Transformers. Produkt: Zavádění cizojazyčné terminologie do výuky odborných předmětů a do laboratorních cvičení

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1 Název projektu: Automatizace výrobních procesů ve strojírenství a řemeslech Registrační číslo: CZ..07/..30/ Příjemce: SPŠ strojnická a SOŠ profesora Švejcara Plzeň, Klatovská 09 Tento projekt je spolufinancován Evropskou unií a státním rozpočtem České republiky Produkt: Zavádění cizojazyčné terminologie do výuky odborných předmětů a do laboratorních cvičení Transformers Návod v anglickém jazyce Číslo tématu: 6b Monitorovací indikátor:

2 INSTRCTIONS FOR TOPIC: 6b Created in school year: 0/03 Branch: 6-4-M/0 Electrical Engineering - Mechatronics Subject: Measurement and diagnostics Year: 3. Prepared by: Ing. Milan Nechanický; translated by: Bc. Veronika Mádlová Transformers Introduction Transformer is an electrical non-rotating machine It works on a principle of electromagnetic induction (Faraday's law of induction) It converts AC voltage to AC voltage of different intensity (or the same intensity in case of isolation transformer) Transformation ratio p p N N I I Single Phase Transformer Basic parts of a transformer: - magnetic circuit made of transformer sheets - windings (primary and secondary)

3 nloaded Transformer Magnetic flux changes sinusoidally in a time period and its course is 90 delayed after the voltage. Magnetic fluxes of an unloaded transformer are real, caused by current I Phasor Diagram of Ideal nloaded Transformer The resistence of winding, leakage flows and the losses of iron are neglected. Basic Relations of Ideal Transformer: 3

4 4 Phasor Diagram of Real nloaded Transformer Formula of Effective Value of Induced Voltage: R = R = 0 0 dt d N dt d N N N N N I I I I

5 i i d N dt jn m e jt j t e m imax N m f ief N f imax m 4, 44 fn m Ideal Loaded Transformer: Magnetic fluxes of a loaded transformer are fictive fluxes. The other fluxes are real. 5

6 Equivalent Circuit of Loaded Transformer : Pouze magnetický tok přenáší energii ze strany primární na stranu sekundární. Full Equivalent Circuit of Loaded Transformer: Full Phasor Diagram of Loaded Transformer: 6

7 Simplified Equivalent Circuit of Loaded Transformer : 7

8 At large transformers the values R, R, X, X are low and the values X a R fe high. Therefore it is possible to use following simplification: X K = X σ + X σ R K = R + R 8

9 The resistence of windings, iron losses and leakage inductance are neglected. The resistence of winding and iron losses are neglected. 9

10 Iron losses are neglected in this case. 0

11 The resistance of windings and the leakage inductance are neglected. Leakage inductance is neglected.

12 Transformer in Short Circuit Iron losses are neglected in this case. Three-phase Transformer:

13 Possible Winding Circuits of Three-phase Transformer- Hour Angle Dd: Dy: 5 7 Dz: Yd: 5 7 Yy: 0 6 Yz: 5 7 Examples of Winding Circuits of Three-phase Transformer Yy6 3

14 Examples of Winding Circuits of Three-phase Transformer Yy0 Yy0 (0 o ) Examples of Winding Circuits of Three-phase Transformer Dd0 Dd0 (0 o ) 4

15 Examples of Winding Circuits of Three-phase Transformer Dy Dy (30 o ) Examples of Winding Circuits of Three-phase Transformer Dy5 5

16 Dy5 (50 o ) Examples of Winding Circuits of Three-phase Transformer Dy7 Dy7 (0 o ) Secondary Winding Connected to Angled Star The secondary winding is divided into two stages and each one happens on a different core of the transformer. The advantage is that the phase voltage on the secondary side stays the same even if the transformer is asymmetrically loaded (that means there is current in a zero conductor). 6

17 Zdroje: poznámky z předmětu Základy teoretické elektrotechniky -. semestr při ZČ Plzeň BLAHOVEC, A., Elektrotechnika I, Praha: Informatorium s.r.o., 00. ISBN BLAHOVEC, A., Elektrotechnika II, Praha: Informatorium s.r.o., 00. ISBN

18 Transformátory - Transformers - slovníček odborných termínů Vocabulary Slovníček transformátor napětí vinutí nezatížený transformátor zatížený transformátor proud magnetický tok rozptylová indukčnost elektromagnetická indukce odpor zapojení transformer voltage winding unloaded transformer loaded transformer current magnetic flux leakage inductance electromagnetic induction resistance circuit 8