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Question: 81 a threephase 60 hz induction motor runs at 1720...

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8.1 A three-phase, 60 Hz induction motor runs at 1720 RPM and the following losses are known: stator copper loss 50 watts, rotor copper loss 65 watts, combined rotational loss 85 watts. Determine the following: a) Number of Poles (4-pole) b) slip (4.44%) c) Air-gap Power (1,464 watts) d) Output Power (1,314 watts) e) Input Power (1,514 watts) f) Efficiency (86.8%) g) Output Torque (7.3 N-m) h) Apparent Power if the Power Factor is 0.85 Lag (1,781 VA) 8.2 A three-phase, 60 Hz induction motor has the speed-torque characteristic as shown. Also shown is the load characteristic. Determine the following: a) Number of motor poles (8 poles) b) Operating speed (810 RPM) c) slip at maximum torque (25%) d) Motor starting torque (3 N-m) e) Air-gap power at a slip of 1.0 (282.7 N-m) f) Output power at the operating speed, in horse power. (0.34 HP) 6 Motor 4 Load 2 450 900 RPM

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