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 What are transformers all about?

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Cliff Jones
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Join date : 2010-11-22

PostSubject: What are transformers all about?   2012-10-10, 10:42 am

A question of safety has arisen from time to time in, "What is the difference between a AA5 radio and a transformer operated radio?"



There are two types of transformers, the predominant one in use has two windings (or more) of wire, that are insulated from each other. The Iron core transfers the alternating current by magnetic fields (Induction) from the primary winding to the secondary winding.
Depending on the ratio of wire turns it causes Higher, equal, or lower voltages or in the case of multiple windings, multiple voltages. It still is AC voltage though.
The Higher voltages above 12 volts are usually rectified over to DC voltages for use. The lower voltages are used usually to power the filaments. But they can also be used to charge batteries by rectification to DC or supply computer dc voltages usually 3.3vdc, 5vdc and 12vdc.
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On the other hand Auto transformers usually only have one winding but still operate using magnetic induction but use wire taps for different voltages and are not isolated, This type is usually in the form of variacs, but not always. Variacs use a brush that slides over exposed windings to adjust to the desired voltage. I have seen in some radios a tapped auto transformer for obtaining various voltages. Just because it looks like a transformer in the radio but does not always make it a true two isolated windings transformer. This is unusual but does occur and still has the hot chassis issue.
An Isolation transformer is best if you are in doubt or it's questionable as to safety.


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Now on AA5 radios there is no power transformer, so both the tube filaments and the radio it self uses un-isolated direct power from a wall socket. If you have a piece of test equipment that also has no transformer then when you hook up the ground of the test equipment to the radio the chassis may be hot and you will either get an electrical shock in the process of hooking the connection up or you will blow a fuse, circuit breaker, or worse yet have sparks fly from the plug or wires that burn out with a bright white light. NOT GOOD for you or the equipment, in the simplest terms or significantly an electrocution of your personal body. scratch

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