1-electromagnet with a relative permeability of 1000 and a uniform thickness of
10 cm has the dimensions as given in Figure . Calculate the limit value of the current in the
series-connected coils so that the electromagnet can lift the ferromagnetic bar having a relative
permeability of 300 and a mass of 20 kg (Earth’s gravitational constant g=9.81 m/s2).

2-
Consider the two-coil rotating electromechanical system shown in Figure. The
airgap is uniform and the iron core is infinitely permeable. The self inductance of the rotor and
stator coils are Lr = Ls = 0.6 H, and the mutual inductance between them varies with the angular
position (θ) as: Lrs(θ) = Lsr(θ) = 0.5 cos θ, where θ is in degrees.

a) Calculate the torque induced on the rotor when θ = 30o, Is = 5 A and Ir = 2 A, where Is
and Ir are currents in stator and rotor coils, respectively.

b) The rotor coil is open circuited and the stator coil current is fixed to 5 A. Calculate
induced voltage between the terminals of the rotor coil when the rotor is revolving at an
angular speed of 100 rad/s.

 

So how's it going so far with your solution to the questions?
Or are you expecting us to do your homework?

 

So how's it going so far with your solution to the questions?
Or are you expecting us to do your homework?

I have same examples with solutions but in this questions,electromagnet and ferromagnetic bar have infinite permeability.How do we solve that permeabilities are different as question 1.

In question 2b, I try to solve this question by using this formula: e2=Lr(Q)*di2/dt + i2*wm*dLr(Q)/dQ + Ls(Q)*di1/dt + i1*wm*Ls(Q)/dQ

I find -250sinQ, is it true?