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What is an Armature and how does it work?

2016-12-22

Armature is a power-producing component of a motor and its key function is to convert electrical energy to mechanical energy. Armatures used in starter motors are made up of coils which carry current and rotate in a magnetic field. The armature wiring in copper enhances electrical efficiency due to its higher electrical conductivity. 
An armature has a continuous series of windings from each bar on the commutator, which loops around the iron stack teeth and connects to the next bar on the commutator. The winding continues to loop all the way around the armature in the same manner. Loops are either single or parallel conductors and might circle any number of times around the stack teeth turns in a coil. This phenomenon is commonly called 'Turning in a Coil'. The wire may vary in gauge, as is required by the design of the motor. Each wire is insulated with an enamel coating or insulation, isolated from every other wire in the loop and only terminating at the commutator bar. The turns in every coil wrap around the iron stack to create an electromagnet. When energized, an electromagnetic field is generated in the motor armature. This electromagnetic field interacts with the magnetic fields of permanent magnets in the motor, in the case of permanent magnets in the motor, otherwise the electromagnetic forces work to attract each other, inducing a torque on the armature shaft thus causing it to turn. 
The armature winding will start rotating due to force exerted on it and will cut the flux lines. Thereafter, according to Faraday's Law of Electromagnetic Induction, emf is induced in it. When this winding carries on, it produces its own mmf (magnetomotive force), which is known as an Armature Reaction. Such an armature's reaction generates eddy current in the armature which may result in losses in the machine. Due to the armature's reaction, the flux in the air gap is strong at one end and weak at the other. This effect is called the Cross-Magnetizing Effect. 

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