Original poster: Ed Phillips <evp@xxxxxxxxxxx> Tesla list wrote:
Original poster: "Scott Bogard" <teslas-intern@xxxxxxxxxxx> Hey all, Here is a question for all you mathy theoretical technical guys.I heard In physics class tonight, that if you use a higher frequency you can use a smaller core for a transformer. In my mind this means, if you use a higher frequency, you can pump more voltage through your primary, and consequently get more out of your secondary. This means (provided you have enough insulation) you could use a much higher voltage in your TC primary, with the same transformer, by changing the input voltage and frequency, without saturating the transformer core. So my question is, is this beneficial in any way? Is this even true, or is my logic flawed? I (as of right now) have no means with which to experiment with frequency and input voltage, but mabey somebody else out there does. Thanks a heap.Scott Bogard.
Your statements are true oversimplified. For a given transformer running at the same core flux density the allowable voltage increases directly with the frequency. A transformer designed to operate at 120 volts on the primary with 60 Hz power could be run at 360 volts with 180 Hz power, etc. However, the core losses will go up with frequency if the flux density is constant as in this example. If you keep the same voltage and increase the frequency the flux density will go down (it's inversely proportional to frequency if all other parameters are constant) and the losses will decrease. In order to minimize the size and cost, transformers normally operate at perhaps 80% of the saturation flux density of the core material. As a result, increasing the frequency (most common example is use of 400 Hz in aircraft power systems) permits a very substantial reduction in transformer size. "Better" core materials (thinner laminations and possibly different steel) are necessary to keep the core losses low. Here's a good reference to look at:
http://www.tabtronics.com/TECHNOLOGY/ElectromagneticBasics/TransformerBasics/tabid/110/Default.aspx#The_Universal_EMF_equationStart with the "Universal EMG Equation" ties together core area, flux density, frequency, number of turns, and voltage.
Ed