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Re: power transformer design ...



Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 3 Dec 2003, at 8:08, Tesla list wrote:

 > Original poster: "Rajesh Seenivasan" <rajeshkvs-at-hotmail-dot-com>
 >
 > Dear forum members,
 >
 > I know this topic doesnt exactly match with the Tesla mailing list.
 > But, when I saw few discussions here I understood that the Tesla
 > experts can solve my problem too ...
 >
 > I am trying to design a Tesla coil and an induction heating system at
 > my home. I need to design a power transformer. It should be: Ferrite
 > cored, operates in the freq range 20KHz to 200KHz, A 25KW inverter
 > drives the primary coil, Ratio between primary and secondary is 20:1
 > ... and I want that to be very economical
 >
 > My assumptions(!) for this design are:
 > Any EE cores available in the market, the length of core (parameter A)
 > can be 100mm-150mm. I can have 2 or 3 such cores placed parallely to
 > form a single EE core. The primary winding can have "X" turns of
 > insulated #14 wire used for house wiring. The secondary will be 8mm
 > copper tube with few turns, which will be used as the Induction coil
 > which heats the metals. The whole transformer will be dipped in oil. I
 > assume that 420Vpeak-peak, 40A current should flow through the
 > primary.
 >
 > Any suggestions for the design will be very helpful for me.
 > Thanks in advance.
 >
 > .... also, anybody knows about companies which manufacture large
 > ferrites ? I get small ferrites only in the electronics market nearby.
 >
 > Thanks and regards,
 > Raj.

I wouldn't regard wire used for house wiring as at all suitable for
use in transformers. The insulation is (in my opinion) not robust
enough and also too thick (reduces the packing factor and increases
leakage inductance in the winding). Strap or litz conductors for the
primary would be much better. You would be better off operating
towards the higher of the frequencies you suggest.

Malcolm