• When the armature of a motor spins, anything it is attached to also turns.Motor coche image by Marco Antonio Fdez. from Fotolia.com
  
  Basic motor design involves an armature, which is often an electromagnet, held inside a magnetic field and allowed to spin when a current is passed through it to generate its own electromagnetic field. The spinning of the armature produces the torque used to power devices attached to the motor. A motor can use alternating current (AC) or direct current (DC), and there are several main forms of both types of motor.
  
  

Shunt Motor

• A shunt motor enables a relatively constant motor speed to be maintained regardless of the load placed on the motor. This is achieved by maintaining a nearly constant field flux by modulating the field created by the armature, which is built in parallel to the windings of the shunt field. This allows the electromagnetic field strengths of the armature and shunt to be altered independent of one another, to cancel out any changes.
  
  

Series Motor

• A DC series motor is a simple circuit where the armature is set up in series with the motor's electromagnetic field coils. This allows the speed of the motor to be changed by varying the load, as the two electromagnetic fields are not working against one another to maintain a predetermined strength. Because they produce a high initial torque before tapering off, series motors are commonly found in starter motors.
  
  

Induction Motor

• An AC induction motor uses stationary coils of wire around metal bars to form an electromagnet around the armature and induce it to spin, instead of passing the current through the armature itself, as in a DC motor. The simplest induction motors have no initial torque, and must therefore "spin up" to speed.
  
  

3-Phase Asynchronous Motor

• The three-phase asynchronous motor is an enhanced version of the induction motor that uses three separate sets of coils to induce rotation in the armature. Each set of coils is connected to a different AC supply, none of which match, and a current is induced that is in a different phase to the other coils. The result is the armature is pulled rapidly in a circle between the six poles created by the pairs of coils.