You are absolutely correct about the pitfalls of putting 100 KHz on the primary of a 60 Hz transformer. The thing would get very hot very fast. I am sure that everyone on this list knows that the magnetics becomes smaller as frequency increases. That is why switchers use high frequency magnetics. The 60 Hz equivalent of this transformer would be one heavy baby, a very large, I might add. But about the high frequency for lower frequency magnetics, Variable speed AC motor controllers utilize up to 25 KHz. I don't know if there are any theory of AC motor control pages on the WEB for those who might be curious. ----- Original Message ----- From: "Sean Breheny" To: "Microcontroller discussion list - Public." Sent: Saturday, August 09, 2008 11:34 AM Subject: Re: EE > As usual I realized after I hit send that you probably just divided :) > I should further engage brain before engaging mouth (or typing > fingers). > > Hmmm...somehow, though, it sounds to me like he wants to put a 100KHz > sine wave through a transformer designed for 50 or 60Hz. If so, I > don't think that will work very well in terms of core losses, skin > effect losses, winding capacitance, reduced coupling from pri to sec, > etc. > > If, on the other hand, he is using 100KHz PWM to synthesize a 50Hz > sine wave, for example, then that should work well (although the PWM > frequency is a bit high). > > Sean > > > On Sat, Aug 9, 2008 at 8:42 AM, Apptech wrote: >>> Where did you get 16 ohms from? >> >> R = V/I. >> The driver sees the load reflected via the transformer. If >> 230 VAC causes 14 amps to flow then the AC is seeing 230/14 >> ~= 16. >> >> In the absence of load the actual transformer impedance will >> be seen but it will very usually b swamped when loaded. >> >> >> Russell >> >>>>>> I have to drive a transformer primary at 230 VAC @ 14 >>>>>> Amps @ 100KHz. I have not yet measured the primary >>>>>> impedance, but I will. >>>> >>>> The impedance you see will be about 16 ohms - ie the >>>> load, >>>> more or less regardless of the transformer's unloaded >>>> impedance. >>>> >>>> >>>> Russell >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist