EBK ELECTRIC MOTOR CONTROL
10th Edition
ISBN: 9780100784598
Author: Herman
Publisher: YUZU
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Textbook Question
Chapter 26, Problem 5SQ
What is meant by the low or poor starting economy of a primary resistor starter?
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L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no
Find the number of resistance sections and the resistance of each section of a starter for a 3.7 kW, 230 V, dC series motor from the following data:-Starting current varies from 1 to 1.5 times full load current Full load efficiency = 85%
Motor circuit resistance 1.4 ohm
Assume flux increases by 10% as the current rises from 1 to 1.5 times the rated full load current.
Q2 A DC shunt motor is connected to a 220 V supply. Figurel below shows the time/current
characteristics with a resistance starter. If armature resistance is 0.12 0,
a) What is the maximum current that is flowing in the armature at the instant of starting?
b) What is the minimum current in the armature?
c) How many sections does this starter resistance have? Show your work.
d) Calculate the required starter resistance required to limit the current to the maximum
value.
270
162
13
t.
Chapter 26 Solutions
EBK ELECTRIC MOTOR CONTROL
Ch. 26 - What is the purpose of inserting resistance in the...Ch. 26 - Why is the power not interrupted when the motor...Ch. 26 - If the starter is to function properly and a...Ch. 26 - How may additional steps of acceleration be added?Ch. 26 - What is meant by the low or poor starting economy...Ch. 26 - Prob. 6SQ
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