Power Transformers 50Hz vs 60Hz

[GainFreak]

Thanks to R.G. for the thorough explanation as usual

That does not mean that they are magnetically asymmetrical, only that one is wound with more copper wire length than the other, as it would be if one was wound first, then the second on top of the first. The turns get longer as the wire layers build up. If they have exactly the same number of turns, they may be paralleled safely even if the resistances are different. If they have different numbers of turns, they may NOT be paralleled safely even if the resistances are equal.

I think they have the same number of turns.

[J M Fahey]

A 60Hz transformer on 50Hz mains will run *somewhat* hotter , yes, specially on idle, because the magnetizing current will be higher, and saturate somewhat earlier on full power, but that should no mean fireworks or smoke.
It should be not more than *extra* 15ºC or thereabouts, and a somewhat higher turn on thump, compared to a proper 50Hz one.
I live in Argentina (220v 50Hz) where the professional musician norm seems to be an US made amp, 110 to 120V 60Hz, bought in Miami, NY or LA, used here with a 220/110 auto transformer, with no problems at all.
I guess the exploding transformers mentioned must be *very* cheaply made, marginal even on the original power grid.
The *very* overloaded camel , yes, gets its back broken by an extra straw, but it isn't the straw's fault.
Yet I have used and repaired tons of 60Hz amplifiers for *other* problems, not those.
I'm talking of old (up to early 90's) US made Fenders, Peaveys, Acoustics, Ampegs; the US version, not the export type bought legally on Argentine shops.
Modern "famous US/UK/Japan label/cheap Orient manufacturing" *do* burst in flames, for that and for other reasons as well.
Probably the transformer that worries you is a cheap orient manufacturer product, even if bought from a reputable US dealer.

[tubeswell]

I live in Argentina (220v 50Hz) where the professional musician norm seems to be an US made amp, 110 to 120V 60Hz, bought in Miami, NY or LA, used here with a 220/110 auto transformer, with no problems at all.

Yes if you are running a drop down transformer in front, then even though the cycle is 50Hz, the amp's PT is still not having to deal with as much power (because you have already dropped the voltage to 110) - Are we not talking about the area under the sine wave function here?

[Steve Conner]

Not really. Euro transformers are larger because the frequency is lower, not because the voltage is higher. Some parts of Canada used to have 25Hz power: here's a pic of an old tube radio for that market. Can you spot the PT?
http://oak.cats.ohiou.edu/~postr/bapix/CGE_KL70.htm

If a transformer was designed for X volts at Y Hz, then increasing the voltage or decreasing the frequency will both make it run hotter and hum louder.

If you decreased the frequency to (5/6)*Y, then also decreased the voltage to (5/6)*X, then it wouldn't get any hotter or buzz any louder. But the secondary voltages would all be down, and the transformer's VA rating would only be 5/6 of what it was, too. So it follows that a 50Hz transformer is about 6/5 the size of a 60Hz one at the same VA rating, and the Canadian ones were twice the size of 50Hz ones.

Doesn't matter whether it was designed for 115, 230, or universal. Changes in voltage are with respect to the nameplate voltage: ie the value of X that the transformer designer was told to work off.

[tubeswell]

So help me in my understanding then. (I can't recall much about basic physics). If you have two sine waves thus;

The one of amplitude A and frequency 60

The other of an amplitude 2A and frequency 50

Then is the work in/powerout of the one not smaller than the other?

And if the One is smaller than the Other, then is not the energy carried by the One less than the Other?

And if a PT designed for the one is transferring this energy to the secondary, does its power handling capability not need to be as great as the Other?

(Sorry if I am really slow to understand this)

[Steve Conner]

Yes, the above is all true.

But a transformer designed for 230V will have twice as many primary turns as one designed for 115V. If the transformer is the same physical size and VA rating, the wire will have to have half of the cross-sectional area, to make twice as many turns fit.

So the actual input voltage doesn't matter: it all ends up the same in terms of Webers of flux, amp-turns of MMF, and watts of copper and core losses. The 115V transformer will draw twice the primary current of the 230V one, as required by conservation of energy. (It only has half of the turns, so it needs twice the current to generate the same MMF.)

Ditto if you take a universal transformer, with two identical windings to be seriesed for 230V and paralleled for 115. Half the voltage, twice the current, same VA.

The frequency is irrelevant, power/work is a function of voltage * current, no mention of frequency at all! Where frequency comes into the equation is that lower frequencies need a bigger core, or else it'll saturate, which is where the humming and overheating comes from.

[jean marc]

hello i m new on on this forum. i live in France and i can confirm that the weber 25130 EU can't stand the 230v . five of them had shorted in 5 differents Princeton clone. after one hour they start to be very hot. really not a good choice if you built something pro.