EBK ELECTRICAL TRANSFORMERS AND ROTATIN
4th Edition
ISBN: 9781337025867
Author: Herman
Publisher: VST
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Chapter 15, Problem 20RQ
To determine
The efficiency of the motor.
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Question 2 Calculate the amount of DC current required for the magnetic circuit given below to generate a
flux density of 1.0 T in the airgap. The details are
Number of turns, N = 400
The core is made up of steel, the B-H characteristic has been given below
The magnetic core length, le = 500 mm
The airgap length, Ig = 2 mm
The cross-sectional area of the core, Ag = 100 mm²
Neglect leakage and fringing.
Core
Cross-sectional
i(1)
area
as
Air gap
Magnetic path
length
Figure 1
2.0
1.8
B-H Curves for Various Metals
Steel
1.6
1.4
Magnetic
Saturation
1.2
1.0
0.8
Iron
근 0.4
Air
0.2
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Magnetic Field Strength - H (A/m)
Figure 2
Flux Density - B (T)
The working current has a power of 100 kW and a power factor of 0.50. After a capacitor of 75 KVAR is installed, what does the
power factor become?
A 0.84
B 0.71
C 0.63
D 0.78
E 0.92
A motor works when it is connected to AC. By mistake you connect it to
DC, but you see it also works with DC. What kind of motor is it?
Chapter 15 Solutions
EBK ELECTRICAL TRANSFORMERS AND ROTATIN
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- A motor develops 189 ft-lb of torque at 1745 RPM. What is the horse-power output of the motor?arrow_forwardAssume that a primary current of 75 amperes flows through the windings of the transformer in question 4. How much current will flow in the secondary winding?arrow_forwardA current transformer has 4 turns of wire in its primary winding. How many turns of wire are needed in the secondary winding to produce a current of 2 amperes when a current of 60 amperes flows in the primary winding?arrow_forward
- If the secondary of the transformer in question 5 supplies a current of 9.6 amperes to a load, what is the primary current? (Disregard excitation current.)arrow_forwardA motor develops 225 ft-lb of torque at 860 RPM. What is the horsepower output of the motor?arrow_forwardIf a single-phase load is connected across the two line conductors and neutral of the transformer in question #2, and one line has a current of 80 amps and the other line has a current of 68 amps, how much current is flowing in the neutral conductor?arrow_forward
- A current transformer has a ratio of 600:5. If three loops of wire are wound through the transformer core, how much primary current is required to produce 5 amperes of current in the secondary winding?arrow_forwardA 3 kVA motor operates from a 240 V supply at 50 Hz and has a power factor of 0.6. Determine the active power Select one: 1800 W Non of the Answers 1900 W 2000 Warrow_forwardTwo transformers rated at 100 kVA each are connected in an open-delta connection. What is the total output power that can be supplied by this bank?arrow_forward
- A CT has a current flow of 80 amperes in its primary winding and a current of 2 amperes in its secondary winding. What is the ratio of the CT?arrow_forwardA motor is operating a load that requires a torque of 750 lb–in and is turning at a speed of 1,575 RPM. How much horsepower is the motor producing?arrow_forwardQuestion 2 Beli vifth Slack side Motor (imprut) Tight side Beli thickpess\ Centre distance Figure 2 Figure 2 shows an open flat belt drive connected to a motor and a pulley. The motor transmits 20 kw to the connect pulley of 450 mm diameter and is rotating at 850 r/min to a second pulley rotating at 400 r/min. The distance between pulley centres is approximately 2 m. The belt is 6 mm thick and has a density of 970 kg/m. The maximum stress in the belt is not to exceed 2,7 MPa. The coefficient of friction for both pulleys is 0,3. Determine: 2.1. The diameter of the second pulley. 2.2. The length of the belt. 3.3. The width of the belt taking centrifugal tension into account.arrow_forward
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