1. A6pole, 3 phase induction motor develops a power of 22.38 kW, including mechanical losses which total 1. 492 kW at a speed of 950 rpm on 550 -V50 Hz mains. The power factor is 0.88. Calculate for this load a. Slip b. The rotor copper loss c. The total input if the stator losses are 2000 W d. Efficiency e. Line current f. The number of complete cycles of the rotor electromotive force per minute

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 A 6-pole, 3-phase induction motor develops a power of 22.38kW, including mechanical losses which total 1.492 kW at a speed of 950 rpm on 550-V, 50 Hz mains. The power factor is 0.88. Calculate for this load (a) the slip (b) the rotor copper loss (c) the total input if the stator losses are 2000 W (d) the efficiency (e) the line current (1) the number of complete cycles of the rotor electromotive force per minute. [(a) 0.05 (b) 1175 (c) 25.6 kW (d) 82% (e) 30.4 A (1) 150

 

 

1. A6pole, 3 phase induction motor develops a power of 22.38 kW, including mechanical losses
which total 1. 492 kW at a speed of 950 rpm on 550 - V50 Hz mains. The power factor is 0.88.
Calculate for this load
a. Slip
b. The rotor copper loss
c. The total input if the stator losses are 2000 W
d. Efficiency
e. Line current
f. The number of complete cycles of the rotor electromotive force per minute
2. A3-phase, 40o V, Y connected induction motor has an equivalent T-drcuit consisting of R, =
11, X1 = 2 N, equivalent rotor values are R' = 1.2 fN, X,' = 1.5 N The exciting branch has an
impedance of 4 + j40 N. If the slip is 5% find the
a) Current
b) Efficiency
c) Power factor
d) Output
Assume friction loss to be 250 w.
3. A4 pole, 3 phase 50 Hz induction motor has a voltage between slip ring on open - circuit of
520V. The star connected rotor has a standstill reactance and resistance of 2.0 and 0.4 ohm per
phase respectively. Determine
a. The full – load torque if full - load speed is 1, 425 RPM
b. The ratio of starting torque to full load torque
c. The additional rotor resistance required to give maximum torque at stand still.
4. A6 pole, 50 Hz squirrel – cage induction motor runs on load at a shaft speed of 970 RPM
Calculate:
a. Percentage slip
b. Frequency of induced current in the rotor
5. In a certain 8-pole, 50 Hz machine, the rotor resistance per phase is 0.04 ohm and the maximum
torque occurs at a speed of 645 RPM. Assuming that the air gap flux is constant at all loads,
determine the percentage of maximum torque
a. At starting
b. When the slip is 3%
Transcribed Image Text:1. A6pole, 3 phase induction motor develops a power of 22.38 kW, including mechanical losses which total 1. 492 kW at a speed of 950 rpm on 550 - V50 Hz mains. The power factor is 0.88. Calculate for this load a. Slip b. The rotor copper loss c. The total input if the stator losses are 2000 W d. Efficiency e. Line current f. The number of complete cycles of the rotor electromotive force per minute 2. A3-phase, 40o V, Y connected induction motor has an equivalent T-drcuit consisting of R, = 11, X1 = 2 N, equivalent rotor values are R' = 1.2 fN, X,' = 1.5 N The exciting branch has an impedance of 4 + j40 N. If the slip is 5% find the a) Current b) Efficiency c) Power factor d) Output Assume friction loss to be 250 w. 3. A4 pole, 3 phase 50 Hz induction motor has a voltage between slip ring on open - circuit of 520V. The star connected rotor has a standstill reactance and resistance of 2.0 and 0.4 ohm per phase respectively. Determine a. The full – load torque if full - load speed is 1, 425 RPM b. The ratio of starting torque to full load torque c. The additional rotor resistance required to give maximum torque at stand still. 4. A6 pole, 50 Hz squirrel – cage induction motor runs on load at a shaft speed of 970 RPM Calculate: a. Percentage slip b. Frequency of induced current in the rotor 5. In a certain 8-pole, 50 Hz machine, the rotor resistance per phase is 0.04 ohm and the maximum torque occurs at a speed of 645 RPM. Assuming that the air gap flux is constant at all loads, determine the percentage of maximum torque a. At starting b. When the slip is 3%
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