Question

Q1 Consider a 24 slot machine. This machine is designed to have 4-poles
a) If the phase winding 5/6 pitched, draw winding diagram of phase A.
b) What is the mechanical angle between the poles of a phase?
c) What is the electrical angle between the poles of a phase?
d) Calculate the number of coils per phase.
e) Each coil has 10 turns. What is the number of turns per phase?
f) The phase A current is 5 A. Draw MMF diagram of phase A.

Q2 Place a 3-phase 4-pole winding in the available (24) slots.
a. Draw the winding diagram.
b. The winding is star connected. Show how you would connect the 3-phase windings.
c. Each phase has 40 turns. Phase currents are given by the following expressions.
İa= 10sinwt ib=10sin (wt-2/3) ic=10sin (wt-4/3)
Draw resultant MMF distribution for the instant wt=0

Q3 Suppose that the motor in Q2 has peak flux density of 1T in the air gap.
The inner diameter of stator is 15cm. The core lenght is 15cm.
a. What is the flux per pole?
b. If the motor is supplied with 380 V, 50 Hz line voltage and the phases are star
connected, what is the number of turns per phase?

Q4 Nameplate on a 460-V, 50-hp, 50-Hz, four-pole induction motor indicates that its speed
at rated load is 1455 r/min. Assume the motor to be operating at rated load.
a. What is the slip of the rotor?
b. What is the frequency of the rotor currents?
c. What is the angular velocity of the stator-produced air-gap flux wave with
respect to the stator? With respect to the rotor?
d. What is the angular velocity of the rotor-produced air-gap flux wave with
respect to the stator? With respect to the rotor?

Q5 Consider a 3-phase, 50 Hz, 4 pole machine with a double-layer fractional pitch (150
degrees electrical) AC armature winding distributed over 24 slots. Each coil side has 6 turns.
The fundamental air-gap flux per-pole is 120 mWb.
a. Draw the winding diagram
b. Plot MMF variation for IA = I, IB = IC = - I/2
c. Calculate the generated fundamental voltage

Answer 1