JNTU
JNTU B.Tech II ELECTRICAL MACHINES I Previous Question Paper (September/October - 2023 - R13)
i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What are the categories of electromechanical energy conversion device?
Answer
Electromechanical energy conversion devices are broadly categorized into three types: transducers (sensors and actuators), force-producing devices (solenoids, relays, and electromagnets), and continuous energy conversion devices (rotating electrical machines like motors and generators).
Give examples for single and double excited systems.
Answer
A singly excited system has only one electrical input port, such as a relay or a simple solenoid. A doubly excited system has two electrical input ports, such as a synchronous machine where both the stator and rotor are independently excited.
Mention the role of interpole in DC Machine.
Answer
Sign in to view the complete answer paper.
Compare lap and wave windings.
Answer
Sign in to view the complete answer paper.
State the condition under which a DC shunt generator fails to excite.
Answer
Sign in to view the complete answer paper.
How the critical field resistance of a dc shunt generator is estimated from its OCC Characteristics?
Answer
Sign in to view the complete answer paper.
Why do we need a starter for dc motors?
Answer
Sign in to view the complete answer paper.
Enumerate the factors on which the speed of a dc motor depends.
Answer
Sign in to view the complete answer paper.
How to minimize hysteresis losses?
Answer
Sign in to view the complete answer paper.
What are the limitation of field tests?
Answer
Sign in to view the complete answer paper.
Part B
Derive the expression for field energy and mechanical force.
Answer
Sign in to view the complete answer paper.
With a neat sketch explain multiple excited system of electromechanical energy conversion.
Answer
Sign in to view the complete answer paper.
Obtain the expression for energy in attracted armature relay magnetic systems.
Answer
Sign in to view the complete answer paper.
Explain about magnetic field in rotating machines.
Answer
Sign in to view the complete answer paper.
Explain the working principle of DC Generator in detail.
Answer
Sign in to view the complete answer paper.
The OCC of a separately excited DC generator driven at 600 rpm is as follows. If the machine is connected as shunt generator and driven at 600 rpm and has a field resistance of 100Ω, find the open circuit voltage and exciting current.
Answer
Sign in to view the complete answer paper.
Explain the armature reaction in dc machines.
Answer
Sign in to view the complete answer paper.
A 100V DC shunt motor runs at 1000 rpm at no load and takes 10A. The total armature and shunt field resistances are given by 0.25Ω and 250Ω respectively. Calculate the speed when loaded and taking 40A. Assume the flux to be constant.
Answer
Sign in to view the complete answer paper.
Briefly explain the parallel operation of dc series generators.
Answer
Sign in to view the complete answer paper.
Discuss in detail, the load characteristics of DC Series and Shunt generators.
Answer
Sign in to view the complete answer paper.
Draw and explain the characteristics of dc shunt motor.
Answer
Sign in to view the complete answer paper.
A DC shunt motor rated 10kw connected to 250V Supply is loaded to draw 35A armature current running at a speed of 1250 rpm. Given armature resistance=0.5 ohms. Determine the load torque if the rotational loss is 500W.
Answer
Sign in to view the complete answer paper.
Discuss in detail applications of shunt, series and compound motors.
Answer
Sign in to view the complete answer paper.
Derive the torque equation of a DC Motor.
Answer
Sign in to view the complete answer paper.
Compare the different methods of speed control of dc motors.
Answer
Sign in to view the complete answer paper.
What is mean by armature control method and flux control method? Explain.
Answer
Sign in to view the complete answer paper.
Explain in detail about the purpose of conducting various tests on DC machines.
Answer
Sign in to view the complete answer paper.
A 440V DC Shunt motor takes 4A at no load. Its armature and field resistances are 0.4Ω and 220Ω respectively. Estimate the kW output and efficiency when the motor takes 60A on full load.
Answer
Sign in to view the complete answer paper.
With the help of neat diagram, explain the Swinburne test and derive the relations for efficiency.
Answer
Sign in to view the complete answer paper.
Explain the procedure of conducting brake test on D.C machine with a neat circuit diagram.
Answer
Sign in to view the complete answer paper.