thus avoiding unnecessary overheating of the motor and allowing it operate using the lowest possible supply of current to drive its intended load.