# EFE1 DC-AC invertere, sinsformet AC Mohahan Kap

## Presentation on theme: "EFE1 DC-AC invertere, sinsformet AC Mohahan Kap"— Presentation transcript:

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

Switch-Mode DC-AC Inverters
Chapter 8 Switch-Mode DC-AC Inverters X converters for ac motor drives and uninterruptible power supplies

Switch-Mode DC-AC Inverter
Block diagram of a motor drive where the power flow is unidirectional

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

Switch-Mode DC-AC Inverter
Four quadrants of operation

One Leg of a Switch-Mode DC-AC Inverter
The mid-point shown is fictitious

Synthesis of a Sinusoidal Output by PWM

Details of a Switching Time Period
Control voltage can be assumed constant during a switching time-period

Harmonics in the DC-AC Inverter Output Voltage
Harmonics appear around the carrier frequency and its multiples

Eksempel

Valg af switch frekvens fs

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

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

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

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

Single-Phase Full-Bridge DC-AC Inverter
Consists of two inverter legs

PWM to Synthesize Sinusoidal Output
The dotted curve is the desired output; also the fundamental frequency

Eksempel

DC-side currents id Small fictitious filters eliminate the switching-frequency related ripple

DC-side currents Bi-Polar Voltage switching

Similar presentations