ELECTRICITY FOR TRADES
3rd Edition
ISBN: 9780078118630
Author: Petruzella
Publisher: RENT MCG
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Textbook Question
Chapter 7.2, Problem 20RQ
A 400-W 4-Ω public address speaker is to be fused for overload protection. What maximum current rating of a fuse should be used? (Hint: P = I2R.)
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2. A three-phase, four-wire, 208 V, ABC system supplies a Y-connected load in
which Zд = 100°N, Z = 15/30° and Zc = 104-30°. Find the line
currents, the neutral current and total real and reactive powers. Draw the phasor
diagram of the phase voltages and currents.
ZA
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3. A three-phase, three-wire, 208 V, ABC system supplies a Y-connected load in
which ZA 100°, ZB = 15230° and Zc = 10-30°. Find the line
currents, the phase voltages across the load impedances, the total real and reactive
powers and the voltage Von
VA
ZA
Don't use ai to answer I will report you answer
Discuss the importance of power-factor correction in
a.c. systems.
A 400 V, 50 Hz, three-phase distribution system
supplies a 20 kVA, three-phase induction motor load
at a power factor of 0.8 lagging, and a star-connected
set of impedances, each having a resistance of 10 Ω
and an inductive reactance of 8 Ω. Calculate the
capacitance of delta-connected capacitors required to
improve the overall power factor to 0.95 lagging.
ANS: 75 µF/ph
Chapter 7 Solutions
ELECTRICITY FOR TRADES
Ch. 7.1 - What is the base unit and symbol used for...Ch. 7.1 - Write the metric prefix and symbol used to...Ch. 7.1 - Convert each of the following: a. 2,500 to...Ch. 7.2 - State Ohms law.Ch. 7.2 - List the three formulas associated with Ohms law.Ch. 7.2 - Calculate the unknown value for each circuit (a)...Ch. 7.2 - A pilot lamp with 12 volts applied to it draws a...Ch. 7.2 - A resistor has a resistance of 220 . The current...Ch. 7.2 - An electric soldering iron with a 40- heating...Ch. 7.2 - A baseboard heater draws a current of 8 A when...
Ch. 7.2 - A sensor module has an internal resistance of...Ch. 7.2 - The current through and the voltage drop across a...Ch. 7.2 - The heating element for an electric floor heating...Ch. 7.2 - How much power is lost in the form of heat when 25...Ch. 7.2 - The voltage drop across a 330- resistor is...Ch. 7.2 - A digital multimeter display indicates a reading...Ch. 7.2 - Calculate the unknown value for each circuit (a)...Ch. 7.2 - Assume that applying 120 volts to a resistive load...Ch. 7.2 - The voltage drop across a 10-W, 330- resistor is...Ch. 7.2 - The cold resistance of a tungsten lamp filament is...Ch. 7.2 - An electric baseboard heater is rated for 1200 W...Ch. 7.2 - A lamp dimmer switch is rated for 5 A at 120 V....Ch. 7.2 - A 400-W 4- public address speaker is to be fused...
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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
- A 60hp,3-phase motor absorbs 50 kW from a 600 V,3-phase line. If the line current is 60 A, calculate the following: a. The efficiency of the motor b. The apparent power absorbed by the motor c. The reactive power absorbed by the motor and the power factor of the motorarrow_forwardThree 15Ω resistors and three 8Ω reactors are connected as shown in Fig. 18. If the line voltage is 530 V, calculate the following: a. The active, reactive, and apparent power supplied to the 3 -phase load b. The voltage across each resistorarrow_forwardThree resistors are connected in delta. If the line voltage is 13.2kV and the line current is 1202 A, calculate the following: A) the current in and the voltage acroos each resistor B) The power supplied to each resistor and the 3 phase load C) The ohmic value of each resistorarrow_forward
- With the aid of a phasor diagram show that the active power and power factor of a balanced three-phase load can be measured by two wattmeters. For a certain load, one wattmeter indicated 20 kW and the other 5 kW after the voltage circuit of this wattmeter had been reversed. Calculate the active power and the power factor of the load. ANS: 15 kW, 0.327arrow_forwardState the advantages to be gained by raising the power factor of industrial loads. A 400 V, 50 Hz, three-phase motor takes a line current of 15.0 A when operating at a lagging power factor of 0.65. When a capacitor bank is connected across the motor terminals, the line current is reduced to 11.5 A. Calculate the rating (in kVA) and the capa citance per phase of the capacitor bank for: (a) star connection; (b) delta connection. Find also the new overall power factor. ANS: 3.81 kvar, 70.5 µF, 23.5 µF, 0.848 laggingarrow_forwardA single wattmeter is used to measure the total active power taken by a 400 V, three-phase induction motor. When the output power of the motor is 15 kW, the efficiency is 88 per cent and the power factor is 0.84 lagging. The current coil of the wattmeter is connected in the yellow line. With the aid of a phasor diagram, calculate the wattmeter indication when the voltage circuit is connected between the yellow line and (a) the red line, (b) the blue line. Show that the sum of the two wattmeter indications gives the total active power taken by the motor. Assume the phase sequence to be R–Y–B. ANS: 11.7 kW, 5.33 kWarrow_forward
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