A 4-pole, 60 hz, 3-phase induction motor has a blocked rotor reactance per phase that is...
A 4-pole, 60 hz, 3-phase induction motor has a blocked rotor reactance per phase that is four times the rotor resistance per phase. At what speed will the motor develop maximum torque?
1200 rpm
1500 rpm
1350 rpm
1620 rpm
What is the ratio of maximum to full load torque in a motor having slip of 4% at full load and 20% at maximum torque?
15
3
2.6
5.2
If a motor has a slip of 2% at rated voltage, determine the approximate value of the slip when developing the same torque at 10% above rated voltage (Esas Board Prob. April’ 95)
1.8%
1.75%
1.55%
1.65%
Homework Answers
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A 4-pole, 60 hz, 3-phase induction motor has a blocked rotor
reactance per phase that is...
A 3-phase, 460 V, 1740 rpm, 60 Hz, 4-pole wound-rotor induction motor has the following parameters...
A 3-phase, 460 V, 1740 rpm, 60 Hz, 4-pole wound-rotor induction motor has the following parameters per phase: R1 = 0.25 Ω, ' 2R = 0.2Ω, ' 1 2 X = X = 0.5Ω, 30 m X = Ω. The rotational losses are 1700 W. With the rotor terminals short-circuited, find: 1. at starting: • current when started direct on full voltage, • a torque 2. at full load: • slip • current • ratio of starting current to full-load...
A wound rotor, induction motor has a rotor resistance of 0.6 ohms per phase and a...
A wound rotor, induction motor has a rotor resistance of 0.6 ohms per phase and a rotor leakage reactance of 8 ohms . a) What is the operating speed (rpm) of this 2-pole induction motor fed from a 50 Hz supply if the slip is 5%? b) If maximum torque occurs when R2 = sX2, what is the slip at maximum torque? c) What resistance must be added to the rotor circuit to give maximum starting torque?
Problem Solving: 1. A 220V, 4-pole, 60Hz, 1-phase induction motor has an effective rotor resistance and...
Problem Solving: 1. A 220V, 4-pole, 60Hz, 1-phase induction motor has an effective rotor resistance and leakage reactance of 0.5 Ohms and 5 ohms respectively. It is running at a speed of 1,800 rpm. Determine: a. Frequencies of forward and backward rotor current components b. Relative magnitudes of forward and backward fluxes. Neglect magnetizing current and stator impedance. A 220-W, 2-pole, 115-V, 60-Hz single-phase induction motor delivers rated output at a slip 10%. The total copper loss at full load...
5 Marks) A 4-pole, 3 phase, 50 Hz, 230 V induction motor. Each phase of rotor winding b) has one-fourth the number of t...
5 Marks) A 4-pole, 3 phase, 50 Hz, 230 V induction motor. Each phase of rotor winding b) has one-fourth the number of turns of each stator. The full-load speed is 1,455 rpm. The rotor resistance is 0.3 Ω and rotor standstill reactance is 1.0 Ω per phase. The rotor and stator windings are similar. Stator losses are equal to 50 Watts. Friction and windage losses are equal to 30 W. Calculate ) Blocked rotor voltage per phase. 2 Marks)...
3) A four pole 75 HP 50 Hz induction motor with an efficiency of 93.4% has...
3) A four pole 75 HP 50 Hz induction motor with an efficiency of 93.4% has equivalent resistance and equivalent reactance per phase of 0.3000and 0.78 000OTHE blocked rotor voltage per phase is 175V. If the rotor is turning at 1425 rpm, determine synchronous speed, slip, rotor impedance, rotor current, total three phase apparent power crossing the air gap, its active and reactive components, rotor power factor, shaft speed, mechanical power developed and developed torque. (30 Points)
4.6. A 460-V, 75 kW, 4-pole, delta-connected, 60-Hz, three- phase induction motor has a full-load slip of 5 percent, an efficiency of 92 percent and a power-factor of 0.87 lagging at full-load. At st...
4.6. A 460-V, 75 kW, 4-pole, delta-connected, 60-Hz, three- phase induction motor has a full-load slip of 5 percent, an efficiency of 92 percent and a power-factor of 0.87 lagging at full-load. At start-up, the motor develops 1.9 times the full load developed torque but draws 7.5 times the rated current at the rated voltage. This motor is to be started with an auto- transformer reduced-voltage starter. Assume the stator resistance and the stator core loss to be negligible. Calculate...
A 3 phase, 4 pole, 60 Hz., AC Induction Motor has a rated Torque of 150...
A 3 phase, 4 pole, 60 Hz., AC Induction Motor has a rated Torque of 150 Nm. with the phase voltage of 254v. Its parameters are: R1 = 0.20 Ohms, R2’ = 0.32 Ohms and X = 0.50 Ohms. Find its approximate slip at the rated load and speed.
Question 2 [10 marks) A six pole, three phase induction motor, with a star connected stator...
Question 2 [10 marks) A six pole, three phase induction motor, with a star connected stator winding is energised from a 380V, 50Hz supply. The ratio of the stator to rotor turns is assumed 1.8 and a full load slip of 4%. If the respective per phase rotor resistance and standstill reactance are 0.120 and 0.8502, determine: a. Torque developed at full load b. The maximum torque and the speed at maximum torque
1. A six pole, 240V, 50 Hz three phase squirrel-cage induction motor has a no-load speed...
1. A six pole, 240V, 50 Hz three phase squirrel-cage induction motor has a no-load speed of 103 rad/s and a speed regulation of 5% at rated load. Find the amount of slip (in rpm) at full load for this motor. 2.. A 2 HP, 240 VAC, 60 Hz, capacitor-start motor is 75% efficient and draws 10 A at full load. What is this motor's power factor at rated load? 3. A wound rotor, 3 phase induction motor in Mr....
A 3 phase, 460V, 60Hz, 6-pole induction motor has the following equivalent circuit parameters per phase:...
A 3 phase, 460V, 60Hz, 6-pole induction motor has the following equivalent circuit parameters per phase: R1 = 0.2 ohms R2 = 0.28 ohms X1 = X2 = 1.055 ohms Xm = 33.9 ohms The no load losses, comprising friction, windage, and iron losses equal 26W. The motor is coupled to a load and connected to a 460V supply, and the rotor speed is found to be 1156 RPM. For this motor connected to a 460V supply calculate the following:...
Problem Solving: 1. A 220V, 4-pole, 60Hz, 1-phase induction motor has an effective rotor resistance and leakage reactance of 0.5 Ohms and 5 ohms respectively. It is running at a speed of 1,800 rpm. Determine: a. Frequencies of forward and backward rotor current components b. Relative magnitudes of forward and backward fluxes. Neglect magnetizing current and stator impedance. A 220-W, 2-pole, 115-V, 60-Hz single-phase induction motor delivers rated output at a slip 10%. The total copper loss at full load...
5 Marks) A 4-pole, 3 phase, 50 Hz, 230 V induction motor. Each phase of rotor winding b) has one-fourth the number of turns of each stator. The full-load speed is 1,455 rpm. The rotor resistance is 0.3 Ω and rotor standstill reactance is 1.0 Ω per phase. The rotor and stator windings are similar. Stator losses are equal to 50 Watts. Friction and windage losses are equal to 30 W. Calculate ) Blocked rotor voltage per phase. 2 Marks)...
3) A four pole 75 HP 50 Hz induction motor with an efficiency of 93.4% has equivalent resistance and equivalent reactance per phase of 0.3000and 0.78 000OTHE blocked rotor voltage per phase is 175V. If the rotor is turning at 1425 rpm, determine synchronous speed, slip, rotor impedance, rotor current, total three phase apparent power crossing the air gap, its active and reactive components, rotor power factor, shaft speed, mechanical power developed and developed torque. (30 Points)
4.6. A 460-V, 75 kW, 4-pole, delta-connected, 60-Hz, three- phase induction motor has a full-load slip of 5 percent, an efficiency of 92 percent and a power-factor of 0.87 lagging at full-load. At start-up, the motor develops 1.9 times the full load developed torque but draws 7.5 times the rated current at the rated voltage. This motor is to be started with an auto- transformer reduced-voltage starter. Assume the stator resistance and the stator core loss to be negligible. Calculate...
Question 2 [10 marks) A six pole, three phase induction motor, with a star connected stator winding is energised from a 380V, 50Hz supply. The ratio of the stator to rotor turns is assumed 1.8 and a full load slip of 4%. If the respective per phase rotor resistance and standstill reactance are 0.120 and 0.8502, determine: a. Torque developed at full load b. The maximum torque and the speed at maximum torque
1. A six pole, 240V, 50 Hz three phase squirrel-cage induction motor has a no-load speed of 103 rad/s and a speed regulation of 5% at rated load. Find the amount of slip (in rpm) at full load for this motor. 2.. A 2 HP, 240 VAC, 60 Hz, capacitor-start motor is 75% efficient and draws 10 A at full load. What is this motor's power factor at rated load? 3. A wound rotor, 3 phase induction motor in Mr....
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