Convert US standard 115V to International 230V - Page 1
Forum section: electronics / beginners

author: am1
author_rank: Contributor
timestamp: April 22, 2024, 06:04:48 pm
content: Hi all,I am working on a medical device that operates at US standard 115V and 50-60Hz (with estimated 20Amps, we require 20A outlet). We are being considered for out first international sale that requires 230V and 60 Hz. Im assuming this is commonly done and will involve some kind of step down transformer. I haven't done something like this before... could someone please explain the process and components that would be needed to achieve this? Additionally, how would I go about testing said system after it is complete and prior to sending out the device (how would I test the now 230V system in the US to do verification testing)? Thank you all.

author: Benta
author_rank: Super Contributor
timestamp: April 22, 2024, 06:26:54 pm
content: First, it's 230 V50 Hz.Second, it's usually done by design today, using power supplies with 90...250 V input range (switching PSUs).The transformer solution is possible, but heavy and bulky.I suggest a revisit of your design. Medical is normally not very cost sensitive, so there should be space for a respin.

author: themadhippy
author_rank: Super Contributor
timestamp: April 22, 2024, 06:38:27 pm
content: Quotenot always,theres the odd place or 2 ,like south korea , were its 60Hz

author: shapirus
author_rank: Super Contributor
timestamp: April 22, 2024, 06:54:00 pm
content: Quote from: themadhippy on April 22, 2024, 06:38:27 pmActually a lot:https://en.wikipedia.org/wiki/Mains_electricity_by_country

author: edpalmer42
author_rank: Super Contributor
timestamp: April 22, 2024, 06:58:20 pm
content: The easiest way to get from 120 to 220 volts is with an autotransformer. Yes, it's large and heavy, but if you're looking at a 20A outlet, this probably isn't a portable device.Benta is correct that it's usually 220V @ 50 Hz so the transformer won't fix that. He's also correct that a universal input medical-grade switching supply is the preferred solution. They're available as off the shelf items with whatever voltage and current ratings you need. Note that the 'medical grade' tag will result in a significant cost increase. But unless there are some specific reasons why a switching supply isn't appropriate, that's the recommended solution. Using a standard, certified power supply may also help when it comes to electrical certification for your unit.Ed

author: am1
author_rank: Contributor
timestamp: April 22, 2024, 07:02:17 pm
content: Yes, this country in particular's standard is 230V and 60 Hz as mentioned.My concern with changing design of the controls is in regard to IEC testing. Currently the device is IEC compliant, so changes to those critical internal components would likely require retesting which is costly and difficult to do logistically for a device of this size. Im sure the use of an autotransformer would also require some certification updates. The system has both a 24V and 26V PSU, I am assuming swapping both units out would be necessary?

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2024, 07:07:58 pm
content: Quote from: am1 on April 22, 2024, 06:04:48 pmNote, US standard is 120 V (not 115), and is 60 Hz (not 50).Note that, in general, a 20 A circuit can provide 16 A continuously. If your device needs 20 A continuously, you would need a 30 A circuit, which generally is not done with 120 V and you would need to move to a 240 V supply anyway. If you do move to a 240 V supply for the US market, then you would automatically be compatible with the overseas market you are considering.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 22, 2024, 07:09:51 pm
content: I think the design should go back to really what kind of power your device requires? Is it DC and possibly multiple DC voltages? If so you would build a power supply to run from 85-250VAC 50-60Hz to supply the power. Some company can surely design and build such a power supply for you if you don't want to do it yourself.

author: am1
author_rank: Contributor
timestamp: April 22, 2024, 07:16:02 pm
content: Apologies for any confusion regarding the system specs.The device I am referring to has an operating voltage range of 115Vac +/-10%, and 50-60Hz, and uses a 20A outlet. The prospective customer would like 220-240Vac and a frequency range of 50-60Hz.

author: themadhippy
author_rank: Super Contributor
timestamp: April 22, 2024, 07:22:16 pm
content: cant you just supply a separate step up transformer in a nice box ,your device remains unchanged so still complys

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 22, 2024, 07:41:19 pm
content: If you expect to sell a few unit a step down transformer would be fine as your device is good for either 50 or 60Hz. If you expect to sell a lot you may want to consider building a unit what can work with both voltage.

author: TimFox
author_rank: Super Contributor
timestamp: April 22, 2024, 07:44:16 pm
content: When I was working with a major manufacturer of large medical devices, they designed the actual system (power supplies, motors, etc.) to work at, I believe, 240 VAC, 50-60 Hz.They supplied a suitable transformer in the main switch box with taps to cover a range of voltages from 100 to 440 VAC to satisfy their export market.Depending on your power level, a common configuration for medical-grade power/isolation transformers is a toroid, e.g.https://talema.com/products/medical-grade-toroidal-transformers/

author: IanB
author_rank: Super Contributor
timestamp: April 22, 2024, 07:51:48 pm
content: Quote from: am1 on April 22, 2024, 06:04:48 pmQuote from: am1 on April 22, 2024, 07:16:02 pmIf you were an engineer responsible for the design of the device, then you would know how to reengineer the internal design and would not be asking here.So we have to assume you are not in that position, and that the device has an existing design that is already certified and you cannot modify it.In that case, what you need is an external step-down transformer. Such devices are readily available, but you would have to select one that has the appropriate rating and certification for medical use. For a 20 A output it would need to be rated at 2.5 kVA or so, which would make it somewhat big and heavy.QuoteSince the USA has a 240 V domestic mains supply, you could test it in part with a 240 V outlet in the USA. (But in commercial/industrial settings the supply may be 208 V, which is not quite the same.)However, an overseas supply may likely be 230 V Line/Neutral/Ground (as opposed to the US supply of Line/Line/Ground). If you wish to test with the exact Line/Neutral/Ground arrangement, you would need to consult the services of an electrical engineer to set up an appropriate test rig (a bit like TimFox mentions above).

author: TimFox
author_rank: Super Contributor
timestamp: April 22, 2024, 08:03:37 pm
content: Side note: "115 V" is an obsolete value for US single-phase power distribution.Many nameplates for manufactured electrical gear are technically out-of-date.Historically, it started out at 110 V, then 115 V, then 117 V, but has been 120 V (nominal) +/-5%, for decades, defined in standard ANSI C84.1 (1954).

author: CaptDon
author_rank: Super Contributor
timestamp: April 22, 2024, 11:36:10 pm
content: Since the supply side is 220/240 and the output side is 120 you would be looking for a medical grade STEP DOWN TRANSFORMER. Using this external device to power your medical machine will not cause you to re-certify your machine. Simple. Done. Heavy. A toroid core auto-transformer will be the best design choice as an auto-transformer in general requires less copper and a smaller core than a transformer with totally isolated primary and secondary windings. You don't need isolation, only voltage correction. Be aware of what you are selecting!!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: April 22, 2024, 11:59:06 pm
content: It seems more logical to re-design the power supply itself instead of adding something to it.Apparently it's already transformer based, so a different primary winding and a selector switch could be all that is needed.

author: Odd-Job
author_rank: Unknown
timestamp: April 23, 2024, 05:50:49 am
content: Hi am 1,If you are expected to come up with an answer for your employer to fix this little problem, then all that is needed is a redesign of the primary winding's of your I.P transformer and maybe slightly more 'iron' lamination's. If it is as you say 115 VAC @60hz with 20 A max then we are about 2.3 kVA worst case. 230-240 Vac will halve to 10 Amps so we are still around 2.3kVA. Suggest you get transformer supplier to wind one with 2X120V windings that can be configured to be in parallel( 120 Volt 20 A) or series (240 Volt 10 Amps) either way about same kVA. Oh and make sure it is wound for 50 Hz so it will not overheat when humming @ 50 cps.This is all said whilst assuming it is not a SMPSU in said unit. BTW is it a elephant defibrillator your involved in?As Dr and us wrote;Quote from: Doctorandus_P on April 22, 2024, 11:59:06 pm

author: am1
author_rank: Contributor
timestamp: April 23, 2024, 11:01:22 pm
content: Thank you all for the suggestions, this is very helpful. It is a stationary robotic gait trainer for those wondering, and this is an existing system that I am now involved in. I am a bit confused by those mentioning it already being transformer, could you please elaborate, for reference the 2 PSU I am using in the system are Meanwell HRP-150-24 and HRP-600-36 units.I am leaning towards something external due to the retesting and timeline concerns mentioned previously.. I was initially looking for step down transformers for the voltage conversion that would be a simple plug and play system. I would need the inlet transformer to accept the NEMA 5-20P power cord from our device and the transformer power cord in the appropriate cord type for Saudi (country in question). Is anyone familiar with options like this?This is one example I came across that can be step up/down and has a toroidal core. It has a US plug type though so unsure of this unit in particular. Is there a reason to avoid this type of solution for a short term option until a system redesign can occur (reliability, safety, etc.)? I appreciate the advice from everyone, thanks.https://www.vevor.com/variable-transformer-c_10755/vevor-step-up-down-transformer-voltage-converter-3500w-240v-110v-110v-240v-us-uk-p_010501337904?adp=gmc&srsltid=AfmBOoqn1_dCr4bXi68PtPUSOyP3iJSVOoAxBIdkQxGat7TJNGC4JEms_XI

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 23, 2024, 11:09:12 pm
content: If your machine is powered only by that 2 power supply then it can run on 230V as is. Just need the right plug.

author: IanB
author_rank: Super Contributor
timestamp: April 23, 2024, 11:14:02 pm
content: Quote from: am1 on April 23, 2024, 11:01:22 pmThose power supplies are already universal voltage input units. You don't need to do anything, they will work just as they stand.Haven't you looked them up already?https://www.meanwell.com/productPdf.aspx?i=427https://www.meanwell.com/Upload/PDF/HRP-600/HRP-600-SPEC.PDFIdeally, you will just purchase and use an appropriate IEC power cord for the local market. I say ideally, because ideally the machines will have an IEC connector, and will not have captive power cords. If they have captive power cords, you will have to replace the power cords.Also, those two power supplies at full load will consume about 900 W, or 7.5 A. That should be well within the capabilities of a NEMA 15 A outlet. Who has estimated 20 A and said you need a 20 A outlet? Does this device have additional power requirements other than those two Meanwell power supplies?

author: am1
author_rank: Contributor
timestamp: April 24, 2024, 12:10:23 am
content: Quote from: IanB on April 23, 2024, 11:14:02 pmWow, not sure how I missed that with the PSU. That is great. There is a IEC C19 to 5-20P power cord on the device, and a power cable is connected to a Schaffner FN2090B-20-06 Filter, from there there are breakers for the each PSU. Looks like the filter has a 250V voltage rating, so the power cord or connector swap could be the fix here as yall mentioned.Quote from: IanB on April 23, 2024, 11:14:02 pmThe filter has a 20A rating, so perhaps that was the rationale. But I am slowly finding many questionable choices with the design as I have worked on this project... They are no longer on the project, but if I ask why specific choices were made electrically or software wise, I get a "Im not too sure" or "it was a fast solution".

author: radiolistener
author_rank: Super Contributor
timestamp: April 24, 2024, 07:14:06 am
content: As mentioned above, 240V mains usually has 50 Hz, while 120V mains have 60 Hz, so if you're needs to convert 120V@60Hz to 240V@50Hz it cannot be solved with simple 1:2 voltage transformer.There are two approaches to solve it:1) Old approach is to use umformer (electric motor + alternator). In your case the motor will work from 120V@60Hz and the alternator will generate 240V@50Hz. This way was widely used in old military equipment where voltage/frequency conversion is required (they often are designed for 400 Hz AC power source).For example:2) Modern way is to replace power supply in your equipment with switching mode power supply that support both standards.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 24, 2024, 09:25:39 am
content: He doesn't need to do any of that.

author: radiolistener
author_rank: Super Contributor
timestamp: April 24, 2024, 04:15:55 pm
content: Quote from: BeBuLamar on April 22, 2024, 07:41:19 pmNo, step down transformer cannot convert 50 Hz AC to 60 Hz AC.

author: TimFox
author_rank: Super Contributor
timestamp: April 24, 2024, 04:24:02 pm
content: Note that the op’s application involves equipment rated for operation at either 50 or 60 Hz, and the frequency conversion is not required.

author: IanB
author_rank: Super Contributor
timestamp: April 24, 2024, 04:37:34 pm
content: Radiolistener, can you delete your posts?You have not read the thread, and you are just adding a whole bunch of useless noise on the end of a solved problem.

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 09:52:25 am
content: Quote from: TimFox on April 24, 2024, 04:24:02 pmIn order to support both 50 Hz and 60 Hz standards, the device needs to be rated to work at least within frequency range from 48.5 Hz to 61.8 Hz. This is because it needs to support allowed mains frequency variation ±3%.If it really supports all frequency range which include both standard, then he can use 1:2 voltage transformer. But it requires that device needs to be carefully checked and tested in order to comply with both frequency standards.

author: shapirus
author_rank: Super Contributor
timestamp: April 25, 2024, 09:58:27 am
content: Quote from: radiolistener on April 25, 2024, 09:52:25 amOnce again, did you read the thread? It was figured out already that the device is using switching power supplies which support both AC voltage and frequency variants on the input.

author: Zero999
author_rank: Super Contributor
timestamp: April 25, 2024, 10:10:49 am
content: Quote from: IanB on April 24, 2024, 04:37:34 pmUnfortunately, that would mean him admitting he's mistaken and going by his posting history, is something he appears to be unable to do.

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 10:21:09 am
content: Quote from: shapirus on April 25, 2024, 09:58:27 amyes, I read, the topic starter mentioned that his equipment consume 20 A from 115V mains, this is about 2300 Watt power.He also mentioned example of 2 PSU which is used in his system: Meanwell HRP-150-24 and HRP-600-36. This is 150W and 600W SMPS power supplies which already have universal AC input with 47 - 63 Hz frequency range.These PSU can be used directly. But this is just 750W power consumption.But what about power supply for the rest 1550 Watt power consumption?Are you sure that they also compatible with both frequency standard?There is also another possible issue which is critical for medical devices, even if he using PSU which all are compatible with all mains standards, it still needs to be tested with both mains frequency. Note that the mains frequency has leakage through PSU in a form of a ripple and/or interferences and can affect equipment functions, especially if this is device which uses sensitive measurements.For example precise ADC can have configurable rejection filter which can be software configured for 50 or 60 Hz depends on user environment. And it needs to be taken into account very carefully especially for medical devices (which is the case for topic starter question). And this example is not abstract this is example of a real case for medical devices.

author: shapirus
author_rank: Super Contributor
timestamp: April 25, 2024, 11:04:31 am
content: Yes that's good point. It's not clear if those PSUs are theonlyPSUs the device uses, given the strange difference in the power levels mentioned initially.

author: IanB
author_rank: Super Contributor
timestamp: April 25, 2024, 02:32:13 pm
content: According to the OP, the two power supplies are the only mains loads. The reason for the 20 A requirement was unclear, due to an earlier designer who has now left the project. It may simply have been a very conservative design.Quote from: radiolistener on April 25, 2024, 10:21:09 amIt is 750 W output power. Allowing for power supply efficiency the input power is closer to 900 W. But once again, this was covered earlier in the thread.Quote from: radiolistener on April 25, 2024, 10:21:09 amThere is a mains input filter in the design. Described earlier in the thread.

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 02:55:28 pm
content: Quote from: IanB on April 25, 2024, 02:32:13 pmMains filter cannot help. In case that I mentioned it was interference induced on sensors due to near field coupling with mains wires around room. It was not related to PSU.This is why I said that the device should be carefully tested if it's planned to use it within environment with mains frequency which is different than one which is used during device design, debugging and testing.Even if PSU can work with all mains standards, it cannot guarantee that the device will works ok with it. It was designed and tested for 60 Hz environment and you cannot predict it's behavior with 50 Hz environment because no one tested it.

author: shapirus
author_rank: Super Contributor
timestamp: April 25, 2024, 03:02:06 pm
content: Then again, frequency will be the same: it's 60 Hz in both cases.

author: Terry Bites
author_rank: Super Contributor
timestamp: April 25, 2024, 03:45:39 pm
content: No!Adding an external transformer voids the 60601 compliance.Modding any MD will require retest to 60601 using approved test devices and methods.You have been warned!

author: am1
author_rank: Contributor
timestamp: April 25, 2024, 07:29:12 pm
content: Hi all, yes, those are the only PSU used in the device. However, there are several breakers used as well (listed). All are rated for more than the needed 220-240V, but would I need to replace them with double pole line-neutral breakers? System uses the following:Circuit Breaker 2P 20A 240VAC/60DC Blk Rckr SCHURTER Allied Electronics 4430.2196Circuit Breaker 1-P 4A 480Y/277VAC ABB SU201M-C4Circuit Breaker 1-P 2A 480Y/277VAC ABB SU201M-C2Circuit Breaker 1-P 16A 480Y/277VAC ABB SU201M-C16Circuit Breaker 1-P 3A 480Y/277VAC ABB SU201M-K3Circuit Breaker 1-P 15A 480Y/277VAC ABB SU201M-K15Circuit Breaker 1-P 10A 480Y/277VAC ABB SU201M-K10Quote from: Terry Bites on April 25, 2024, 03:45:39 pmIf the equipment selected is already ME certified through IEC, I believe there are sometimes only documentation updates required by them.. but I could be wrong. I believe we bypassed additional testing when a power cord change was made because it was an already CE/UL certified part. Even if this is true, though, I have not been able to find any ready to use 3000W step down transformers in my research so far. We may ask the customer to self-provide the SDT themselves, but I would like to have options available on our end as well.

author: IanB
author_rank: Super Contributor
timestamp: April 25, 2024, 09:08:47 pm
content: You might want to plug the device into a Kill-A-Watt and measure the power consumption under full load. I suspect it won't be more than 1000 W, but this way you can measure it and find out.

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 09:14:56 pm
content: Quote from: IanB on April 25, 2024, 09:08:47 pmI'm afraid that such approach is not acceptable for safety critical devices development because it don't guarantee that device will never consume more power under some specific conditions.

author: IanB
author_rank: Super Contributor
timestamp: April 25, 2024, 09:22:39 pm
content: Quote from: radiolistener on April 25, 2024, 09:14:56 pmBut if you can't identify and test what those specific conditions are, then the device could never be certified?Also, it has not been specified that a robotic gait trainer is a safety-critical device. If it stops working for any reason, it is hard to see what harm would come to the person using it.

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 09:59:38 pm
content: Quote from: IanB on April 25, 2024, 09:22:39 pmUndefined/unspecified behavior of device is not acceptable because it is unpredictable and can make harm to the patient. This is uncontrolled potentially life threatening risks for the patient and it's presence shows serious issue in validation/verification process and broken quality management system.

author: IanB
author_rank: Super Contributor
timestamp: April 25, 2024, 10:42:07 pm
content: Quote from: radiolistener on April 25, 2024, 09:14:56 pmQuote from: radiolistener on April 25, 2024, 09:59:38 pmThe above two statements are in contradiction with each other. Either you can specify the designed behavior, or you cannot. If you specify the behavior, then you cannot also say, "but this is unacceptable, because it may behave in ways other than those specified".

author: radiolistener
author_rank: Super Contributor
timestamp: April 25, 2024, 11:10:02 pm
content: Quote from: IanB on April 25, 2024, 10:42:07 pmI don't see contradiction. If you're designed device properly, then your device already has defined/specified valid range for the power consumption, which can be used for device testing. But if power consumption is unknown and you're using DMM to discover it, then power consumption of your device is undefined/unspecified.

author: tooki
author_rank: Super Contributor
timestamp: April 26, 2024, 07:56:29 pm
content: Quote from: shapirus on April 25, 2024, 09:58:27 amQuote from: Zero999 on April 25, 2024, 10:10:49 amI find it quite remarkable how someone whose username is “radiolistener” can be so very bad atlistening!

author: Zero999
author_rank: Super Contributor
timestamp: April 26, 2024, 08:54:03 pm
content: Quote from: tooki on April 26, 2024, 07:56:29 pmMy favourite one was when it took several pages to explain why acapacitor connected to a generatordoesn't increase the power consumption, ignoring the tiny extra I2R losses.

author: tooki
author_rank: Super Contributor
timestamp: April 26, 2024, 09:23:51 pm
content: Quote from: Zero999 on April 26, 2024, 08:54:03 pmI missed that thread at the time. And it was before I learned anything about AC theory anyway, so it would have been lost on me then. But I read it now and the obstinance made some of my brain cells commit seppuku. I find it hilarious that the thread contains aliteralcrayon drawing that explains it clearly, but still it continued for pages and pages…

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 01:42:38 am
content: Quote from: Zero999 on April 26, 2024, 08:54:03 pmFor what reason you're writing it in that way like I was claimed that capacitor will consume the power? This is false. I didn't claimed that.We're talked how the power returned from capacitor to generator affects its mechanical rotation. And looking at that discussion now, it appears that I missed to clarify that I was talked aboutinstantaneouspower and my opponents are talked aboutaveragepower and it leads to confusion.To be clear, if you connect capacitor it will lead to higher instantaneous power consumption during one part of cycle and less instantaneous power consumption during another part of cycle. Average power consumption during full cycle will be the same (if we exclude higher power loss on wires).My opponents claimed that adding capacitor don't affects power applied to generator rotor, just because they talked about average power which is really will be the same, but I didn't agreed with them because I was talked about instantaneous power which will be increased.Regarding to the power consumption, it is obvious that it will increase power consumption due to heat losses in the wires, because energy will flows back and forth between the generator and capacitor and of course it will increase power losses in wires in comparison with pure active load where power loss happens only once when power is transferred in single direction from generator to the load.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 02:07:47 am
content: Quote from: radiolistener on April 27, 2024, 01:42:38 amNo, the wording doesn’t say the power consumption isinthe capacitor, just that you thought adding the capacitor increased power consumption in total. Which is something you stated in the thread over and over and over.We could substitute “reading comprehension” for listening, and you just proved our point: you don’t listen, or in this case, read carefully. You’re seeing what you want to see, not what’s actually written.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 02:36:54 am
content: Quote from: tooki on April 27, 2024, 02:07:47 amYes, I see, but you wrote it in that way that it looks like I was said that capacitor will consume power. But that's not true.Quote from: tooki on April 27, 2024, 02:07:47 amNo. I don't have that thought.Quote from: tooki on April 27, 2024, 02:07:47 amI didn't stated that. I was talk about different thing.You're needs to apply additional power to charge capacitor, this is why instantaneous power will be higher. That additional power will not be loss, it remains in the system, but it is required to be taken from generator. Which requires to apply more power on generator rotor.After all, I don't understand - what is the reason to link that discussion in this topic? Could you please clarify?I think it will be more correct to discuss it in original topic. Isn't it?Quote from: tooki on April 27, 2024, 02:07:47 amYou're just pull an owl on a globe. It looks like you're see what you want to see, not what actually is.Really, I don't see the reason for your aggression. You are acting like a bully, trying to find a reason to quarrel. For what?Сould you please calm down and communicate on the topic instead of expressing your subjective opinion about persons?

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2024, 08:06:17 am
content: Just to clarify, North American standard household voltage to both 120V and 240V @ 60Hz. Being split phase.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 09:28:29 am
content: This thread makes me want to bang my head against the wall. Besides all the noise and useless arguing, there is something that bothers me and it is that I believe the OP is just not qualified or certified and should not be making this type of decisions. It is one thing to ask in a forum for personal things or for professional things if one has the appropriate knowledge and background, but this, to me, screams like a bad idea.There are too many unknown variables and the OP is, clearly, not qualified. A medical device sold professionally and for export and this is how it is being designed? In America? Really? Nobody thinks there is something wrong in this scenario? Really?My response would be that you need to hire a qualified engineer who does not need to ask this type of questions and who is responsible for their work.Some months ago a friend asked me if I could repair an automatic watering system box device which had not lasted long. Proudly designed and made in the USA ... and complete crap. The power supply part was designed by someone totally unqualified for the job. Among other things it had a resistor making lots of heat right next to components which could not take the heat and all enclosed in a weather-proof box with no ventilation. It was crap and there was really no good repair except to replace the unit with something else. ... probably designed and made in China with better design and quality.I am all for helping people learn and develop their own projects but for commercial, professional products you need a pro.Just the way I see it.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 10:50:55 am
content: Quote from: soldar on April 27, 2024, 09:28:29 amCompletely agree. I wanted to politely bring the topic to the point that this is not easy decision for medical devices, because there are too many pitfalls which is not visible for non medical devices staff, but it appears that discussion going into wrong direction and my attempt was failed. Unfortunately some users decided that since they see simple and easy solution, they can just ignore medical devices specific and advocate their solution as the best solution and fiercely rejecting and criticizing all arguments against.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 11:49:26 am
content: Quote from: radiolistener on April 27, 2024, 02:36:54 amNo, I did not say that, and neither did Zero999.Quote from: radiolistener on April 27, 2024, 02:36:54 amYes, you did, and you said it repeatedly in many different ways. If what yousaidisn’t what youmeant, then you need to be a lot more careful in what you say and how you say it.Quote from: radiolistener on April 27, 2024, 02:36:54 amI think you’re confusing me and Zero999. They posted the link, not me. Again,you need to read carefully.And that was the whole point: you don’t listen, you don’t read carefully. You are frustrating because you read the thread poorly, then reply with something that is not relevant and not helpful. And you do this a lot.Quote from: radiolistener on April 27, 2024, 02:36:54 amI have no idea what that is supposed to mean. I think that’s a word-for-word translation of some idiom in Ukrainian (every example of it, when googled, was from Ukrainian sources), but in English it has no meaning.Quote from: radiolistener on April 27, 2024, 02:36:54 amSo you’re just childishly pretending you can turn it around and say the same about me? “No I’m not, YOU are!” is literally what little kids say to each other. Meanwhile countless people on the forum have made the same observation about you as I did. You. Don’t. Listen. And that is super frustrating.Quote from: radiolistener on April 27, 2024, 02:36:54 amIt is not aggression, it’s frustration.Quote from: radiolistener on April 27, 2024, 02:36:54 amSomehow we need to get through to you that you havegotto be more receptive to feedback and more accepting of others’ expertise, and tomake a real effort to read carefully and thoroughlybefore responding to threads.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 12:32:28 pm
content: Quote from: tooki on April 27, 2024, 11:49:26 amI don't know why you decided that I don't listen to feedback. Regarding to the point that OP uses PSU which is already compatible with both standard, I heard this argument and accepted it. But I didn't agreed that this is enough info to make decision that there is no change required for medical device.IanBtried to ague that the medical device power consumption can be checked with a cheap Chinese meter and that information can be used to decide if used power supply is enough. But I argued that such approach is not acceptable for medical devices. ThenZero999decided to supportIanBmistaken idea that there is nothing to worry about and all can be checked with cheap meter. And then you're join and supportZero999...As I can see you're didn't listen to my feedback. Instead you're started to blame me that I don't listen.Usually person starts to blame some other person when he don't have enough knowledge for proper argument on the subject, that's the child way for discussion. And I see that you're started to talking about persons instead of topic subject. Isn't it?I already proposed you to talk about technical subject instead of sharing your zero-cost subjective opinion about persons. If you don't have technical arguments, then I leave that discussion.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 12:45:55 pm
content: Quote from: radiolistener on April 27, 2024, 12:32:28 pmBecause you don’t, and that entire reply isproof of this. You just bark back, but never accept responsibility for mistakes, nor accept that others are correct. Look at the part of my sentence above that is in italics. (And which was in italics in the original.)Your first reply in this thread, long after OP had listed the part numbers of the power supplies used, you suggested 1. using a motor-generator set, and 2. to consider switching to an SMPS inside.Both of those suggestions are completely irrelevant and uselessat that point in the discussionbecause it hadalreadybeen established that it uses two universal-input SMPSs. This shows you did NOT read the discussion before replying. When this was pointed out to you, you responded that the total power didn’t add up, even though this also had already been explained in the prior discussion. Rather than just saying “oh crap, sorry, I responded before reading everything” or “my apologies, you’re right, I missed that detail when reading” (which are things that happen to ALL of us!), you just keep digging and digging for why you can’t possibly be wrong… And that’s why people (plural) got annoyed, and expressed that.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 27, 2024, 01:19:37 pm
content: IanB suggested to use the Kill-a-watt which is kind of cheap but it's not Chinese. It's Taiwanese. The Taiwanese is not pleased if you call them Chinese.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 02:04:09 pm
content: Quote from: tooki on April 27, 2024, 12:45:55 pmYour personal subjective opinion about persons is off-topic.Quote from: tooki on April 27, 2024, 12:45:55 pmWhen I posted my first reply in this topic I didn't seen complete list of power supplies which are used on OP device. And correct me if I'm wrong, there is still no such list. Also I noted in the first OP post that his device power consumption is about 2300 Watt. And two PSU which he later provided for example is about 750-900 Watt in total, which is just about 40% of total device power consumption. So there is no way to decide if all of his PSU are compatible with all mains standards. I already explained it, but for some reason you're didn't read it.I don't see why my post is completely irrelevant, the second part covers SMPS with universal input.But even if all of their PSU are compatible with all mains standards, that is not enough to claim that medical device which uses these PSU will be compatible with all mains standards.Regarding to the mains filter mentioned byIanB, it doesn't related with 50/60 Hz at all, their goal is to remove common mode currents in order to reduce EMI. I was talked about different filter which is used on device sensors ADC and in DSP stack to reject 50 or 60 Hz carrier from measured signal which appears due to interference from mains wires and due to leakage through PSU. It is software configured depends on used user environment. In medical device some signals working range may be very close to 50/60 Hz and even may cover that frequency and needs to be carefully processed with take into account the frequency of used mains line. Because interference level from mains frequency is pretty strong and it's presence can affect measurement results. This is why using PSU with universal input is not enough to decide that device is compatible with all mains standards.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 02:46:03 pm
content: Quote from: radiolistener on April 27, 2024, 02:04:09 pmI did read your explanation, but AGAIN you missed the fact that OP clarifiedbefore your first replythat the 20A input was NOT the actual maximum input current established by some empirical means, but a mystery number from a long-gone employee. The list of power supplies shownisthe entire list of loads in the device. This was already explained to you by someone else and you STILL don’t seem to grasp it.Quote from: radiolistener on April 27, 2024, 02:04:09 pmByfullyunderstanding the thread up to the point where you first replied, you would have already known thatallof the system is powered by the two SMPSs, both of which are already universal input. So you’re suggesting doing what it already did.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 02:51:01 pm
content: Quote from: BeBuLamar on April 27, 2024, 01:19:37 pmI could argue with that but I won't because it would lead to a sterile tangent.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 03:16:43 pm
content: Quote from: BeBuLamar on April 27, 2024, 01:19:37 pmThe point was is that using blind method to determine device specification with some meter is not acceptable for medical devices. Just because it don't cover all possible modes and as result it may lead to unexpected failure of device in future and as result uncontrolled risk for the patient life. In addition any measurement equipment used for medical device testing requires to be validated.What is the risk of smartphone charger failure? It can kill the user, you probably hear about these incidents...Medical device should not allow such kind of risk.

author: radiolistener
author_rank: Super Contributor
timestamp: April 27, 2024, 03:37:39 pm
content: Quote from: tooki on April 27, 2024, 02:46:03 pmYes, when I posted my first message in this topic, I didn't notice that he don't have other power supplies and 20A is a mystery number.And what? This is the reason you're attacking me?Sorry, but it looks very strange from my point of view.Quote from: tooki on April 27, 2024, 02:46:03 pmAnd? I don't see a big problem here. It was clarified in the followed messages and we just follow forward. Isn't it? What is the reason to return back again and again?And I don't see why it leads to such kind of aggression and attempt to shift discussion to persons instead of technical topics?Don't you think you're fixated on some nonsense which makes no sense to devote so much time?

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 05:23:13 pm
content: Quote from: radiolistener on April 27, 2024, 03:37:39 pmNot attacking. Explaining our frustration.

author: sanleontexas
author_rank: Contributor
timestamp: April 27, 2024, 05:55:15 pm
content: The transformer really doesn't care if it's 50 or 60 Hz, it'll run fine either way. If it's a50Hz transformer it'll actually run slightly cooler at 60Hz because it may have morecopper in it. And a SMPS will generally also run OK at either line frequency.Unless there's some kind of frequency sampler circuit that wants to see a particularline frequency(which would be rather odd), it's not worth the bother to design thedevice for one or the other.

author: TimFox
author_rank: Super Contributor
timestamp: April 27, 2024, 06:01:03 pm
content: As a practical matter, most modern electronic equipment is designed to work equally well at 50 or 60 Hz.The more likely problem is 100 vs 120 vs. 240 V.Possible exceptions include "Sola transformers", which are less popular now, that depend directly on the frequency, or motors whose speed depends directly on frequency.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 06:53:02 pm
content: Quote from: sanleontexas on April 27, 2024, 05:55:15 pmThere is no transformer, just two SMPS.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2024, 06:53:57 pm
content: Quote from: TimFox on April 27, 2024, 06:01:03 pmIt’s already established that the device runs on two universal-input SMPSs. Model numbers much earlier in the thread.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 08:11:29 pm
content: Quote from: sanleontexas on April 27, 2024, 05:55:15 pmIf you bother to read the thread you will learn that this is not relevant or applicable.And, as a general statement it is also wrong.

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2024, 08:16:06 pm
content: Quote from: sanleontexas on April 27, 2024, 05:55:15 pmOn a SMPS, frequency of the mains voltage doesn't matter because the mains power is rectified to DC then the frequency is set by the PWM for the transformer.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 08:25:26 pm
content: Quote from: Jwillis on April 27, 2024, 08:16:06 pmYou 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.

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2024, 08:41:09 pm
content: Quote from: soldar on April 27, 2024, 08:25:26 pmI agree that the statement is a simplified explanation of how a SMPS works. But if you look at main stream switching power supplies on the market they are designed for a broad range of frequencies and input voltages. You need to choose a power supply rated for the application to which it is intended. There are SMPS's rated for medical applications. So why reinvent the wheel just get a power supply rated for your application.Electrolytic's standard testing is between 100Hz 20Coand 120Hz at 25Co. The DC ripple in a SMPS after rectification is either 100Hz or 120Hz.Electrolytic capacitors show very little change to behaviour between 10Hz and 1kHz depending on temperature. So to say that there would be any significant change in behaviour between 50Hz and 60Hz at an ambient temperature of 20Coto 25Cois over thinking that a problem can occur.https://www.cde.com/resources/technical-papers/AEappGuide.pdf

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 10:04:07 pm
content: Quote from: Jwillis on April 27, 2024, 08:41:09 pmYou are missing my point. It has nothing to do with SMPS. The point is that a bridge rectifier followed by a capacitor is highly dependent on frequency because the capacitor needs to hold enough energy to power whatever it powers during a longer time, until the next pulse to recharge it comes along. Lower the input frequency and you increase the ripple, decreasing the voltage level to which it falls. If you reduce the frequency by 50% you need to double the capacitance in order to maintain ripple and not increase voltage drop. It does not matter what follows, SMPS, linear or whatever. I have dealt with adapting 120 V, 60 Hz machines to 220 V 50 Hz, including linear PSU, motors and transformers and I am quite familiar with the issues. That was long time ago, in a previous life.

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2024, 10:34:26 pm
content: Quote from: soldar on April 27, 2024, 10:04:07 pmThe frequency of mains supply after rectification 100Hz or 120Hz depending on where you live. AND THERE IS NO SIGNIFICANT BEHAVIOUR CHANGE OF AN ELECTROLYTIC CAPACITOR BETWEEN 100Hz AND 120Hz AT 20 to 25CoIt makes no damn difference whether it's on a linear supply or an SMPS. That tiny change in Value and ESR between 100Hz and 120Hz won't make a damn bit of difference to the ripple voltage. Electrolytic capacitors have as much as 20% tolerance in value and your saying that a fraction of a uF can make a significant difference to ouptut ripple? That's absurd! Just to reduce the output ripple voltage by half, the capacitance needs to double.

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 10:51:21 pm
content: Quote from: Jwillis on April 27, 2024, 10:34:26 pmCanadian, eh? Now, now, there is no need to be rude. I see you don't get it and you get defensive.I insist that with lower frequency (everything else being equal) the voltage at the filter capacitor falls further. Model an AC voltage source, followed by a rectifier bridge, a capacitor and a constant current load. My prediction is that the voltage at the capacitor and load falls further with decreasing frequency. It must be obvious to anyone.This is my last word to you on this topic as I have no interest in putting up with rudeness. Maybe others can chime in if interested.

author: IanB
author_rank: Super Contributor
timestamp: April 27, 2024, 11:03:04 pm
content: Quote from: soldar on April 27, 2024, 10:51:21 pmI 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?

author: Jwillis
author_rank: Super Contributor
timestamp: April 27, 2024, 11:17:22 pm
content: 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.

author: IanB
author_rank: Super Contributor
timestamp: April 27, 2024, 11:57:06 pm
content: Quote from: Jwillis on April 27, 2024, 11:17:22 pmNeither ESR, nor change in capacitance with frequency, has been mentioned as of any significance to the discussion at hand. So it remains puzzling why you keep introducing them?

author: soldar
author_rank: Super Contributor
timestamp: April 27, 2024, 11:59:21 pm
content: Quote from: IanB on April 27, 2024, 11:03:04 pmMy point, as I said, is thatYou 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:Quote from: soldar on April 27, 2024, 08:25:26 pm

author: IanB
author_rank: Super Contributor
timestamp: April 28, 2024, 12:11:40 am
content: 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.

author: soldar
author_rank: Super Contributor
timestamp: April 28, 2024, 12:25:14 am
content: Quote from: IanB on April 28, 2024, 12:11:40 amWe 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.

author: Zero999
author_rank: Super Contributor
timestamp: April 28, 2024, 12:56:18 pm
content: Quote from: Jwillis on April 27, 2024, 11:17:22 pmIrrelevant.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.

author: wasedadoc
author_rank: Super Contributor
timestamp: April 28, 2024, 03:01:32 pm
content: 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?

author: Zero999
author_rank: Super Contributor
timestamp: April 28, 2024, 03:08:05 pm
content: Quote from: wasedadoc on April 28, 2024, 03:01:32 pmThat's too bad if the capacitor and switching regulator are only rated to 200v.

author: soldar
author_rank: Super Contributor
timestamp: April 29, 2024, 10:20:54 am
content: Quote from: Zero999 on April 28, 2024, 12:56:18 pmThank you for explaining and illustrating my point so well.

author: Haenk
author_rank: Super Contributor
timestamp: April 29, 2024, 12:55:50 pm
content: 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)

author: tooki
author_rank: Super Contributor
timestamp: April 29, 2024, 03:11:15 pm
content: 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!

author: am1
author_rank: Contributor
timestamp: May 01, 2024, 01:43:55 pm
content: 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.

author: johnk0gcj@gmail.com
author_rank: Contributor
timestamp: May 02, 2024, 05:23:07 pm
content: If you reread the first post you'll note that a step-up transformer may be required.

author: johnk0gcj@gmail.com
author_rank: Contributor
timestamp: May 02, 2024, 05:24:53 pm
content: Reread my last sentence.

author: IanB
author_rank: Super Contributor
timestamp: May 02, 2024, 07:14:28 pm
content: Quote from: johnk0gcj@gmail.com on May 02, 2024, 05:23:07 pmIt also may not be required. What is your point?

author: tooki
author_rank: Super Contributor
timestamp: May 02, 2024, 07:38:21 pm
content: 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.

author: shapirus
author_rank: Super Contributor
timestamp: May 02, 2024, 10:03:23 pm
content: Quote from: tooki on May 02, 2024, 07:38:21 pmCan simply be plugged into the washer/dryer outlet, no?

author: radiolistener
author_rank: Super Contributor
timestamp: May 02, 2024, 10:28:48 pm
content: Quote from: shapirus on May 02, 2024, 10:03:23 pmNo, simple plugging it to outlet and see if it works is not the expected way for medical device certification.

author: shapirus
author_rank: Super Contributor
timestamp: May 03, 2024, 07:34:08 am
content: Quote from: radiolistener on May 02, 2024, 10:28:48 pmThe question was about how to perform testing on the 230V configuration, not how to "see if it works".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.

author: radiolistener
author_rank: Super Contributor
timestamp: May 04, 2024, 12:20:32 am
content: Quote from: shapirus on May 03, 2024, 07:34:08 amThe answer is the same. Simple plug to 230V mains outlet and see if it works is not enough for medical device.