rent. A 115 V dc generator delivers 120 A to a load. If the generator has an efficiency of 81 percent, calculate the mechanical power needed to drive it [hp].
rent. A 115 V dc generator delivers 120 A to a load. If the generator has an efficiency of 81 percent, calculate the mechanical power needed to drive it [hp].
College Physics
11th Edition
ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter1: Units, Trigonometry. And Vectors
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Question
Numbers 10 and 11
![EFFICIENCY AND ING OF ELECTRICAL MACHINES
133
Intermediate level
A dc motor connected to a 240 V line pro-
6.
duces a mechanical output of 160 hp.
Knowing that the losses are 12 kW, calculate
the input power and the line current.
A 115 V dc generator delivers 120 A to a
load. If the generator has an efficiency of
81 percent, calculate the mechanical
needed to drive it [hp].
power
11
Calculate the full-load current of a 250 hp,
s: 500 kg.
230 V dc motor having an efficiency of
92 percent.
A machine having class B insulation attains
a temperature of 208°C (by resistance) in a
torrid ambient temperature of 180°C.
a. What is the temperature rise?
b. Is the machine running too hot and, if so,
by how much?
12
ze as a 10 kW motor
ey develop the same
refore much more
s of equal power.
drives, it is often
1 motor with a gear
ed motor directly
13 The efficiency of a motor is always low
when it operates at 10 percent of its nominal
power rating. Explain.
14
Calculate the efficiency of the motor in Ex-
ample 2 when it delivers an output of 1 hp.
15 An electric motor driving a skip hoist with-
draws 1.5 metric tons of minerals from a
trench 20 m deep every 30 seconds. If the
hoist has an overall efficiency of 94 percent,
calculate the power output of the motor in
T.
Ow can they be
horsepower and in kilowatts.
16 Thermocouples are used to measure the in-
fa
of a machine
tomperature o
ternol h](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F585e4a80-646c-4418-ada9-cb992a2ce44b%2F809c00b0-cc2e-404d-86a7-43c67ff49a70%2Fxfxowaf.jpeg&w=3840&q=75)
Transcribed Image Text:EFFICIENCY AND ING OF ELECTRICAL MACHINES
133
Intermediate level
A dc motor connected to a 240 V line pro-
6.
duces a mechanical output of 160 hp.
Knowing that the losses are 12 kW, calculate
the input power and the line current.
A 115 V dc generator delivers 120 A to a
load. If the generator has an efficiency of
81 percent, calculate the mechanical
needed to drive it [hp].
power
11
Calculate the full-load current of a 250 hp,
s: 500 kg.
230 V dc motor having an efficiency of
92 percent.
A machine having class B insulation attains
a temperature of 208°C (by resistance) in a
torrid ambient temperature of 180°C.
a. What is the temperature rise?
b. Is the machine running too hot and, if so,
by how much?
12
ze as a 10 kW motor
ey develop the same
refore much more
s of equal power.
drives, it is often
1 motor with a gear
ed motor directly
13 The efficiency of a motor is always low
when it operates at 10 percent of its nominal
power rating. Explain.
14
Calculate the efficiency of the motor in Ex-
ample 2 when it delivers an output of 1 hp.
15 An electric motor driving a skip hoist with-
draws 1.5 metric tons of minerals from a
trench 20 m deep every 30 seconds. If the
hoist has an overall efficiency of 94 percent,
calculate the power output of the motor in
T.
Ow can they be
horsepower and in kilowatts.
16 Thermocouples are used to measure the in-
fa
of a machine
tomperature o
ternol h
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