Answered: What is the full-load current of a…

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter30: Dc Motors

Section: Chapter Questions

Problem 3RQ

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Similar questions

If the power measured per phase is increasing, what will happen to the speed of the three phase induction motor? a. Decrease b. Equal c. Increase d. Zero
The rotor of the 4-pole three-phase squirrel cage induction motor has been replaced with the rotor of the three-phase 4-pole rotor wound induction motor. When the motor is fed with normal supply, the machine will a) Does not work b) Runs at a very slow pace c) Runs at slightly lower speed than normal speed d) Runs at a slightly higher speed than normal speed e) none
2. How many poles does a synchronous motor have if it operates at 200 rpm when connected to a 60-cycle source?
A three-phase, 60-Hz induction motor runs at 890 r/min at no load and at 840 r/min at full load. (a) How many poles does this motor have? (b) What is the slip at rated load? (c) What is the speed at one-quarter of the rated load? (d) What is the rotor’s electrical frequency at one-quarter of the rated load?
2. A synchronous motor is running with a certain load, how you will ascertain whether it is running at lagging power factor or a leading power factor without the use p.f. meter?
What is the reason why a synchronous motor can be found running at no load?
A 125-hp, 480-V, 50-Hz, 6-pole, Y-connected induction motor has the per-phase equivalent circuit parameters as follows: Nominal code Locked rotor, letter kVA/hp R = 0.15 2 R2 = 0.10 2 X1 = 0.360 X2 = 0.36 2 C 3.55 – 4.00 =8.362 D 4.00 – 4.50 E 4.50 – 5.00 F 5.00 – 5.60 The core-losses are 1.7 5.60 – 6.30 kW, mechanical losses are 1.8 kW, and stray losses are 50 W. a) b) Calculate the speed at the pullout torque in rpm, the pullout torque, and the starting torque using exact Thevenin parameters. c) Find the starting code letter assigned to this motor.
A 208-V, 50-Hz, 12-pole, Y-connected, three-phase induction motor has a stator impedance of 0.1 + j0.3 W phase and a rotor impedance of 0.06 + j0.8 R/phase at standstill. The core-loss resistance is 150 R/phase, and the magnetization reactance is 750 W phase. The friction and windage loss is 2 kW. When the motor operates at its full-load slip of 5%, determine (a) the power input, (b) the stator copper loss, (c) the rotor copper loss, (d) the air-gap power, (e) the power developed, (f) the power output, (g) the effi- ciency, (h) the shaft torque, and (i) the horsepower rating of the motor.
If a 60-Hz synchronous motor is to be operated at 50 Hz, will its synchronous reactance be the same as at 60 Hz, or will it change? Justify your answer.
A 230-V, 50-Hz, 4-pole, class-A, single-phase induction motor has the following parameters at an operating temperature 63°C: = 2.51 ohms, r = 7,81 ohm, X 150.88 ohm, X= 4.62 ohm, X =4.62 ohms Determine stator main winding current and power factor when the motor is running at a slip of 0.05 at the specified temperature of 63°C. [3.74 248.24", 0.666] (AMIE See. B Elect. Machines (E-B) Summer 1991)
A 6-pole, 230-V, 60-Hz, Y-connected, three-phase induction motor has the following parameters on per-phase basis: R1=0.5 N, R2=0.25 N, X1=0.75 N, X2=0.5 , Xm=100 Q and R=500 N. The friction and windage loss is 150W. The rated slip is 2.5%. Determine: a) Rated speed b) Stator current c) Power factor d) Pcony and Pout e) Tind and tiload f) Efficiency
A 125-hp, 480-V, 50-Hz, 6-pole, Y-connected induction motor has the per-phase equivalent circuit parameters as follows: Nominal code Locked rotor, letter kVA/hp R = 0.15 Q R2 = 0.10 2 X1 = 0.362 X2 = 0.36 2 C 3.55 – 4.00 XM =8-362 D 4.00 – 4.50 E 4.50 – 5.00 F 5.00 – 5.60 The core-losses are 1.7 G 5.60 – 6.30 kW, mechanical losses are 1.8 kW, and stray losses are 500 W. a) For a slip of 4% find the line current, the rotor copper losses, the load torque, and the efficiency of the motor under the given conditions.

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What is the full-load current of a 230-volt, 3-phase, 125-horsepower synchronous motor when it is operated at an 80% power factor?