# Tutorial_C7 - Chapter 7 Tutorial Questions 1 A 220-V...

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Chapter 7 – Tutorial Questions 1. A 220-V, three-phase, two-pole, 50-Hz induction motor is running at a slip of 5 percent. Find: (a) The speed of the magnetic fields in revolutions per minute [3000rpm] (b) The speed of the rotor in revolutions per minute [2850rpm] (c) The slip speed of the rotor [150rpm] (d) The rotor frequency in hertz [2.5Hz] 2. The name plate on a 460-V, 50 hp (Note: 1hp = 746 W), 60-Hz, four-pole induction motor indicates its speed at rated load is 1755r/min. Assume the motor to be operating at rated load. i. What is the slip of the rotor? [2.5%] ii. What is the frequency of the rotor currents in hertz? [1.5Hz] iii. What is the angular velocity of the stator-produced air gap flux wave with respect to the stator? With respect to the rotor? iv. What is the angular velocity of the rotor-produced air gap flux wave with respect to the stator? With respect to the rotor? 3. A 50-kW, 440-V, 50-Hz, six-pole induction motor has a slip of 6 percent when operating at full-load conditions. At full-load conditions, the friction and windage losses are 300 W, and the core losses are 600 W. Find the following values for full-load conditions: (a) The shaft speed n m [940rpm] (b) The output power in watts [50kW] (c) The load torque t load in newton-meters [507.94Nm] (d) The induced torque t ind in newton-meters [517.08Nm] (e) The rotor frequency in hertz

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Tutorial_C7 - Chapter 7 Tutorial Questions 1 A 220-V...

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