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I understand what you are saying, but surely the design would have to be very marginal before this had an impact on the following section of the power supply?
My point, as I said, is that You have to be very careful when making such very general statements. That is all. In most cases you can get away with it but you have to be aware of these issues because they can bite you.
Electrolytics degrade over time. Sometimes not much, sometimes a lot. About 45 years ago the company I worked for imported two machines from America. I went there to do the training etc and the machines were shipped here and installed in customers premises. Almost immediately one started giving problems and it turned out to be a faulty capacitor which was marginal in the USA but insufficient here. I replaced it not only with a good one of the same value but with a higher value. It was a linear PSU and headroom was tight. With 60 Hz it still worked, with 50 Hz it was starting to fail, with 400 Hz it could have gone on for years.
With tolerances, failures, etc. the question is whether you would say absolutely and with no qualifications to a medical life support machine manufacturer or to a Boeing assembly plant "yeah, sure, plug it in as it is, no problem".
Those machines needed some weird adaptations. Instead of changing the electric motors (120 v 60 Hz) we installed a transformer to lower the voltage from 220 V 50 Hz to 100 V 50 Hz because at 120 V they would overheat. And they turned slower so we had to change the pulley diameter and make it bigger. The entire adaptation was quite complex and a bit on the Mickey Mouse side of things. The minicomputer read the program from a paper tape which took forever. Good times.
The loss of headroom with diminishing frequency is something which most of times will not cause problems but the engineer must be aware if life or limb of Boeing shares are on the line.
In summary, you should be very careful when making general absolute statements. And doubly so with electrolytics.
To quote myself:You have to be very careful when making such very general statements. A SMPS designed for 60 Hz will have greater ripple at the capacitor when connected to 50 Hz. Most of the time the capacitor will have enough margin but if the capacitor is very tight initially or if it loses some of its capacitance it could lead to problems.
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I asked if the design would have to be marginal before there was a problem? And you replied, yes, the design would have to be marginal. So I don't see any disagreement here?
To avoid generalization, the power supplies in this case are specified with an input rating of 85 - 264 V AC or 120 - 370 V DC, and an AC frequency range of 47 - 63 Hz. There is also a derating curve for low voltages. It is to be assumed that they will perform to specification.
One other thing, the equipment which is the subject of this thread is not a medical life support device, it is something along the lines of an advanced gym machine, somewhat akin to a sophisticated treadmill. There is no danger to life or limb if it stops working for any reason. -
I asked if the design would have to be marginal before there was a problem? And you replied, yes, the design would have to be marginal. So I don't see any disagreement here?
We are in agreement in everything. I was not referring to these specific PSUs but rather to a general statement that voltage or frequency do not matter ever. That is too broad and needs some qualification. I am well aware that it has been determined the PSUs in this case do not need any adaptation.
To avoid generalization, the power supplies in this case are specified with an input rating of 85 - 264 V AC or 120 - 370 V DC, and an AC frequency range of 47 - 63 Hz. There is also a derating curve for low voltages. It is to be assumed that they will perform to specification.
One other thing, the equipment which is the subject of this thread is not a medical life support device, it is something along the lines of an advanced gym machine, somewhat akin to a sophisticated treadmill. There is no danger to life or limb if it stops working for any reason. -
Capacitor ESR decreases as frequency decrease and ESR increases as frequency increases. So whether it 50 to 60Hz or 100 to 120Hz it won't make any difference worth worrying about to output voltage ripple. This can be easily tested with any LCR meter with variable frequency. If your getting a huge change in value between 50Hz and 60Hz then the capacitor is nearing end of life anyway and needs to be changed.
Irrelevant.
The problem is 50Hz will increase the ripple on the smoothing capacitor, so the voltage will drop to a lower level during the troughs. This shouldn't be a problem with a properly designed power supply, as the capacitor should be adequately oversized, but it will be a problem, if it's marginal and perhaps the voltage is also on the lower end of the operating range.
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If the circuitry after the capacitor has no problem with the voltage dips between refreshes from 120 V 60 Hz supply, there will be plenty of headroom for the slightly deeper dips when the supply is 230V 50Hz.
Except half of Japan, does anywhere else have 100 V 50Hz supply? -
If the circuitry after the capacitor has no problem with the voltage dips between refreshes from 120 V 60 Hz supply, there will be plenty of headroom for the slightly deeper dips when the supply is 230V 50Hz.
That's too bad if the capacitor and switching regulator are only rated to 200v. -
The problem is 50Hz will increase the ripple on the smoothing capacitor, so the voltage will drop to a lower level during the troughs. This shouldn't be a problem with a properly designed power supply, as the capacitor should be adequately oversized, but it will be a problem, if it's marginal and perhaps the voltage is also on the lower end of the operating range.
Thank you for explaining and illustrating my point so well. -
I assume the Meanwell PSUs are easily good enough to handle 50Hz&60Hz, and likely the filtering does not need to be super critical, otherwise one would likely find a very-highly-priced US PSU in there.
However, I'm not so sure the medical certification will still be valid when used at a different voltage - as the supply voltage is probably one of the stated test parameters (unless they do state something like "90-270V 45-65Hz supply voltage" in their certification sheet) -
As a complete aside: most 120V, 50-60Hz power supplies will also work fine on the 115V*, 400Hz power used on aircraft systems. But most are not certified for it, or only mention it in footnotes.
*And yes, this is 115V nominal, not 120V! -
Hi all, for those concerned with my knowledge level, there are outside consulting engineers we will be reaching out to as well. I am a fresh graduate and I'm aware that I am limited in my knowledge. I was more so hoping to use this thread to educate myself on the options and critical things to consider for this task and common ways this is done, as I am sure universal compatibility/conversion is a common practice, just hasn't been done for my company. So I was looking for perspectives on how others would approach this from least "invasive" to most, the pros and cons of each, and the regulatory perspective before getting input from outside engineers.
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If you reread the first post you'll note that a step-up transformer may be required.
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Reread my last sentence.
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If you reread the first post you'll note that a step-up transformer may be required.
It also may not be required. What is your point? -
I think they’re referring to OP’s original post, which also raises the question of how to perform testing on the 230V configuration in USA before sending it overseas.
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I think they’re referring to OP’s original post, which also raises the question of how to perform testing on the 230V configuration in USA before sending it overseas.
Can simply be plugged into the washer/dryer outlet, no? -
Can simply be plugged into the washer/dryer outlet, no?
No, simple plugging it to outlet and see if it works is not the expected way for medical device certification. -
The question was about how to perform testing on the 230V configuration, not how to "see if it works".Can simply be plugged into the washer/dryer outlet, no?
No, simple plugging it to outlet and see if it works is not the expected way for medical device certification.
Besides, when it comes to that, the certification will likely need to be done from scratch in the destination country anyway, if it is required there, once the customer is ready to buy. -
The question was about how to perform testing on the 230V configuration, not how to "see if it works".
The answer is the same. Simple plug to 230V mains outlet and see if it works is not enough for medical device.