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Power Electronics

11. Power Electronics. Device. Device symbol. i. D. Diode. A. K. +. –. v. AK. i. G. Thyristor. A. A. K. i. G. Gate turn-off. thyristor. (GTO). A. A. K. G. Triac. i. A. A. K. C. npn . BJT. B. E. C. IGBT. G. E. D. n. -channel. MOSFET. G. S.

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Power Electronics

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  1. 11 Power Electronics

  2. Device Device symbol i D Diode A K + – v AK i G Thyristor A A K i G Gate turn-off thyristor (GTO) A A K G Triac i A A K C npn BJT B E C IGBT G E D n -channel MOSFET G S Figure 11.1 Classification of power electronic devices

  3. G T 1 1 + v = V sin t S m – R L AC supply + – + v o v S – T 2 G 2 v S V m t 0 2 – V m v o V m t 0 + 2 Figure 11.2 AC-DC converter circuit and waveform

  4. v S V m G 0 2 t – V + + m AC v = V sin t v R S m o L supply v – – o V m + 0 2 t – V m Figure 11.3 AC-AC converter circuit and waveform

  5. V BE 1 + 0.5 Duty cycle = = / T t 1 + 0 t T t 1 V V S BE – v o DC supply V S Load v – o 0 t T t 1 Figure 11.4 DC-DC converter circuit and waveform

  6. V , V G 1 G 2 1 0.5 + M M 1 3 0 T /2 T t V V G 1 G 3 V , V G 3 G 4 V S 1 DC Load supply 0.5 0 T /2 T t M M 4 2 v V V o G 4 G 2 – V S 0 T /2 T t – V S 0 0.5 1 Figure 11.5 DC-AC converter circuit and waveform

  7. i Z + i Z 1 R Z v Z – V 0 V v – Z Z Voltage regulator Unregulated Load supply Figure 11-6 Zener diode characteristic and voltage regulator circuit

  8. i _ C + V CE _ + I L V + BE + R + B v V ~ R _ S L L V i Z Z _ _ Figure 11.7

  9. i C (1) I C max i P B (2) 1 max Saturation i B 2 i B 3 (3) i B 4 v CE V V Cutoff CE sat CE max Figure 11.13 Limitations of a BJT amplifier

  10. V B V 1 0 t – V 2 i B I B 1 0 t – I B 2 i C t t I s r CS 0.9 I CS 0.1 I CS t t t d f Figure 11.14 BJT switching waveforms

  11. v G V 1 0 t v GS t t r f V 1 V GSP V T 0 t t t d ( on ) d ( off ) Figure 11.15 MOSFET switching waveforms

  12. C R MOD R BE G E Figure 11.16 IGBT simplified equivalent circuit

  13. i L D 1 + L + _ v ~ v AC L R – Simple half-wave rectifier D 1 L + v ~ D _ AC 2 R Same arrangement with free-wheeling diode Figure 11.17 Rectifier connected to an inductive load

  14. v L ( t ) A V A L v V L = L 0 v t AC i L ( t ) I L V L I = L R 0 t Figure 11.18 Operation of free-wheeling diode

  15. a b c Primary i c i L c + D D D v 1 3 5 cn i a – + n R v L – – + a v – an v bn D D D + 4 6 2 i b b Bridge rectifier Secondary Figure 11.20 Three-phase diode bridge rectifier

  16. Diodes on 5 – 6 6 – 1 1 – 2 2 – 3 3 – 4 4 – 5 v v v v v v cb ab ac bc ba ca 3 V m 0 t – 3 V m v L 3 V m /3 2 /3 4 /3 5 /3 2 t Figure 11.21 Waveforms and conduction times of three-phase bridge rectifier

  17. A (anode) A + i P A G N v (gate) AK G P – N K K (cathode) Figure 11.22 Thyristor structure and circuit symbol

  18. i A Holding current Latching current Gate Holding current triggered i L Reverse i H breakdown v Forward leakage voltage AK current Reverse leakage current Figure 11.23 Thyristor i-v characteristic

  19. A P N G P N K A P N N P P G N K A i A i = i B C Q p n p i C p Q G n i i G B n K Figure 11.24 Thyristor two-transistor model

  20. v trigger + + ~ Load v ( t ) _ v ( t ) AC i ( t ) L L – Figure 11.25 Controlled rectifier circuit

  21. v trigger t v s V m 0 2 t – V m v o V m 0 2 t Figure 11.26 Half-wave controlled rectifier waveforms

  22. i II I Reverse Motoring braking (forward) (generation) v Forward Motoring braking (reverse) (generation) III IV Figure 11.33 The four quadrants of an electric drive

  23. + I a V T a m – m Figure 11.34 DC motor

  24. i o + S Chopper L a + R a V S v o + E T a – m – – m Figure 11.35 Step-down chopper (buck converter)

  25. v o i o V S i o v o 0 0 t T 1 Figure 11.36 Step-down chopper waveforms

  26. + v – L L S I S + L + a S R V a v S o T – – m m Figure 11.37 Step-up chopper (boost converter)

  27. v (t) o <v > o V S t Figure 11.38 Step-up chopper output voltage wave-form (ideal)

  28. v + – L I L + S a + S R V a S v o – T – m m Figure 11.39 Step-up chopper used for regenerative braking

  29. D S 1 2 + i o V S + S v 2 DC motor o – D 1 – i o II I S D 1 1 v o S D 2 2 III IV Figure 11.40 Two-quadrant chopper

  30. + S V 1 D S 1 2 – v + – o Load + S 2 i V D S o 2 2 – Figure 11.41 Half-bridge voltage source inverter

  31. S 1 0 T /2 T S 2 0 T /2 T V v S o 2 S D 1 2 i o 0 T /2 T S D – V S 2 1 2 Figure 11.42 Half-bridge voltage source inverter wave-forms

  32. D D S S 1 3 1 3 + v – o + Load V S – i o S S D D 4 4 2 2 Figure 11.43 Full-bridge voltage source inverter

  33. v o V S 0 T /2 T – V S Figure 11.44 Half-bridge voltage inverter output voltage waveform

  34. + S D S D S D V 1 3 5 1 3 5 S 2 – o a b c + S S S 4 6 2 D D D V 4 6 2 S 2 – a b c i i i a b c Load n Figure 11.45 Three-phase voltage source inverter

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