Electric machinery fundamentals
5th Edition
ISBN: 9780073529547
Author: Chapman, Stephen J.
Publisher: MCGRAW-HILL HIGHER EDUCATION
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Question
Chapter 1, Problem 1.21P
(a)
To determine
The initial force and initial current flow in the bar at starting.
(b)
To determine
The no-load steady state speed of the bar.
(c)
To determine
New steady-state speed of the bar after loading. Efficiency of the machine under these circumstances.
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The flux linking to 200 turns coil
changes from 2 mWb to 5 mWb in
1ms to 3 ms. Determine the induced
voltage.*
300 V
400 V
500 V
600 V
What is the magnetomotive force
created when 5 A current flows
through 300 turns coil? *
1000 At
2000 At
1200 At
1500 At
The reluctance of a non-magnetic path is 12 AT-Wb. Find the flux needed to be set up if surrounded by a coil 600 turns carrying a current of 3 A.
ferromagnetic
core is shown in Figure P1-2.
The depth of the core is 5 cm. The other
dimensions of the core are as shown in the
figure. Find the value of the current that will
produce a flux of 0.005 Wb. With this
current, what is the flux density at the top of
the core? What is the flux density at the right
side of the core? Assume that the relative
permeability of the core is 800.
-10cm-
-20 cm-
500 turns
a.
670 kA t/Wb
b. 330 kA t/Wb
c.
500 kA t/Wb
d.
256 kA t/Wb
Core depth = 5 cm
15cm
+
15cm
15cm
5
E
Chapter 1 Solutions
Electric machinery fundamentals
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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- An iron circuit with a small 0.75 mm air gap is shown in Figure 1. A 6000 turn coil carries a current I = 18 mA which sets up a flux within the iron and across the air gap. The cross section of the iron is a consistent 0.8 cm², and the mean length of the flux path is 0.15 m. a) Redraw the magnetic circuit using schematic symbols of an electric circuit with reluctance in each part of the circuit. b) State's Ohm's Law for magnetic circuit. c) By neglecting the effect of fringing, calculate the reluctance of the circuit. d) Find the flux within the core. N = 6000 Iron circuit (ur = 800 for iron).arrow_forwardAn iron circuit with a small 0.75 mm air gap is shown in Figure 1. A 6000 turn coil carries a current I = 18 mA which sets up a flux within the iron and across the air gap. The cross section of the iron is a consistent 0.8 cm2, and the mean length of the flux path is 0.15 m. a) Redraw the magnetic circuit using schematic symbols of an electric circuit with reluctance in each part of the circuit. b) State's Ohm's Law for magnetic circuit. c) By neglecting the effect of fringing, calculate the reluctance of the circuit. d) Find the flux within the core. N = 6000 Iron circuit (4, = 800 for iron).arrow_forwardThe full-scale deflecting torque of a 20 A moving-iron ammeter is 6 x 105 N-m. What is the rate of change of self-inductance with respect to the deflection of the pointer of the ammeter at full scale?arrow_forward
- An iron circuit with a small 0.75 mm air gap is shown in Figure 1. A 6000 turn coil carries a current I = 18 mA which sets up a flux within the iron and across the air gap. The cross section of the iron is a consistent 0.8 cm?, and the mean length of the flux path is 0.15 m. a) Redraw the magnetic circuit using schematic symbols of an electric circuit with reluctance in each part of the circuit. b) State's Ohm's Law for magnetic circuit. c) By neglecting the effect of fringing, calculate the reluctance of the circuit. d) Find the flux within the core. N = 6000 Iron circuit (4, = 800 for iron). Figure 1arrow_forwardAn iron circuit with a small0.75 mm air gap is shown in Figure 1. A 6000 turn coil carries a current I = 18 mA which sets up a flux within the iron and across the air gap. The cross section of the iron is a consistent 0.8 cm2, and the mean length of the flux path is 0.15 m. a) Redraw the magnetic circuit using schematic symbols of an electric circuit with reluctance in each part of the circuit. b) State's Ohm's Law for magnetic circuit. c) By neglecting the effect of fringing, calculate the reluctance of the circuit. d) Find the flux within the core. N = 6000 Iron circuit (u, = 800 for iron). Figure 1arrow_forward1-5. A ferromagnetic core is shown in Figure P1-2. The depth of the core is 5 cm. The other dimensions of the core are as shown in the figure. Find the value of the current that will produce a flux of 0.005 Wb. With this current, what is the flux density at the top of the core? What is the flux density at the right side of the core? Assume that the relative permeability of the core is 800. 5cm -20-cm- -10cm- To 500 ABS Core depth = 5 cm 15cm 15 cm 15 cmarrow_forward
- A dc machine has hysteresis loss of 300 W and an eddy current loss of 200 W when running at 1200 rpm. At what speed will the total core losses be a quarter of the original if the flux is to be twice as the original.arrow_forwardTHIS QUESTION IS FROM BOOK ELECTRIC MACHINE 1 FROM TOPIC DC MOTOR A 220V DC series motor derives a load certain speed load and it takes a current of. Botharmature and field resistances are equal to 0.75Ω. The speed needs to be reduced by 70%by making some amendments in the motor circuit. One possible design is adding an extraresistance in series with a motor circuit. In this design, torque is not remained constant andis proportional to the square of the speed of the motor. (a) Estimate this extra resistance. Draw the amended circuit diagram. (b) Also suggest any other possible design ( with circuit diagram) to reduce the speed as torqueremains constant. (c) Is there any risk to start this machine without load without any amendment? If yes, pleaseexplain.arrow_forwardA ferromagnetic core is shown in Figure PI-2. The depth of the core is 5 cm. The other dimensions of the core are as shown in the figure. Find the value of the current that will produce a flux of 0.005 Wb. With this current, what is the flux density at the top of the core? What is the flux density at the right side of the core? Assume that the relative permeability of the core is 1000. -10 cm- - 20 cm- 15 cm 400 turns 15 cm 15 cm Core depth 5 cmarrow_forward
- For the magnetic circuit shown in the figure, the iron core with N = 500 turns -Magnetic permeability is 200. its average length is 10 cm -The diameter of the cross-sectional area is 1 cm. Find the current that must pass through the winding to produce 0.5 mWb of flux in a 1mm air-gap magnetic circuit?arrow_forwardA ferromagnetic core is shown in Figure Pl-2. The depth of the core is 5 cm. The other dimensions of the core are as shown in the figure. Find the value of the current that will produce a flux of 0.005 Wb. With this current, what is the flux density at the top of the core? What is the flux density at the right side of the core? Assume that the relative permeability of the core is 800. 1-5. 10 cm- 5em 20 em 15 cm 15 cm 15 cm Coe depth - Scm SOLUTION There are three regions in this core. The top and bottom form one region, the left side forms a second region, and the right side forms a third region. If we assume that the mean path length of the flux is in the center of each leg of the core, and if we ignore spreading at the corners of the core, then the path lengths are I, = 2(27.5 cm) = 55 cm, I, = 30 cm, and /, = 30 cm. The reluctances of these regions are:arrow_forward1.Consider the magnetic core below.All dimensions are shown on the figure. The core is made up of legs with 2 different cross-sectional areas.The depth of core is 10cm.The relative permeability of the core is 2000. The current in the magnetising coil is 1 A. The number of turns of the coil is 2000.Calculate: (i)the reluctances and draw the magnetic circuit (ii)the flux in the core (iii)Flux densities B and field intensities H in legs having different cross-sectional areas. (iv)Verify Ampere's Law. Depth: 10 cm I=1A 20cm 2000 Turns 65cm 15cm 15cm 50cm 15cm ndo un ofarrow_forward
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