Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 26, Problem 6SQ
To determine
Explain how the starter provides smooth acceleration and a gradual increase of torque.
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A 250 V, 37 KW, dc shunt motor has to expert a maximum torque of 150% of full load torque during the starting period. The resistance of armature circuit is
0.2Ω and full load efficiency is 84%. The no.of studs is 8 Derermine
:-The upper and lower limit of current during starting.
A 200 V d.c. shunt motor takes 4 A at no-load when running at 700 rpm. The field resistance is 100 Ω. The armature resistance at standstill gives a drop of 6 V across armature terminals when 10 A were passed through it. Calculate (i) the speed full-load, (ii) the armature torque, (iii) efficiency. The normal input of motor is 8 kW
Design a suitable 8 section starter for a 14.92 kW, 250 volt, 1000 rpm d.c. shunt motor from the following data:
Maximum starting torque= full load torque
Armature circuit resistance = 0.4 ohm
Full load efficiency = 0.85
Chapter 26 Solutions
Electric Motor Control
Ch. 26 - What is the purpose of inserting resistance in the...Ch. 26 - Why is the power not interrupted when the motor...Ch. 26 - If the starter is to function properly and a...Ch. 26 - How may additional steps of acceleration be added?Ch. 26 - What is meant by the low or poor starting economy...Ch. 26 - Prob. 6SQ
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- Why do we use starter for a DC motor?arrow_forwardGrade the resistance of a 5 section starter for a 3.7 kW, 250 V, 1000 rmp D.C. shunt motor from the following date. Maximum torque at starting = 1.5 times full load torque, full load efficiency= 0.82, Armature circuit resistance = 1Ω field current = 1.2 Amp.arrow_forwardQ/ When a series dc motor is operated without a load, which of the following conditions occurs? * Ans 1- The armature draws excessive current 2- The armature speeds out of control 3- The armature will not turn 4-The voltage requirement increasesarrow_forward
- A 4 pole, 500V shunt motor has 720 wave connected conductors on its armature. The full load armature current is 60A and flux per pole is 0.03Wb. The armature resistance is 0.2Ω and contact drop per brush is 1V. What is the back emf? What is the developed torque?arrow_forwardA 500-V, 37.3 kW, 1000 RPM DC shunt motor has on full-load an efficiency of 90 percent. The armature circuit resistance is 0.24 and there is total voltage drop of 2 V at the brushes. The field current is 1.8 A. Determine total resistance in motor starter to limit the starting armature current to 1.5 times the full-armature current.arrow_forwardWhat is the name of the speed control by varying the flux of the DC motor? a. Flux control method b. Voltage control method c. None of the above d. Armature control methodarrow_forward
- 15/ What is the name of the speed control by varying the field current of the DC motor? a. Flux control method b. None of the above c. Armature control method d. Voltage control methodarrow_forwardA 4 pole, 220 V d.c. shunt motor, lap wound has 960 conductors. The flux per pole is 20 mWb. Determine the torque developed by the armature when the current drawn by the motor is 28 A. The armature resistance is 0.1 ohm and the shunt field resistance is 125 ohm. The rotational losses of the machine amounts to 800 wattsarrow_forwardANSWERE FAST PLEASE QUESTION from book ELECTRIC MACHINE-1 LAB BASESD QUESTION Answer precisely keeping in view the experiments performed with the equipment in the lab. iv. What effect will the load have on a DC shunt motor with significantly high armature resistance?v. For the four-point DC starter kit, what will happen if the series resistances are connected in reverseorder. Draw and explain how this combination is better than the 3 points started.arrow_forward
- 2- A 200V d.c shunt motor has an armature resistance of 2 Ώ and it is running with 100 rpm , the armature current of 10A. Assume armature current is constant. Find the speed when external resitance added with armature is same as actual value. a. 102.6 rpm b. 94.7 rpm c. 88.9 rpm d. 89.5 rpmarrow_forwardB.2. Discuss the advantages of following ac motor starting methods (consider Starting torque, the possibility of using as a speed controller) 1.Star Delta Starter 2.VFD 3.Soft Starter Voltage Rampingarrow_forward6 ) A 250 v shunt motor on no load runs at 1000 rpm and takes 5 A. The armature and shunt field resistances are respectively 0.2 and 250 n Calculate the speed when loaded and taking a current of 50 A , if the armature reaction weakens the field by 3 % .arrow_forward
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