Q1 (a) A 3 phase induction motor operating at rated power can be represented by a balanced delta connected load (ZRY etc) of (3G7 + j10) 2 and is connected to a 3 phase, 4G65 V and 50 Hz supply.
Q1 (a) A 3 phase induction motor operating at rated power can be represented by a balanced delta connected load (ZRY etc) of (3G7 + j10) 2 and is connected to a 3 phase, 4G65 V and 50 Hz supply.
Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN:9781305632134
Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Chapter12: Power System Controls
Section: Chapter Questions
Problem 12.4P
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Transcribed Image Text:Q1 (a)
A 3 phase induction motor operating at rated power can be represented by a
balanced delta connected load (ZRY etc) of (3G7 + j10) N and is connected to
a 3 phase, 4G65 V and 50 Hz supply.
Calculate:
(i)
The three load phase currents (IRY, IYB and IBr).
(ii)
The three line currents (IR, ly and IB).
(iii)
The real power (W) in each phase of the load -
different methods to calculate this.
using 2
(iv)
The real power (W) supplied by each of the supply phases.
The total real power (W) from the supply if the induction
motor is star connected.
(v)
(b)
A local 3 phase distribution network operating from a 1G6 kV 60 Hz supply
has a star connected load with nominally balanced load impedances of
(1G¬0+j30) Q. In the event of a fault in any of the phases a fourth wire is
included between the star point of the load and the neutral point of the
supply.
Using the information above determine the following for a faulted red phase
load which results in the red phase load resistance and inductance values
being halved (e.g. (150 +j30 becomes 75 +j15):
(i)
Calculate the 3 lines currents (IR, Iy and IB).
(ii)
Draw a scaled phasor diagram indicating all phase and line
voltages, and the three line currents.
(iii)
Using the scaled phasor diagram or otherwise determine the
star-neutral current ISN and suggest the minimum wire diameter
to maintain a current density less than 2 A/mm?.
(c)
Calculate the total 3 phase supply power (W) for the faulted condition in (b)
using both the 3 Wattmeter and 2 Wattmeter methods. Comment on the
results.
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