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Since hi-fi stuff is somehow cheaper in the States I'd like to buy some goods over there... will the (e.g.) 110 V / 60 Hz Luxman amplifier work in UK ? The voltage will be changed by the high quality transformer but what about the 'frequency' ? Let me know, please... thanks in advance !
Yours
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Most "international" companies use the same power transformers and conversion is a matter of re-wiring (but not always). Have you contacted Luxman? Many manufacturers will do this for a fee if you ship them the amp, but it's not worth it most of the time.
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The only problem I have ever encountered is that the laminations in the transformer can buzz when encountering a frequency the unit was not designed for. However that has not happened for years as transformers are better designed and made these days, particularly in audio gear.John
No cure possible or is solicited for this audio, video and classical music obsession. I love it!
Yes it will work fine..I lived in Germany on and off for 12 years. I was stationed there while in the Army. Before the PX/BX started selling dual voltage electronics I used many transformers to run my electronics. That included things such as TVs,stereo, Clothes Iron, and washing machines.
ONLY ONE item in all those years did not work correctly ..my AR XA turntable. make of that what you will.
PS..The stateside distributors would not honor the warranties on the dual volatage electronics sold by the PX/BX .
I had an AR turntable when I was stationed in Germany...worked fine after changing to the 50 hz motor pulley.A syncronous motor depends on the line frequency for speed control.
I said "*ONLY ONE item in all those years did not work correctly ..my AR XA turntable*" I should of added "without modification or additonal parts" eh. It would be nice to know ahead of time that there might be a problem with turntables. That was the point.
turntable makes sense- the only big difference is electric motors where the speed will be altered. Many things don't matter if it's a little different, but a turntable would!
I imported a Fisher 500C to the UK I run it from a workmans 240 to 110V transformer and it works perfectly. So don't worry buy what you wish it'll work fine in the UK.
Transformers are designed to accommodate the total area under the voltage waveform. Visualize a sine wave, then imagine it drawn on a piece of graph paper. The total number of squares under the drawn line is the area in question. A sine wave of 50 Hz extends farther along the horizontal axis of the graph (the time axis) than one of 60 Hz, so the 50 Hz wave will have more area under its line.The area under the voltage curve requires a certain amount of iron in the core. A transformer that will work at 60 Hz may not have enough iron to work at 50 Hz. This is not a fault of the transformer design, just the fact of how it was designed for the application.
You may encounter a transformer that was designed to work at 50 Hz as well as 60 Hz to avoid the extra costs of stocking different units. It should say so on the transformer, or the manufacturer may be able to provide confirmation. However, if it buzzes when plugged in to 50 Hz AC, turn it off immediately!
It is so many years since I did any maths but what you have said seems plain wrong (but it could be me!)The area under a curve (your sine wave) is its integral. the integral of a sine wave is another sine wave but phase shifted.
I don't think the frequency gets into the equation. Yes more iron is needed at lower frequencies, but what is that to do with areas?
On a more practical level, having used I don't know how many items of electronics from around the world here in the UK at 50Hz (and I did personally import a lot of stuff after living in CA for 3 years) I have NEVER had a problem.Anyone who specced a transformer so tightly that it is OK at 60 but not at 50 deserves to be shot!
Maybe some really nasty wall-wart stuff, but nothing vaguely serious should give any problem.
Torodal transformers have a greater spread of frequency caperbilities than Iron core so the differance are only about 1/6.
So im guessing we are really talking about Iron cored transformers.
going from 60Hz to 50Hz will result in a less effecient power convertion and a small increase in the losses. But will work ok imo (ignoring all the disussions on mains impeadance (cable effects) etc and its effect on the sound.
Using 50Hz on 60Hz mains will increase the losses due the increased reactance. (yes the core materila are chosen for a very tight spec for max effecency, as it runs on a square law) the tranny will get much hotter.
If it ever burst into flames your insurance co may not pay out on the claim.
The voltage applied to the primary coil of the transformer leads to changing magnetic flux in the core which generates a back-emf to oppose the applied voltage, so that only a very small ("magnetizing") current flows if there is no load connected to the secondary coil. The back-emf is given by Faraday's Law, Vback = -N*A*(delta B/delta t).This works until the core saturates, whence delta B becomes very small and the back-emf collapses. The current is then limited only by the primary coil resistance and can become very large.
The area under the sine curve, for half the sine wave, and the core composition, determine how close the core comes to saturation before the exciting voltage reverses polarity. Any real-world core has a finite capability to be magnetized. The so-called B-H curve for the material flattens out for sufficient B. Making the core bigger allows for lower-frequency operation because it is the product of B and A (the cross-section area) that goes into Faraday's Law.
You may be right about transformers with sufficient over-design, but I've read enough horror stories about UK-sourced equipment designed for the 60 Hz USA standard to be cautious about blanket assurances of safety.
Al,Cliff is obviously right that the integral of B over half a waveform is not frequency dependent. B is proportional to I, so the question is whether I varies with frequency. As Ted pointed out, it does, due to the change in the reactance. However, the change in reactance between 50 Hz and 60 Hz should be totally insignificant compared to the reflected load resistance in any consumer electronic device. I think a modest change in mains voltage (e.g. 120V versus 110V) would actually have a greater effect on the peak energy storage in the core than a 10 Hz change in frequency.
Having said that, there could be products in existance which are so close to the edge that any small change in mains voltage or frequency would pose a problem. But I think that 99.9% of the time, a change from 60 Hz to 50 Hz will be fine as long as the voltage is within the original design limits. In fact, the vast majority of power supplies in consumer electronics are spec'ed for 50 Hz and 60 Hz operation.
Dave
Visualize a transformer with the primary connected to a 120 volt DC, current-limited power supply through a switch, and with the secondary left open-circuit. The current limit on the power supply is set for one ampere to keep from blowing things up.At time t = 0 the switch is closed. What is the time response of the current in the primary?
It will not rise immediately to one ampere, but will do so after the core is saturated.
The core switches its magnetization to provide the back-emf that prevents short-circuit current from flowing. The product of 120 volts and the time it takes to saturate the core should be greater than the integral under the half-wave sine curve if the transformer is to work properly at the sine wave frequency, whatever it is (25 Hz, 50 Hz, 60 Hz, 400 Hz).
I've greatly oversimplified here to get the basic point across. Transformers are designed to avoid core saturation for maximum expected primary voltage at some particular frequency. The lower the frequency, the more magnetic flux the core must contain without saturating. This is why the transformers in switching power supplies are so small.
This is only the beginning of the design. The maximum current determines the size of the wire, which determines the size of the coils, and on and on. It may be cheaper to just design the thing for 50 Hz and sell it into both the 50 Hz and 60 Hz markets (so-called "World" transformers as carried by Mouser, etc.), so a device that uses one of these would be perfectly safe to use in either area. However, this is not guaranteed.
Visualize a transformer with the primary connected to a 120 volt DC, current-limited power supply through a switch, and with the secondary left open-circuit. The current limit on the power supply is set for one ampere to keep from blowing things up.Well, your example is somewhat irrelevant because you're asking me to analyze the step response of a simple RL circuit and not the steady state sine wave response of a transformer, but I'll play along.
At time t = 0 the switch is closed. What is the time response of the current in the primary?Below your arbibrary 1 amp hard limit on the current, it's a simple RL response:
I(t) = 120 * R * (1 - e^(-L*t/R))
where L, R are the series inductance and resistance of the primary. Once it reaches your hard limit of 1 amp, it will obviously be 1 amp.
It will not rise immediately to one ampere, but will do so after the core is saturated.That depends on R & L. It could reach 1 amp before saturation.
The core switches its magnetization to provide the back-emf that prevents short-circuit current from flowing.In the case of steady state AC, the effect of the back-emf you are referring two is called inductive reactance. Inductive reactance is frequency dependent, X_L = 2*pi*f*L. For steady state AC, it's a constant.
For steady state DC, it's zero, and nothing but the series resistance prevents short circuit current from flowing.
For a step response, it exponentially decays to zero, so the impedance is initially larger but then decays to just the series resistance once the core saturates.
The product of 120 volts and the time it takes to saturate the core should be greater than the integral under the half-wave sine curve if the transformer is to work properly at the sine wave frequency, whatever it is (25 Hz, 50 Hz, 60 Hz, 400 Hz).Yes, and the frequency dependence you speak of is captured in the inductive reactance.
I've greatly oversimplified here to get the basic point across. Transformers are designed to avoid core saturation for maximum expected primary voltage at some particular frequency. The lower the frequency, the more magnetic flux the core must contain without saturating.I don't think you're making a technical error, but I do think that the point you're making is largely irrelevant in this application. For power supply transformers in consumer electronics, the inductive reactance is generally insignificant compared to impedance of the load reflected from the secondary side to the primary. In fact, with transformers designed for this application, manufacturers usually don't even bother to specify the series inductance.
Also, the change in frequency is pretty insignificant too in this case. We're talking about a difference between 50 Hz and 60 Hz, not 60 Hz and 400 Hz.
Finally, the most relevant point is that the input voltage and load impedance are far more important than the mains frequency in determining whether the core is going to saturate. In any reasonable linear power supply, a reduction in frequency from 60 Hz to 50 Hz is going to produce a much smaller increase in VA than will typical variations in mains voltage from place to place.
This is why the transformers in switching power supplies are so small.No, transformers in switching power supplies are smaller because they are used in a different way. In a switching power supply, the transformer follows the switching circuit, so it is operating at a very high frequency. Not to mention it's impedance looks totally different than a transformer used in a linear power supply.
This is only the beginning of the design. The maximum current determines the size of the wire, which determines the size of the coils, and on and on. It may be cheaper to just design the thing for 50 Hz and sell it into both the 50 Hz and 60 Hz markets (so-called "World" transformers as carried by Mouser, etc.), so a device that uses one of these would be perfectly safe to use in either area. However, this is not guaranteed.I didn't say it was guaranteed. However, in the vast majority of cases, probably 99.9%, it won't be a problem. And if there are designs out there which are so close to the edge that a small frequency change causes a problem, these same designs won't be able to handle small changes in mains voltage either. So they would generally be considered defective by most designers.
(or a huge inductor) until the core saturates. It will conduct some small magnetizing current until the core saturates, then it will look like a short-circuit. The nonlinear behavior of the core makes it look a lot more like an ideal transformer than an inductor until the core saturates.It will only look like an inductor with a time constant comparable to the inverse of the power frequency if such an inductor is attached to the secondary as a load.
Sorry to curtail this discussion, but I'm going out of town and won't be back before 13 May.
I don't know what you mean by "the nonlinear behavior of the core makes it look a lot more like an ideal transformer than an inductor until the core saturates". A transformer with only one winding connnected is by definition an inductor. There's no arguing with that. It's only when you connect a source to one winding and a load to another winding that it becomes a transformer in circuit terms. Inductors have cores that saturate too of course. At this point, I think your example has sidetracked this discussion more than helped advance it.Anyway, here is the basic point I wanted to make. If you go shopping for a mains transformer, you're going to see specs for input voltage, output voltage for the secondaries, current capacities for the secondaries, usually resistances of the primary and secondaries, and usually an overall VA rating. Rarely, if ever, will you see a frequency rating, because mains transformers are designed for 50/60 Hz mains application.
The way these transformers are designed, you're not going to saturate the core unless there is DC on the mains or you exceed the overall VA rating. You exceed the overall VA rating by over-driving the input with too large a mains voltage or by over-loading the outputs. And since mains transformers have several secondary windings to supply different output voltages, you're not going to saturate the core by over-loading just one ouput.
So, I think it would be basically impossible for a designer to use the full core capacity of a mains transformer at 60 Hz while staying within the specs of each secondary. And if there are out of spec designs out there which push the limits, I think that above average mains voltages would cause most of the problems.
and still do not see it as helpful.The extra losses I do understand; it is an inverse square law thing. Likely consequence is some extra heat production in the iron. I still maintain that any thing more untoward will only come from seriously crappy equipment.
:(
HowdyNever minding the "area under the curve" explanation, the higher the freq the smaller a transformer can be. Like Al says it's quite conceivable that some would design too close to the edge and a heavy load could cause an undersized transformer to heat at a lower freq.
A quick Google search turned up:
-Ted
All else being equal, the transformer's inductive reactance decreases when you lower the line frequency. This will cause the tranny to draw slightly more current. Overheating and a shortened life span are possible, but I wouldn't worry about it.
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