Explore topic-wise MCQs in Electrical Machines.

This section includes 12 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

The rating of the alternator is decided by _________

A. losses
B. voltage
C. armature current
D. temperature
Answer» B. voltage
Discussion
2.

Alternator compounding characteristic is obtained by _________

A. keeping Vt constant
B. keeping Ef constant
C. keeping Ia constant
D. varying Vt
Answer» B. keeping Ef constant
Discussion
3.

Mark the plot for terminal voltage vs armature current for the alternator.

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d.png"><img alt="The plot for terminal voltage vs armature current for the alternator - option a" class="alignnone size-medium wp-image-124462" height="238" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d-300x238.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d-300x238.png 300w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d-100x80.png 100w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d.png 352w" width="300"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b.png"><img alt="The plot for terminal voltage vs armature current for the alternator - option b" class="alignnone size-medium wp-image-124463" height="243" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-300x243.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-300x243.png 300w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-100x80.png 100w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b.png 346w" width="300"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11c.png"><img alt="The plot for terminal voltage vs armature current for the alternator - option c" class="alignnone size-medium wp-image-124464" height="245" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11c-300x245.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11c-300x245.png 300w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11c.png 329w" width="300"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d1.png"><img alt="The plot for terminal voltage vs armature current for the alternator - option d" class="alignnone size-medium wp-image-124465" height="238" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d1-300x238.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d1-300x238.png 300w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d1-100x80.png 100w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11d1.png 352w" width="300"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b.png"><img alt="The plot for terminal voltage vs armature current for the alternator - option b" class="alignnone size-medium wp-image-124463" height="243" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-300x243.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-300x243.png 300w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b-100x80.png 100w, https://www.sanfoundry.com/wp-content/uploads/2016/05/op-11b.png 346w" width="300"/></a>
Discussion
4.

If the machine was operating at upf, then the new excitation voltage will be _________

A. greater than 1 pu
B. less than 1 pu
C. 1 pu
D. zero
Answer» B. less than 1 pu
Discussion
5.

With the alternator running at rated terminal voltage Vt, at rated current Ia = 1 per unit. What happens if load current is reduced to zero, if it was operating at leading power factor?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8a.png"><img alt="Load current is reduced to zero if operating at leading power factor - option a" class="alignnone size-full wp-image-124456" height="235" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8a.png" width="154"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8b.png"><img alt="Load current is reduced to zero if operating at leading power factor - option b" class="alignnone size-full wp-image-124457" height="186" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8b.png" width="170"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8c.png"><img alt="Load current is reduced to zero if operating at leading power factor - option c" class="alignnone size-full wp-image-124458" height="166" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8c.png" width="138"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8d.png"><img alt="Load current is reduced to zero if operating at leading power factor - option d" class="alignnone size-full wp-image-124459" height="215" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8d.png" width="146"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8b.png"><img alt="Load current is reduced to zero if operating at leading power factor - option b" class="alignnone size-full wp-image-124457" height="186" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-8b.png" width="170"/></a>
Discussion
6.

With the alternator running at rated terminal voltage Vt, at rated current Ia = 1 per unit. What happens if load current is reduced to zero, if it was operating at lagging power factor?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7a.png"><img alt="The alternator at rated terminal voltage Vt at rated current Ia = 1 per unit - option a" class="alignnone size-full wp-image-124451" height="232" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7a.png" width="140"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7b.png"><img alt="The alternator at rated terminal voltage Vt at rated current Ia = 1 per unit - option b" class="alignnone size-full wp-image-124452" height="191" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7b.png" width="124"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7c.png"><img alt="The alternator at rated terminal voltage Vt at rated current Ia = 1 per unit - option c" class="alignnone size-full wp-image-124453" height="247" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7c.png" width="177"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7d.png"><img alt="The alternator at rated terminal voltage Vt at rated current Ia = 1 per unit - option d" class="alignnone size-full wp-image-124454" height="189" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7d.png" width="162"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7b.png"><img alt="The alternator at rated terminal voltage Vt at rated current Ia = 1 per unit - option b" class="alignnone size-full wp-image-124452" height="191" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-7b.png" width="124"/></a>
Discussion
7.

A 315V, 3-phase 400 MVA alternator is running at zero power factor leading at constant excitations. The most appropriate representaion in space domian is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6a.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at zero power factor leading - option a" class="alignnone size-full wp-image-124448" height="167" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6a.png" width="87"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at zero power factor leading - option b" class="alignnone size-full wp-image-124449" height="233" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6b.png" width="144"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6c.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at zero power factor leading - option c" class="alignnone size-full wp-image-124450" height="185" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6c.png" width="129"/></a>
D. none of the mentioned
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at zero power factor leading - option b" class="alignnone size-full wp-image-124449" height="233" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-6b.png" width="144"/></a>
Discussion
8.

A 315V, 3-phase 400 MVA alternator is running at zero power factor lagging at constant excitations. The most appropriate representation in space domain is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5a.png"><img alt="A 315V, 3-phase 400 MVA alternator is at zero power factor lagging - option a" class="alignnone size-full wp-image-124441" height="159" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5a.png" width="137"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5b1.png"><img alt="A 315V, 3-phase 400 MVA alternator is at zero power factor lagging - option b" class="alignnone size-full wp-image-124444" height="159" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5b1.png" width="117"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5c.png"><img alt="A 315V, 3-phase 400 MVA alternator is at zero power factor lagging - option c" class="alignnone size-full wp-image-124443" height="231" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5c.png" width="181"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5d.png"><img alt="A 315V, 3-phase 400 MVA alternator is at zero power factor lagging - option d" class="alignnone size-full wp-image-124445" height="231" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5d.png" width="162"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5b1.png"><img alt="A 315V, 3-phase 400 MVA alternator is at zero power factor lagging - option b" class="alignnone size-full wp-image-124444" height="159" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-5b1.png" width="117"/></a>
Discussion
9.

A 315V, 3-phase 400 MVA alternator is running at unity power factor at constant excitations. The most appropriate representation in space domain is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4a.png"><img alt="A 315V, 3-phase 400 MVA alternator at unity power factor at constant excitation - option a" class="alignnone size-full wp-image-124437" height="188" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4a.png" width="151"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4b.png"><img alt="A 315V, 3-phase 400 MVA alternator at unity power factor at constant excitation - option b" class="alignnone size-full wp-image-124438" height="261" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4b.png" width="157"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4c.png"><img alt="A 315V, 3-phase 400 MVA alternator at unity power factor at constant excitation - option c" class="alignnone size-full wp-image-124439" height="235" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4c.png" width="178"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4d.png"><img alt="A 315V, 3-phase 400 MVA alternator at unity power factor at constant excitation - option d" class="alignnone size-full wp-image-124440" height="152" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4d.png" width="84"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4b.png"><img alt="A 315V, 3-phase 400 MVA alternator at unity power factor at constant excitation - option b" class="alignnone size-full wp-image-124438" height="261" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/op-4b.png" width="157"/></a>
Discussion
10.

A 315V, 3-phase 400 MVA alternator is running at leading power factor load at constant excitations. The most appropriate representation in space domain is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33a.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at leading power factor load - option a" class="alignnone size-full wp-image-124432" height="236" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33a.png" width="172"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at leading power factor load - option b" class="alignnone size-full wp-image-124433" height="156" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33b.png" width="96"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3c.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at leading power factor load - option c" class="alignnone size-full wp-image-124434" height="202" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3c.png" width="143"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3d.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at leading power factor load - option d" class="alignnone size-full wp-image-124436" height="261" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3d.png" width="168"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at leading power factor load - option b" class="alignnone size-full wp-image-124433" height="156" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-33b.png" width="96"/></a>
Discussion
11.

A 315V, 3-phase 400 MVA alternator is running at lagging power factor at constant excitations. The most appropriate representation in space domain is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3a.png"><img alt="A 315V, 3-phase 400 MVA alternator is at lagging power factor - option a" class="alignnone size-full wp-image-124427" height="261" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3a.png" width="157"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3b.png"><img alt="A 315V, 3-phase 400 MVA alternator is at lagging power factor - option b" class="alignnone size-full wp-image-124429" height="224" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3b.png" width="166"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-2c.png"><img alt="A 315V, 3-phase 400 MVA alternator is at lagging power factor - option c" class="alignnone size-full wp-image-124430" height="168" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-2c.png" width="94"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-2d.png"><img alt="A 315V, 3-phase 400 MVA alternator is at lagging power factor - option d" class="alignnone size-full wp-image-124431" height="186" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-2d.png" width="133"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3b.png"><img alt="A 315V, 3-phase 400 MVA alternator is at lagging power factor - option b" class="alignnone size-full wp-image-124429" height="224" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-3b.png" width="166"/></a>
Discussion
12.

A 315V, 3-phase 400 MVA alternator is running at no load at constant excitations. The most appropriate representation in space domain is?

A. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1a.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at no load at constant excitation - option a" class="alignnone size-full wp-image-124421" height="282" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1a.png" width="90"/></a>
B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at no load at constant excitation - option b" class="alignnone size-full wp-image-124422" height="253" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1b.png" width="120"/></a>
C. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1c.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at no load at constant excitation - option c" class="alignnone size-full wp-image-124423" height="269" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1c.png" width="83"/></a>
D. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1d.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at no load at constant excitation - option d" class="alignnone size-full wp-image-124424" height="258" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1d.png" width="50"/></a>
Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1b.png"><img alt="A 315V, 3-phase 400 MVA alternator is running at no load at constant excitation - option b" class="alignnone size-full wp-image-124422" height="253" src="https://www.sanfoundry.com/wp-content/uploads/2016/05/operating-1b.png" width="120"/></a>
Discussion