The AM Forum

Title says it all (almost).

Found an interesting power transformer (Toroid) for class -e ....
They are 120volt primaries (x2), (tap for 100volts)
And 54.4volt CT secondaries (x2)  @ 19 amps each.

So, while no perfect... could be VERY usefull...

Especially the price of about $50. each


BUT, the spec sheet says they are 50 hertz....


The big question is....
Are they useable at all with 60 hertz mains.....?

Maybe derated a bit?

Seems like I should know this...but, well....

Comments?
Thanks.

I think that it will be o.k. fine.

The problem is when running a 60 Hz. only design at 50 Hz., very bad news.

Should work fine business.

Problems arise when using 60 hz iron on 50 hz mains.  Not enough "metals" in the xformer to get enough flux.


--Shane

Your peak current may be down just a bit but good chance the transformer will be more efficient so it ends up a wash. As a designer of 50 hz transformers we tried to use as few primary turns as possible so saturation voltage was down a bit. This was so we could get good performance at 60 hz. 60 hz transformer on 50 Hz the saturantion voltage comes down by  X 5/6.  You need almost 20 % more primary turns to get the same performance on 50 Hz.
A 50 Hz transformer on 60 Hz would have no problem with a step up tap on a variac.

Thanks Frank
(and Tom, and Shane)....

I thought that was the way it worked, but needed a little reassurance....

Was thinking of getting one to see what happens...
The voltage might be a touch high... but I can easily stick a transformer from and old line regulator ahead of it.... (steps down from 120 to 115, 110 etc and up to 125 I think)

But whatever, for $50 at that voltage/current rating, even if de-rated 10%.... Still would be usefull for something.....

I may hold off for now...
Forgot to think about the $19. shipping...
Still a good deal for a toroid transformer....
But, mayby not to just have sitting on the shelf..

By the way, the guy has, I guess about 10 of these on ebay...
Here's the link if anyone's interested.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290184977474

Well if the voltage is too high just add a few turns in series with the primary...
BTW that 100 volt winding at 50 hz is darn close 117 at 60 hz. But that would increase the output voltage.

Hi guys,

The rule of thumb is you can go up in frequency but not down, the core energizing/excitation current (Ix) becomes excessive and the precious smoke is released. An increase of only 10Hz shouldn't change the output voltage too much but like the man said you can always add a few turns to the primary.

I said add a few turns to the primary if the voltage is too high rather than using another transformer upstream. Or you could strip a few turns off the secondary if you are feeling lucky. You want excitation current slope linear up to about 135 volts to keep from letting too much input current release smoke. Extra primary turns raised the saturation voltage at the expense of extra turns of wire and a very small increase in series resistance.

What happens?
You'll get heavier gear than needed. More bot-anchor, I would say... ;)

Power transformers have been used as modulation transformers, and they pass power up into the kilohertz range.  Changing from 50 to 60 Hz should have almost no effect, except maybe the unit could provide a little bit more power at the higher frequency.

If the output voltage is critical, you could put a Variac on the input and set it precisely, otherwise a few more turns on the primary should do the trick.