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WorksheetsAC Machines 1
Total questions: 15
Worksheet time: 37mins
A single-phase induction motor is rated 5 hp, 75% power factor and 220 volts. What is the full-load current? Assume 100% efficiency.
22.6
20.5
16.9
18.5
A 1/20-HP 1,550 rpm shaded-pole motor takes 120 watts when operating at full-load . What is its efficiency?
39.71%
23.98%
31.08%
93.20%
What percent of the rated torque does a 1/20 hp 3,600 rpm shaded-pole motor develop at starting, if the average starting torque is 5.0 oz-in?
45.83%
36.00%
50.64%
40%
A ½ -hp 1,750-rpm capacitor motor develops 350 percent starting torque. What is the starting torque in pound-feet?
6.36
7.23
5.25
8.46
In performing a brake-load test upon ¼-hp capacitor start motor with its output adjusted to rated value , the following data were obtained: E = 115 volts, I = 3.8 amp, P = 310 watts, RPM = 1,725. Calculate: efficiency.
93.52%
60.16%
65.02%
83.29%
In performing a brake-load test upon ¼-hp capacitor start motor with its output adjusted to rated value , the following data were obtained: E = 115 volts, I = 3.8 amp, P = 310 watts, RPM = 1,725. Calculate power factor.
0.654
0.846
0.906
0.709
In performing a brake-load test upon ¼-hp capacitor start motor with its output adjusted to rated value , the following data were obtained: E = 115 volts, I = 3.8 amp, P = 310 watts, RPM = 1,725. Calculate torque in pound-inches.
9.13
9.86
8.27
8.93
How many poles is a motor wound that operates at 1,130 rpm from a 60-Hz source?
6
4
8
2
A 3-phase motor is rated 750 hp at 480 volts line to line, 0.85 pf lagging and 0.95 efficiency. Solve for the rated current.
869.64 A
702.23 A
405.43 A
917.32 A
A 40-hp, 3-phase , 4-pole, 230-volt , 60-Hz induction motor operating at 0.90 efficiency, 0.85 power factor and 3 percent slip, drives a water pump. Determine the current at which the motor is operating.
94.531 A
96.234 A
97.915 A
93.351 A
Calculate the speed of a 60-Hz , 14-pole motor is the slip is 5%.
514.28
488.57
456.32
429.63
The rotor speed of a six-pole, 50-Hz induction motor is 960 rpm. Calculate the percent slip.
5%
2%
4%
3%
A 50-hp three-phase motor rated 220 V, 60 Hz , 75% power factor has 6 poles . The slip at full load is 3%. What is the frequency of the rotor current at full load?
1.8 Hz
60 Hz
5.4 Hz
58.2 Hz
A 150-HP, 3-phase 6-pole, 460-V, 60-Hz induction motor drives 195 A line current at full load speed of 1170 rpm and 0.85 pf. Solve for the percent slip at full load.
2.5%
3.0%
2.8%
2.0%
A 30-hp, 4-pole, 3-phase , 230-volt , 60-Hz induction motor operating at 90% efficiency, 85% power factor and 2.5% slip drives a water pump for a reservoir. Find the current and speed at which the motor is operating.
73.4 A, 1755 rpm
62.39 A, 1755 rpm
73.4 A, 1800 rpm
62.39 A, 1800 rpm
