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Transformer modification? Answered

2 questions about transformers:

- If a certain transformer (let's say, for a power amplifier) is needed, and for example, a microwave transformer is available, can the steel frame be cut to take out the secondary coil, to be replaced by a new one, and subsequently be re-attached (by clamps or so)? Would it need some treatment, like putting varnish, or oil over it?  Would this cutting and re- attaching cause a loss in efficiency, or cause heat build-up? Would it cause more noise in the output?

- Some amps have a toroid transformer. Is this just fashionable or is it for a reason? Some industrial amps use sheets of copper instead of wire. Why is this better for industrial, why, and if not for common stuff...?


1.) DON'T cut the iron off - you'll not make an acceptable magnetic circuit again. Microwave transformers, being really horribly cheap though are often assembled by welding the stack on the edges. Grind that off, and you end up with a big pile of "E" and "I" shaped laminations, and the coil on a former. Remove the secondary, but leave the primary attached.

2.) Toroidals are more efficient than EI transformers. They also have better regulation - in other words the output voltage changes less on load than with an EI transformer.

3.) Copper sheets are used for very high currents, and also as shielding between the windings.

Some torroid transformers are used to BOOST voltage and frequency.  This is especially true in CAR AUDIO big power amplifiers.  What they do, is take the 12 volts... pulse it into a torroid transformer at several hundred Hertz (cycles per second).  This produces a higher voltage at the OUTPUT of the torroid and at a higher frequency.  This higher frequency pulse is easier to filter back to SMOOTH DC using smaller filter capacitors (electrolytics).  The car audio amplifier needs to do this because only 12 volts dc is available from the car battery... which limits the amp power to about 5 watts per channel.  Thats fine for grandmaw, but the youngsters want 3000 watts per channel in their car.  These "PULSED POWER SUPPLIES" are also used in cameras to make the flash voltage and also in your computers power supply for the purpose of reducing the size of filtering capacitors. (lower cost). by the way... LOWER COST is the driving force behind it all... not "being fashionable."  Hope that helps... seems STEVEASTROUK  did a good job answering all the other questions.

Not sure I see how a linear transformer can create higher frequency components ?