AC Machinery Laboratory EEC631L
Experiment No.2 Three Phase Alternator
EXPE!MENT N". 2
Three Phase Alternator #n$er Loa$ "%&ECT!'E( 1. To determine determine the voltage voltage regulation regulation characterist characteristics ics of the alternator alternator with resistive, resistive, capacitive capacitive and inductive loading 2. To observe observe the effe effect ct of unbalanc unbalanced ed loads on the output output voltage voltage
)!(C#((!"N The output voltage of an alternator depends essentially upon the total flux in the air-gap. At no load, this flux is established and determined exclusively by the D field excitation. !nder load, however, the air-gap flux is determined by the ampere-turns of the rotor and the ampereturns of the stator. The latter may aid or oppose the magnetomotive force of the rotor depending upon the power factor of the lo ad. "eading power factors assist the rotor, and lagging power factors oppose it. #ecause the stator magnetomotive force has such an important effect upon the magnetic flux, the voltage regulation of alternators is $uite poor, and the D field current must continuously be ad%usted to &eep the voltage constant under variable load conditions. 'f one phase of a three-phase alternator is heavily loaded, its voltage will decrease due to the '( and ')" drops in the stator winding. This voltage drop cannot be compensated by modifying the D field current because the voltages of the two other phases will also be changed. Therefore, it is essential that three-phase alternators do not have loads that are badly unbalanced.
APPAAT#( APPAAT#( E*#!E) E*#!E ) 1 uni unitt 1 uni unitt 1 uni unitt 1 unit nit 1 unit nit 1 unit nit 1 uni unitt 1 uni unitt 1 uni unitt 1 uni unitt 1 unit nit 2 pc pcs 1 unit 1 unit
*$uipment +1 +11 o obile /or&station *$ui *$uipm pmen entt +20 +201 1 ync ynchr hron onou ous s ot otor or3 3en ener erat ator or odu odule le *$ui *$uipm pmen entt +2 +211 D o otor tor3en 3ener erat ator or odul odule e *$uipment +411 (esis esisttance odule *$uipment +441 apacitance odule *$uipment +421 'nductance odul dule *$ui *$uipm pmen entt ++2 ++21 1 5ow 5ower upp upply ly odu odule le 6 7 12 12 8dc, 8dc, 12 12 8dc 8dc99 *$ui *$uipm pmen entt +02 +02: : A et eter erin ing g od odul ule e 62; 62; 2; 2; 2; 2; 89 89 *$ui *$uipm pmen entt +0 +02; 2; A eter eterin ing g odule dule 62.; 2.; A9 *$ui *$uipm pmen entt +0 +012 12 D eter eterin ing g odule dule 62.; 2.; A9 *$uipment +<2 =and Tachomete eter * +< +<01 o onnecting /i /ires +<02 onnection #elt *lectronic ulti-tester
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AC Machinery Laboratory EEC631L
Experiment No.2 Three Phase Alternator
C-EC!N/ ACT!'!T!E( CA#T!"N0
-i+h olta+es are present in this experiment0 )" N"T mae any connections ith the poer on0 Mae s4re that the 1. main sitch o5 the Poer (4pply mo$4le is in the ero 789 position: 2. its ariable s4pply nob is set to M!N!M#M: an$ 3. the set is #NPL#/. *lectronic ulti-tester 1. 2. 4.
hec& battery level by turning the device on hec& calibration for voltage A reading by observing a >ero reading. 'f not, inform the instructor 5ut the selector switch and instrument mode for continuity test function. "in& together the probes to chec& for a beep sound
+<01 onnecting /ires 1. hec& each wire for continuity using the continuity test function of the electronic multi-tester 2. hec& for visible sign of insulation tear or damage *$uipment +201 ynchronous otor3enerator odule 1. 2.
hec& the fiber glass protection panel for any brea& or damage ?pen the fiber glass protection panel and chec& smooth rotation of roller bearing assembly mounted at the side of the module 4. 8isually chec& the visible part of the stator and rotor copper windings for evidence of burn or insulation brea&down. 'f there is, inform the instructor. 'f none, proceed. 0. hec& for smooth rotation of the rotor ;. hec& for a good connection of the wires coming from inside the machine and into the connector leads mounted on the fiber glass protection panel :. lose the fiber glass protection panel and perform continuity test for the three windings 6terminal pairs 1-0, 2-;, and 4-:9 of the ynchronous otor @. et rheostat &nob to minimum setting. lose switch 1 and connect the multi-tester at terminal pair @-+. et instrument to measure resistance. (otate rheostat &nob to increase resistance. ?bserve multi-tester resistance reading if it increases. ?pen switch 1. *$uipment +211 D otor3enerator odule 1. 2.
hec& the fiber glass protection panel for any brea& or damage ?pen the fiber glass protection panel and chec& smooth rotation of roller bearing assembly mounted at the side of the module 4. 8isually chec& the visible part of the armature and field copper windings for evidence of burn or insulation brea&down. 'f there is, inform the instructor. 'f none, proceed. 0. hec& for smooth rotation of the armature ;. hec& for a good connection of the wires coming from inside the machine and into the connector leads mounted on the fiber glass protection panel
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AC Machinery Laboratory EEC631L
:. @. +. <.
Experiment No.2 Three Phase Alternator
5ress once the blac& resetfuse button located at the lower right portion inside the fiber glass panel to ensure that the fuse is not tripped. lose the fiber glass protection panel and perform continuity test for the armature circuit 6terminal pair 1-29 of the D motor 5erform continuity test for the hunt circuit 6terminal pair ;-:9 of the D motor et rheostat &nob to minimum setting. onnect the multi-meter tester at terminal pair @-+. et instrument to measure resistance. (otate rheostat &nob to increase resistance. ?bserve multi-meter if resistance reading increases.
*$uipment +411 (esistance odule and *$uipment +421 'nductance odule 1. 2. 4. 0. ;.
hec& the toggle switch for any loose part when you toggle the switch. Turn off all switches. onnect in parallel each ban& of resistors 5lug the probes of the multi-tester one on top and the other at the bottom !sing the resistance setting of the multi-tester, chec& the resistance of each resistor by turning on each switch and compare the multi-tester reading with the indicated resistance value in the front panel of the module.
*$uipment +441 apacitance odule 1. 2.
hec& the toggle switch for any loose part when you toggle the switch. Turn off all switches.
*$uipment +02: A 8oltmeter, *$uipment +02; A Ammeter, and *$uipment +012 D Ammeter 1. hec& the front panel for any brea&s or damage 2. hec& the good connection of the wires inside the meter modules and into the connector leads mounted on the panel 4. et all meter needles to >ero. Ad%ust plastic screw on the front panel below the meter view screen for each meter instrument using a screw driver if necessary *$uipment ++21 5ower upply odule 1.
et the main switch to ?BB 6 position9 and the control &nob to >ero 6full counter cloc&wise, minimum9 2. !sing an A 8oltmeter module, connect each meter to each terminal pairs 1-2, 2-4, and 4-1. 4. et meter selector switch to @-C. 0. 5lug and turn on the 5ower upply module. ?bserve uniformity of all three pilot lamps. 'f not, inform the instructor. ;. ?bserve the voltmeters if the voltage across each pair terminals 1-2, 2-4, and 4-1 is 2+ 8 A thereabouts. 'f not, inform the instructor. :. ?bserve the built-in meter if it will indicate a value of 128 D thereabouts. 'f not, inform the instructor. @. Turn the &nob to minimum 6full counter cloc&wise9, turn off the 5ower upply odule and unplug the wor& station. *$uipment +<2 =and Tachometer 1. hec& the rubber cone at the tip of the apparatus 2. lide the switch to ontact position Pa+e 11
AC Machinery Laboratory EEC631L
4.
Experiment No.2 Three Phase Alternator
5ress the blac& button on the right side and chec& if a number >ero is indicated in the view screen.
+<02 onnection #elt 1. hec& for visible signs of wear and tear
M")#LE( (ET #P ACT!'!T!E( 1. 2. 4. 0. ;. :. @. +.
5lace the D otor odule at the lower center slot 6beside the 5ower upply odule9 of the obile /or&station 5lace the ynchronous otor3enerator odule at the lower right slot of the obile /or&station 5lace the A 8oltmeter odule on top of the ynchronous otor3enerator odule 5lace the D 8oltmeterAmmeter odule on top of the D otor odule 5lace the A Ammeter odule on top of the 5ower upply odule 5lace the 'nductive "oad odule on top of the A Ammeter odule 5lace the (esistive "oad odule on top of the D 8oltmeterAmmeter odule 5lace the apacitive "oad odule on top of the A 8oltmeter odule
P"CE)#E( 1.
!sing your Three-5hase ynchronous otor3enerator, D otor3enerator, (esistive "oad, 5ower upply, A Ammeter, A 8oltmeter and D 8oltmeterAmmeter, connect the circuit shown in Bigure 2.1. Cote that the balanced resistive load is wye-connected to the three-phase output of the alternator. The alternator rotor is connected to the variable -12 8 D output of the power supply, terminals @ and C. The D hunt otor winding is connected to the fixed 12 8 dc output of the power supply, Terminals + and C.
;i+4re 2.1 2.
a. ouple the D motor to the alternator with the connection belt. b. et the D motor field rheostat at its full cloc&wise position for minimum resistance. c. et the alternator field rheostat at its full cl oc&wise position for maximum resistance. d. Ad%ust each resistance section for a resistance of 4 . Pa+e 12
AC Machinery Laboratory EEC631L
4.
Experiment No.2 Three Phase Alternator
a. Turn on the power supply and, using the hand tachometer, ad%ust the D motor rheostat for a motor speed of 1+ rpm. N"TE< This spee$ m4st be ept constant 5or the remain$er o5 the experiment0
b. lose switch 1 in the synchronous generator 6alternator9. c. Ad%ust the D excitation of the alternator until the output voltage * 1 E 2+ 8 A. easure and record the full load ' 1 and '2. 72 points9 '1 E FFFFFFFFF A A
'2 E FFFFFFFFF A D
d. ?pen the three resistance load switches for a no load condition on the alternator and measure and record the no load * 1 and '2. (emember to chec& the motor speed and read%ust to 1+ rpm if re$uired. 72 points9 *1 E FFFFFFFFF 8 A
'2 E FFFFFFFFF A D
e. (eturn the voltage to >ero and turn off the power supply. f. alculate the alternator regulation with resistive loading. 72 points9 %regulation
V NL V FL −
=
V FL
x100%
G regulation E FFFFFFFFF G
0.
a. !sing the 'nductive "oad odule, replace the resistive load with an inductive load. b. Ad%ust each inductance section for a reactance ) " of 4 . c. (epeat procedure 4 and record the full load values of ' 1 and '2. 72 points9 '1 E FFFFFFFFFF A A
'2 E FFFFFFFFF A D
d. ?pen the three inductive load switches for a no load condition on the alternator and measure and record the no load * 1 and '2. (emember to chec& the motor speed and read%ust to 1+ rpm if re$uired. 72 points9 *1 E FFFFFFFFFF 8 A
'2 E FFFFFFFFF A D
e. (eturn the voltage to >ero and turn off the power supply. f. alculate the alternator regulation with inductive loading. 72 points9 %regulation
V NL V FL −
=
V FL
x100%
G regulation E FFFFFFFFFFF G
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AC Machinery Laboratory EEC631L
Experiment No.2 Three Phase Alternator
g. /ith inductive load, does the stator magnetomotive force air or oppose the rotor magnetomotive forceH 71 point9 FFFFFFFFFFFFF ;.
a. !sing the apacitive "oad odule, replace the resistive load with an inductive load. b. Ad%ust each capacitance section for a reactance ) of 4 . c. (epeat procedure 4 and record the full load values of ' 1 and '2. 72 points9 '1 E FFFFFFFFFFF A A
'2 E FFFFFFFFFF A D
d. ?pen the three capacitive load switches for a no load condition on the alternator and measure and record the no load * 1 and '2. (emember to chec& the motor speed and read%ust to 1+ rpm if re$uired. 72 points9 *1 E FFFFFFFFFFF 8 A
'2 E FFFFFFFFFF A D
e. (eturn the voltage to >ero and turn off the power supply. f. alculate the alternator regulation with capacitive loading. 72 points9 %regulation
V NL V FL −
=
V FL
x100%
G regulation E FFFFFFFFFF G g. /ith capacitive load, does the stator magnetomotive force air or oppose the rotor magnetomotive forceH 71 point9 FFFFFFFFFFFFFF :.
a. /ith a capacitive reactance load of 12 per phase, turn on the power supply and ad%ust for a motor speed of 1+ rpm.
b. Ad%ust the D excitation of the alternator until the output voltage * 1 E 2+ 8 A. c. 'ncrease the capacitive loading switching on an additional reactance of : in parallel with each of the 12 sections and observe what happens. 72 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF d. 'ncrease the capacitive loading further by switching the 4 across each section and record the observation. 72 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF e. (eturn the voltage to >ero and turn off the power supply.
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AC Machinery Laboratory EEC631L
Experiment No.2 Three Phase Alternator
f. *xplain your observation. 72 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF @.
a. onnect the circuit shown in Big. 2.2. Cote that only one of the alternator phases has a load.
;i+. 2.2
b. Turn on the power supply and ad%ust the D motor rheostat for a motor speed of 1+ rpm. c. Ad%ust the D excitation of the alternator until the voltage across the : load *1 E 2+ 8 A. easure and record the two other phase voltages * 2 and *4. 72 points9 *2 E FFFFFFFFF 8 A
*4 E FFFFFFFFF 8 A
d. Turn off the power supply without touching any of the variable controls. e. (econnect the three A voltmeters so that they will measure the voltage across each of the three stator windings. f. Turn on the power supply. easure and record the voltage across each of the three stator windings. 72 points9 *10 E FFFFFFFFFF 8 A
*2; E FFFFFFFFF 8 A
*4: E FFFFFFFFFF 8 A
g. (eturn the voltage to >ero and turn off the power supply. h. Did the single-phase load produce a large imbalanceH FFFFFFFFFF
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AC Machinery Laboratory EEC631L
Experiment No.2 Three Phase Alternator
E'!E? *#E(T!"N( 1. /hy the alternator output voltage decreases with resistive loadH 72 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF 2. omment on the full-load rotor currents measured at inductive loading compared to a resistive and capacitive loading. omment on the basis that at each loading type, a terminal voltage of 2+ 8olts is maintained. 73 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF 4. /hy is it dangerous to connect an alternator to a long transmission line that behaves li&e a capacitorH 72 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF 0. The rotor of an alternator, at rated power, dissipates more heat at a low lagging power factor load that at high power factor load. *xplain. 73 points9 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF FFFFFFFFF F
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