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MMLU-Pro / 11680 / (i) An eight-pole, 60 Hz SCIM is deliberately loaded to a point where pull-out…

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question

(i) An eight-pole, 60 Hz SCIM is deliberately loaded to a point where pull-out or stalling will occur. The rotor resistance per phase is 0.3 ohm, and the motor stalls at 650 rpm. Calculate: (a) The breakdown slip,s_b (b) The locked-rotor reactance (the standstill reactance) (c) The rotor frequency at the maximum torque point. (ii) The induced voltage per phase in the rotor of the induction motor is 112 V. Using the data of the part (i) induction motor, determine (a) The added rotor resistance (b) The rotor power factor which will produce the same starting torque (twice the rated torque) as with the rotor short-circuited (c) The starting current.

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engineering

options

  1. Breakdown slip, s_b = 0.35, Locked-rotor reactance X_lr = 1.4 Ω, Rotor frequency at maximum torque point f_r = 17 Hz, Added rotor resistance R_x = 2.5 Ω, Rotor power factor = 0.92, Starting current I_r = 29 A
  2. Breakdown slip, s_b = 0.31, Locked-rotor reactance X_lr = 1.7 Ω, Rotor frequency at maximum torque point f_r = 17.5 Hz, Added rotor resistance R_x = 4.0 Ω, Rotor power factor = 0.89, Starting current I_r = 33 A
  3. Breakdown slip, s_b = 0.25, Locked-rotor reactance X_lr = 0.95 Ω, Rotor frequency at maximum torque point f_r = 15.5 Hz, Added rotor resistance R_x = 2.8 Ω, Rotor power factor = 0.87, Starting current I_r = 31 A
  4. Breakdown slip, s_b = 0.22, Locked-rotor reactance X_lr = 1.3 Ω, Rotor frequency at maximum torque point f_r = 16 Hz, Added rotor resistance R_x = 3.8 Ω, Rotor power factor = 0.90, Starting current I_r = 27.5 A
  5. Breakdown slip, s_b = 0.33, Locked-rotor reactance X_lr = 1.6 Ω, Rotor frequency at maximum torque point f_r = 14 Hz, Added rotor resistance R_x = 3.3 Ω, Rotor power factor = 0.97, Starting current I_r = 25 A
  6. Breakdown slip,s_b = 0.5, Locked-rotor reactance X_lr = 2.1 Ω, Rotor frequency at maximum torque point f_r = 20 Hz, Added rotor resistance R_x = 4.57 Ω, Rotor power factor = 0.88, Starting current I_r = 30 A
  7. Breakdown slip,s_b = 0.278, Locked-rotor reactance X_lr = 1.08 Ω, Rotor frequency at maximum torque point f_r = 16.7 Hz, Added rotor resistance R_x = 3.57 Ω, Rotor power factor = 0.963, Starting current I_r = 28 A
  8. Breakdown slip,s_b = 0.4, Locked-rotor reactance X_lr = 1.2 Ω, Rotor frequency at maximum torque point f_r = 18 Hz, Added rotor resistance R_x = 3.2 Ω, Rotor power factor = 0.9, Starting current I_r = 27 A
  9. Breakdown slip,s_b = 0.3, Locked-rotor reactance X_lr = 1.5 Ω, Rotor frequency at maximum torque point f_r = 15 Hz, Added rotor resistance R_x = 3.0 Ω, Rotor power factor = 0.95, Starting current I_r = 26 A
  10. Breakdown slip, s_b = 0.45, Locked-rotor reactance X_lr = 2.0 Ω, Rotor frequency at maximum torque point f_r = 19 Hz, Added rotor resistance R_x = 5.0 Ω, Rotor power factor = 0.85, Starting current I_r = 32 A

src

stemez-ElectricalMachines

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Source and history

upstream_id / Original problem ID
11680
task_id
3e513b80-d633-5ac1-a88c-b795882a2ba8
task_key
default--test--11680
task_revision_id
1
config / split
default / test

Official source

initial import