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All Textbook Solutions for Delmar's Standard Textbook Of Electricity
Assume that the circuit shown in Figure 17-2 is connected to a 480-V, 60-Hz line. The inductor has an inductance of 0.053 H, and the resistor has a resistance of 12 . ET480VITZVAPFERIRR12PELILXLVARsLL0.053H FIGURE 17-2 R-L series circuit.Assume that the voltage drop across the resistor, ER, is 78 V, that the voltage drop across the inductor, EL, is 104 V, and the circuit has a total impedance, Z, of 20 . The frequency of the AC voltage is 60 Hz. ETITZ20VAPFER78VIRRPEL104VILXLVARsLLAssume the circuit shown in Figure 17-2 has an apparent power of 144 VA and a true power of 115.2 W. The inductor has an inductance of 0.15915 H, and the frequency is 60 Hz. ETITZVA144PFERIRRP115.2WELILXLVARsLL0.15915HAssume the circuit shown in Figure 17-2 has a power factor of 78%, an apparent power of 374.817 VA, and a frequency of 400 Hz. The inductor has an inductance of 0.0382 H. ETITZVA374.817PF78%ERIRRPELILXLVARsLL0.0382HIn an R-L series circuit, ET=240volts,R=60,andXL=75.FindEL.In an R-L series circuit, ET=208volts,R=2.4k,andXL=1.5k. Find PF.In an R-L series circuit, ET=120volts,R=35,andXL=48. Find reactive power.In an R-L series circuit, the apparent power is 560 VA, PF = 62%. Find reactive power.9. An R-L series circuit is connected to a 60-Hz, 208-volt power line. A clamp-on ammeter indicates a current of 18 amperes. The inductor has a reactive power of 1860 VARs. What is the value of R?
In an R-L series circuit, Z=88,R=32.FindXL.In an R-L series circuit, apparent power = 450 VA, reactive power = 224 VARs. Find true power.In an R-L series circuit, =22, true power = 94 watts. Find reactive power.An R-L series circuit contains two resistors and two inductors. The resistors have values of 120 and 300 . The inductors have reactive values of 220 and 470 . Find impedance.An R-L series circuit contains two resistors and two inductors. The resistors dissipate powers of 96 watts and 125 watts. The inductors have reactive powers of 100 VARs and 78 VARs. What is the power factor?An R-L series circuit contains two resistors and two inductors. The resistors are 68 and 124 . The inductors have inductive reactances of 44 and 225 . The total voltage is 240 volts. Find the voltage drop across the 124- resistor.An R-L series circuit contains two resistors and two inductors. The resistors are 86 k and 68 k . The inductors have inductive reactances of 24 k and 56 k . The total voltage is 480 volts. Find the voltage drop across the 56-k inductor.1. When an inductor and a resistor are connected in parallel, how many degrees out of phase are the current flow through the resistor and the current flow through the inductor?
2. An inductor and resistor are connected in parallel to a 120-V, 60-Hz line. The resistor has a resistance of 50 ohms, and the inductor has an inductance of 0.2 H. What is the total current flow through the circuit?
3. What is the impedance of the circuit in Question 2?
4. What is the power factor of the circuit in Question 2?
How many degrees out of phase are the current and voltage in Question 2?6. In the circuit shown in Figure 18-1, the resistor has a current flow of 6.5 A and the inductor has a current flow of 8 A. What is the total current in this circuit?
7. A resistor and an inductor are connected in parallel. The resistor has a resistance of 24 ohms, and the inductor has an inductive reactance of 20 ohms. What is the impedance of this circuit?
The R-L parallel circuit shown in Figure 18-1 has an apparent power of 325 VA. The circuit power factor is 66%. What is the true power in this circuit?The R-L parallel circuit shown in Figure 18-1 has an apparent power of 465 VA and a true power of 320 W. What is the reactive power?How many degrees out of phase are the total current and voltage in Question 9?Incandescent lighting of 500 W is connected in parallel with an inductive load. A clamp-on ammeter reveals a total circuit current of 7 A. What is the inductance of the load connected in parallel with the incandescent lights? Assume a voltage of 120 V and a frequency of 60 Hz.You are working on a residential heat pump. The heat pump is connected to a 240-V, 60-Hz power line. The compressor has a current draw of 34 amperes when operating. The compressor has a power factor of 70%. The backup strip heat is rated at 10 kW. You need to know the amount of total current draw that will occur if the strip heat comes on while the compressor is operating.Assume that the circuit shown in Figure 18-1 is connected to a 60-Hz line and has a total current flow of 34.553 A. The inductor has an inductance of 0.02122 H, and the resistor has a resistance of 14 . ET ER EL IT34.553A IR IL Z R14 XL VA P VARSL PF L0.02122HAssume that the current flow through the resistor, IR, is 15 A; the current flow through the inductor, IL is 36 A; and the circuit has an apparent power of 10,803 VA. The frequency of the AC voltage is 60 Hz. ET ER EL IT IR15A IL36A Z R XL VA10,803 P VARSL PF LAssume that the circuit in Figure 18-1 has an apparent power of 144 VA and a true power of 115.2 W. The inductor has an inductance of 0.15915 H, and the frequency is 60 Hz. ET ER EL IT IR IL Z R XL VA144 P115.2 VARSL PF L0.15915HAssume that the circuit in Figure 18-1 has a power factor of 78%, an apparent power of 374.817 VA, and a frequency of 400 Hz. The inductor has an inductance of 0.0382 H. ET ER EL IT IR IL Z R XL VA374.817 P VARSL PF78 L0.0382HIn an R-L parallel circuit, R=240 and XL=360. Find impedance.In an R-L parallel circuit, IT=0.25 amps, IR=0.125 amps. The inductor has a reactive power of 75 VARs. What is ET?In an R-L parallel circuit, ET=120 volts, R=120,XL=150. Find IL.In an R-L parallel circuit, ET=48 volts, IT=0.25 amps, R=320. Find XL.In an R-L parallel circuit, ET=240 volts, R=560 R = 560 2, and XL=330. Find reactive power.In an R-L parallel circuit, ET=240 volts, R=560, and XL=330. Find apparent power.In an R-L parallel circuit, ET=208 volts, R=2.4k, and XL=1.8k. Find IT.In an R-L parallel circuit, ET=480 volts, R=16, and XL=24. Find PF.In an R-L parallel circuit, IT=1.25 amps, R=1.2k, and XL=1k. Find IRIn an R-L parallel circuit, true power =4.6 watts and reactive power =5.4 VARs. What is the apparent power?An R-L parallel circuit is connected to 240 volts at 60 Hz. The resistor has a resistance of 68 , and the inductor has an inductive reactance of 48 . What is the reactance of the inductor?An R-L parallel circuit has an applied voltage of 208 volts and a total current of 2 amperes. The resistor has a value 180 . Find IL.1. What is the dielectric?
List three factors that determine the capacitance of a capacitor.A capacitor uses air as a dielectric and has a capacitance of 3 F. A dielectric material is inserted between the plates without changing the spacing, and the capacitance becomes 15 F. What is the dielectric constant of this material?4. In what form is the energy of a capacitor stored?
Four capacitors having values of 20 F, 50 F, 40 F, and 60 F are connected in parallel. What is the total capacitance of this circuit?f the four capacitors in Question 5 were to be connected in series, what would be the total capacitance of the circuit?A 22-F capacitor is connected in series with a 90-k resistor. How long will it take this capacitor to charge?8. A 450-pF capacitor has a total charge time of 0.5 second. How much resistance is connected in series with the capacitor?
Can a nonpolarized capacitor be connected to a DC circuit?Explain how an AC electrolytic capacitor is constructed.What type of electrolytic capacitor will be permanently damaged if connected to the incorrect polarity?A 500-nF capacitor is connected to a 300-k resistor. What is the total charge time of this capacitor?A film-type capacitor is marked 253 H. What are the capacitance value and tolerance of this capacitor?A postage stamp mica capacitor has the following color marks starting at the upper left dot: yellow, violet, brown, green, no color, and blue. What are the capacitance value, tolerance, and voltage rating of this capacitor?A postage stamp capacitor has the following color marks starting at the upper-left dot: black, orange, orange, black, silver, and white. What are the capacitance value and tolerance of this capacitor?You are changing the starting relay on a central air-conditioning unit when you notice that the identifying mark on the compressor-run capacitor is connected to the run winding of the compressor. Should you change the capacitor connection so that the identifying mark is facing the line side or is it correct as connected? Explain your answer.You are an electrician working in an industrial plant. You discover that the problem with a certain machine is a defective capacitor. The capacitor is connected to a 240-volt AC circuit. The information on the capacitor reveals that it has a capacitance value of 10 mF and a voltage rating of 240 VAC. The only 10-mF AC capacitor in the storeroom is marked with a voltage rating of 350 WVDC. Can this capacitor be used to replace the defective capacitor? Explain your answer.You find that a 25-F capacitor connected to 480 VAC is defective. The storeroom has no capacitors with a 480-VAC rating. However, you find two capacitors rated at 50 F and 370 VAC. Can these two capacitors be connected in such a manner that they can replace the defective capacitor? If yes, explain how they are connected and why the capacitors will not be damaged by the lower voltage rating. If no, explain why they cannot be used without damaging the capacitor.Fill in all the missing values. Refer to the formulas that follow. Resistance Capacitance Time constant Total time 150 k 100 F 350 k 35 s 350 pF 10 s 0.05 F 1.2 M 0.47 F 12F 0.05 s 86 k 1.5 s 120 k 470 pF 250 nF 100 ms 8 F 150 s 100 k 150 ms 33 k 4 F =RCR=CC=R Totaltime=5Two capacitors having values of 80 F and 60 F are connected in series. What is the total capacitance?Three capacitors having values of 120 F, 20 F, and 60 F are connected in parallel. What is the total capacitance?Three capacitors having values of 2.2 F, 280 F, and 470 pF are connected in parallel. What is the total capacitance?A 470-F capacitor is connected in series with a 120-k resistor. How long will it take the capacitor to charge completely?Can current flow through a capacitor?What two factors determine the capacitive reactance of a capacitor?How many degrees are the current and voltage out of phase in a pure capacitive circuit?Does the current in a pure capacitive circuit lead or lag the applied voltage?5. A 30- capacitor is connected into a 240-V, 60-Hz circuit. What is the current flow in this circuit?
6. A capacitor is connected into a 1250-V, 1000-Hz circuit. The current flow is 80 A. What is the capacitance of the capacitor?
7. A capacitor is to be connected into a 480-V, 60-Hz line. If the capacitor has a voltage rating of 600 VDC, will the voltage rating of the capacitor be exceeded?
On the average, by what factor is the life expectancy of a capacitor increased if the capacitor is operated at half its voltage rating?A capacitor is connected into a 277-V, 400-Hz circuit. The circuit current is 12 A. What is the capacitance of the capacitor?A capacitor has a voltage rating of 350 VAC. Can this capacitor be connected into a 450-VDC circuit without exceeding the voltage rating of the capacitor?A utility company plans to connect a total of 20 F of capacitance to a 7200-V line. To make this connection, four capacitors will be connected in series. What is the capacitance of each capacitor?What is the minimum AC voltage rating of each capacitor in Question 11?What is the total current flow through the circuit in Question 11?What is the minimum KVAR rating of each capacitor in Question 11? (Round off the value to the nearest KVAR.)You are working as an electrician in an industrial plant. You are given an AC oil-filled capacitor to install on a 480-V, 60-Hz AC line. The capacitor has the following marking: (15 F 600 VDC). Will this capacitor be damaged if it is installed? Explain your answer.You are working in an industrial plant. You have been instructed to double the capacitance connected to a machine. The markings on the capacitor, however, are not visible. The capacitor is connected to 560 volts and an ammeter indicates a current of 6 amperes flowing to the capacitor. What size capacitor should be connected in parallel with the existing capacitor? What is the minimum AC voltage rating of the new capacitor? What is the minimum DC voltage rating of the new capacitor? What is the minimum KVAR size that can be used in this installation?Capacitive Circuits Fill in all the missing values. Refer to the formulas that follow. XC=12fCC=12fXCf=12CXc Capacitance XC Frequency 38 F 60 Hz 78.8 400 Hz 250 pF 4.5 k 234 F 10 kHZ 240 50 Hz 10 F 36.8 560 nF 2 MHz 15 k 60 Hz 75 nF 560 470 pF 200 kHz 6.8 k 400 Hz 34 F 450A 4.7-F capacitor is connected to a 60-Hz power source. What is the capacitive reactance of the capacitor?A capacitor is connected to a 208-volt, 60-Hz power source. An ammeter indicates a current flow of 0.28 amperes. What is the capacitance of the capacitor?A 0.47-F capacitor is connected to a 240-volt power source. An ammeter indicates a current of 0.2 ampere. What is the frequency of the power source?Three capacitors having capacitance values of 20F,40F, and 50F are connected in parallel to a 60 - Hz power line. An ammeter indicates a circuit current of 8.6 amperes. How much current is flowing through the 40F capacitor?A capacitor has a capacitive reactance of 300 when connected to a 60-Hz power line. What is the capacitive reactance if the frequency is increased to 100 Hz?A pure capacitive circuit is connected to a 480-volt, 60-Hz power source. An ammeter indicates a current flow of 24 amperes. The circuit current must be reduced to 16 amperes by connecting a second capacitor in series with the first. What is the value of the existing capacitor? What value capacitor should be connected in series with the original capacitor to limit the circuit current to 16 amperes?In a pure capacitive circuit, does the current lead or lag the voltage?A series circuit contains a 20- resistor and a capacitor with a capacitance of 110.5 F. If the circuit has a frequency of 60 Hz, what is the total impedance of the circuit?An RC series circuit has a power factor of 76%. How many degrees are the voltage and current out of phase with each other?An RC series circuit has a total impedance of 84 . The resistor has a value of 32 . What is the capacitive reactance of the capacitor? XC=Z2R2A capacitor has a capacitive reactance of 50 when connected to a 60-Hz line. What will be the capacitive reactance if the capacitor is connected to a 1000-Hz line?A 15-F AC capacitor is connected in series with a 50 resistor. The capacitor has a voltage rating of 600 WVDC. The capacitor and resistor are connected to a 480-V, 60-Hz circuit. Is the voltage rating of the capacitor sufficient for this connection?An RC series circuit is connected to a 120-V, 60-Hz power source. The resistor is 25 and has a voltage drop of 65 volts. What is the capacitance of the capacitor?An RC series circuit is connected to a 240-V, 60-Hz power source. An ammeter indicates a current of 20 amperes, and a wattmeter indicates that the circuit has a true power of 3 kW. What is the circuit power factor, and what is the capacitance of the capacitor?1PPAssume that the voltage drop across the resistor, ER, is 78 V; the voltage drop across the capacitor, EC, is 104 V; and the circuit has a total impedance, Z, of 20 . The frequency of the AC voltage is 60 Hz. Find the missing values. ET ER78V EC104V IT IR IC Z20 R XC VA P VARSC PF CAssume the circuit shown in Figure 21-1 has an apparent power of 432 VA and a true power of 345.6 W. The capacitor has a capacitance of 15.8919 F, and the frequency is 60 Hz. Find the missing values. ET ER EC IT IR IC Z R XC VA432 P345.6W VARSC PF C15.8919FAssume the circuit in Figure 21-1 has a power factor of 68%, an apparent power of 300 VA, and a frequency of 400 Hz. The capacitor has a capacitance of 4.7125 F. Find the missing values. ET ER EC IT IR IC Z R XC VA300 P VARSC PF68 C4.7125FIn a series RC circuit, ET=240 volts, R=60, and XC=85. Find EC.In a series RC circuit, ET=120 volts, R=124, and XC=64. Find reactive power.In a series RC circuit, ET=208 volts, IT=2.4 amperes, and R=45. Find the power factor.In a series RC circuit, ET=460 volts and =44. Find EC.In a series RC circuit, ET=240 volts at 60 Hz. An ammeter indicates a total current of 0.75 amperes. The resistor has a value of 140 . What is the capacitance of the capacitor?In a series RC circuit, the apparent power is 4250 VA and the reactive power is 2125 VARs. What is the true power?When a capacitor and a resistor are connected in parallel, how many degrees out of phase are the current flow through the resistor and the current flow through the capacitor?A capacitor and a resistor are connected in parallel to a 120-V, 60-Hz line. The resistor has a resistance of 40 , and the capacitor has a capacitance of 132.6F. What is the total current flow through the circuit?What is the impedance of the circuit in Question 2?What is the power factor of the circuit in Question 2?How many degrees out of phase are the current and voltage in Question 2?Refer to the formulas in Appendix B in the Resistive-Capacitive Parallel Circuits section. A resistor and capacitor are connected in parallel to a 208-V, 60-Hz power source. An ammeter indicates a total circuit current of 46 amps, and a wattmeter indicates a true power of 4975 W. What is the resistance of the circuit?What is the capacitance of the capacitor in Question 6?A resistor and capacitor are connected in parallel to a 277-V, 60-Hz power source. The resistor has a value of 50 and the capacitor has a value of 40 F. What is the circuit power factor?1PP2PPAssume that the circuit shown in Figure 22-2 is connected to a 600-Hz line and has a current flow through the resistor of 65.6 A and a current flow through the capacitor of 124.8 A. The total impedance of the circuit is 2.17888 . Find the missing values. ETITZ2.17888VAPFERIR65.6ARPECIC124.8AXCVARsCCAssume that the circuit shown in Figure 22-2 is connected to a 1000-Hz line and has a true power of 486.75 W and a reactive power of 187.5 VARs. The total current flow in the circuit is 7.5 A. Find the missing values. ETIT7.5AZVAPFERIRRP486.75WECICXCVARsC187.5CIn an RC parallel circuit, R=3.6kandXC=4.7k. Find Z.In an RC parallel circuit, IR=0.6amperes,R=24,andXC=33.FindIC.In an RC parallel circuit, ET=120volts,IT=1.2 amperes, and R=240.FindXC.In an RC parallel circuit, the apparent power is 3400 VA and =58. Find reactive power.In an RC parallel circuit, the true power is 780 watts and the reactive power is 560 VARs. Find the power factor.In an RC parallel circuit, ET=7.5 volts at 1 kHz. The circuit current is 2.214 amperes. R = 4 . What is the value of the capacitor connected in the circuit?What is the phase angle relationship of current and the voltage dropped across a pure resistance?What is the phase angle relationship of current and the voltage dropped across an inductor?What is the phase angle relationship of current and the voltage dropped across a capacitor?An AC circuit has a frequency of 400 Hz. A 16- resistor, a 0.0119-H inductor, and a 16.6F capacitor are connected in series. What is the total impedance of the circuit?If 440 V are connected to the circuit, how much current will flow?6RQWhat is the true power of the circuit in Question 6?What is the apparent power of the circuit in Question 6?What is the power factor of the circuit in Question 6?How many degrees are the voltage and current out of phase with each other in the circuit in Question 6?You are an electrician working in a plant. A series resonant circuit is to be used to produce a high voltage at a frequency of 400 Hz. The inductor has an inductance of 15 mH and a wire resistance of 2 . How much capacitance should be connected in series with the inductor to produce a resonant circuit? The voltage supplied to the circuit is 240 V at 400 Hz. What is the minimum voltage rating of the capacitor?The circuit shown in Figure 23-2 is connected to a 120-V, 60-Hz line. The resistor has a resistance of 36 , the inductor has an inductive reactance of 100 , and the capacitor has a capacitive reactance of 52 . ET120VITZVAPFERIRR36PELILXL100VARsLLECICXC52VARsCCThe circuit is connected to a 400-Hz line with an applied voltage of 35.678 V. The resistor has a true power of 14.4 W. and there are 12.96 inductive VARs and 28.8 capacitive VARs. ET35.678VITZVAPFERIRRP14.4WELILXLVARsL12.96LECICXCVARsC28.8CThe circuit is connected to a 60-Hz line. The apparent power in the circuit is 29.985 VA, and the power factor is 62.5%. The resistor has a voltage drop of 14.993 V, the inductor has an inductive reactance of 60 , and the capacitor has a capacitive reactance of 45 . ETITZVA29.985PF62.5%ER14.993VIRRPELILXL60VARsLLECICXC45VARsCCThis circuit is connected to a 1000-Hz line. The resistor has a voltage drop of 185 V. the inductor has a voltage drop of 740 V, and the capacitor has a voltage drop of 444 V. The circuit has an apparent power of 51.8 VA. ETITZVA51.8PFER185VIRRPEL740VILXLVARsLLEC444VICXCVARsCCA series RLC circuit contains a 4-k resistor, an inductor with an inductive reactance of 3.5 k , and a capacitor with a capacitive reactance of 2.4 k . A 120-VAC, 60-Hz power source is connected to the circuit. How much voltage is dropped across the inductor?A series RLC circuit contains a resistor with a true power of 18 watts, an inductor with a reactive power of 24 VARs, and a capacitor with a reactive power of 4 VARs. What is the circuit power factor?Is the power factor in Question 6 a leading or lagging power factor? Explain your answer.A series RLC circuit contains a resistor with a resistance of 8 , an inductor with a reactance of 12 , and a capacitor with a reactance of 16 . ER=17.8volts.FindEC.A series RLC circuit has an applied voltage of 240 volts and an apparent power of 600 VA. The circuit power factor is 62%. Find the value of the resistor.A series RLC circuit is connected to a 60-Hz power line. The resistor has a value of 240 . The inductor has an inductance of 0.796 henrys and the capacitor has a capacitance of 5.89F. Find Z.An AC circuit contains a 24 resistor, a 15.9-mH inductor, and a 13.3F capacitor connected in parallel. The circuit is connected to a 240-V, 400-Hz power supply. Find the following values. XL=XC=IR=AIL=AIC=AP=WVARsL=VARsC=IT=AVA=PF=%=An RLC parallel circuit contains a resistor with a resistance of 16 , an inductor with an inductive reactance of 8 , and a capacitor with a capacitive reactance of 20 . What is the total impedance of this circuit?The circuit shown in Figure 24-2 has a current of 38 A flowing through the resistor, 22 A flowing through the inductor, and 7 A flowing through the capacitor. What is the total circuit current?A tank circuit contains a capacitor and an inductor that produce 30 of reactance at the resonant frequency. The inductor has a Q of 15. The voltage of 277 V is connected to the circuit. What is the total circuit current at the resonant frequency?A 0.796-mH inductor produces an inductive reactance of 50 at 10 kHz. What value of capacitance will be needed to produce a resonant circuit at this frequency?An AC motor is connected to a 560-V, 60-Hz line. The motor has a current draw at full load of 53 A. A wattmeter indicates a true power of 18,700 W. Find the power factor of the motor and the amount of capacitance that should be connected in parallel with the motor to correct the power factor to 100%, or unity.A single-phase AC motor is connected to a 240-V, 60-Hz supply. A clamp-on ammeter indicates the motor has a current draw of 15 A at full load. A wattmeter connected to the motor indicates a true power of 2.2 kW. What is the power factor of the motor, and how much capacitance is needed to correct the power factor to 95%?The circuit in Figure 24-2 is connected to a 120-V, 60-Hz line. The resistor has a resistance of 36 , the inductor has an inductive reactance of 40 , and the capacitor has a capacitive reactance of 50 . ET120VITZVAPFERIRR36PELILXL40VARsLLECICXC50VARsCC2PPThe circuit in Figure 24-2 is connected to a 60-Hz line. The apparent power in the circuit is 48.106 VA. The resistor has a resistance of 12 . The inductor has an inductive reactance of 60 , and the capacitor has a capacitive reactance of 45 . ETITZVA48.106PFERIRR12PELILXL60VARsLLECICXC45VARsCCThe circuit in Figure 24-2 is connected to a 1000-Hz line. The resistor has a current flow of 60 A, the inductor has a current flow of 150 A, and the capacitor has a current flow of 70 A. The circuit has a total impedance of 4.8 . ETITZ4.8VAPFERIR60ARPELIL150AXLVARsLLECIC150AXCVARsCCIn an RLC parallel circuit, the resistor has resistance of 24 k , the inductor has a reactance of 36 k , and the capacitor has a reactance of 14 k . Find Z.In an RLC parallel circuit, the resistor has a resistance of 60 , the inductor has a reactance of 180 , and the capacitor has a reactance of 80 . Find the circuit power factor.In an RLC parallel circuit, the true power is 260 watts. The inductor has a reactive power of 360 VARs, and the capacitor has a reactive power of 760 VARs. By how many degrees are the voltage and current out of phase with each other?An RLC parallel circuit has an apparent power of 400 VA. The inductor has a reactive power of 450 VARs, and the capacitor has a reactive power of 200 VARs. Find the true power or watts.In an RLC parallel circuit, the resistor has a value of 12 and a current flow of 40 amperes. What is the voltage drop across the capacitor (EC)?An RLC parallel circuit is connected to 240 volts. The resistor has a power dissipation of 600 watts. If the circuit power factor is 75%, what is the total circuit current (IT)?Describe the difference between a voltage surge and a voltage spike.Explain why voltage spikes and surges are high-frequency occurrences.If a voltage surge lasts for 20 microseconds, what is the frequency of the surge?If a voltage spike lasts for 1.5 nanoseconds, what is the frequency of the spike?What two characteristics of capacitors enable them to help eliminate voltage spikes and surges?What electrical component is employed in surge and spike protectors to help eliminate current spikes and surges?7RQWhat electrical component is used to protect against an overheat condition?What unit of measure is used to indicate the amount of protection against surges and spikes?In reference to the load, how are capacitors connected to help prevent voltage spikes and surges? Are capacitors connected in parallel or in series with the load?In reference to the load, how are MOVs connected to help prevent voltage spikes and surges? Are MOVs connected in parallel or in series with the load?How are electronic lightning arresters constructed?How are electronic lightning arresters constructed?How many degrees out of phase with each other are the voltages of a three-phase system?What are the two main types of three-phase connections?A wye-connected load has a voltage of 480 V applied to it. What is the voltage dropped across each phase?A wye-connected load has a phase current of 25 A. How much current is flowing through the lines supplying the load?A delta connection has a voltage of 560 V connected to it. How much voltage is dropped across each phase?A delta connection has 30 A of current flowing through each phase winding. How much current is flowing through each of the lines supplying power to the load?A three-phase load has a phase voltage of 240 V and a phase current of 18 A. What is the apparent power of this load?If the load in Question 7 is connected in a wye, what would be the line voltage and line current supplying the load?An alternator with a line voltage of 2400 V supplies a delta-connected load. The line current supplied to the load is 40 A. Assuming the load is a balanced three-phase load, what is the impedance of each phase?What is the apparent power of the circuit in Question 9?You are working in an industrial plant. A bank of capacitors is to be used to correct the power factor of a 480V, three-phase motor. The capacitor bank is connected in a wye. Each of the three capacitors is rated at 25F and 600VDC . You have been told to reconnect these capacitors in delta. Can these capacitors be changed from wye to delta without harm to the capacitors?You are a journeyman electrician working in an industrial plant. A 480V , three-phase, 60Hz power panel has a current draw of 216 A. A three-phase wattmeter indicates a true power of 86kW . You have been instructed to reduce the current draw on the panel by adding three 400F capacitors to the system. The capacitors are to be connected in wye. Each capacitor will be connected to one of the three-phase lines. What should be the current flow on the system after the bank of capacitors is added to the circuit?You are an electrician working in an industrial plant. A 30-hp three-phase induction motor has a current draw of 36 amperes at full load. The motor is connected to a 480-volt line. A three-phase wattmeter indicates a true power of 22 kW. Determine the power factor of the motor and the amount of capacitance needed to correct the power factor to 95. Also determine the minimum voltage rating of the capacitors. The capacitors are to be connected in wye.Refer to the circuit shown in Figure 26-19 to answer the following questions, but assume that the alternator has a line voltage of 240 V and the load has an impedance of 12 per phase. Find all the missing values. EP(A)IP(A)EL(A)240VIL(A)PEP(L)IP(L)EL(L)IL(L)Z(PHASE)12Refer to the circuit shown in Figure 26-20 to answer the following questions, but assume that the alternator has a line voltage of 4160 V and the load has a resistance of 60 per phase. Find all the missing values. EP(A)IP(A)EL(A)4160VIL(A)PEP(L)IP(L)EL(L)IL(L)Z(PHASE)60Refer to the circuit shown in Figure 26-21 to answer the following questions, but assume that the alternator has a line voltage of 560 V. Load 1 has an resistance of 5 per phase, and Load 2 has a resistance of 8 per phase. Find all the missing values. EP(A)IP(A)EL(A)560VIL(A)PEP(L1)IP(L1)EL(L1)IL(L1)Z(PHASE)5EP(L)2IP(L)2EL(L)2IL(L)2XL(PHASE)8Refer to the circuit shown in Figure 26-22 to answer the following questions, but assume that the alternator has a line voltage of 480 V. Load 1 has a resistance of 12 per phase. Load 2 has an inductive reactance of 16 per phase, and Load 3 has a capacitive reactance of 10 per phase. Find all the missing values. EP(A)IP(A)EL(A)480VIL(A)VAEP(L1)IP(L1)EL(L1)IL(L1)R(PHASE)12PEP(L)2IP(L)2EP(L)2IL(L)2XL(PHASE)16VARsLEP(L)3IP(L)3EL(L)3IL(L)3XC(PHASE)10VARsCWhat is a transformer?What are common efficiencies for transformers?What is an isolation transformer?All values of a transformer are proportional to its __________________ ___________________.What is an autotransformer?What is a disadvantage of an autotransformer?Explain the difference between a step-up and a step-down transformer.A transformer has a primary voltage of 240 V and a secondary voltage of 48 V. What is the turns ratio of this transformer?A transformer has an output of 750 VA. The primary voltage is 120 V. What is the primary current?A transformer has a turns ratio of 1:6. The primary current is 18 A. What is the secondary current?What do the dots shown beside the terminal leads of a transformer represent on a schematic?A transformer has a primary voltage rating of 240 V and a secondary voltage rating of 80 V. If the windings were connected subtractive, what voltage would appear across the entire connection?If the windings of the transformer in Question 12 were to be connected additive, what voltage would appear across the entire winding?The primary leads of a transformer are labeled 1 and 2. The secondary leads are labeled 3 and 4. If polarity dots are placed beside leads 1 and 4, which secondary lead would be connected to terminal 2 to make the connection additive?You are working in an industrial plant. You must install a single-phase transformer. The transformer has the following information on the nameplate: Primary voltage13,800 V Secondary voltage240 V Impedance5% 150 kVA The secondary fuse has a blow rating of 800 A and an interrupt rating of 10,000 A. Is this interrupt rating sufficient for this installation?You have been given a transformer to install on a 277-V line. The transformer nameplate is shown in Figure 27-69. The transformer must supply a 120-V, 20-A circuit. The transformer capacity should be not less than 115% of the rated load. Does the transformer you have been given have enough kVA capacity to supply the load? To which transformer terminals would you connect the incoming power? To which transformer terminals would you connect the load?EP120VIPNP300TurnsRatioEs24IsNsZ=3EP240VIPNPRatioEs320VIsNs280Z=500EPIPNPRatio1:2.5Es160VIsNs80TurnsZ=124PP5PPES480VIPNS275turnsRatioESISNS525turnsZ=1.2kES208VIPNP800turnsES1320VIS1NS1Ratio1:R112kES2120VIS2NS2Ratio2:R26ES324VIS3NS3Ratio3:R38EP277VIPNP350TurnsES1480VIS1NS1Ratio1:R1200Es208VIS2Ns2Ratio2:R260ES3120VIS3NS3Ratio3:R324How many transformers are needed to make an open-delta connection?Two 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?How does the NEC specify that the high leg of a four-wire delta connection be marked?An open-delta three-phase transformer system has one transformer center-tapped to provide a neutral for single-phase voltages. If the voltage from line to center tap is 277 V, what is the high-leg voltage?If a single-phase load is connected across the two line conductors and neutral of the transformer in Question 4 and one line has a current of 80 A and the other line has a current of 68 A, how much current is flowing in the neutral conductor?A three-phase transformer connection has a delta-connected secondary, and one of the transformers has been center-tapped to form a neutral conductor. The phase-to-neutral value of the center-tapped secondary winding is 120 V. If the high leg is connected to a single-phase load, how much voltage will be applied to that load?A three-phase transformer connection has a delta-connected primary and a wye-connected secondary. The center tap of the wye is used as a neutral conductor. If the line-to-line voltage 480 V. what is the voltage between any one phase conductor and the neutral conductor?A three-phase transformer bank has the secondary connected in a wye configuration. The center tap is used as a neutral conductor. If the voltage across any phase conductor and neutral is 120 V, how much voltage would be applied to a three-phase load connected to the secondary of this transformer bank?A three-phase transformer bank has the primary and secondary windings connected in a wye configuration. The secondary center tap is being used as a neutral to supply single-phase loads. Will connecting the center-tap connection of the secondary to the center-tap connection of the primary permit the secondary voltage to stay in balance when a single-phase load is added to the secondary?Referring to the transformer connection in Question 9, if the center tap of the primary is connected to a neutral conductor on the incoming power, will it permit the secondary voltages to be balanced when single-phase loads are added?You are working in an industrial plant. A three-phase transformer bank is connected wye-delta. The primary voltage is 12,470 V, and the secondary voltage is 480 V. The total capacity of the transformer bank is 450 kVA. One of the three transformers that form the three-phase bank develops a shorted primary winding and becomes unusable. A suggestion is made to reconnect the bank for operation as an open-delta. Can the two remaining transformers be connected open-delta? Explain your answer as to why they can or why they cannot be connected as an open-delta. If they can be reconnected open-delta, what would be the output capacity of the two remaining transformers?2PARefer to the transformer shown in Figure 28-14 and find all the missing values. PrimaryEPIPEL4160VILRatio SecondaryEPIPEL440VILZ=3.5 LoadEPIPELILPrimaryEPIPEL7200VILRatio SecondaryEPIPEL240VILZ=4 LoadEPIPELILRefer to the transformer connection shown in Figure 28-41 and fill in the missing values. PrimaryEPIPEL13,800VILRatio SecondaryEPIPEL480VILZ=2.5 LoadEPIPELILPrimaryEPIPEL23,000VILRatio SecondaryEPIPEL280VILZ=3 LoadEPIPELILWhat is a generator?2RQ3RQ4RQWhat are interpoles, and what is their purpose?How are interpoles connected in relation to the armature?7RQHow is the series field connected in relation to the armature?How is the shunt field connected in relation to the armature?What is armature reaction?What is armature reaction proportional to?What are eddy currents?What condition characterizes overcompounding?What is the function of the shunt field rheostat?Explain the difference between cumulative- and differential-compounded connections.Explain the difference between cumulative- and differential-compounded connections.What three factors determine the amount of output voltage for a DC generator?What is the voltage regulation of a DC generator proportional to?19RQ20RQYou are working as an electrician in a large steel manufacturing plant, and you are in the process of doing preventive maintenance on a large DC generator. You have megged both the series and shunt field windings and found that each has over 10 M to ground. Your ohmmeter, however, indicates a resistance of 1.5 across terminals S1andS2. The ohmmeter indicates a resistance of 225 between terminals F1andF2. Are these readings normal for this type machine, or is there a likely problem? Explain your answer.1RQ2RQ3RQ4RQWhat type of motor is known as a constant-speed motor?What is CEMF?7RQ8RQ9RQWhat type of motor should never be operated at no load?11RQWhat is the most common way of changing the direction of rotation of a compound motor?13RQ14RQWhat device is used to disconnect power to the armature if the shunt field current drops below a certain level?16RQWho was the first person to establish a measurement for hp?One horsepower is equal to how many W?A motor is operating a load that requires a torque of 750 lb-in. and is turning at a speed of 1575 RPM. How much hp is the motor producing?The motor in Question 19 is connected to a 250-VDC line and has a current draw of 80 A. What is the efficiency of this motor?1PAWhat conditions must be met before two alternators can be paralleled together?How can the phase rotation of one alternator be changed in relationship to the other alternator?What is the function of the synchronizing lamps?What is a synchroscope?Assume that Alternator A is supplying power to a load and that Alternator B is to be paralleled to A. After the paralleling has been completed, what must be done to permit Alternator B to share the load with Alternator A?What two factors determine the output frequency of an alternator?At what speed must a six-pole alternator turn to produce 60 Hz?What three factors determine the output voltage of an alternator?What are sliprings used for on a revolving-field-type alternator?10RQ11RQWhat two devices are used to eliminate the induced voltage produced in the rotor when the field excitation current is stopped?What are the three basic types of three-phase motors?What is the principle of operation of all three-phase motors?What is synchronous speed?What two factors determine synchronous speed?5RQName three factors that determine the torque produced by an induction motor.Is the synchronous motor an induction motor?8RQWhy must a synchronous motor never be started when DC excitation is applied to the rotor?Name three characteristics that make the synchronous motor different from an induction motor.What is the function of the field-discharge resistor?Why can an induction motor never operate at synchronous speed?