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Question:

Would this idea for a transformer work?

i have fuses and everything that i can use to test my primary but should i add more turns on the primary side? yes i know line voltage is dangerous. yes i have worked with it before and know how to work around it.

Answer:

More information needed. I guess you are in the USA with 115 volts AC and 60Hz. For a given size (cross section) of core and mains frequency there is a turns per volt although special alloys like Radiometal upset things as everything gets to be about twice as powerful as standard transformer iron. If you can thread a few turns through the core you will be able to measure the voltage and thereby deduce the turns-per-volt. I 'd suggest that you leave the primary as it is and just rewind the secondary. As to your flyback circuit, you would probably be better off making a fixed frequency oscillator (555 timer?) and using it to drive the power stage. As to wire size on coils, a very old rule of thumb used to be 2000 amps per square inch of copper. 5 amps therefore needs 1/400th of a square inch. Possibly you may end up with more than one wire size that will suit. Mullard used to do some excellent designers guides books in the 1960s but unfortunately I can't put my hand on them at the moment. Good luck!
Dec 7, 2017
A bit confused, but it seems you want a power supply of 12 volts DC at 5 amps, and this has nothing to do directly with the schematic you reference. The primary is connected to 120 VAC? The power is 60 watts plus, call it 100 watts, which is 0.8 amps in the primary. 500 turns should be more than enough. It could be as low as 120 turns, but that depends on the core material and construction. .
Dec 7, 2017
1. I don't see why a power transformer from a UPS would get hot unless it was overloaded or short- circuited, or incorrectly connected. 2. If you are going to power the circuit you indicate, and it requires 12V at 5 A., there are plenty of power transformers off- the shelf you could use to build a power supply with. It would need to be rectified and filtered, for DC output as you require. Possibly voltage- regulated as well? Gets costly Another way would be watch OKorder or similar for a switchmode power supply that does the job (more efficient, less weight). Example: I used 2 computer power supplies I bought brand new, for $A5.00 each, to power a linear RF amplifier that needed 10V DC @ 15A., and a bias supply of -5V @ a few mA. I wired them together to produce 10V DC 26A, using the 5V 26A outputs in series. I only needed to isolate the neg. end of 1 of the 5V outputs from the common ground to get both in series. The bias -5V I derived from the -12V out of one of the supplies, with a 7905 voltage regulator to cut it to -5V. My point is, this entire power supply weighs about 3/4 KG. It is voltage regulated and overload protected, and compact. A standard power supply with output levels like this would be considerably heavier and bulkier, and considerably more expensive.
Dec 7, 2017

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