1. In a balanced 2-phase voltage s ystem, the phase voltage are 120volts, what is the line to line voltage? a. 120volts b.170 volts c. 240 volts d. 60 volts 2. he three phase r!ral distrib!tion system has a phase to ne!tral voltage is 7"67 volts, what is the line to line voltage? a.1#200 volts b. 7"67 volts c. 11000 volts d. 1#$00 volts #. % balanced three phase wye connected s o!rce has !sing positive phase se&!ence, 'ca(2#0 'rms with "0 degrees angle. )etermine 'bc. a. 2#0*+0' b. -1""-+11' c. -11-+1""' d. +2#0' 4. % balanced three phase wye connected s o!rce has !sing negative phase se&!ence, 'ab(#$1'rms 'ab(#$1'rms with 60 degrees angle. )etermine 'cn a. 1"0.-+110' b. -110*+110' c. -1"0.-+110' d. +220' . he wye connected three phase %/ voltage so!rce has 'c(24'rms with -240 degrees angle. ind the line to line voltage 'ab. a. 20$*+120 b. #60*+20$ c. 20$-+120 d. #60-+20$ 6. three e&!al resistors o 100 ohms are connected in delta across 240 volts, # phase lines. hat is the total power with the same resistors wye connected rom the same s!pply? a. 240 b. 100 c. 172$ d. 76 7. hree 100 ohms resistors are connected in wye across 4$0 volts, # phase so!rce. I one o the resistor is open, what is the power absorbed by the two resistors? a. 112 b. 1#6 c. 76$ d. 2#0 $. three identical resistance connected in delta carry a line c!rrent o #00%mp. I the same resistances are connected in wye across the same s!pply, what is the line c!rrent? a. 10% b. 600% c. #00% d. 100% ". % circ!it consisting o three resistor rated3 10ohms, 1ohms and 20ohms are connected in wye. hat wo!ld be the resistances o the o the e&!ivalent delta connected load? a. ##, 2# 1 ohms b. #0, 40 0ohms c. 70, 44.4 #6.7ohms d. 6, 4#.# #2.ohms 10. hree capacitors, each having a capacitance o 75 are connected in star to 400', #ph, 0h s!pply. /alc!late the delta e&!ivalent capacitance so that when they are connected in the same s!pply, the line c!rrent will remain the same. a. 105 b. 25 c. 225 d. 75 11. 11. % balance delta connected load o 4.+# ohms per phase is connected to a #phase 2#0 ' s!pply. hat is the line c!rrent? a. $0% b. 46% c. 2#% d. ##% 12. he metering o a # phase ind!ctive load indicated the ollowing val!es3 4000, #4.', $08 p. hat is the '%? a. #000 b. 4000 c. 000 d. 7000 1#. % balanced wye connected load o impedance $*+6 ohms is connected to a three phase balanced so!rce o 400 volts 609. ind the power per phase: a. 4267 b. 12$00 c. ### d. #1"$ 14. the phase b voltage and the phase b c!rrent o a balance #-phase system are3 '(220sin;wt*210<= and I(10sin;wt-1$0<=. hat is the power o the system? a. 716 b. #$10 c. 1"0 d. ##00 1. % balanced delta connected load draws 10%mp line c!rrent and # at 220'. he reactance o each phase o the load in ohms is>. a. #0 b. 2#. c. #$.1 d. 20 16. % three phase so!rce o 2#0' s!pplies the ollowing three phase loads. 20 at "08 power actor leading, 0 at $08 power actor lagging and 10 at !nity power actor. hat is the total '% and c!rrent? a. $.7 22% b. "4.7 1$2.$% c. $4.7 212.6% d. $4.7 "2.$$% 17. hree identical impedances o 1 cis 60< ohms are connected in star to a #phase, # wire, 240' system. he lines between the s!pply and the load have impedances o 2*+1 ohms. ind the magnit!de o the line voltage at the load. a. 220' b. 1$' c. 240' d. 21#' 1$. % balanced delta connected load o impedance 1#.*+" ohms are connected to a three phase balanced s o!rce o 4160volts 609 thro!gh a line with 0. ohm resistance and 2 ohms reactance. ith 'an(24000, ind the line c!rrent !sing %/ se&!ence. a. $7.$*+#27.$% b. 6".#-+2% c. -#27.$-+$7.$% d. 240-+240% 1". % balanced #phase, # wire, 240',609 so!rce s!pplies power to a star connected load @a(10*+0A, @b(10*+10A and @c(10*+0A. hat is the line c!rrent? a. 11.#% b. 10.02% c. 1."#% d. 16."7% 20. he power inp!t to a 100hp, 4$0 volts, $8 eiciency and 78 power actor #phase motor at !ll load is meas!red by two wattmeter connected at lines %/. hat are the readings in ? a. 66.2# 21. b. 6". 1$.26 c. $7.76 11.7 d. 67.$" #0.4 21. % three phase ind!ction motor taes #000 at $08 p. wo wattmeters are !sed to meas!re the power, a c. a reading is.. a. 2000 b. #000 c. 210 d. 200 22. In a balanced # phase, 20$ volts circ!it, the line c!rrent is 100%. he power is meas!red by two wattmeter method, one reads 1$ and the other is ". hat is the p o the load? a. 0.$ b. 0. c. 0.$66 d. 0." 2#. %n !nbalanced wye connected loads on a # phase 4-wire system consist o @1(10*+, @2($*+4 and @#(20*+0. he wye connected generator load has balanced voltage to ne!tral to 120 volts. hat is the wattmeter reading at @1? a. 720 b. ##12 c. 1440 d. 112 24. It is re&!ired to increase the power actor o a 70 three phase balanced load rom 708 lagging to "08 lagging. he line voltage is 6"00', 609. Bpeciy the capacitor re&!ired to increase the power actor o this wye connected load in micro-arad per phase. a. 20.4 b. 22.#" c. 22.#" d. 17.22 2. % #phase 10hp, 4$0 ' s ynchrono!s motor with rated eiciency o "08 is operating at rated load. It is in parallel with #phase balanced load o 400 at 0.7 p lagging. In order to improve to p to 0." lagging, the eCcitation o the motor was increased. /alc!late the operating power actor o the motor. a. 0.6 b. 0.#$ c. 0.7 d, 0.$2 26. % 7.hp wo!nd-rotor, #phase ind!ction motor draws a line c!rrent o 1$.4% at 2#0' line when operating at rated o!tp!t and eiciency o $8. %pplying artiicial ne!tral method o meas!ring #-phase power !sing only one wattmeter, hat is the wattmeter reading? a. #17" b. 2126 c. 211" d. 1"0 27. hat is 1*%*%D2 in rectang!lar orm? a. 0.*+0.$66 b. -0.-+0.$66 c. 0*+1.7#2 d. 0 2$. he three phase !nbalanced c!rrent are3 Ia(10cis;-#0<=%, ib(0 and Ic(10cis10<%. ind the negative se&!ence c!rrent o phase b. a. $.66cis#0< b. .77cis;-60<= c. -.77 d. .77cis60< 2". Eiven the ollowing phase c!rrent3 Ia(cis4
#0. he line c!rrents o !nbalance delta connected load are3 Ia(0cis0<, Ib(40cis240< and Ic(4.$cis1#0."<. )etermine the phase ero se&!ence component. a. ero b. 4-+2." c. 16*+7.2 d. -+2."
