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EFE1 DC-AC invertere, sinsformet AC Mohahan Kap. 8.1-2-3 J.Nybo 07.03.03 Rev.:05.03.08.

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Presentation on theme: "EFE1 DC-AC invertere, sinsformet AC Mohahan Kap. 8.1-2-3 J.Nybo 07.03.03 Rev.:05.03.08."— Presentation transcript:

1 EFE1 DC-AC invertere, sinsformet AC Mohahan Kap J.Nybo Rev.:

2 Side 2 af 15 Chapter 8 Switch-Mode DC-AC Inverters • converters for ac motor drives and uninterruptible power supplies XXXXXX

3 Side 3 af 15 Switch-Mode DC-AC Inverter • Block diagram of a motor drive where the power flow is unidirectional

4 Side 4 af 15 Switch-Mode DC-AC Inverter • Block diagram of a motor drive where the power flow can be bi-directional

5 Side 5 af 15 Switch-Mode DC-AC Inverter • Four quadrants of operation

6 Side 6 af 15 One Leg of a Switch-Mode DC-AC Inverter • The mid-point shown is fictitious

7 Side 7 af 15 Synthesis of a Sinusoidal Output by PWM

8 Side 8 af 15 Details of a Switching Time Period • Control voltage can be assumed constant during a switching time-period

9 Side 9 af 15 Harmonics in the DC-AC Inverter Output Voltage • Harmonics appear around the carrier frequency and its multiples

10 Side 10 af 15 Eksempel

11 Side 11 af 15 Valg af switch frekvens fs

12 Side 12 af 15 Harmonics due to Over-modulation • These are harmonics of the fundamental frequency Bedre udstyring, men flere harmoniske. (sinus klippes i toppen) Det anbefales at bruge synkron PWM.

13 Side 13 af 15 Output voltage Fundamental as a Function of the Modulation Index • Shows the linear and the over-modulation regions; square-wave operation in the limit

14 Side 14 af 15 Square-Wave Mode of Operation • Harmonics are of the fundamental frequency Fordele: Bedre udnyttelse af DC spændingen. Square-Wave modulation Er et specialtilfælde af PWM, Hvor amplitude modulations Indekset er meget større en 1

15 Side 15 af 15 Single-phase: Half-Bridge Inverter • Capacitors provide the mid-point Ingen Dc komponent i vo pga C+ og C-. Velegnet sammen med transformatorer.

16 Side 16 af 15 Single-Phase Full-Bridge DC-AC Inverter • Consists of two inverter legs

17 Side 17 af 15 PWM to Synthesize Sinusoidal Output • The dotted curve is the desired output; also the fundamental frequency

18 Side 18 af 15 Eksempel

19 Side 19 af 15 DC-side currents i d • Small fictitious filters eliminate the switching- frequency related ripple

20 Side 20 af 15 DC-side currents • Bi-Polar Voltage switching


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