Q4 (a) Outline the locked rotor and no load tests for an induction motor and indicate the necessary measurements and calculations to determine equivalent circuit parameters. (b) The per phase equivalent circuit parameters for a 3 phase, 4 pole star connected induction machine operating off a 230 V (phase voltage), 50 Hz supply are shown on Table Q4b. Assuming that friction and windage losses are negligible, determine the following for operation at a slip of 0.025: (i) (ii) (iii) (iv) (v) (vi) The per phase equivalent circuit (including values below) The actual motor speed (rpm) The mechanical power (W) The torque (Nm) The motor losses (W) The motor efficiency (%) Parameter Value XM R. 352 1052 R, 0.20 0.152 1.50 R, Х Table Q4b (c) Induction motors can also operate off 2 phase AC supplies. Outline the necessary electrical supply and mechanical winding arrangements for this type of motor.

Q4 (a) Outline the locked rotor and no load tests for an induction motor and indicate the necessary measurements and calculations to determine equivalent circuit parameters. (b) The per phase equivalent circuit parameters for a 3 phase, 4 pole star connected induction machine operating off a 230 V (phase voltage), 50 Hz supply are shown on Table Q4b. Assuming that friction and windage losses are negligible, determine the following for operation at a slip of 0.025: (i) (ii) (iii) (iv) (v) (vi) The per phase equivalent circuit (including values below) The actual motor speed (rpm) The mechanical power (W) The torque (Nm) The motor losses (W) The motor efficiency (%) Parameter Value XM R. 352 1052 R, 0.20 0.152 1.50 R, Х Table Q4b (c) Induction motors can also operate off 2 phase AC supplies. Outline the necessary electrical supply and mechanical winding arrangements for this type of motor.

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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Q4. (A)- Indicate whether the following statements are true or false and correct the false statements 1. The inter pole winding is connected in parallel to field winding. 2. The produced sparks at the brushes of a de machine is due to friction losses. 3. Series DC motors are used for low torque applications. 4. In series DC generator, Increasing the load current will decrease the magnitude of the generated voltage. 5. The compensation windings are place at the pole face and used to mitigate the effect of the armature reaction.
1a
An 8 pole, lap-wound armature has 1200 conductors and a flux pole is 0.06wb. Determine the emf generated when the dc machine running at 600 rev/min.(CLO2)
A 150 kW, 250-volt compound DC generator has its field windings which are connected in long shunt. If the shunt-field winding resistance is 20 ohms, what is the current in the series-field winding? (Note that the series field resistance is connected in series with the armature.)
QUESTION 1 a) Write down three (3) factors that will determine the induced torque in a DC machine. b) Explain why higher voltage applied to a motor doesn't always mean that it will have a higher induced torque. You can give an example of the scenario to answer this question. c) When a motor is powered up and rotates, it will induce an internal generated voltage. Is this statement true or false? Justify your answer. d) For the core design shown in Fig. 1: i. Design the magnetic circuit model. Indicate clearly for each part that you use in the magnetic circuit which part of the core is represented. ii. Predict what will happen to the total reluctance if the depth is increased. Justify your answer. rl r2 r4 9 cm 9 cm -25 cm 15 cm to -25 cm- 9 cm 2 A 200 turns -0.04 cm 25 cm 9 ém
A 3 phase, 50 Hz. 2 pole alternator is excited to generate the bus ber Example 3.32.5 voltages of 11 kV at no load, Calculate the synchronizing power per degree of mechanical displacement of the rotor. The machine is star connected and the short circuit current for this excitation is 1200 amperes. Neglect armature winding resistance
c) A 3 phase 6 pole star connected induction machine operates from a 120 V (phase voltage) and 50 Hz supply. Given the equivalent circuit parameters shown in Table Q4, and assuming the friction and windage loss is negligible, calculate the following parameters when operating at 1200 rpm: i. The slip (%). ii. The mechanical power (W). iii. The torque (Nm). iv. The efficiency (%). v. The no load current (A). d) Determine the following parameters for the motor in Q4c at start-up (zero speed): i. The motor phase current (A). ii. The power factor. iii. The input supply power (W). Parameter Value XM Units 85 Ω Re 250 250 R Xeg R Ω 200 Table Q4
the basic requirement of DC armature winding is that it must be: a) a closed one b) a lap winding c) a wave winding d) either (b) or (c)
(c) Electric machines can be classified into two categories, state both categories. (d) Describe THREE (3) methods to control the speed of the DC motor. (e) State why induction (asynchronous) machines are not suitable to be used as a generators, (f) An induction machine is the most rugged machine and is widely used in domestic and industry. State its application in single phase and three phase systems.
Example 4-13 A 5.5-kW 220-V shunt generator has a field resistance of 140 , armature resistance of 0.52, and stray power losses of 95 W at rated conditions. Find at rated load: (a) The field current (b) The load current (c) The armature current (d) The generated voltage (e) The total copper loss (f) The efficiency (g) The voltage regulation (for this, assume that the flux, hence E., remains constant)*
A 220 V , 60 Hz , supply is connected to 200 – turn armature winding of reluctance 1.7x105 At / Wb . Find the magnetizing reactance , the rms values of the ( magneto – motive force , exciting and armature currents , magnetic flux ) , and the inductance Draw the phasor diagram of the circuit .
For a dc generator, the current of the shunt winding is small as compared to armature current true False