Hi Rich, Is there a reason why you are using such a high frequency to transfer power? What does the secondary voltage/current look like? What kind of core material does your transformer use? When the coupling between primary and secondary is close enough to 1 and the impedance of the load is significantly smaller than the inductive reactance of the windings, then a transformer looks "ideal" in that the input impedance looks like the square of the turns ratio times the load impedance. I do not think that you want to create a 50 ohm load - you have already specified the input voltage and current so your input impedance is determined (do you really have a setup which will draw a constant 14A at 230V?). I also doubt that you want to create an LC circuit. That is usually done when filtering is desired and the coupling between pri and sec is much less than 1 (so that the Q of the LC circuit isn't too spoiled by the load resistance). In "wireless" power transmission it is also sometimes done to get around some of the effects of having poor coupling coefficient (due to distance between the pri and sec). IGBTs or any other switching element for that matter will NOT of itself create a sine wave. If you go that route, you will either be driving the transformer with a square wave or you will have to do PWM which is of a significantly higher freq than the sine wave you want to generate. You could also go back to making an LC circuit and create a class C amplifier, but that will likely make things bulky and somewhat inefficient. Could you say a bit more about your application? The focus on transmitting kilowatts at 100KHz seems odd. Sean On Sun, Aug 10, 2008 at 1:23 AM, Rich wrote: > I wonder if I am mistaken here. The transformer primary is an inductive > element. True, there is distributed coil capacity, and a frequency > component that makes the system complex. So there will be some "natural" > resonance that may not be at 100 KHz and may have a very low Q, regardless > of the fact that the transformer was designed to operate at 100 KHz. But by > adding the properly selected components, could one not design starting from > the LCR characteristic of the primary winding to create a tuned circuit at > 100 KHz and 50 ohms Z? Also, would it be true that if the Q is high the > stability of the oscillator must be high in order to stay within the > resonant bandwidth? So, a high Q may not be desireable and the R component > would be a factor? All comments, criticisms, "Oh what stupidity" comments > are welcome. > > > ----- Original Message ----- > From: "Vasile Surducan" > To: "Microcontroller discussion list - Public." > Sent: Saturday, August 09, 2008 9:07 AM > Subject: Re: EE > > >> Nice way of computing... A square signal bumped with a positive glich >> at the end of the rising edge will increase the current with 10-20% at >> the same secondary load. >> Does the primary impedance seen by the driver will be different ? >> >> Vasile >> >> On 8/9/08, 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 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist