THEORY OF TORQUE PREDICTION
to Faradays laws of electromagnetic induction
reluctance of magnetic circuit can be varied, inductance L and the flux
linkages λ can also be varied.
a magnetic circuit as shown in fig. 2.29.
stator consists magnetic core with two pole arrangement. Stator core carries a
coil. Rotor is also made up of ferrous material. The motor core is similar to a
salient pole machine. Let the angle between the axis of stator pole and rotor
pole be θ. let the angular displacement be illustrated using fig. 2.29 (a, b
Case 1: θ = 0
in fig. 2.29 (a) the air gap between the stator and rotor is very very small.
Thereby the reluctance of the magnetic path is least. Due to minimum
reluctance, the inductance of the circuit is minimum. Let it be Lmax
Case 2 : θ = 450
in fig. 2.29(b) in this only a portion of rotor poles cover the stator poles.
Therefore reluctance of the magnetic path is more than that of case 1.due to
which the inductance becomes less than Lmax
Case 3: θ = 900
in fig. 2.29(c) the air gap between the stator poles has maximum value. Thereby
reluctance has a value yielding minimum inductance. Let it be Lmax.
in inductance with respect to the angle between the stator and rotor poles is
shown in fig. 2.30.
Derivation for reluctance torque
faradays law of electromagnetic induction an emf induced in an electric circuit
when there exists a change in flux linkages.
direction of current I is opposite to that of e, then the electric power is
transferred from the source to the inductor. On the other hand, if the
direction of current I is same as that of e, then the source gets the
electrical power from the inductor.
basis of magnetic circuit/field theory it is known that the stored energy in a
of change of energy transfer due to variation in stored energy or power due to
variation in stored energy.
power developed/consumed = power received from the electrical source – power
due to change in stored energy in the inductor
received from the electrical source = ei
* Torque is
proportional to i2 : Therefore it does not depend upon the direction of the