Original source about TEC lifetime reduction when the TEC ripple cureent is high: https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1991-02.pdf Page 74 I suspect that someone there may have been bitten by the short TEC life experienced without the LC filter. Although they used relatively small TECs the size of the individual Peltier element is the determining factor for the ripple current frequency dependence of TEC life. HP used a 40kHz PWM frequency.
There should be a relatively uniform temperature gradient along the length of each Peltier element. TEC module datasheets are generally silent on the effect of ripple current on TEC lifetime. CUI merely indicate that keeping the TEC ripple current below 5% ensures that TEC performance is maximised. Peltier element solder junctions to the ceramic endplates usually fail after 3000 cycles or therabouts. CUI use a compliant thermally conductive adhesive to achieve a longer cycle life. Bruce > On 22 December 2020 at 12:43 Hal Murray <[email protected]> wrote: > > > [Old mail, context is TECs] > > [email protected] said: > > If the drive current ripple is too high fatigue failure from cyclic > > thermomechanical stress can be significant. > > Do good data sheets say anything about that? > > Is there a frequency term in there? Can I use PWM, which is as much ripple > as > you can get, as long as the frequency is high enough? If yes, ballpark of > how > high? > > Physically, where is the heat/cold generated? Is it mostly at the junction? > > -- > These are my opinions. I hate spam. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
