INDUCTION MOTOR QUESTIONS FOR PRACTICES

1.      Drive the output equation of a 3-phase induction motor and also explain how the magnetic and electric loading is selected.

2.      Write down the steps to find out the main dimensions of a 3-phase IM. Also draw a flow chart for it.

3.      Explain and find out flux density in stator teeth.

4.      Explain how the rotor is designed of a 3-phase ship ring induction motor. Also draw a flow chart for it.

5.      Estimate the stator slot leakage reactance for 1-Layer winding.

6.      Write down step by step how the circle diagram is drawn for an induction motor?

7.      Calculate the main dimension, turns per phase, Number of conductors, slots, cross-section of the  conductor of a 50 KW, 415 volts, 3 phase,, 50 Hz, 1000 RPM, slip ring  induction motor. Given B_av = 0.52T, η= 0.9, pf =0.89 lagging, =32000 ac /m, δ= 5A /mm².

8.      A 20-kw, 3-phase, 6-pole, 50-Hz, 400 V delta connected cage rotor induction motor has 54 stator slots, each containing 10 conductors. Design suitable number of rotor slots and determine the value of bar and end ring currents. The machine has efficiency of 85% and power factor 0.85 lagging. Also find the bar and end ring sections, if current density is 6.0 A/mm². Assume rotor mmf as 85% of the stator mmf.

9.      Describe the significance of B₃₀ in a  3-phase induction motors. A 75 kw, 3300V, 50 Hz, 8-pole, 3-ph, star connected induction motor has a magnetizing current which is 35% of full load current. Calculate the number of stator winding turns per phase if the mmf required for flux density at 60⁰ from the inter polar axis is 500 A. Assume winding factor = 0.95, full load efficiency = 0.94 and full load power factor = 0.86.

10.  Estimate the main dimensions & air gap length for a 3-phase, 20 HP, 400 V, 6-pole, 50 Hz, 970 RPM induction motor suitable for a star-delta starting. Assume magnetic and electric specific loadings as 0.45 wb/m² and 23000 ac/m respectively, ratio of core length to pole pitch 0.85, full load efficiency 0.88 and power factor 0.89.

11.  Estimate the main dimensions, number of radial ducts, number of stator slots, number of turns per phase, conductors per slot and slot dimensions for 7.5 kW, 415 V, 3-phase, delta-connected, 4-pole, 50 Hz squirrel-cage induction motor. The flux per pole is 0.015 Wb. Assume efficiency 85% and power factor as 0.85 lagging.

12.  Determine the main dimensions, turns per phase, number of slots, conductor section and slot area of 200 H.P, 3 phase, 50Hz, 400 Volts, 1480 r.p.m. slip ring induction motor. Assume Bav = 0.5 wb/m², ac = 30,000 amp conductor / meter, efficiency = 0.9 and power factor = 0.9, current density = 3.5 amp per mm².

13.  Design a 10 HP, 415 V, 3-phase, 50 Hz, 1440 rpm, squirrel cage induction motor. The machine is to be started by a star delta starter. Assume all suitable data yourself.