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Fig.1: Half-bridge circuit with current and voltage waveforms when switching IGBT1
Due to the changing current a voltage drop of Ls * dioff/dt occurs across the stray inductance Ls. It is overlayed to the DC link voltage VCC and seen as a voltage spike across the turning-off IGBT1. According to the RBSOA diagram, this spike must be limited to the blocking voltage VCES of the IGBT module (measured at the chip, means measured at the CE auxiliary terminals). Also a derated curve is given in the data-sheet for measurements at the power terminals, taking into account the internal module stray inductance between main and auxiliary terminals of the module.ÎÄÕÂÀ´Ô´£ºhttp://www.minaco-uk.com/il/150.html
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Ls = DV / di/dt.
Fig.2: Switching curves of current and voltage when turning on an IGBT
Example:
i: 400A / div (green) v: 200V / div. (black)
¸Ãµçѹ½µ·¢ÉúµÄʱ¿Ì£¬¶þ¼«¹ÜÈÔȻûÓÐ×è¶ÏÄÜÁ¦¡£Òò´Ëµçѹ½µÖ»ÄÜÊÇÓÉÔÓÉ¢µç¸Ð²úÉú£¬²»Ð迼ÂÇÆäËûµÄÓ°Ïì¡£The circuit stray inductance is calculated according to the above shown formula at zero
crossing of current. We get the following values:
DV » 230V
di/dt » 3200A/800ns
Å Ls » 58nH
