GATE EE 2014 Set 2 — Question 46
Go beyond PYQs with Success TrackerAI-powered personalised practice and doubt support. Unlimited practice on eligible plans; AI usage limits apply.NAT+2 / -0MediumGenerator & Motor CharacteristicsDC MachinesElectrical Machines
Electrical Machines → DC Machines → Generator & Motor Characteristics
Last updated
Question
A 250 V dc shunt machine has armature circuit resistance of 0.6 and field circuit resistance of 125 . The machine is connected to 250 V supply mains. The motor is operated as a generator and then as a motor separately. The line current of the machine in both the cases is 50 A. The ratio of the speed as a generator to the speed as a motor is ____________.
Correct answer
1.22 to 1.32
Solution
Given:
Supply Voltage, V
Armature resistance,
Field resistance,
Line current, A (for both cases)Step 1: Calculate the field current ():
AStep 2: Calculate the generated EMF () when operating as a generator:
In a generator, A
VStep 3: Calculate the back EMF () when operating as a motor:
In a motor, A
VStep 4: Calculate the ratio of speeds:
For a dc shunt machine, flux is constant since the supply voltage is the same.
We know that , so .
The ratio of the speed as a generator to the speed as a motor is approximately 1.27.
Supply Voltage, V
Armature resistance,
Field resistance,
Line current, A (for both cases)Step 1: Calculate the field current ():
AStep 2: Calculate the generated EMF () when operating as a generator:
In a generator, A
VStep 3: Calculate the back EMF () when operating as a motor:
In a motor, A
VStep 4: Calculate the ratio of speeds:
For a dc shunt machine, flux is constant since the supply voltage is the same.
We know that , so .
The ratio of the speed as a generator to the speed as a motor is approximately 1.27.
Continue learning with Success Tracker
A step still unclear? Work through it with support
Use Success Tracker to ask about the reasoning, then try another GATE EE question to check your understanding.
AI-powered practice· Unlimited practice on eligible plans
- PYQs with solutions
- Attempt available previous-year questions, then compare your reasoning with the worked solution. Coverage varies by stream.
- Practice that adapts
- Choose a topic, work on weaker areas and bookmark questions to revisit. Your attempts feed your progress tracking.
- AI doubt support
- Ask follow-up questions about a step or concept while practising, instead of stopping at the final answer.
Unlimited practice is available on eligible plans. Free practice and AI usage have limits; check the current plan allowances before choosing.
This page stays readable without an account. AI responses can be wrong; check them against the solution and source material.
More questions on DC Machines
2026 Set 1 Q17A 15 kVA, 1100 V/220 V, single-phase two-winding transformer is configured as a 1.32 kV/1.1 kV…2026 Set 1 Q20A certain application requires power at a frequency of , while the available grid…2026 Set 1 Q21Which one of the following options is correct regarding the typical double-squirrel-cage structure…2026 Set 1 Q22The figure shows the single-line diagram of a synchronous generator delivering …2026 Set 1 Q31A 220V/12V single-phase transformer is designed for use in India and rated 100 VA at 50 Hz. Later,…