Delmar's Standard Textbook Of Electricity
7th Edition
ISBN: 9781337900348
Author: Stephen L. Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 32, Problem 1PA
You are working as a plant electrician. It is your job to install a 300-hp three-phase squirrel-cage induction motor. The supply voltage is 480 V. The power company has determined that the maximum amount of starting current that can be permitted by any motor in the plant is 3000 A. The motor nameplate is as follows:
| Phase: 3 | FLA: 352 |
| Volts: 480 | RPM: 1755 |
| Frame: XXX | Code: L |
Will it be possible to start this motor across the line, or will it be necessary to use a reduced-voltage starter to reduce starting current?
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What are the following statements are true for a three-phase induction motor?
I. Three-phase induction motor stator winding is fed from a three-phase supply
II. Stator carries a three-phase winding
III. Rotor carries a short circuited winding
a.
I and II only
b.
I,II and III
c.
II and III
d.
I only
Electrical Engineering
DRAW THE FOLLOWING DIAGRAMS OF INDUCTION MOTOR AND LABEL THEM
( MAKE SURE THAT THE DIAGRAMS SHOULD BE NEAT AND SHOULD BE HAND DRAWN WITH BLUE BALL PEN ON BLANK PAGES )
1) 3-phase 2-pole motor
2) 3-phase 4 pole motor
3) 3-phase 6 pole motor
4) 3-phase 8 pole moto
A four-pole induction motor drives a load at 2478
rpm. This is to be accomplished by using an
electronic converter to convert a 400-V dc source
into a set of three-phase ac voltages.
Part A
Find the frequency required for the ac voltages assuming that the slip is 4 percent.
The load requires 2 hp.
Express your answer to three significant figures and include the appropriate
units.
f=
Submit
Part B
Value
I =
HA
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If the dc-to-ac converter has a power efficiency of 90 percent and the motor has a
power efficiency of 80 percent, estimate the current taken from the dc source.
Express your answer to three significant figures and include the appropriate
units.
HÅ
Value
Units
Request Answer
?
Units
?
Chapter 32 Solutions
Delmar's Standard Textbook Of Electricity
Ch. 32 - What are the three basic types of three-phase...Ch. 32 - What is the principle of operation of all...Ch. 32 - What is synchronous speed?Ch. 32 - What two factors determine synchronous speed?Ch. 32 - Prob. 5RQCh. 32 - Name three factors that determine the torque...Ch. 32 - Is the synchronous motor an induction motor?Ch. 32 - Prob. 8RQCh. 32 - Why must a synchronous motor never be started when...Ch. 32 - Name three characteristics that make the...
Ch. 32 - What is the function of the field-discharge...Ch. 32 - Why can an induction motor never operate at...Ch. 32 - A squirrel-cage induction motor is operating at...Ch. 32 - Prob. 14RQCh. 32 - Prob. 15RQCh. 32 - Prob. 16RQCh. 32 - Name three factors that determine the amount of...Ch. 32 - Why will the rotor of a wound-rotor motor not turn...Ch. 32 - Why is the starting torque per A of starting...Ch. 32 - When is a synchronous motor a synchronous...Ch. 32 - What determines when a synchronous motor is at...Ch. 32 - How can a synchronous motor be made to have a...Ch. 32 - Is the excitation current of a synchronous motor...Ch. 32 - Prob. 24RQCh. 32 - Prob. 25RQCh. 32 - You are working as a plant electrician. It is your...Ch. 32 - You have been given the task of connecting a...Ch. 32 - You are an electrician working in an industrial...
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- A 400V, 60HZ, 6-pole wye connected , 30 induction motor draws 75KW with a line current of 100A. The core loss is 2KW, Friction and Windage loss is 1.2KW. The stator resistance between two terminals is 0.352. What is the efficiency if the motor runs at a slip of 2.5%?arrow_forwardYou are working as a plant electrician. It is your job to install a 300-hp three phase squirrel-cage induction motor. The supply voltage is 480 V. The power company has determined that the maximum amount of starting current that can be permitted by any motor in the plant is 3000 A. The motor nameplate is as follows: Will it be possible to start this motor across the line, or will it be necessary to use a reduced-voltage starter to reduce starting current? Phase: 3 FLA: 352 Volts: 480 RPM: 1755 Frame: Code: Larrow_forward2.a) 50 hz induction motor has 2 poles and run at 2,850 rpm. What is the percent slip?arrow_forward
- A 150 HP, 3-phase, 6 pole, 460 V, 60 Hz induction motor draws 195 A line current at full load speed of 1170 rpm and 0.85 pf. Solve for the percent slip at full load. (a). 2.5% (b). 3.0% (c). 2.8% (d). 2.0%arrow_forwardCalculate the rotor reactance per phase of an 8 pole, 50Hz, 3Ø induction motor which develops a maximum torque at a speed of 660rpm. The resistance per phase of the rotor is 0.5Ωarrow_forward5. A 220 V dc shunt motor takes 4 A at no-load and runs at 700 rpm. Ra = 0.60 ohm and Rf = 110 ohms. What is the speed of the motor when the motor input is 8800 W?arrow_forward
- A 110 V, 60 Hz, 6 — pole single phase induction motor 1/3 hp has the following equivalent circuit impedances: RI = 1.52 ohm, R2 = 3.13 ohm and xl =2.10 ohm, x2 =1.56 ohm. Xm=58.2 ohm, The friction, windage and stry losses =16W, the core loss = 35 W. For a slip of 0.05, calculate (a) input current, (b) power factor, (c) developed power, (d) output power, (e) speed (f) in put power (g) air gab power (h) T ind (i) T load (j) efficiency.arrow_forward١٣arrow_forwardInduction motorarrow_forward
- 7- Iron loss in the rotor of a 3-phase induction motor is negligible due to (a) Very low frequency of emf induced in the rotor (c) Very low flux density in rotor parts 8- The starting current of a 3-phase induction motor is about (a) Half (c) 5 to 7 times (b) Twice (d) 8 to 10 times 9- During plugging of an induction motor (a) Phase sequence is reversed (b) A de source is connected to stator (e) One phase is open circaited (d) Power is ied back to mains 10- Direct online (D.O.L.) starter is used for induction motors (a)Less than 5 h.p. (b) Less than 10 h.p. (c) Greater than 10 h.p. (d) For any capacity (b) Very low emf induced in the rotor (d) Constant magnitude of flux linking the rotor core of its full load rated currentarrow_forwardThe power input to the rotor of a 440 V, 60-Hz, three-phase, 6 pole induction motor is 60 kW. The rotor makes 108 complete cycles per minute. Find the rotor resistance per phase if the rotor current is 50 A. Answer: 0.24 ohmsarrow_forwardWhat is the freq. of a 10-pole alternator when running at 360 rpm? (b) At what speeds should a 6-pole alternator run to yield 25, 30, 50, and 60 cycles per second?arrow_forward
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