EE311EDCA

Module 1

Theory Questions:

1. Give the classification of the DC generators depending upon their field excitationwith simple

sketches.

2. Draw the open circuit characteristics of a DC shunt generator and define criticalresistance.

3. With the help of a neat circuit diagram explain the procedure for obtaining the internal and

external characteristics of a DC shunt generator.

4. Write any two methods for compensating the effects of armature reaction in DC generators.

5. Derive an expression for the e.m.f generated in a dc machine.

6. What is meant by armature reaction? How does it will affect the main field flux?

7. Define critical speed and critical field resistance of a dc shunt generator.

8. With a sketch explain the working principle of a dc generator.

9. What is the basic difference between self and separately excited generators?

10. Define critical resistance of a dc generator.

11. Derive the e.m.f. equation of a dc generator.

12. Explain the working principle of a dc generator.

13. What is armature reaction in a dc generator and what are its effects?

14. Explain the different characteristics of self-excited dc shunt generator.

EE311 EDCA

KTU Tutorials:Module 1 DC Generators

1. An 8-pole wave connected DC generator has 1000 armature conductors and flux per pole is

0.035Wb. At what speed must it be driven to generate 500V?

2. A 6 pole lap wound dc generator has 1200 conductors on its armatures. The flux per pole is

10 mWb. Calculate the speed at which generator should be driven to generate 250 volts.

3. A DC shunt generator having a terminal voltage of 250V delivers a load current of 195A.

The armature and shunt field resistances are 0.05 ohm and 50 ohms respectively. Calculate:i)

Armature current ii) Generated e.m.f in armature.

4. A 6 pole DC shunt generator has 780 wave connected armature conductors and running at

600 r.p.m supplies a load of 13Ω resistance at a terminal voltage of 240V.The armature

resistance is 0.3Ω and field resistance is 260Ω.Calculate the i)induced e.m.f ii)flux per pole.

5. The OCC of a dc shunt generator operating at 850rpm is given below

E0(V): 12 40 102 176 210 240 256

If(A): 0 0.5 1 2 3 4 5

The machine has 6 poles. The type of winding is lap. The number of conductors in the

armature is 540. Calculate i) residual flux per pole.ii) the no load e.m.f for a total shunt field

resistance of 120 Ω iii) the critical field resistance of the field circuitiv) thecritical speed for

the shunt field resistance of 120Ω.

6. The magnetization curve of a dc shunt generator at 1500 rpm is

E0(V): 6 60 120 172.5 202.5 221 231 237 240

If (A): 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.0

For this generator find i) No load e.m.f for a total shunt field resistance of 100Ω. ii) critical

field resistance at 1500 rpm iii) draw the magnetization curve at 1200 rpm and find the open

circuit voltage for a field resistance of 100 Ω.

DC Generators - Practice Tutorials

1. A 4 pole 1200 rpm lap wound DC generator has 760 conductors. If the flux per pole is 0.02 Wb,

Calculate the generated e.m.f. Also calculate the e.m.f. if the armature is wave wound.

2. A 4 pole wave wound DC generator has 48 slots, each slot containing 20 conductors. The useful flux

per pole is 30 mWb. If the generator is driven at 800 r.p.m, calculate the generated e.m.f in the

armature.

3. An 8 pole DC Generator has 750 conductors. The flux per pole is 25 mWb. If the armature is wave

wound and is rotating at a speed of 1250 r.p.m. Find the generated e.m.f. What must be speed at

which the armature is to be driven to generate the same e.m.f., if the armature is lap wound?

4. A DC shunt generator delivers 450 A at 230V and armature resistance is 0.03 Ω and shunt field

resistance is 50 Ω. Calculate the generated e.m.f. (Ans: Eg= 243.64 V)

5. A 25kW, 500V DC series generator has armature resistance of 0.05 Ω and field resistance of 0.03 Ω.

Calculate generated e.m.f and armature current at Full load. (Ans: Eg= 504V: Ia= 50A)

6. In a 110 V compound generator, the resistance of armature, shunt field and series field are 0.06Ω,

25Ω and 0.04Ω respectively. Load consists of 200 lamps each rated at 55W, 110V. Find the total

e.m.f. generated and armature current when the machine is connected for (i) Long shunt (ii) Short

shunt. (Ans: (i) Eg= 120.44 V: Ia= 104.4 A (ii) Eg= 120.27 V: Ia= 104.56 A)

7. Calculate the generated e.m.f. in the armature winding of a 4 pole lap wound DC machine

having 728 conductors running at 1800 rpm. The flux per pole is 30 mWb.

8. A 4 pole wave wound armature has 1000 conductors and flux per pole is 0.05 Wb. Calculate

the generated e.m.f. when the generator is running at a speed of 1200 rpm.

9. A 4 pole lap connected D.C. generator has no load generated e.m.f of 500V when driven at 1000

r.p.m. Calculate the flux/pole if the armature has 100 slots with 5 conductors/slot. If each conductor

has a resistance of 0.01 ohm, find the resistance of the armature winding.

10. A Shunt generator gave the following results in the OCC test at a speed of 800 r.p.m:

Field current (A): 1 2 3 4 6 8 10

EMF(V) : 90 185 250 290 325 345 360

The field resistance is adjusted to 50 ohm and the terminal voltage is 300 V on load. Armature resistance

is 0.1 ohm. Assuming that the flux is reduced by 5% due to armature reaction, calculate the load

supplied by the generator.

11. The OCC of a D.C. machine at 400 r.p.m. is as follows:

Field current in Amps: 2 3 4 5 6 7 8 9

Generated volt (V) : 110 155 186 212 230 246 260 271

Find (i) the voltage to which the machine will build up as self excited shunt generator, if field circuit

resistance is 35 ohm (ii) critical field resistance at 700 r.p.m (iii) critical speed if field resistance is

80% of critical resistance 400 r.p.m.

EE 311 EDCA

Module II DC Motors

Theory Questions:

1. Explain how the torque is developed in a DC Motor?

2. What is meant by back e.m.f in DC Motors?

3. Give the classification of DC motors with applications.

4. Draw the power conversion stages of a DC Motor.

5. With a neat figure explain the method for conducting load test in a DC Shunt Motor.

6. Why starter is necessary in a DC Motor?

7. Derive an expression for the electromagnetic torque developed in a DC Motor.

8. Derive the speed-torque characteristics of a DC Shunt and DC Series Motor.

9. What are the losses occurring in a DC Motor and how do they vary with load current?

10. Derive the condition for maximum efficiency in a DC Machine.

11. List out the application of Series, Shunt and Compound Motors.

12. What are the applications of Shunt, Series and Compound Motors?

13. What is the purpose of using starter in a DC Motor?

14. Explain the different characteristics of DC Shunt Motor, Series Motor & Compound Motor.

EE311 EDCA

KTU Tutorials: Module 1I DC Motors

1. A DC Shunt Motor runs at 1300 rpm on no-load drawing 5 A from 220 V mains. Its armature

and field resistance are 0.24 Ω and 110 Ω respectively. When loaded the motor draws 60 A

from the mains. Calculate the speed when the motor is loaded. Assume that the armature

reaction demagnetizes the field by 3%. Also calculate the internal torque developed at no

load and on load. What is the motor shaft torque at load?

2. A 230 V DC Shunt Motor takes 32 Amp at full load. Find the back e.m.f on full load if

resistances of motor armature and shunt field windings are 0.2 ohm and 115 ohms

respectively.

3. A 220 V Shunt Motor has armature and field resistance of 0.2 Ω and 220 Ω respectively .The

motor is driving a constant load torque and running at 1000 rpm drawing 10 A current from

supply. Calculate the new speed & armature current if an external armature resistance of 5 Ω

is inserted in armature circuit. Neglect armature reaction and saturation.

4. A 6 pole 600 V wave connected shunt motor has 1200 armature conductors and useful flux

per pole of 22 mWb. The armature and field resistances are 0.75 Ω and 250 Ω respectively.

Calculate the speed and armature torque developed by the motor when it draws 25 A from

the supply mains. If the magnetic and mechanical losses amount to 920 watt. Find the i) shaft

torque ii) output power in kW iii) efficiency at this load

PRACTICE TUTORIALS

1. A 220V DC shunt motor takes 30A at full load. Find the back e.m.f. developed if the

armature and shunt field resistances are 0.5 Ω and 110 Ω respectively.

2. The power input to a 230V DC shunt motor is 8.477 kW. The field resistance is 230 Ω and

armature resistance is 0.28 Ω. Find input current, armature current and back e.m.f.

3. A 220V DC shunt motor draws a current of 50A at full load. The armature resistance is 0.2 Ω

and shunt field resistance is 40 Ω. Calculate the back e.m.f.

4. A 120V DC shunt motor draws a current of 200A. The armature resistance is 0.02 Ω and

shunt field resistance is 30 Ω. Find the back e.m.f.

5. A 220 V DC series motor takes a current of 20A. The armature resistance is 0.1 Ω and series

field resistances is 1.2 Ω. Find the back e.m.f.

6. A 200 V series motor has a total resistance of 0.5 Ω. It runs at 800 rpm taking an input of

10A. Find the series resistance required to reduce the speed to 600 rpm, the input current

being kept constant.

7. A 250 V DC shunt motor has an armature resistance of 0.5 Ω and a field resistance of 250 Ω.

The motor draws 21A when driving a constant torque load at 600 rpm. What will be the new

speed of the motor if an additional 250 Ω resistance is inserted is inserted in the field circuit?

8. A 6 pole 250 V series motor is wave connected. There are 240 slots and each slot has 4

conductors. Flux per pole is 0.175 mWb when the motor is taking 80A. The field resistance

is 0.05 Ω, the armature resistance is 0.1 Ω and the iron and frictional loss is 0.1 kW.

Calculate (i) speed (ii) BHP (iii) shaft torque (iv) the pull in Newtons at the rim of the pulley

of diameter 25 cm.

9. A 4 pole lap wound Shunt motor has 600 conductors in the armature. The effective resistance of the

armature path is 0.05 Ω. The resistance of the shunt field is 25 Ω. Find the speed of the motor when it

takes 120A from D.C. mains of 100V supply. Flux per pole is 2 x 10-2

Wb.

10. Determine the value of the torque in Nm of a 4 pole motor having 774 conductors, two paths in

parallel, flux of 24mWb per pole when total armature current is 50A.

11. A 460V Series motor runs at 500 r.p.m. taking a current of 40A. Calculate the speed and % change in

torque, if the load is reduced so that the motor is drawing 30A. Total resistance of armature and field

circuit is 0.8 Ω. Assume flux and field current are proportional.

12. A D.C. Shunt motor runs at 9000 r.p.m. from a 400V supply when taking an armature current of 25A.

Calculate the speed at which it will run from a 230V supply when taking an armature current of 15A.

The resistance of the armature circuit is 0.8 Ω. Assume the flux per pole with 230V to have decreased

to 75% of its value at 400V.

13. A shunt motor develops a total torque of 250 Nm at rated load. When it is subjected to a 15%

decrease in field flux, the armature current increases by 40%. Calculate the new torque produced as a

result of change in field flux.

14. A 6 pole D.C. machine has 300 conductors and each conductor is carrying 80 A without excessive

temperature rise. The flux/pole is 0.015 Wb, and the machine is driven at 1800 rpm. Calculate the

total current, e.m.f., power developed in the armature and the electromagnetic torque, if the armature

conductors are lap connected.

15. A 200V D.C. Shunt motor has an armature resistance of 0.25 Ω and field resistance of 200 Ω. When

running on no-load, it takes 5A. Calculate the hp output and the efficiency of the motor, when loaded

to take a line current of 40A.

ADDITIONAL QUESTIONS

1. A 230V motor has an armature circuit resistance of 0.6 If the full-load armature current is 30A and the no-load armature current is 4A, find the change in back e.m.f. from no load to

full-load. (Ans: e.m.f = 15.6V)

2. A D.C. motor has 6 poles, flux per pole is 0.05Wb with lap wound armature of 600

conductors. Motor speed is 500 rpm. Determine the applied voltage and back e.m.f. Given

armature resistance as 0.25 and armature current 40A. (Ans: V= 260V, Eb= 250V)

3. A 4-pole 250V D.C series motor has a wave wound armature with 1254 conductors. The flux

per pole is 22 mWb when the motor is taking 50A. Armature resistance is 0.2 and series field resistance of 0.2. Calculate the speed. (Ans: N= 250 r.p.m)

4. A 220 V, 4-pole, D.C. shunt motor runs at 1,000 r.p.m. The useful flux per pole is 30 mWb.

Find the number of armature conductors, if it is lap wound. (Ans: 420 cond.)

EE 311 EDCA

Module III Transformers

Theory Questions:

1. Draw the phasor diagram of a single-phase transformer with inductive load and mark

each phasor clearly.

2. What is an auto transformer? With suitable derivations, prove that there is saving of

copper in auto transformer compared to ordinary transformer.

3. Define the all-day efficiency of a distribution transformer. What is its significance?

4. What are instrument transformers? Give its types.

5. Derive the e.m.f equation of a single phase transformer.

6. Draw the phasor diagram of a 1-phase transformer at no load and derive the equivalent

circuit.

7. Explain the difference between an ideal transformer and an actual transformer.

8. What are the losses produced in a transformer and derive the condition for maximum

efficiency.

9. Explain the working principle of a transformer under no load. Also draw the vector

diagram at no load.

10. Define all day efficiency of a transformer.

11. Derive the condition for maximum efficiency of a transformer

12. Explain how the equivalent circuit parameters are obtained from transformer tests. Also

draw the equivalent circuit.

13. Explain with diagram, the principle of operation of a single phase Transformer.

14. Explain with diagram, the working principle of Current and Potential Transformers.

15. By conducting OC and SC tests, derive the equivalent circuit of a single phase

Transformer.

16. Which are the losses present in a Transformer?

KTU Tutorials

1. A 40 kVA single phase transformer has 400 turns on the primary and 100 turns on the

secondary. The primary is connected to 2000 V, 50 Hz supply. Determine: i) The Secondary

voltage on open circuit ii) Maximum value of flux.

2. Obtain the approximate equivalent circuit with respect to low voltage side of a given

200/2000 V single phase 30 kVA transformer having the following test results.

O.C test: 200V, 6.2A, 360W on L.V. side

S.C test: 75 V, 18A, 600W on H.V side

3. The maximum flux density in the core of a 250/3000V, 50 Hz single transformer is 1.2

Wb/m2. If the emf/turn is 8V. Determine i) primary and secondary turns ii) Area of core.

4. A 40kVA single phase transformer has iron loss of 450W and full load copper loss of 850W.

If the pf of the load is 0.8 calculate: i) The full load efficiency. ii) The maximum efficiency.

iii) The load at which maximum efficiency occur.

PRACTICE TUTORIALS

1. A single phase transformer has 400 turns and 1000 turns on primary and secondary windings.

The net c.s.a of the core is 60 cm2. If the primary winding is to be connected to a 50 Hz

supply at 500V, calculate (i) peak value of flux density in the core (ii) voltage induced in the

secondary winding.

2. The maximum value of flux density in the core of a 250 / 3000 V, 50 Hz single phase

transformer is 1.5 Tesla. If the e.m.f. per turn is 8V, determine (i) no. of turns of primary &

secondary (ii) c.s.a. of the core.

3. A 30 kVA, single phase transformer has 500 turns and 30 turns on primary and secondary

windings. If the primary winding is connected to a 3300 V, 50 Hz supply, calculate (i)

Maximum flux of the core (ii) secondary e.m.f. (iii) Full load Primary and Secondary

currents.

4. A 25 kVA, single phase transformer has 600 turns and 1200 turns on primary and secondary

windings. The net c.s.a of the core is 50 cm2. If the primary winding is connected to a 230 V,

50 Hz supply, calculate (i) secondary e.m.f. (ii) Maximum flux density of the core (iii) Full

load Primary and Secondary currents.

5. A single phase transformer is to have a voltage rating of 3300 /240 V. Find the no. of turns in

the primary and secondary if the frequency of operation is 50 Hz. Maximum value of flux

may be taken as 0.04 Wb.

6. A single phase transformer has a core whose c.s.a. is 150 cm2, operates at a maximum flux

density of 1.1 T from a 50 Hz supply. If the secondary winding has 66 turns, determine the

output kVA when connected to a load of 4 Ω impedance. Neglect any voltage drop on

transformer.

7. A 150 kVA single phase transformer has an iron loss of 750 W and FL copper loss of 2000

W. Calculate the percentage efficiency at Full load, 0.8 pf lag & Half load, 0.8 pf lag.

8. Maximum efficiency of a transformer occurs at unity pf and at FL. If the full load copper loss

is 60 W, calculate the total loss at FL, ¾ FL, ½ FL and ¼ FL.

9. A 40 kVA transformer has a core loss of 450 W and a full load copper loss of 850 W. If the

power factor of the load is 0.8, calculate (i) Full load efficiency (ii) maximum efficiency (iii)

the load at which maximum efficiency occurs. (Ans: FL,0.8 pf= 96.1%,, load kVA= 29.1kVA,

m= 96.27%)

10. A 200 kVA rated transformer has a full load Copper loss of 1.5 kW and an Iron loss of 1 kW.

Determine the transformer efficiency at Full load and 0.85 power factor.

11. A 1000/800V, 8 kVA autotransformer supplies rated current to a load on low voltage side. Draw a

schematic diagram and mark input current, output current and current in the section of the winding

common to high voltage and low voltage sides.

12. Reading from OC & SC test on a 8 kVA, 400/200V, 50 Hz transformer are

OC Test: 200V, 2A, 80W; (LV side) SC Test: 10V, 20A, 120W; (HV side).

Compute the equivalent circuit of the transformer as referred to HV side.

13. A 600W single phase transformer working at unity power factor has an efficiency of 95 percent at

both half full load and full load. Determine the efficiency at 70 percent of full load.

14. A load of 6 kW is supplied by an autotransformer at 120 V and u.pf. If the primary voltage is 240 V,

determine (i) Transformation ratio (ii) Secondary current (iii) primary current (iv) Number of

secondary turns if the total number of turns is 280

15. A 200kVA, three phase transformer is in circuit continuously. For 8 hrs in a day, the load is 160 kW

at 0.8 p.f., for 6 hrs the load is 80 kW at u.p.f. and for the remaining period of 24 hrs, it runs at no

load. FL Copper loss is 3.02 kW and iron loss is 1.6 kW. Find all day efficiency.

16. Two transformers A and B each rated for 40 kVA have core losses of 500W and 250W respectively

and FL Copper loss of 500W and 750W respectively. Compare the all day efficiency of the two

transformers, if they are used to supply a lighting load with output varying as follows:

O/P – FL for 4 hrs, HL for 8 hrs, NL for remaining 12 hrs. Justify your answer.

EE 311 EDCA

Module IV 3 Phase Induction Motor

Theory Questions:

1. With neat sketch, explain the development of rotating magnetic field in a three phase

induction motor.

2. Define slip and draw the torque slip characteristics of a three-phase induction motor.

3. Draw the equivalent circuit per phase of a three-phase induction motor and explain.

4. Explain the principle of operation of a 3-phase induction motor.

5. Differentiate between squirrel cage and slipring induction motor.

6. Write short notes on torque-slip characteristics of a 3-phase induction motor

7. Explain no load and blocked rotor test on a 3-phase induction motor and derive the

equivalent circuit parameters.

8. What is meant by circle diagram of a induction motor? What are the information’s that

can be obtained from the circle diagram?

9. Explain with the help of neat diagram the working of any two methods of starting a 3-

phase induction motor.

10. List out the difference between slipring and squirrel cage induction motor

11. Explain the torque- slip characteristics of three phase induction motor

12. What is meant by slip of an Induction motor

13. What is meant by circle diagram of a Induction motor?

14. By conducting no load and blocked rotor test, write the procedure to draw the circle

diagram of a three phase induction motor

15. What is the significance of the term slip of an induction motor?

16. Explain how rotating magnetic field is produced in a three phase induction motor. Also

prove that its magnitude of resultant flux is constant at different angles.

17. Draw and explain the constructional details of a 3 phase Squirrel Cage Induction Motor.

18. Draw and explain the constructional details of a 3 phase Slip Ring Induction Motor.

19. Define the terms (i) Synchronus speed (ii) Slip (iii) slip speed (iv) Rotor speed.

20. Give the relative merits of slip ring and squirrel cage rotors for a 3-phase Induction Motor.

EE 311 EDCA

Module IV 3 Phase Induction Motor

KTU TUTORIALS

1. A 40 kW 6 pole three phase induction motor delivers full load output at 950 rpm at 0.85p.f

when connected to a 500 volt, 50 Hz supply. Friction and windage loss equals 1.5kW and

stator losses are 1.8kW. Determine for this load: i) Total copper loss ii) Efficiency.

2. A 40 kW 6 pole 3 phase induction motor delivers full load output of 950 rpm at 0.85 power

factor when connected to a 500 V, 50 Hz supply. Friction and windage loss equals 1.5 kW

and stator losses are 1.8 kW. Determine for this load i) Total rotor copper loss ii) Efficiency

iii) Line current

3. A three phase induction motor has 2 poles and is connected to 400 V, 50 Hz supply.

Calculate the actual rotor speed and rotor frequency when slip is 4%.

Practice Tutorials

1. The frequency of emf in the stator of a 4 pole induction motor is 50 Hz, and that in the rotor

is 1.5 Hz. What is the slip and at what speed is the motor running?

2. A 4 pole 3 phase induction motor runs at 1440 rpm at rated load. Calculate the percentage

slip. Supply frequency is 50 Hz.

3. A 6 pole 50 Hz Induction motor runs at 970 rpm. Calculate (i) slip (ii) frequency of induced

current in the rotor.

4. A 6 pole 3 phase Induction motor operates from a supply whose frequency is 50 Hz. Calculate

(i) the speed at which the magnetic field of the stator is rotating (ii) speed of the rotor when

the slip is 0.03.

5. Calculate the speed of a 6 pole, 50 Hz, 400 V 3 phase Induction Motor when it is operating at

a slip of 2%.

6. A 3 phase 50 Hz Induction Motor has a full load speed of 960 rpm. Find the (i) slip (ii) No: of

poles (iii) frequency of rotor induced emf.

7. A 415V, 4 pole, 50 Hz, 3 phase Induction Motor delivers a torque of 101.6 Nm at 1410

r.p.m. with a p.f. of 0.87 when the supply frequency is 48.5 Hz. If the mechanical torque lost

in friction is 4 Nm and stator losses total 950W, find the (i) slip (ii) rotor copper loss (iii)

Input power (iv) Line Current

8. The power input to a 4 pole, 50 Hz, 3 phase Induction Motor is 42 kW, the speed being 1455

r.p.m. The stator losses are 1.2 kW and mechanical losses are 1.8 kW. Find (a) the rotor input

(b) rotor copper loss (c) ŋ 9. A 440V, 6 pole, 50 Hz, 3 phase Induction Motor delivers a mechanical load of 15 kW at 950

r.p.m with a p.f. of 0.84. The mechanical losses total 0.75 kW. Calculate for this load the

following quantities (a) slip (b) the rotor copper loss (c) the input if the stator losses total 1.5

kW (d) the line current.

10. The real power input to a 415 V, 6 pole, 50 Hz, 3 phase induction Motor running at 970 rpm

is 41 kW. The input p.f. is 0.9. Stator losses account to 1.1 kW and mechanical losses total

1.2 kW. Calculate (a) Line current (b) slip (c) rotor copper loss (d) mechanical power output

(e) efficiency of the motor (f) Torque.

11. A Slip ring Induction motor has a rotor resistance of 0.03 Ω and a standstill reactance of 0.12

Ω. Find approximately the value of external resistance to be added to the rotor resistance

starter in order to develop maximum torque at starting.

12. Estimate approximately the starting torque of a three phase Induction motor in terms of its

FL torque when started by means of an autotransformer starter with 60% tapping. The motor

draws 6 times the FL current when switched ON directly and FL slip is 4%.

13. Determine the suitable tapping on an auto transformer starter for an Induction Motor required

to start the motor with 36% of the full load torque. The short circuit current of the motor is 5

times the full load current and full load slip is 4%. Also determine the current in the supply

leads as a percentage of full load current.

14. A 415 V, 29.84 kW, 50Hz Induction motor gave the following test results.

No load Test : 415V 21A 1,250 W

Blocked rotor test : 100V 45A 2,730 W

Construct the circle diagram and determine (i) Line current, p.f. and efficiency for the rated

output (ii) Maximum torque and corresponding slip. Assume stator and rotor copper losses

equal at standstill.

EE 311 EDCA

Module V 3 Phase Induction Motor

Module 5

SINGLE PHASE INDUCTION MOTOR

1. Describe principle of working of single phase induction motors with neat sketches. 2. Explain the constructional details of single phase induction motor

3. Explain any two methods of starting of single phase induction motors

4. Explain double field revolving theory of a single phase induction motor

5. Explain with diagram the Working of a capacitor start induction motor.

6. What are the applications of capacitor start induction motors?

UNIVERSAL MOTORS

1. What are universal motors? Explain their working. Mention its applications also.

2. What is a universal motor? What are the applications of this type of motors?

ALTERNATOR

1. With suitable graphs explain the method to determine voltage regulation of an alternator by

EMF method. 2. Derive the e.m.f equation of an alternator.

3. Define distribution factor and pitch factor of an alternator.

4. What is meant by regulation of an alternator?

5. Explain synchronous impedance of an alternator. How can it be determined?

6. How can you determine the regulation of an alternator by e.m.f method? Explain.

7. What is meant by regulation of an alternator?

8. Explain synchronous impedance of an alternator. How can it be determined?

9. Explain how regulation of alternator is conducted by EMF Method.

Tutorials

1. A three-phase star connected alternator is rated at 1600 kVA, 13500 Volt. The armature

resistance and synchronous reactance are 1.5 and 30 ohms respectively per phase. Calculate

the percentage voltage regulation for a load of 1820 kW at 0.8leading p.f.

2. A 3 phase, 1500 kVA, star connected 50 Hz, 2300 V alternator has a resistance of 0.12 Ω per phase. A field current of 70 A produces a short circuit current equal to full load current of

376 A in each line. The same field current produces an e.m.f of 700 V on open circuit.

Determine the synchronous reactance of the machine and its full load regulation of 0.8 p.f.

lag

SYNCHRONOUS MOTORS

1. Write a note on the starting of synchronous motors.

2. Draw and explain the ‘V’ curves of a synchronous motor. 3. Why synchronous motor has no net starting torque?

4. Explain the methods of starting synchronous motor.

5. What is a synchronous condenser?

6. Explain the working principle of a synchronous motor.

7. Which are the methods of starting synchronous motors?

8. What is the purpose of synchronous condenser?

9. List any two advantages and two disadvantages of synchronous motors.

10. Explain the V curve of a synchronous motor.

EE 311 EDCA

Module VI Stepper Motors / Control & Automation

Module 6

STEPPER MOTORS

1. Draw the schematic diagram of a variable reluctance motor and explain its working.

2. What is micro stepping? Determine the step angle of a variable reluctance stepper motor

with 12 teeth in stator and 8 rotor teeth.

3. Draw the stepper motor characteristics and explain. Also list the applications of stepper

motors.

4. With suitable block diagrams, explain the control of stepper motors.

5. With a neat sketch, explain the working of a permanent magnet stepper motor.

6. List out the classification of stepper motors and compare them.

7. Draw and explain the torque-speed characteristics of stepper motor. 8. What are the applications of stepper motors?

9. With neat diagram explain the working principle of linear stepper motors.

10. What is meant by stepping angle of variable reluctance motor?

11. With the help of block diagram explain the different control of stepper motors. 12. Explain with diagram the working of a multi stack variable reluctance stepper motor.

13. Explain the principle of operation of a stepper motor.

CONTROL & AUTOMATION

1. Give the two major classifications of general control systems and explain them with

suitable block diagrams. Give examples for each type.

2. Write a note on different types of controllers for automation. 3. Explain the with block diagram, the working of open loop and closed loop control of a

stepper motor.

4. What are the applications of programmable logic controller?

5. Explain the working of a digital controller used for Automation.

6. Explain the applications of axis controller and machine tool controller in Industrial

Automation.

7. Write short notes on servo control and digital controllers.

8. What is machine tool controller?

9. With neat diagram explain programmable logic controllers.

10. Explain Servo control and Digital control used for automation

11. Explain the features and applications of PLC.

12. What is machine tool controller?