Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
expand_more
expand_more
format_list_bulleted
Concept explainers
Videos
Textbook Question
thumb_up100%
Chapter 27, Problem 1SQ
Why is it desirable to remove the autotransformers from the line when the motor reaches its rated speed?
Expert Solution & Answer
To determine
Explain the reason why it is desirable to remove the autotransformer starters from the line when the connected motor reaches its rated speed.
Explanation of Solution
Autotransformer starter is placed between the motor and supply power lines to limit the supply voltage that is provided across the terminals of the motor during accelerating of the connected motor. With the lower accelerating voltage, motor draws less current and produces less torque in motor. Taps are provided on the autotransformer starters to permit the user to initiate the motor at an increasing speed from 50 percent, 60 percent, 75 percent or 85 percent of the line voltage.
The autotransformer starters are removed from the line connection when the motor attains the rated speed to obtain the required electrical energy by removing the magnetizing current, iron, and copper losses. Generally, the insulating life of the autotransformers may extend due to reduced heat and voltage applications.
Conclusion:
Thus, the reason why it is desirable to remove the autotransformer starters from the line when the connected motor reaches its rated speed is explained.
Want to see more full solutions like this?
Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Students have asked these similar questions
(B)- Indicate whether the following statements are true or false and correct the false statements
1-In d.c shunt motor the main advantage of rheostatic control method, the speed up to zero is
possible
The imaginary component of no load current for transformer is responsible for the consumption
of iron loss
3- The speed of d.c series motor is decreased if the armature current is increased
4- The armature voltage of d.c series generator is not affected by load current
5-The regulation at rated load of a transformer same at 0.8 pf lag and 0.8 pf lead
tuo
H.W/ Definition all these terms:
1- Slip rings
2- armature reaction
3- synchronous motor V curve
4- damper windings
5- Synchronous machine ratings
Shunt generator will build up its voltage
when:
Olts field resistance higher than critical value.
Olts field resistance is less than critical value.
Chapter 27 Solutions
Electric Motor Control
Ch. 27 - Why is it desirable to remove the autotransformers...Ch. 27 - What is meant by an open transition from start to...Ch. 27 - Which of the following applies to an...Ch. 27 - How are reduced voltages obtained from...Ch. 27 - Prob. 5SQCh. 27 - What is a disadvantage of starting with...Ch. 27 - What is one advantage of using an autotransformer...
Knowledge Booster
Learn more about
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
- 23. When the circuit breaker is always tripping, most likely There is an overloading c. The supply line are open a. b. There is an over current d. The load is removed 24. The synchronous motor is not inherently self- starting because the rotating magnetic field does not have enough poles b. the rotating magnetic field is produced by only 50 HZ frequency currents the force required to accelerate the rotor is to the synchronous speed in an instant is d. the starting devices to accelerate the rotor to near synchronous speed is absent 25. Synchronous motor has speed a. slight drop in speed on full load b.high speed at low torque а. с. c. constant speed d. low speed at high -arrow_forwardWhy it is much prefer in alternator to have station armature androtating poles?arrow_forwardPlease answer question number 1 thank youarrow_forward
- Q2] Fill in the blank (9 Marks) 1-The current drwan by the armature of D.C. motor is directly proportional to 2- The speed of a D.C. shunt-wound motor will shunt field regulator is increased. 3- The synchronous speed of a three-phase induction motor is number of pairs of poles. Rotor copper losses Rotor input power in induction motor = 5- A 4-pole three-phase induction motor has a synchronous speed of 25 r.p.s. The frequency of the supply to the stator is_ Hz. 6- The power input to a mains transformer is 200VA. If the primary current is 2.5A, the secondary voltage is 2V and assuming no losses in the transformer, the turns ratio step down. is 7- A 200kVA transformer has an iron loss of 1 kW and full load cu loss of 2 kW. Its load kVA corresponding to maximum efficiency is kVA. 8- If cu loss of a transformer at 7/8th full load is 4900 W, then its full-load cu loss would be watt. 4- if the value of resistance of the proportional to the 9- The slight curvature at the lower end of the open…arrow_forwardOne type of failure that's more common with 200 HP motors than with 10 HP motors is A. rotor bar failure.B. contactor failure.C. bearing failure. D. stator failures.arrow_forwardDraw the circuitarrow_forward
- What effect does increasing rotor circuit resistance have on the breakdown torque and on slip at which breakdown occurs.arrow_forward19. What effect does slip have on rotor reactance of a 3-phase squirrel-cage induction motor? a) rotor reactance increases with increases in slip b) rotor reactance decreases with increases in slip c) rotor reactance is not influenced by slip d) none of the abovearrow_forwardQ2- Indicate whether the following statements are true or false and correct the false statements 1- The brushes of d.c machine always are placed at the magnetic neutral axis 2- The field current of d.c shunt generator is not affected by load current. 3-The armature voltage of d.c series generator is not affected by load current. 4- A lap winding is most suitable for higher voltage rating machines 5- In de generator, the critical resistance can be increased by increasing its speed 6-In LAP winding the front pitch equal to (yr Ye- yb). 7- The speed of d.c series motor is decreased if the armature current is decreased 8- The compensating winding carrying the field current 9- By tapping field method, the speed of d.c series motor can be controlled below rated value 10- To solve the Commutation Problem in small machines, this can be achieved by increasing the brush widtharrow_forward
- The windings of short-shunt compound dc generator have the following resistances: Armature, shunt field, interpole and series field are 0.5 ohm, 253 ohms, 0.2 ohm and 0.15 ohm respectively When the generator delivers 40 amperes at 500 Volts, its total drop is 2 Volts. What is the generated power?arrow_forward1- What is the starting torque developed by a split-phase or a capacitor start motor? 2- What is the current in-rush at the time of starting the motor? Does it cause severe fluctuations on the line?arrow_forward14. Under line voltage control of induction motor the speed regulation occurs: a) by change of the slip of the motor. b) by change of the synchronous speed of the motor. c) by adding additional resistance in the rotor circuit. d) by changing the stator resistance of the motor.arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Electricity for Refrigeration, Heating, and Air C...Mechanical EngineeringISBN:9781337399128Author:Russell E. SmithPublisher:Cengage Learning
Electricity for Refrigeration, Heating, and Air C...
Mechanical Engineering
ISBN:9781337399128
Author:Russell E. Smith
Publisher:Cengage Learning
TRANSFORMERS - What They Are, How They Work, How Electricians Size Them; Author: Electrician U;https://www.youtube.com/watch?v=tXPy4OE7ApE;License: Standard Youtube License