Electrical Engineering ⇒ Topic : Principle of d.c motor
PRINCIPLE OF OPERATION
The electric motor is a machine which converts electrical energy into mechanical energy.
The principle of motor action can be stated as follows :
"Whenever current carrying conductor is placed in a magnetic filed, it experiences a force whose direction is given by Fleming's left hand rule."
Fig. (a) The principle of motor action Fig.(b). Motoring operation
The force (F) developed in the conductor is given by the relation,
F = BIL newtons
where B = flux density, T (Wb/m2)
I = current in conductor, A
L= exposed length of conductor, m
For a motor : V = Eb + IaRa ...known as voltage equation of a motor., (1)
For a generator : Eg = V + IaRa (2)
where V = applied voltage (measurable terminal voltage) across the armature
Eb = back or counter e.m.f. developed in the armature of the motor
Eg = generated e.m.f. developed in the generator armature
IaRa = armature voltage drop due to a flow of armature current through an armature of a given resistance, Ra.
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