Q5. (A) Select the correct answer for the alternatives given1-In transformer, the load current at maximum efficiency is equal to rated load current multipliedbya)PeuPaPruPi2- When a series de motor is operated without a load, which of the following conditions occur?b) The voltage requirement increasesd) The armature speeds out of controla) The armature draws excessive currentc) The armature will not turnP₁d)Peu3- A 220V shunt motor develops a torque of216 N.m at an armature current of 40 A. The torquedeveloped when the armature current is 20 Ab)108 N.mc) 864 N.ma) 432 N.md) 54 N.m4-A single phase transformer has maximum efficiency at 75% of full load. Its copper loss at fullload should bea) equal to core loss, b) less than core loss. c) more than core loss, d) equal to 75% of core loss5- The efficiency of a transformer is 98% at full-load with 0.8 lagging power factor, what will bethe efficiency when supplies full-load with 0.8 leading power factor?c) more than 98 %, d) none of the abovea) less than 98%, b) 98%,6-During short circuit test of a transformera) primary is supplied rated voltage, b) primary is supplied full load current at rated voltagec) primary is supplied full load current with small voltage, d) primary is supplied rated kVA7-A 500kVA transformer has iron loss of 500W and copper losses of 2000W at full load. what isthe kVA rating should the transformer operates to achieve maximum efficiency?a)250KVA$) 500KVA,1000KVA125KVA(B)- Find the back, front and commutation pitch of 4-poles, 17 slots wave connected DC machine,if the selected developed windings diagram is duplex progressive.

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Q5. (A) Select the correct answer for the alternatives given 1-In transformer, the load current at maximum efficiency is equal to rated load current multiplied Pcu c) P₁ P₁ d) by Pcu Pcu Peu ceries de motor is operated without a load whil

Q5. (A) Select the correct answer for the alternatives given 1-In transformer, the load current at maximum efficiency is equal to rated load current multiplied Pcu c) P₁ P₁ d) by Pcu Pcu Peu ceries de motor is operated without a load whil

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

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.28MCQ

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Concept explainers

Synchronous Motor

The synchronous motor is an AC electric type motor where at a steady-state the shaft rotation is synchronized with the supply current variable-frequency. To an integral number of AC cycles, the rotation period is exactly equal. The stator of the motor in the synchronous motor contains multi-phase AC electromagnets due to which a magnetic field is created that rotates in time with the oscillation of the line current. The rotor contains a permanent magnet and the rotor rotates in synchronization with the stator field at the same rate and provides the second synchronized magnetic field which is rotating in nature as a result. When the synchronous motor is supplied with independently excited multi-phase AC electromagnets on both the rotor and the stator, it is termed as a doubly-fed machine. The most widely used AC-type motors are the synchronous AC motor and the induction AC motors.

Question

100%

Q5. (A) Select the correct answer for the alternatives given
1-In transformer, the load current at maximum efficiency is equal to rated load current multiplied
by
a)
Peu
Pa
Pru
Pi
2- When a series de motor is operated without a load, which of the following conditions occur?
b) The voltage requirement increases
d) The armature speeds out of control
a) The armature draws excessive current
c) The armature will not turn
P₁
d)
Peu
3- A 220V shunt motor develops a torque of216 N.m at an armature current of 40 A. The torque
developed when the armature current is 20 A
b)108 N.m
c) 864 N.m
a) 432 N.m
d) 54 N.m
4-A single phase transformer has maximum efficiency at 75% of full load. Its copper loss at full
load should be
a) equal to core loss, b) less than core loss. c) more than core loss, d) equal to 75% of core loss
5- The efficiency of a transformer is 98% at full-load with 0.8 lagging power factor, what will be
the efficiency when supplies full-load with 0.8 leading power factor?
c) more than 98 %, d) none of the above
a) less than 98%, b) 98%,
6-During short circuit test of a transformer
a) primary is supplied rated voltage, b) primary is supplied full load current at rated voltage
c) primary is supplied full load current with small voltage, d) primary is supplied rated kVA
7-A 500kVA transformer has iron loss of 500W and copper losses of 2000W at full load. what is
the kVA rating should the transformer operates to achieve maximum efficiency?
a)250KVA
$) 500KVA,
1000KVA
125KVA
(B)- Find the back, front and commutation pitch of 4-poles, 17 slots wave connected DC machine,
if the selected developed windings diagram is duplex progressive.

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