6.1 Noem DRIE onderdele van 'n kuorotor - NSC Electrical Technology Power Systems - Question 6 - 2023 - Paper 1
Question 6
6.1 Noem DRIE onderdele van 'n kuorotor.
6.2 Verwys na FIGUUR 6.2 hieronder en antwoord die vrae wat volg.
6.2.1 Identifiseer punt X.
6.2.2 Definieer die term rot... show full transcript
Worked Solution & Example Answer:6.1 Noem DRIE onderdele van 'n kuorotor - NSC Electrical Technology Power Systems - Question 6 - 2023 - Paper 1
Step 1
Noem DRIE onderdele van 'n kuorotor.
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Die drie onderdele van 'n kuorotor is:
Rotor geleistawer
Eindinge
Staal lamineringe
Step 2
Identifiseer punt X.
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Punt X is die punt waar die roterende spoed van die rotor gelyk is aan die sinchrono spoed.
Step 3
Definieer die term rotorglip.
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Rotorglip is die verskil tussen die sinchrono spoed en die rotorspoed.
Step 4
Verduidelik waarom die wringkrag nou is wanneer die rotorspoed by punt X is.
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By punt X is die rotorspoed gelyk aan die sinchrono spoed, wat beteken dat daar geen relatiewe beweging tussen die stator en die rotoreilande is nie, en gevolglik geen wringkrag getrek kan word nie.
Step 5
Sinchrono spoed
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Die sinchrono spoed kan bereken word met die formule:
n_s = rac{60 imes f}{p}
waar:
f = frekwensie (50 Hz),
p = aantal pols (4), wat gegee is.
Dus:
n_s = rac{60 imes 50}{4} = 750 ext{ o/min}
Step 6
Rotorspoed indien die glip 5% is.
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Die rotorspoed (nR) kan bereken word deur die glip te gebruik:
ext{% Glip} = rac{n_s - n_R}{n_s} imes 100
In hierdie geval, as 5% glip gegee is:
n_R = n_s imes (1 - rac{5}{100}) = 750 imes (1 - 0.05) = 712,5 ext{ o/min}
Step 7
Saamgestelde ware drywing van die twee motors.
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Die saamgestelde ware drywing (Pt) van die twee motors is die som van hul individuele drawwings:
Pt=P1+P2=75extkW+50extkW=125extkW
Step 8
Saamgestelde reaktiewe drywing van die twee motors.
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Die saamgestelde reaktiewe drywing (Qt) is die som van die reaktiewe drywing van die twee motors:
Qt=Q1+Q2=45extkVAr+21,79extkVAr=66,79extkVAr
Step 9
Skydrywing nadat Motor 2 by die stelsel gevoeg is.
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Die skydrywing (S) nadat Motor 2 bygevoeg is, kan bereken word met:
S=extsqrt(Pt2+Qt2)=extsqrt(1252+66,792)=141,72extkVA
Step 10
Arbeidsfaktor van die stelsel nadat Motor 2 by die stelsel gevoeg is.
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Die arbeidsfaktor (extcosheta) van die stelsel kan bereken word met:
ext{cos} heta = rac{P_t}{S} = rac{125 ext{ kW}}{141,72 ext{ kVA}} = 0,88
Step 11
Noem die kontakte wat die grendelverbindingsfunksie in die kring hierbo skep.
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Die kontakte wat die grendelverbindingsfunksie skep, is HK2 N/T.
Step 12
Verduidelik waarom 'n normaal geslote kontak van die oorbelasting in plaas van 'n normaal oop kontak gebruik word.
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'n Normaal geslote kontak laat stroom in die kring vloei, wat beteken HK1 sal ontgrendel wanneer die motor van die toevoer is, terwyl 'n normaal oop kontak daarenteen sal wees.
Step 13
Met verwysing na die kontrolemekanismes in die beheerkring, verduidelik waarom kontak HK2 nie op dieselfde tyd as HK1 geaktiveer kan word nie.
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Kontak HK2 is geconfigureer om nie gelyktydig met HK1 geaktiveer te word nie omdat dit 'n sekuriteitsmeganisme is om oorspanning of kortsluitings te voorkom.
Step 14
Verduidelik hoe die werking van die kring beïnvloed sal word wanneer HK1 N/O foutief en permanent oop is.
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As HK1 N/O foutief en permanent oop is, sal AANSIT 1 nie geaktiveer wees nie, wat die hele werking van die kring sal belemmer en die motor nie kan aanloop nie.
