How is gain of an ideal op-amp determined in common configurations?

In ideal op-amp analysis, the closed-loop gain is determined by the feedback network (resistor values) rather than the op-amp's infinite open-loop gain.

What are the core materials CRGO vs hot-rolled steel in transformers?

CRGO cores support higher flux density with lower losses compared to hot-rolled steel; higher flux capability can reduce material and/or improve efficiency, depending on design.

What does flux density indicate in transformer cores?

Flux density indicates the magnetic flux per unit area; exceeding material limits causes saturation and excessive core losses.

What are typical values of maximum flux density for CRGO and conventional steel cores?

CRGO cores typically handle higher flux density (e.g., up to around 1.6 T or more depending on grade) with lower losses than hot-rolled steel; conventional cores saturate earlier (around 1.2 T for some steels).

What is the purpose of the transformer path length and μ0 in flux calculations?

Path length and μ0 are used in magnetic circuit calculations to estimate magnetizing force, flux and voltage ratings, ensuring the core does not saturate under given operating conditions.

Electrical Eng Paper-II 2017- UPSC ESE

Name: Electrical Eng Paper-II 2017- UPSC ESE
Creator: Engineering Services Examination
Keywords: Starting Torque, DOL Starting, Stator Resistance, Blocked Rotor, 3-Phase Transmission Line, Nominal-T, Sending End Voltage, Efficiency, Regulation, Ripple Factor, Form Factor, Utilization Factor, Unit Step Response, Open-Loop Poles, Static Error Constants

Central Government Jobs Engineer 2017

Year 2017
Conducted By Engineering Services Examination
Questions 8
Maximum Marks 300
Duration Three Hours Maximum Marks: 300
Languages English

Exam Details

Detail	Information
Examination	Electrical Engineering Paper-II
Year	2017
Conducting Body	Engineering Services Examination
Paper	Electrical Engineering Paper-II
Subject	Electrical Engineering
Duration	Three Hours Maximum Marks: 300
Maximum Marks	300
Number of Questions	8
Question Type	Mixed (section a & b; descriptive + potentially mcq)

This document presents Electrical Engineering Paper-II from the 2017 Engineering Services Examination. Page 1 outlines the exam structure: eight questions total, candidates must attempt five, with questions 1 and 5 compulsory, across two sections. Page 2 contains Section-A problems including numerical subparts on induction motor starting torque, nominal-T transmission-line representations, rectifier performance, unit-step response analysis, and an ideal op-amp circuit. It also includes a transformer-core problem comparing hot-rolled steel with CRGO core. The repair OCR clarifies line breaks and separates merged stems, preserving sub-parts (a)-(e) for each main question. The content covers motor starting, transmission-line calculations, rectifier metrics, control-system dynamics, op-amp analysis, and transformer design implications, forming a comprehensive practice set for ESE Electrical Engineering aspirants.

Major Topics Covered

Induction Motors
Direct On Line Starting
Stator Resistance
Blocked Rotor
Transformer Core Materials
CRGO Core
Flux Density
Mean Magnetic Path
Magnetic Terms
Nominal-T Representation
Transmission Line Parameters
R, L, C parameters
Power Factor
Rectifiers
Ripple Factor
Form Factor
Utilization Factor
Unit Step Response
Control Systems
Open-Loop Poles

Why This Paper is Important

Useful for Electrical Engineering Paper-II preparation
Helps understand the latest exam pattern
Useful for practice and self-assessment
Covers frequently asked General Studies topics
Helpful for analysing question trends

Related Resources

Instructions

There are EIGHT questions divided in two Sections.
Candidate has to attempt FIVE questions in all.
Question Nos. 1 and 5 are compulsory and out of the remaining, THREE are to be attempted choosing at least ONE question from each Section.
The number of marks carried by a question/part is indicated against it.
Attempts of questions shall be counted in sequential order.
Unless struck off, attempt of a question shall be counted even if attempted partly.
Any page or portion of the page left blank in the QCA Booklet must be clearly struck off.
Assume suitable data, if considered necessary and indicate the same clearly.
Unless otherwise mentioned, symbols and notations carry their usual standard meanings.
Answers must be written in ENGLISH only.

Questions (page 2)

Q1. 1.

() (a) is excited by 90 V with blocked rotor. The machine consumes 1350 watts and draws 35 A from a.c. mains. The d.c. resistance of stator winding per phase is 0.6 Ω. Assuming effective a.c. resistance per phase to be 1.2 times the d.c. value, compute the starting torque for direct on line starting. Assume x2

() (b) The per phase parameters of 50 Hz, 100 km long, 3-phase transmission line are R = 10 Ω, L = 111.7 mH, C = 0.9954 μF. The transmission line delivers 20 MW at a power factor of 0.8 lagging and 66 kV to a balanced load. Calculate the sending end voltage, efficiency and regulation using nominal-T representation.

() (c) Determine the ripple factor, form factor and utilization factor for a single-phase
(c) diode bridge rectifier supplying a purely resistive load.

() (d) The unit step response of a unity feedback system is C(t) = 1 + e^{-4t} - 2e^{-2t}. Determine- the type and order of the system; the static error constants of the system; the open-loop poles of the system.

() (e) Find the gain vo/vi for the ideal OP-AMP shown in the figure below :

Q2. 2.

() (a) 80 kg of copper) in primary and secondary windings, is wound over hot-rolled steel core μ_r = 6000) of uniform cross-sectional area of 80 cm² weighing 100 kg. What will be the maximum primary voltage at 50 Hz that can be applied to primary winding which does not force the flux in core to exceed 1.2T? What is the corresponding exciting current? If the core of this transformer is replaced by CRGO with maximum flux density capability of 1.6T, find the saving in core and wire material assuming volume density of both core materials to be approximately same and they have same core flux. Assume mean magnetic path length of 160 cm and μ0 = 4π × 10^{-7}.

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Frequently asked questions

What is the pattern of UPSC Engineering Services 2017 Electrical Engineering Paper-II?

The paper consists of eight questions. Candidates must attempt five questions in total, with Q1 and Q5 compulsory; at least one question from each section must be attempted.

What is nominal-T representation in transmission lines?

Nominal-T is an equivalent circuit model for a medium-length transmission line where the line is represented by a series impedance split into two halves with a shunt capacitance in the middle.

How is starting torque for a DOL-started induction motor computed?

Starting torque is computed using stator resistance, supply voltage, starting current, and per-phase parameters; assume X2 << Xm for simplifications and use the slip at start (s=1) when applicable.

What are ripple factor, form factor and utilization factor in rectifiers?

Ripple factor is the ratio of the rms value of the AC component to the DC component of the rectified output. Form factor is the ratio of RMS value to average value. Utilization factor relates to how effectively the transformer is used by the rectifier circuit.

What does unit step response tell you about a control system?

The unit step response reveals the system type, order, damping, and transient behavior; from the expression, poles of the open loop and the nature of the response can be inferred.

What is the significance of open-loop poles in control systems?

Open-loop poles determine the natural modes and stability characteristics of the system; their locations influence transient response.

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