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6-Assignment6_Solution

# 6-Assignment6_Solution - ELECTRICAL ENGINEERING DEPARTMENT...

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ELECTRICAL ENGINEERING DEPARTMENT California Polytechnic State University EE 255 Assignment #6 Solution Problem #1 A dc test is performed on a 208-V, Y-connected induction motor. Each phase of the machine is made of two parallel windings. If the Vdc=9-V and Idc=6-A, what is the resistance of each winding? winding R / . = = 5 1 6 9 Problem #2 A 220-V, three-phase, 60-Hz induction motor is running at a speed of 1140 rpm. Determine: 1. The number of poles of the machine 2. The speed of the magnetic field 3. The slip of the machine 4. The slip speed Solution: (1) Assume rpm n s 1140 = poles 6 316 6 120 1140 = = = = P P p f rpm n s . (2) rpm p f n s 1200 6 60 120 120 = = = * - + dc V 9 R R R R R R dc 6A

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(3) 05 0 1200 1140 1200 . = - = - = s r s n n n S (4) rpm n n speed Slip r s 60 1140 1200 = - = - = Problem #3 A 208-V, three-phase, 4-pole, 50-Hz induction motor is running at a slip of 4%. Determine: 1. The speed of the magnetic field 2. The speed of the rotor 3. The slip speed Solution: 1) rpm p f n s 1500 4 50 120 120 = = = * 2) rpm n S n s r 1440 1500 04 0 1 1 = - = - = ) . ( ) ( 3) rpm Sn speed Slip s 60 1500 04 0 = = = * . Problem #4 A 208-V, three-phase, 12-pole, 60-Hz induction motor is running at a slip of 4%. Determine: 1. The speed of the magnetic field 2. The speed of the rotor 3. The slip speed Solution: 1) rpm p f n s 600 12 60 120 120 = = = * 2) rpm n S n s r 576 600 04 0 1 1 = - = - = * ) . ( ) ( 3) rpm Sn speed Slip s 24 600 04 0 = = = * .
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