Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Textbook Question
Chapter 25, Problem 5SQ
When the voltage is reduced to start a motor, what happens to the
a. torque?
b. current?
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Students have asked these similar questions
A series motor runs at 800 r/min when the voltage is 400 V and the current is 25 A. The armature resistance is 0.4 ohm and the Series field resistance is 0.2 ohm. Determine the following:
(a) The constant of the motor.
If the speed decreases to 600 r/min,the torque increases by 32% and the field increases by 10%, determine the following:
(b) The new armature current.
(c) The new field current.
(d) The new total resistance of the motor in ohm.
(e) The additional resistance inserted in series with the motor in ohm.
2
(B)- Indicate whether the following statements are true or false and correct the false statements
I-A d.c. shunt motor is running with certain load. The effect of adding an external
resistance in armature circuit is to increase the motor speed F Constant speed
2- A de series motor develops a torque of 30 N.m at 4 A of load current. if the current
is increased to 6 A, the torque developed will be 67.5 N.m T
3-If the two field Windings are wound in such a manner that the fluxes produced by the
two always help each other, the motor is called cumulatively compound F
4-The speed of d.c series motor is decreased if the armature current is increased T
5- To solve the Commutation Problem in large machines, this can be achieved by increasing
the brush width.
Tax
In (Rm. Ps)
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Chapter 25 Solutions
Electric Motor Control
Ch. 25 - Prob. 1SQCh. 25 - When can full-voltage starting be used?Ch. 25 - Name the simplest, most rugged, and most reliable...Ch. 25 - Define the term slip.Ch. 25 - When the voltage is reduced to start a motor, what...Ch. 25 - Why is it more advisable to start some machines at...Ch. 25 - Prob. 7SQCh. 25 - Prob. 8SQCh. 25 - Prob. 9SQCh. 25 - Prob. 10SQ
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, electrical-engineering and related others by exploring similar questions and additional content below.Similar questions
- 5. A stepper motor is being used as a crane motor in an expensive toy. The motor has the following properties: Holding torque = 2.52 kg -cm dynamic torque = 1.440 kg-cm detent torque = 0.360 kg-cm The motor turns a 3.81 cm diameter pulley around which a string is wound. How much weight can the crane lift? How much weight can the crane continue to support with the power on; with the power off?arrow_forwardA series motor runs at 700 rev/min when the voltage is 300 V and the current is 20 A. The armature resistance is 0.3 2 and the series field resistance is 0.1 2. Determine the resistance to be connected in series to reduce the speed to 500 rev/min with the same currentarrow_forwardA 240 V D.C. series motor takes the current of 10 A at normal running condition and the field resistance is 0.3 ohm. If Torque remains the same and it is shunted by same field resistance value then line current of motor is (estimated time 2 minutes) a.10 A b.20 A c.15 A d.5 Aarrow_forward
- (7) The only parts suffers from eddy currents in AC motors: a- The stator. b- The rotor. c- The stator and rotor. (8) The unit of torque is a- W (rad. s') b- Js -1 C- Nmarrow_forwardThe intermediate between mechanical energy and electrical energy in electrical machines is... a) A DC battery b) Responsible for energy flow from the rotor to the stator in case of generator mode c) The magnetic field storing energy temporarily d) Responsible for energy flow from stator to rotor in case of generator mode Next Page Page 1 of 4 Submit Quiz O of 4 questions savedarrow_forwardA 22 kW, 230 V Series DC motor runs at 750 rev/min at full load and draws 110 A from the supply. The resistance of the armature is 0.1250 and the series field 0.0250. Calculate the speed when the load is reduced such that the input current reduces to 56 A. Assume that the useful flux per pole at 110 A is 23.9 mWb and the flux for 56 A is be 15.5 mWb.arrow_forward
- Q7/ What are the advantages and disadvantages of the permanent magnets dc motors?arrow_forwardA 500 V shunt motor running at 720 rpm takes an armature current of 50 A. The equivalent armature resistance is 0.4 ohm. What resistance must be placed in series with the armature to reduce the speed to 540 rpm while maintaining the same torque?arrow_forwardColve asaparrow_forward
- 1.49. A 250 V dc shunt motor has an armature resistance of 0.5 N and a field resistance of 250 Q. When driving a constant torque load at 600 rpm, the motor draws 21 A. What will be the new speed of the motor if an additional 250 N resistance is inserted in the field circuit.arrow_forwardH2arrow_forwardA 220 V series motor takes 15 A and runs at 700 rpm. The armature resistance including the resistance of the series winding is 0.8 ohm. At what speed will it run if a 2-ohm resistance is connected in series with supply voltage? Assume the motor is taking the same current.arrow_forward
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