kelistrikan alat berat alternatorDeskripsi lengkap
1. The number number of cycle cycle generated generated in a 6 pole alterna alternator tor in one one revolution revolution is is ______. ______. a. 3 b. 6 c . 50 d. none of the these 2. Determine Determine the number number of electr electrical ical degrees degrees made made per revolution revolution for for an especial especial purpose !0pole alternator. a. 2! 000 b. 1" "00 c. # 200 d . 1 60 0 3. The disadvan disadvantage tage of of a shortpit shortpitch ch coil coil is that _______. a. harmonics are introduced b. $aveform becomes nonsinusoidal c. voltage around the coil is reduced d. both %a& and %b& ". 'f the alternator alternator $inding has a fractional pitch pitch of ( the pitch factor % K K p& is ______. a. 0.!33 b. 0.)51 c. 0.)66 d. 0.)#2 5. * si+ si+ pole( three three phase phase *, *, generator generator has #2 slots slots(( the coil span span is 12. -hat is is the pitch factor a. 1.00 b. 0.)!5 c. 0.)3) d. 0.)66 6. * part part of an alterna alternator tor $inding $inding consist consist sic %6& %6& coils coils in series( series( each coil coil having having an emf of 10 volts induced in it. The coils are placed in successive slots and bet$een each slot and the ne+t( there is an electrical displacement of 30/. The emf of the si+ coils in series is nearest to ______. a. 36.!" olts b. 3!.6" olts c. 60 olts d. )0 olts #. The voltage voltage generated generated across across one inductor inductor of of a 3 alternato alternatorr is 6 volts. volts. There There are 120 slots and " turns in every coil. The coil pitch is short by 2 slots( number of of poles is 10 and freuency is 60 4. The armature $inding correction factor of the alternator is nearest to ______. a. 0.)25 b. 0.)!# c. 0.)6# d. 0.)5# !. * 1"" 1"" slots slots stator stator has a $holecoil $holecoiled( ed( 12 pole( pole( three phase phase $inding. $inding. -hat -hat is the number of coils per phase and per group respectively a. "! " b. 2" " c. 12 " d. 36 " ). ,alculate ,alculate the the voltage voltage generated generated bet$een bet$een lines lines of a $yecon $yeconnected nected alter alternator nator driven at )00 rpm $ith the follo$ing data slots 7 1""( poles 7 !( turns per coil 7 6( flu+ per pole 7 1.! + 106 lines( coil span 7 slots 16 and $inding being $hole coiled. a. 12#6 olts b. 2 200 olts c. 635 olts d. 1 100 olts 10. * 3( 60 4( 6 pole alternator has an air gap flu+ $hich is is sinusoidally distributed. The stator has 5 slots per pole per phase and each slots contains " conductors arranged in t$o layers. The coil pitch is 12 slots $ith normal e+citation and rated speed( the voltage induced per conductor condu ctor is 25 olts. olts. The opencircuit emf of the 8connected 8connected machine bet$een lines $hen all conductors per phase are connected in series is nearest to _______.
a. 2#30 olts
b. 23#0 olts
c. "#30 olts
d. "3#0 olts
11. * 3( 1 200 9* 9*( 6.6 :olt( :olt( $yeconnected turbo alternator $ith effective resistance of 0." ohm and reactance of 6 ohm per phase delivers fullload at 0.!0 pf. ;agging and normal rated voltage and speed. The terminal voltage for the same e+citation and load current of 0.!0 pf. ;eading is nearest to _____. a. # 560 olts b. # )00 olts c. "560 olts d. # 360 olts 12. * 1500 9* 9*( 2300 :olt( :olt( 3phase( ! pole( 60 4 alternator has an ohmic resistance bet$een terminals of 0.0! ohm. The ratio of effective to ohmic resistance is 1.5. The field ta:es #0 *mp at 120 olts olts from e+citer euipment. The ut of the follo$ing follo$ing condition( the one $hich does not have to be met by alternator $or:ing in parallel is a. termi terminal nal volta voltage ge of each each machi machine ne must must be the the same same b. the machines must have the same phase rotation c. the machi machines nes must must oper operate ate at at the same same fre freuenc uencyy d. the machine machine must must have have the the same same ratin ratingg 1". T$o T$o identical 2000 :* alternator operates in parallel. The governor of the first machine is such that the freuency drops uniformly from 50 4 at noload to "! "! 4 at fullload. The The corresponding uniform speed drop of the second machine is 50 4 to "5.# 4. -hat -hat is the ma+imum unity p.f. load that an be delivered $ithout overloading either machine a. 3600 :b. 6300 :c. "000 :d. 1#23 9$ 15. * 3( 8connected( 1000 :*( 6.6 :olt turbo alternator has a synchronous reactance of !.# ohms per phase but negligible negligible resistance. 't is is supplying !#.5 *mp ay !0 = p.f. lagging to a large large po$er system system and the emf is increased increased by 25= %e+citation $as increased& the ne$ value of armature current and p.f. are ____ respectively. a. 1!2."! 0."#6 lagging b.1#5.31 *mp 0.56# lagging c. 1)0.!2 *mp 0.36# lagging d. 1!1."! *mp 0."6# lagging 16. * 3( starconnected( starconnected( 1000 :*( :*( 6.6 olt olt turbosynchronous alternator $ith 20= reactance but of negligible resistance is supplying fullload at !0= p.f. lagging to a large po$er system% infinite infinite busbars& 'f steam supply is suddenly cut ?off. -hat is the ne$ current @eglecting losses. a. ##.5! *mp b. 5#.5! *mp c. "#.5! *mp d. 6#.5! *mp 1#. * 3( 8connected( 8connected( 1000 :*( :*( 6.6 olt olt alternator has a reactance of !.# ohms per phase but negligible resistance. 't is supplying supplying fullload at 0.!0 p.f. lagging to a constant voltage freuency busbars. 'f steam supply is gradually g radually increased
$ithout changing the e+citation( the ma+imum load that the generator can supply before going out of synchronism is nearest to _____. a. 6 600 :b. 1000 :c. 5 600 :d. !00 :1!. * 1000 :* :*( 3.3 :o :olt ( 60 4( " pole 3 starconnected( $oundrotor $oundrotor synchronous alternator reactance of ' ohm per pe r phase and negligible armature resistance. The generator is operating at fullload( 0.!0 p.f. lagging on an infinite bus. 'f a disturbance causes the po$er angle to s$ing by 1A %mechanical&. -hat is the synchroni4ing po$er per phase and synchroni4ing torue respectively a. 133.6 :- and #0!.) @m b. 1"!.5 :- and 50! @m c. 1)0.! :- and 36#.5 @m d. @one of these 1). * 100 B* B*( 2 pole 60 4 alternator has a moment of inertia 50 + 103 :gm2. -hat is the energy stored in the rotor at rated speed a. 5533 BC b. 3355 BC c. 3553 BC d. 5335 BC 20. The imaginary or fictitious fictitious part of synchronous synchronous reactance on alternator ta:es care of _______ a. inductive reactance b. armature reaction c. lea:age reactance d. coper losses 21. 'f the load of an isolated isolated alternator increased $ithout $ithout increasing the po$er input to the prime mover. The alternator a. $ill slo$ do$n b. speed up c. volt voltag agee incr increa ease sess d. fiel fieldd curr curren entt $il $ill incr increa easse 22. The po$er factor of an alternator alternator is #5=. The The operator is ordered to increase increase the po$er factor to !0=. -hat shall $e do a. increase the voltage b. operate the governor c. increase the e+citation d. decrease the e+citation 23. The positive ( negative and 4ero seuence reactance of a 3phase( 13.! :( :( 10B* 10B*( 60 4 alternator are 0.0!( 0.0#( 0.05 p.u. respectively. Determine the fault current deliver for a double linetoground fault( assuming no current flo$s in the net$or: other than due to the fault and its neutral solidly ground. a. 6#00 *mp b. #600 *mp c. 5!00 *mp d. !500 *mp 2". The per unit reactance of a synchronous synchronous generator are 7 1.0( E7 0.35( F7 0.25. The alternator supplies a 1.0 per unit load at 0.!0 po$er factor lagging. ,alculate the voltage behind the subtransient reactance. a. 1.#) pu b. 1.2" pu c. 1.1# pu d. none of these 25. The armature of an alternator alternator $ill be cross magneti4ing magneti4ing %or minimum& ifif the p.f. of the load is _____. a. 0 lagging b. 0 leading c. unity d. 0.!66 leading
26. Damper or G *mortisseurF *mortisseurF $indings are used in alternators alternators to ______. a. achieve synchronism b. reduced $indage losses c. prevent hunting d. start up 2#. The driving po$er from the the prime mover driving an alternator alternator is lost but the alternator remains connected to the supply %i.e. its po$er circuit brea:er failed to trip& and its e+citation is on. The alternator $ill_____ a. behav behaves es as as an ind induct uctor or mot motor or b. stop and get burnt c. behave as as synchron synchronous ous motor motor but $ill rotate rotate in reverse reverse or opposit oppositee direction d. behaves as synchrono synchronous us motor motor and rotate rotate at same same directio directionn 2!. 'n po$er failures( relays relays operate in most standby standby po$er installations $hen normal phase voltage falls to ____= a. )5 b . !0 c . #0 d. 5 0 2). Hetransfer to normal normal supply occurs in automatic standby standby systems $hen voltage in all phase of the normal supply becomes ______ percent or more. a. #5 b. !5 c. )0 d . )5 30. T$o3 T$o3 synchronous generators connected in parallel parallel are driven by $ater$heel $hose speedload characteristics are as follo$s The speed of the first falls uniformly from 62" rpm at noload to 600 rpm at fullload at 1000 9$. The speed of the second $ater$heel falls uniformly from 630 rpm at noload to 600 rpm at 1000 9$ loading. The output of each generators $hen the load is 1250 9*( 9*( 0.!0 p.f. are nearest to _____. a. 500 :- each b. ""5 :- and 555 :c. 66# :- and 333 :d. none of these I
