Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 39, Problem 15SQ
A synchronous motor can be used to increase the power factor of an electrical system by
- a. reducing the speed.
- b. overexciting the stator field.
- c. operating at unity power factor.
- d. applying DC to the stator field.
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1.5 A 10‐pole, 380 ‐V, 50 Hz, D‐connected three‐phase induction motor is rotating a quarry belt conveyor. The machine has the following parameters, referred to the stator, on a per phase basis:
Stator Parameters
Winding Resistance................0.19 Ω .........
Winding Reactance.................1.12 Ω..........
Rotor Parameters
Winding Resistance......................0.29 Ω
Winding Reactance.....................1.12 Ω
Magnetising Reactance................................16.8 Ω
Equivalent Core‐loss Resistance....................900 Ω.
The friction and windage losses are 320 W. When the motor runs at its rated slip of 2.6 %. Determine:
1.5.1 The stator current.
1.5.2 Estimate the Output torque of the motor under the rated conditions.
1.5.3 The Motor…
A DC generator has terminal voltage of 250 V and an induced voltage of 262 V when the generator is loaded. The brush drop is 1 volt per brush and the armature resistance is 0.03 ohm and the shunt field circuit resistance is 35 ohms. Neglected armature reaction and determine the following:
(1) The load current.
(2) The power of the load in kW.
(3) The % voltage regulation.
Chapter 39 Solutions
Electric Motor Control
Ch. 39 - Prob. 1SQCh. 39 - What is the effect of the starting winding of the...Ch. 39 - What are typical applications of synchronous...Ch. 39 - Prob. 4SQCh. 39 - A loaded synchronous motor cannot operate...Ch. 39 - Why must a discharge resistor be connected in the...Ch. 39 - Depending on their power factor ratings, what is...Ch. 39 - At what power factor do incandescent lights...Ch. 39 - Prob. 9SQCh. 39 - The speed of a synchronous motor is fixed by the...
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- A three –phase, 440V, 50 Hz, 6 – pole induction motor running at 950 rpm takes 50 kW at certain load. The friction and windage loss is 1.5 kW and the stator losses = 1.2 kW. Determine the output from the rotor. (a). 42.68 kW (b). 46.48 kW (c). 48.80 kW (d). 44. 86 kWarrow_forward2. A 2-pole, 50 Hz induction motor supplies 15 kW to a load at a speed of 2950 rpm. a. What is the motor's slip? b. What is the induced torque in the motor in N-m under these conditions? c. What will be the operating speed of the motor be if its torque is doubled? d. How much power will be supplied by the motor when the torque is doubled?arrow_forwardAs shown in the figure below, this is a speed regulation method for DC separately excited motor. a) What is the speed regulation method? b) What are the characteristics for this speed regulation method? no ne 11₂ 2 11₂ I I D E Ra R₂ Rs 1 3arrow_forward
- pole. 50-Hz. 3-ϕ induction motor has a full-load speed of 950 rpm. At half load its speed would be ..... rpm a) 475 b) 500 c) 975 d)1000arrow_forwardL-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) noarrow_forwardd) A 2-pole induction motor is fed with a 230 V, 50 Hz supply and is running at no load. i. Calculate its angular speed in rpm. ii. Explain how can we slow down the speed of the motor above, at no load? iii. Explain what will happen to the speed of the motor if we slowly add amechanical load to the motor.arrow_forward
- A DC shunt motor produces an output power of 4.8 kW on the shaft with a speed of 1120 rpm and a terminal voltage of 240 V. The motor has an armature resistance of 0.5 Ohms and a field resistance of 240 Ohms. If the motor at this load has an efficiency of 85%, determine: a. Explain the process of controlling the speed of a DC motor by adjusting the field resistance. b. input power and motor input current. c. Motor speed if motor input power is reduced by 50%arrow_forwardA 240 V, DC series motor takes 44 A, the armature and field resistances are 0.8 Q and 0.05 Q respectively, the back e.m.f of the motor is ..arrow_forwardA 400 V, 50 Hz, 4-pole, 3-phase, star-connected induction motor has the following data: stator impedance per phase is (0.7+ j 0.4), rotor impedance per phase referred to stator side is (0.3 + j 0.2) §, magnetizing reactance per phase is 30 N. The machine is operating at a slip of 4%. Draw the exact equivalent circuit and determine: stator current, motor power factor, input power, and rotor current?arrow_forward
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Working of Synchronous Motor; Author: Lesics;https://www.youtube.com/watch?v=Vk2jDXxZIhs;License: Standard Youtube License