VRAAG 5: DRIEFASEMOTORS EN -ANSITTERS
5.1 FIGUUR 5.1 hieronder toon die rotor van 'n induksiemotor - NSC Electrical Technology Power Systems - Question 5 - 2021 - Paper 1
Question 5
VRAAG 5: DRIEFASEMOTORS EN -ANSITTERS
5.1 FIGUUR 5.1 hieronder toon die rotor van 'n induksiemotor. Beantwoord die vrae wat volg.
5.1.1 Benome onderdeel A en B.
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Worked Solution & Example Answer:VRAAG 5: DRIEFASEMOTORS EN -ANSITTERS
5.1 FIGUUR 5.1 hieronder toon die rotor van 'n induksiemotor - NSC Electrical Technology Power Systems - Question 5 - 2021 - Paper 1
Step 1
5.1.1 Benome onderdeel A en B.
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A is die 'Endring' en B is die 'Laer'.
Step 2
5.1.2 Noem EEN belangrike voordeel van die gebruik van hierdie tipe rotor in vergelyking met die gebruik van 'n rotor wat borrels en sleepringe het.
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Een van die belangrike voordele is dat dit minder instandhouding vereis omdat daar geen borrels of sleepringe is wat kan verslyt nie.
Step 3
5.1.3 Gee EEN rede waarom die rotorstawe skuins is.
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Die skuins rotorstawe verminder die magnetiese gemoet en verbeter die effektiewe transformasieverhouding tussen stator en rotor.
Step 4
5.2.1 Glip
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Glip is die verskil tussen die sinchronose spoed en rotorspoed van 'n induksiemotor in persentasie.
Step 5
5.2.2 EEN in werking stel
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EEN in werking stel is wanneer die motor aan die toevoer en die motor is gereed om sy werk te doen.
Step 6
5.4.1 Poolpare per fase
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Die poolpare per fase is rac{12}{3} = 4. Die totale poolpare is 2.
Step 7
5.4.2 Sinchroone spoed van die motor
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Die sinchronose spoed van die motor kan bereken word met die formule:
n_s = rac{f imes 60}{ ext{pole}}
waar f=50Hz en pole = 12. Dit gee n_s = rac{50 imes 60}{12} = 250 RPM.
Step 8
5.4.3 Rotorspoed met 3% glip
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Die rotorspoed kan bereken word met die formule:
n_r = n_s imes rac{(1 - ext{glip})}{100}
Dus,
n_r = 1500 imes rac{(1 - 0.03)}{100} = 1455 ext{ RPM}.
Step 9
5.4.4 Rendement van die motor
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Die rendement kan bereken word met die formule:
ext{Rendement} ( ext{η}) = rac{P_{in} - P_{verliese}}{P_{in}} imes 100
waar Pin=25000 en Pverliese=800. Dit gee ext{η} = rac{25000 - 800}{25000} imes 100 = 96.8\%.
Step 10
5.5.1 Identifiseer die beheerkring in FIGUUR 5.5.
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Die beheerkring in FIGUUR 5.5 is die 'Vorentoe- agtertoe beheer'.
Step 11
5.5.2 (a) Verduidelik die funksie van die OBN/T.
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Die OBN/T sal oopmaak sodra die stroomvloei die voorafgestelde stroom aanslag oorskry, wat die stroomvloei na HK1 onderbreek en die motor stop.
Step 12
5.5.2 (b) Verduidelik die funksie van die HK2/N/O.
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HK2/N/O is die inhou kontak vir die agtertoe kontak wat verseker dat die stroomvloei na HK2 aanhou, nadat die aansitknop gelos word.
Step 13
5.5.3 Verduidelik waarom die HK1/N/T-kontak in serie met die HK2-kontakspoel verbind is.
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HK1/N/T word as grendel kontak gebruik. Wanneer HK1 (vooraan) geaktiveer is sal HK1/N/T oopmaak wat verseker dat HK2 nie kan aktiveer terwyl HK1 geaktiveer is nie.
Step 14
5.6 Bereken die vollastroom van die motor indien die maksimum aansluiting slegs 100 A is.
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Die vollastroom kan bereken word as 100 A, volgens die gegevens gegee.
