PART 1 Flashcards by Gemmalyn Espenilla

REE Board Exam October 1997

A single phase induction motor is rated 5 hp, 75% power factor and 220 volts. What is its full load current?

A. 22.5 amperes

B. 20.5 amperes

C. 16.5 amperes

D. 18.5 amperes

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EE Board Exam April 1990

A 5 hp, 3-phase motor draws current when connected to 230 V. Determine the current drawn by the motor if the power factor is 0.90 and efficiency of 83%.

A. 12.53 A

B. 15.13 A

C. 13.25 A

D. 14.05 A

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EE Board Exam April 1994

A 3-phase motor is rated 750 hp at 460 volts line to line, 0.85 pf lagging and 0.95 efficiency. Solve for the rated current.

A. 869.64 A

B. 702.23 A

C. 405.43 A

D. 917.32 A

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EE Board Exam April 1985

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.

A. 94.531 A

B. 96.234 A

C. 97.915 A

D. 93.351 A

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EE Board Exam April 1992

Calculate the speed of a 60-cycle, 14-pole motor if the slip is 5%.

A. 514.28 rpm

B. 488.57 rpm

C. 456.32 rpm

D. 429.63 rpm

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EE Board Exam April 1992

The rotor speed of a six-pole, 50-cycle induction motor is 960 rpm. Calculate the percent slip.

A. 5%

B. 2%

C. 4%

D. 3%

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REE Board Exam October 1997

What is the speed of an induction motor of six poles if the percent slip is 2.5%?

A. 1462 rpm

B. 1170 rpm

C. 877 rpm

D. 1755 rpm

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EE Board Exam October 1984

A squirrel cage induction motor with nameplate data of 150 HP, 3-phase, 460 V, 60 Hz, 6-pole, 0.85 p.f. was subjected to certain performance tests. The test result readings were as follows:

Full-load current = 202 A

Full-load torque = 676.8 lb-ft

Solve for the percentage slip.

A. 3.28%

B. 4.15%

C. 3.05%

D. 2.25%

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REE Board Exam March 1998

A 50 HP three-phase motor, rated 220 V, 75% power factor has 6 poles. The slip at full load is 3%. What is the frequency of the rotor current at full-load?

A. 1.8 Hz

B. 60 Hz

C. 5.4 Hz

D. 58.2 Hz

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EE Board Exam April 1986

A 150 HP, 3-phase, 6-pole, 460 V, 60 Hz induction motor draws 195 A line current at fullload speed of 1170 rpm and 0.85 p.f. Solve for the percent slip at full-load.

A. 2.5%

B. 3.0%

C. 2.8%

D. 2.0%

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EE Board Exam October 1986

The deep well pump motor is 50 HP, 3-phase, 4 poles, 230 volts, 60 Hz induction motor, operating at 0.90 efficiency, 0.85 power factor and 3% slip. Determine the current at which the motor is operating.

A. 112.7 A

B. 122.4 A

C. 120.5 A

D. 124.7 A

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EE Board Exam April 1993

The rotor of a 220 V, 60 Hz, 4-pole induction motor has a power input of 80 kW is observed that the rotor emf makes 90 cycles per minute. Calculate the rotor copper loss.

A. 2 kW

B. 5 kW

C. 3 kW

D. 4 kW

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EE Board Exam October 1990

A 10-HP, 4 pole, 25 Hz, 3-phase induction motor is taking 9100 watts from the line. Core loss is 290 watts; stator copper loss is 568 watts; rotor copper loss is 445 watts and the friction and windage loss is 121 watts. Determine the output torque in Newton-meters.

A. 108.4

B. 112.5

C. 101.2

D. 103.3

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EE Board Exam April 1993

The rotor of a 220 V, 60 Hz, 4 pole induction motor has a power input of 80 kW is observed that the rotor emf makes 90 cycles per minute. Calculate the mechanical power developed.

A. 72 kW

B. 78 kW

C. 75 kW

D. 77 kW

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EE Board Exam April 1993

Determine the speed in rpm of the motor at full load with the following circuit elements per phase:

Rotor leakage reactance = 0.65

Stator leakage reactance = 1.12

Rotor resistance = 0.10

Stator resistance = 0.25

Connection = Y – Y

This motor is 500 HP, 3-phase, 2200 volt, 60-cycle, 6- pole induction motor with additional core loss of 2,000 watts and the friction and windage losses total is 10,000 watts.

A. 1200 rpm

B. 1196 rpm

C. 1190 rpm

D. 1188 rpm

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EE Board Exam April 1981, April 1989

A 30 HP, 4 poles, 3-phase, 230 volts, 60 Hz squirrel cage 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.

A. 73.4 A, 1755 rpm

B. 62.4 A, 1755 rpm

C. 73.4 A, 1800 rpm

D. 62.4 A, 1800 rpm

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EE Board Exam October 1980

A 50 HP, 3-phase, 4-pole, 60 Hz, 230 volt squirrel cage induction motor has an efficiency of 90%, a power factor of 85% and a slip of 2% at full-load. Find the torque in lb-ft at full-load.

A. 152.45

B. 148.87

C. 121.34

D. 150.56

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EE Board Exam October 1992

The losses in a 220-V, three-phase, 25 Hz, 4-pole induction motor at full-load are as follows:

Core = 3.0%

Friction and windage = 2.0%

Stator Cu loss = 4.0%

Rotor Cu loss = 2.0%

At 70% of full-load of the machine, determine its efficiency.

A. 90.52%

B. 88.15%

C. 87.24%

D. 89.81%

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EE Board Exam October 1980

A 100 HP, 440 volt, three-phase, 60 Hz induction motor operates with 92 percent efficiency, 0.85 power factor, at rated load. What is the current of the motor?

A. 125 A

B. 115 A

C. 98 A

D. 55 A

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EE Board Exam October 1991

A three-phase wound rotor induction motor, 440 V, 60 cycles, 4 pole is connected to a pump that delivers 1000 cfm of water against an effective head of 8 ft. Under this load, the motor draws 15 kW at a power factor of 0.90. When operated without load, the motor draws 800 watts. The stator resistance per phase is 0.21 ohm and the rotor resistance per phase is 0.022 ohm. The turns ratio between stator and rotor is 4:1. Determine the efficiency of the pump.

A. 83.62%

B. 84.65%

C. 83.16%

D. 84.24%

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REE Board Exam April 1997

A resistor assembly for a wound rotor consists of 20 elements of cast iron grid elements. The rating of each is 0.10 ohm. When joined in series and tested across 220 volts, the measured current was 100 A. How much power was lost in the joints?

A. 1.9 kW

B. 1.8 kW

C. 2.0 kW

D. 2.1 kW

EE Board Exam October 1997

A wound rotor motor, 7.5 HP, 230 volts, 3-phase takes a line current of 18.4 amperes, when operating at rated output at an efficiency of 88%. Calculate the indications on wattmeters when these are inserted to measure power by the two wattmeter method.

A. 4.035 kW, 2.325 kW

B. 4.232 kW, 2.126 kW

C. 3.902 kW, 2.456 kW

D. 3.855 kW, 2.503 kW

EE Board Exam June 1990

Two wattmeter method is used to test a 25 HP, 230 volt, 1800 rpm, 60 cycle, 3-phase induction motor. When the line voltages are 230 volts, one wattmeter reads +13,400 watts and the other +7,400 watts. Determine motor line current.

A. 55.6 A

B. 58.4 A

C. 52.3 A

D. 50.8 A

EE Board Exam April 1992

An induction motor of 30-hp, 220-volts, 3-phase draws 450 percent of the rated current with the rated voltage and delivers during the starting period 130 percent of the rated torque. The fullload efficiency and full-load power factor of this motor is 80% and 70% respectively. If an autotransformer is used as a starting unit and starting torque of the load is only 50 percent of the rated torque of the motor, find the starting voltage.

A. 136.44 volts

B. 130.65 volts

C. 132.36 volts

D. 134.20 volts

25. EE Board Exam October 1989 A 10-HP, 550 volts, 60 Hz, 3-φ induction motor has a starting torque of 160% of full-load torque and starting current of 425% of full-load current. If the motor is used on a 440 volt, 60 Hz system, what will be the starting torque expressed in percent of full-load value? A. 102.4% B. 101.8% C. 104.2% D. 103.5%

26. EE Board Exam October 1989 A 10-HP, 550 volts, 60 Hz, 3-φ induction motor has a starting torque of 160% of full-load torque and starting current of 425% of full-load current. What will be the voltage in order that the starting current be limited to the full-load value? A. 132.47 V B. 129.41 V C. 125.52 V D. 136.75 V

27. REE Board Exam October 1998 A 25 hp, 230 V, three-phase motor with 85% power factor has a starting current of 5.5 times rated current. To reduce the starting current, a wye-delta is installed. What shall be the new starting current? A. 195 amps B. 302 amps C. 135 amps D. 175 amps

28. REE Board Exam October 1997 A squirrel cage motor is started at 50% its rated voltage. What is the starting torque relative to its rated voltage starting torque? A. 50% B. 100% C. 25% D. 75%

29. EE Board Exam April 1989 A delta-connected load induction motor draws 100 A from each line of a three-phase source and develops 40 lb-ft torque at standstill. Find the torque when connected to the same source if the motor is reconnected in wye. A. 13.3 lb-ft B. 120 lb-ft C. 40 lb-ft D. none of these

30. EE Board Exam April 1992 An induction motor of 30-hp, 220-volts, 3-phase draws 450 percent of the rated current with the rated voltage and delivers during the starting period 130 percent of the rated torque. The fullload efficiency and full-load power factor of this motor is 80% and 70% respectively. If an autotransformer is used as a starting unit and starting torque of the load is only 50 percent of the rated torque of the motor, find the starting voltage and starting current of the line. A. 245.78 volts and 301.4 amps B. 136.44 volts and 292.7 amps C. 178.90 volts and 288.6 amps D. 220 volts and 227.3 amps

31. EE Board Exam October 1986 The deep well pump motor is 50 HP, 3-phase, 4 poles, 230 volts, 60 Hz induction motor, operating at 0.90 efficiency, 0.85 power factor and 3% slip. Determine the discharge of the pump in cubic meters per minute, assuming that the total head against which the pump is working is 50 meters and that the density of water is 1000 kg per cubic meter. A. 4.103 B. 4.224 C. 4.563 D. 4.205

32. REE Board Exam September 2000 Find the rotor frequency of an induction motor if the rotor speed is 1,145 rpm. A. 2.75 Hz B. 5.50 Hz C. 1.25 Hz D. 60 Hz

33. REE Board Exam October 1997 A three-phase induction motor is rated 50 hp, 220 volts and 1745 rpm and 78% power factor. What is the percent slip? A. 2.5% B. 3.1% C. 3.5% D. 4.0%

34. REE Board Exam October 1996 An AC squirrel cage induction motor has a speed rating of 1,750 rpm. If the leads are such that they could be reconnected for consequent winding, what would be the resulting speed? A. 3,500 rpm B. 1,780 rpm C. 875 rpm D. 3,450 rpm

35. EE Board Exam April 1993 In a certain industrial plant, they have two motors that are connected in concatenation to drive a load. Machine A has 4 poles is connected to a 50-Hz source, while machine B which has 8 poles is connected to the rotor of machine A. Find the speed of the combination if the slip is 8%. A. 460 rpm B. 750 rpm C. 690 rpm D. 1500 rpm

36. REE Board Exam October 1997 A three phase motor is rated 50 hp, 440 volts and 85% power factor. What is its rated current? A. 57.8 amps B. 57.5 amps C. 55 amps D. 59 amps

37. EE Board Exam October 1992 The losses in a 220 V, three-phase, 25 Hz, 4-pole induction motor at full-load are as follows: Core = 3.0% Friction and windage = 2.0% Stator Cu loss = 4.0% Rotor Cu loss = 2.0% At 70% of full-load of the machine, determine its speed and efficiency A. 1,170 rpm and 88.78% B. 740 rpm and 89.81% C. 1,200 rpm and 89.81% D. 1,800 rpm and 78.93%

38. EE Board Exam April 1992 A 460-volt, 3-φ motor draws 208 amperes with a power factor of 0.91 lagging. Calculate the cost of energy input to the motor during a 40-hr/wk with 5.5 cents/kW-hr. A. Php545.56/week B. Php331.78/week C. Php145.78/week D. Php267.89/week

39. EE Board Exam October 1990 A 10-hp, 4-pole, 25-Hz, 3-φ induction motor is taking 9,100 watts from the line. The core loss is 290 watts; stator copper loss is 568 watts; rotor copper loss is 445 watts; and the friction and windage loss is 121 watts. Determine the output torque in Newton-meter. A. 150.56 B. 190.32 C. 103.32 D. 178.76

40. EE Board Exam April 1988 A Ball Mill rotor is rated 750-hp, 460 volts line to line, 60 Hz, 0.85 power factor lagging and 0.95 efficiency. Solve for the rated current. A. 900 amps B. 870 amps C. 780 amps D. 990 amps

41. REE Board Exam September 2001 A 70-hp, 230-volts, 3-φ induction motor operating at 0.77 power factor has a starting current of 5 times its full-load current. Calculate the starting current. A. 851 amps B. 170 amps C. 295 amps D. 1,475 amps

42. REE Board Exam September 2001 Which of the following is not a reason why a single phase induction motor will not run? A. one of the current is made out of phase between the lines B. hysteresis C. shaded poles D. two windings displaced from each other

43. REE Board Exam October 1996 The following are types of AC motor starters except one A. reactance starter l B. wye-delta starter C. across the line starter D. capacitance starter

44. REE Board Exam April 1995 Motor starting device that will reduce the voltage impressed at motor’s terminals during starting periods. A. autotransformer B. primary resistor-type C. wye-delta starter D. all of these

45. EE Board Exam April 1994, April 1992 Basically all electric motors operate on the principle of repulsion or ______. A. induction B. magnetism C. resistance D. capacitance

46. EE Board Exam April 1994 The principle of operation of induction motor is based on A. Fleming’s right hand rule B. rotating magnetic field C. Faraday’s law D. Ohm’s law

47. EE Board Exam October 1993 A compensator is a device that is used with alternating current motors to ______. A. boost the supply voltage during starting periods B. compensate for low power factor when motor is not fully loaded C. reduce the supply voltage during starting periods D. compensate for voltage drop in the circuit

48. EE Board Exam April 1992 A single-phase motor provided with a squirrel cage winding on its rotor in addition to its regular winding is called A. split-phase induction motor B. repulsion induction motor C. universal motor D. repulsion-start induction motor

49. EE Board Exam April 1992 A test used to determine the equivalent resistance of an induction motor is A. no-load test B. short circuit test C. blocked rotor test D. polarity test

50. EE Board Exam April 1991 Rapid stopping of a motor by momentarily connecting the motor in reverse direction is called A. jogging B. inching C. plugging D. sequence operation