EBK ELECTRIC MACHINERY
5th Edition
ISBN: 9780100253919
Author: Chapman
Publisher: YUZU
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Question
Chapter 1, Problem 1.17P
(a)
To determine
The reasonable maximum flux density for the given core.
(b)
To determine
The total flux in the core for the given flux density.
(c)
To determine
The reasonable number of turns which provide the required flux density for the given case.
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DC MACHINE TORQUE
The armature of a dc motor has 648 conductors, 65 % of which are directly under thepole where the flux density is 48,000 lines per in2. If the core diameter is 7 inchesand its length is 4 inches and the current in each conductor is 20 A. What is thetorque exerted in the armature in N-m?
Suppose that we are designing a 1200-rpm dc motor to run from a 240-V source. We have determined that the flux density will be 1 T because smaller fluxes make inefficient use of the iron and larger fluxes result in saturation. The radius of the rotor (and thus, the torque arm for the armature conductors) is 0.1 m. The lengths of the armature conductors are 0.3 m. Approximately how many armature conductors must be placed in series in this machine?
The current in a conductor on the armature of a dc motor is 300A. The flux under the poles is 850x10-6 Wb. The area per pole is 700 mm2. The length of the conductor on the armature is 640mm. Calculate the force exerted on the conductor.
Chapter 1 Solutions
EBK ELECTRIC MACHINERY
Ch. 1 - What is torque? What role does torque play in the...Ch. 1 - What is Amperes law?Ch. 1 - What is magnetizing intensity? What is magnetic...Ch. 1 - How does the magnetic circuit concept aid in the...Ch. 1 - What is reluctance?Ch. 1 - What is a ferromagnetic material? Why is the...Ch. 1 - How does the relative permeability of a...Ch. 1 - Prob. 1.8QCh. 1 - What are eddy current losses? What can be done to...Ch. 1 - Why are all cores exposed to ac flux variations...
Ch. 1 - What is Faraday law?Ch. 1 - What conditions are necessary for a magnetic field...Ch. 1 - What conditions are necessary for a magnetic field...Ch. 1 - Prob. 1.14QCh. 1 - The linear machine in Figure 1-19 is running at...Ch. 1 - Just how does a decrease in flux produce an...Ch. 1 - Will current be leading or lagging voltage in an...Ch. 1 - What are real, reactive, and apparent power? What...Ch. 1 - What is power factor?Ch. 1 - Prob. 1.1PCh. 1 - A flywheel with a moment of inertia of 4kgm2 is...Ch. 1 - A force of 10 N is applied to a cylinder of radius...Ch. 1 - A motor is supplying 50Nm of torque to its load....Ch. 1 - A ferromagnetic core is shown in Figure P1-2. The...Ch. 1 - A ferromagnetic core with a relative permeability...Ch. 1 - A two-legged core is shown in Figure P1-4. The...Ch. 1 - A core with three legs is shown in Figure P1-5....Ch. 1 - A two-legged core is shown in Figure P1-4. The...Ch. 1 - A wire is shown in Figure P1-7 that is moving in...Ch. 1 - Repeat Problem 1-10 for the wire in Figure P1-8.Ch. 1 - Prob. 1.12PCh. 1 - A core with three legs is shown in Figure P1-10....Ch. 1 - A two-legged magnetic core with an air gap is...Ch. 1 - A transformer core with an effective mean path...Ch. 1 - The core shown in Figure P1-2 has the flux shown...Ch. 1 - Prob. 1.17PCh. 1 - Prob. 1.18PCh. 1 - Prob. 1.19PCh. 1 - Demonstrate that Equation (1-59) can be derived...Ch. 1 - Prob. 1.21PCh. 1 - Prob. 1.22PCh. 1 - For the linear machine of Problem 1-22: When this...
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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
The armature of a 4-pole dc machine rotates at 840 rpm. The armature length and diameter are 40 cm and 30 cm respectively. The flux per pole is 65 mWb. Each armature coil has 5 turns, and develops an average torque of 3 .0 Nm .a. Find the coil emf, current, and conversion power .b. Make a rough estimate of the copper (I2 R) loss in the coil assuming it is made of 1.0 mm 2 copper wire, and the losses during operation raise the temperature to 80 0 c
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A 6-pole lap wound dc shunt motor has 60 conductors. The armature and shunt fields resistance are 0.06Ω and 20 Ω respectively. Find the speed of the dc motor if takes 110 A from a d.c supply of 100 V. (given flux per poles is 0.02 wb)
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A simplex lap wound armature has 580 conductors and carries a current of 125 A per armature current path. If the flux per pole is 20 m weber.
Find:
- the power developed
- the torque developed by the armature.
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An 8-pole DC machine has a simplex wave-wound armature containing 200 coils of 10 turns each. The resistance of each turn is 0.01 Ω. The flux per pole is 0.004 Wb.
What is the internal resistance of the armature in ohms?
What is the current absorbed by this machine in amperes at the instant it's connected to a 100 Vdc source?
What is the internally generated torque produced by the armature of this machine in N-m at the instant it's connected to the 100 Vdc source?
With the DC machine connected to the 100 Vdc source, what is the steady state angular speed of the machine in rpm?
What is the internally generated voltage of the armature of this machine at steady state in volts?
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Q3. B. what are the features of Lap winding of DC machine?
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The 4-pole direct current electric machine works as a generator. In this direct current machine, which also has auxiliary poles, the direction of the excitation flux is from bottom to top at the remaining pole located at the top of the armature from the main poles on the d axis. As the current direction is ๏ in armature conductors corresponding to the same pole;
a. Find the direction of flux at the main poles.b. Find the current direction at the main polesc. Find the direction of flux at the auxiliary poles.d. Find the current direction at the auxiliary poles.e.Show the direction of rotation by drawing a figure.
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Consider the linear dc machine shown in Figure 15.6 on page 754. What happens to the initial force (i.e., starting force) induced in the bar if: a. the source voltage VT is doubled in magnitude; b. the resistance RA is doubled; c. the magnetic flux density B is doubled in magnitude?
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Consider the linear dc machine shown in Figure 15.6 on page 754 with no load force applied. What happens to the steady-state velocity of the bar if: a. the source voltage VT is doubled in magnitude; b. the resistance RA is doubled; c. the magnetic flux density B is doubled in magnitude?
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• A DC shunt machine while running as generator develops a voltage of 250 V at 1000 r.p.m. on no-load. It has armature resistance of 0.5 ohm and field resistance of 250 ohm. When the machine runs as motor, input to it at no-load is 4 A at 250 V. Calculate the speed and efficiency of the machine when it runs as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4 %
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5. A d.c. shunt machine has armature and field resistances of 0.025 Ω and 80 Ω respectively. When connected to constant 400-V bus-bars and driven as a generator at 450 r.p.m., it delivers 120 kW. (a) Calculate its speed when running as a motor and absorbing 120 kW from the same bus-bars. (b) Deduce the direction of rotation of this machine when it is working as a motor assuming a clockwise rotation as a generator
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An eight-pole, 24 KW, 100 V, DC machine has a duplex LAP-wound armature which has 64 coils with 10 turns per coil. Its rated speed is 3000 RPM. Assume a dead zone of 4 coils that are always beyond poles faces. Find the constant K and the flux per pole to produce 80 Volts at no-load conditions Select one:
a. K = 59.5 and flux = 1.27 mWb/pole
b. K = 95.5 and flux = 2.67 mWb / pole
c. None
d. K = 91.5 and flux = 0.267 Wb / pole
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Q3: Each ferromagnetic material has a remanence in its magnetic characteristics, but they are not all suitable to be used in a permanent magnet motor! Explain why? And show the required magnetic characteristics suitable for that job.
This question is about specialized machines
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