ELECTRICITY FOR TRADES
3rd Edition
ISBN: 9780078118630
Author: Petruzella
Publisher: RENT MCG
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Textbook Question
Chapter 5.1, Problem 5RQ
What are the two basic functions of a switch?
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Students have asked these similar questions
A dc compound motor having a rating of 10 kW,
1150 r/min, 230 V, 50 A, has the following losses at
full-load:
bearing friction loss
40 W
brush friction loss
==
50 W
windage loss
=
200 W
(1)
total mechanical losses
=
290 W
(2)
iron losses
=
420 W
(3)
copper loss in the shunt field
=
120 W
copper losses at full-load:
(4)
a. in the armature
b. in the series field
c. in the commutating winding
total copper loss in the
500 W
25 W
70 W
armature circuit at full-load
=
595 W
4 What determines the power rating of a ma-
chine?
-5 If we cover up the vents in a motor, its out-
put power must be reduced. Explain.
-6 If a motor operates in a cold environment,
may we load it above its rated power? Why?
An electric motor driving a skip hoist with-
draws 1.5 metric tons of minerals from a
trench 20 m deep every 30 seconds. If the
hoist has an overall efficiency of 94 percent,
calculate the power output of the motor in
horsepower and in kilowatts.
Chapter 5 Solutions
ELECTRICITY FOR TRADES
Ch. 5.1 - Prob. 1RQCh. 5.1 - Polarity markings are shown on symbols...Ch. 5.1 - Compare the type of voltage produced by a solar...Ch. 5.1 - Explain how circuit breakers and fuses protect a...Ch. 5.1 - What are the two basic functions of a switch?Ch. 5.1 - Compare the operation of a normally open and...Ch. 5.1 - What type of circuit component is a light bulb...Ch. 5.1 - In general, what is the function of resistors...Ch. 5.1 - Two wires are shown on an electrical diagram...Ch. 5.1 - Give one advantage and one limitation of the...
Ch. 5.1 - Explain why schematic diagrams are easier to read.Ch. 5.1 - What is a wiring diagram intended to show?Ch. 5.1 - Prob. 13RQCh. 5.1 - The one-line diagram is often used with a power...Ch. 5.2 - What best describes a simple circuit?Ch. 5.2 - A lamp is to turn ON when either one or the other...Ch. 5.2 - What connection of two or more switches can be...Ch. 5.2 - Three 120-V, 40-W incandescent lamps are connected...Ch. 5.2 - Two 12-V, 10-W lamps are connected in parallel to...Ch. 5.2 - A control system calls for a light to come on when...Ch. 5.2 - One bulb in a 20-string series-connected holiday...Ch. 5.2 - Prob. 8RQCh. 5.2 - Prob. 9RQCh. 5.2 - Prob. 10RQ
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- The efficiency of a motor is always low when it operates at 10 percent of its nominal power rating. Explain.arrow_forwardA dc motor connected to a 240 V line pro- duces a mechanical output of 160 hp. Knowing that the losses are 12 kW, calculate the input power and the line current.arrow_forwardA 115 V dc generator delivers 120 A to a load. If the generator has an efficiency of 81 percent, calculate the mechanical power needed to drive it [hp].arrow_forward
- A machine having class B insulation attains a temperature of 208°C (by resistance) in a torrid ambient temperature of 180°C. a. What is the temperature rise? b. Is the machine running too hot and, if so, by how much?arrow_forward1 Name the losses in a dc motor. 2 What causes iron losses and how can they be reduced? -3 Explain why the temperature of a machine increases as the load increases.arrow_forward20. A tractor weighing 14 kN with a wheel base of 3m carries an 8 kN load on its rear wheel. Compute the maximum bending moment and shear when crossing a 4.5 span. Consider the load only at the wheels.arrow_forward
- A 110-V, three-phase, Y-connected, 8 pole, 48-slot, 6000-rpm, double-layer wound chronoun anı vonorotor boo 10 +1 urn or oilarrow_forward-7 Name some of the factors that contribute to the deterioration of organic insulators. -8 A motor is built with class H insulation. What maximum hot-spot temperature can it withstand?arrow_forwardCalculate the full-load current of a 250 hp, 230 V dc motor having an efficiency of 92 percent.arrow_forward
- Assignment #2 A 110-V, three-phase, Y-connected, 8 pole, 48-slot, 6000-rpm, double-layer wound, synchronous generator has 12 turns per coil. If one side of the coil is in slot 1, the other side is in slot 6. There are 4 parallel paths. When the generator delivers the rated load at a line voltage of 110 V, the voltage regulation is 5%. What is the flux per pole? Draw two consecutive phasegroups of one of the phase windings and connect them (a) in series and (b) in parallel showing the Start (S) and Finish (F) of both connections. (A separate drawing for each connection)arrow_forward3-4 Transmissiva Live of 120km has R= 0.2 ~2/15 X= 0.8 -2/km Y = 15H/6 5/km The line is supplies a load of 45 kV, SOMW, 0.8 lead p.f find sending voltage, Sending Current p.f. Sanding Voltage Regulation ⑨Voltage 5 Ⓒ charching coming! изу usy π cct लेarrow_forwardA (medium) single phase transmission line 100 km long has the following constants : Resistance/km = 0.25 Q; Susceptance/km = 14 × 10° siemen ; Reactance/km = 0.8 Receiving end line voltage = 66,000 V Assuming that the total capacitance of the line is localised at the receiving end alone, determine (i) the sending end current (ii) the sending end voltage (iii) regulation and (iv) supply power factor. The line is delivering 15,000 kW at 0.8 power factor Lead Draw the phasor diagram to illustrate your calculations.arrow_forward
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