"High voltage test (also called hipot or HV test worldwide) has by far the highest priority among all of the electrical safety tests. This test of the dielectric strength is mandatory as it is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC). The often used term insulation test or insulation measurement is wrong in this context as a real, ohmic resistance is measured with the direct voltage in this case. In contrast, the high voltage test is carried out with both direct and alternating current. The result of this test is a leakage current, flowing between live parts and the metallic casing. Devices of protection class I always come with a metal casing, whereas the casing of the devices of protection class II must be replaced by a metallic contour during the test. In reality, the high voltage test is a geometric distance measurement in the DUT (Device Under Test): If the DUT withstands a certain voltage without flashover, an appropriate minimum distance between the metal casing and electrical components in the device is ensured. Thus, the term withstand voltage is also plausible again."
https://www.spselectronic.com/en/products/high-voltage/
Yes, you can. By design, I mean the whole process, not just the components and laying out the PCB, but the materials and how they're physically put together. The video you've linked to demonstrates this perfectly. Proper design could have avoided this fault. Testing could have made this worse by weakening some marginal components, causing them to fail in the Yes. I've seen hi-pot stickers and have never seen the point.The point is to indicate that test was passed. Therefore no untested device may accidentally slip further.QuoteIt won't stop marginal devices from slipping through or show up poor manufacturing. Only disassembly and visual inspection can do that. Yes, you're right, it shouldn't damage the insulation, as long as the test voltage isn't too high (much lower than the withstand voltage) and hasn't been applied for too long.Visual inspection will happily pass most of the faults , it's only good for finding the most obvious defects. It's really obvious you never dealt with actual production. And you cannot inspect inside the parts (where most of the faults happen), and you won't be able to see imperfections in insulation anyway. Exactly Hi-POT test is what weeds out marginal devices.
Withstand voltage means withstand don't confuse that with breakdown voltage.
QuoteI disagree with you about the construction of the transformer. There isn't enough insulation, where the windings pass near one another and it appears too much force has been used when it was wound. Very shoddy.Wire used in secondary winding had reinforced insulation by itself. Basically you could wind primary winding directly on top of it, and it would be just fine. The issue was that a big piece of that insulation was missing because of mechanical damage.
EDIT: Something like this http://www.totoku.com/products/cables/tiw/post-2.php, additional insulation between windings is not required at all.
Mechanical damaged, caused by poor manufacturing process. If the winding machine was incorrectly set, there will be other devices with a similar fault and the high voltage withstand test might not have revealed it.
Mechanical damaged, caused by poor manufacturing process. If the winding machine was incorrectly set, there will be other devices with a similar fault and the high voltage withstand test might not have revealed it.Such fault may happen to one in 100 000 transformers and destructive inspection of sampled devices won't reveal anything wrong. The good thing with Hi-pot test is that 100% of devices are tested and may reveal rare issue with production process.
This test of the dielectric strengh is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC), it is mandatory and there is nothing to discuss about utility of these standarts.
It is like a law .....You must obey or you will have serious troubles....
This is the way a quality control works....you must comply with the standarts....nothing more.
Do you think you are more clever than the people how make these standarts ?
This test of the dielectric strengh is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC), it is mandatory and there is nothing to discuss about utility of these standarts.
It is like a law .....You must obey or you will have serious troubles....
This is the way a quality control works....you must comply with the standarts....nothing more.
Do you think you are more clever than the people how make these standarts ?
It seems that you did not understand what I meant.
When I say "you must comply with the standarts .... nothing more. ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,
It seems that you did not understand what I meant.
When I say "you must comply with the standarts .... nothing more. ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,I understood, but I don't agree. Understanding why you do something is a huge boon.
It seems that you did not understand what I meant.
When I say "you must comply with the standarts .... nothing more. ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,I understood, but I don't agree. Understanding why you do something is a huge boon.This kind of discussion has nothing to do with the topic.
The question is simple,"Is this charger safe ?" the answer is also simple...NO...
The high pot test is mandatory and it is the fundamental test to ensure safety.
Has the charger passed the higt pot test?
Probably not.
Is it safe? NO .... final point.
It seems that you did not understand what I meant.
When I say "you must comply with the standarts .... nothing more. ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,I understood, but I don't agree. Understanding why you do something is a huge boon.
We don't know whether it has been high voltage tested or not and even if it hasn't, it still might be safe.
It's also vital to understand the limitations of the test, in order to design a safe product, otherwise one is just designing something to pass a test, not be safe. The same is true with car emissions tests.
QuoteWe don't know whether it has been high voltage tested or not and even if it hasn't, it still might be safe.Safety is not a lottery...
Your security conception is completely false ... and you continue in your mistakes.
Not long ago, you said that the Hi Pot tests were not mandatory and now you claim that a device can be considered as safe even if it has not passed the hi pot test ....
No at all, if a device has not passed the mandatory tests, it is not safe even if nobody has been electrocuted .... We must not confuse safety with Russian roulette.
QuoteIt's also vital to understand the limitations of the test, in order to design a safe product, otherwise one is just designing something to pass a test, not be safe. The same is true with car emissions tests.Absolutely non sense
If insulation passed a High Pot test of 4240Vdc, we can be sure that it is safe and that there is no risk of insulation failure between primary and secondary with only 230Vac (325Vpeak).
Just a simple question: how many consumers got a Hi Pot tester, know how to use it and test every device? Based on the arguments stated several times we would have to assume that any device is unsafe until proven by a Hi Pot test. The reality is that consumers have to trust fancy certification labels and laws. And we've all seen wall warts with nasty surprises despite several certification labels printed on the enclosure. In theory every wall wart should be Hi Pot tested, in reality they aren't. And it's also reality that we have far more fatal traffic accidents than fatalities caused by poor wall warts.
No special equipment is necessary to test that it's safe. All that's needed is a multimeter and a 10k resistor. Plug the PSU in to the mains, connect a 10k resistor between one of the the output conductors (either + or -) and mains earth and measure the voltage across the resistor. The maximum allowable current is 0.25mA, which means the voltage across the resistor should be below 2.5V. Check both + and - conductors, on AC and DC ranges. If the resistor gets hot or the voltage is higher than 2.5V, then you have a dangerous power supply, which shouldn't be used.
Is a test perfect? no, but it is considered sufficient ...
Is it really?
It is not up to us to decide ...... but standarts have scope of law for the quality control and it is mandatory to respect them.
Anyone who does not respect them becomes criminally responsible in the event of an accident, at least in Europe.
Something is not safe until it is prooven that it is safe and not the opposite!
You play with the lives of other people, comparison with car accidents is not acceptable ....
In Europe, the principle of accepting a victim on 5000 or 10,000 chargers sold is not acceptable (it seems that in China, yes) .... There can not be victims, not one!
All European countries have a penal code that punishes with jail assaults and killings, even through negligence (not carrying out the imposed tests is a negligence)
The hypotheses of melted insulation and others are absurd ..... The hig pot test is not the only test imposed by the standarts ..... if there was a fault such as transformer would heat to the point of melting the insulation, the first fault would be the short circuit between coils and layers, which would cause to blow up the Mosfet and the input fuse.
QuoteNo special equipment is necessary to test that it's safe. All that's needed is a multimeter and a 10k resistor. Plug the PSU in to the mains, connect a 10k resistor between one of the the output conductors (either + or -) and mains earth and measure the voltage across the resistor. The maximum allowable current is 0.25mA, which means the voltage across the resistor should be below 2.5V. Check both + and - conductors, on AC and DC ranges. If the resistor gets hot or the voltage is higher than 2.5V, then you have a dangerous power supply, which shouldn't be used.No sense .... how can you ensure that the insulation resists transient network overvoltages without doing a Hi-Pot test?
I agree, which is why one shouldn't rely on these tests as the only way to ensure the product is safe.
...Melted insulation is a possibility and the fuse could be on the neutral line, if it has a crappy non-polarised EU plug. The PSU would go dead and possibly the user too.
There are other possibilities: a weak coil former (Not possible, would not pass the Hi Pot test), crappy soldering (nothing to do with insulation prmary/secondary), poor PCB mechanical support (nothing to do with insulation primary/secondary) and an unearthed metal enclosure ( this only apply to class I devices...continuity of hearting must also be tested, it is also mandatory. The present charger is a class II device, not a class I ). The tests can't catch everything and will certainly not detect poor/unsafe design/manufacturing. (poor design and unsafe design are totally different things...Standarts have a lot of details about good design, but a bad design is not necessary an unsafe design... The electric test as hi_Pot are basic and mandatory to ensure safety of the user.)The tests should supplement existing quality assurance measures. They're not a replacement and cannot guarantee the design is safe (did you even worked in an industry ? A new product is developped by engineering, a prototype is done, tested, modified, a pre-production is made, eventually some minor modifications are done, the design is then approved, and the production start...the quality control only test the units manufactured to verify if they comply with standarts and with the internal procedure of controls and tests)
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Yes, it won't test for a transient over voltage but it's "good enough" in a domestic situation ( good enough is to pass the HI-Pot test, nothing other is legally allowed...Standarts are mandatory, if it has not passed through the hig Pot test, it can't be declared beeing safe...) and it passes all the basic visual inspection: creapage clearances (impossible to verify the ferrite transformer only by visual inspection) . It certainly reduces the level of risk further. I think we forget the scope of this thread is, assisting someone to determine whether their switched mode power supply is safe, not compliance testing in a factory.
It's common to only do HiPot testing during design and certification phase on the entire power supply.
Then, only safety critical parts need to be tested in production, not the power supply itself.
That's to say, if a PSU with UL certified design uses safety rated PCB (with UL number on it), safety rated optocoupler, safety rated X/Y caps, safety rated fuse and safety rated transformer, then it should be allowed to bear NRTL which is has been certified for.
Also, to bear an NRTL logo, the actual OEM factory must be routinely inspected by an NRTL agency, such as UL. ISO9001 doesn't exempt a factory from NRTL factory inspection.
Since usually transformers are made in house by PSU manufacturers, you will usually see a HiPot pass label on it, but that's usually HiPot for transformer itself, not the entire PSU.
I believe some specialty PSUs, such as medical ones, require 100% individual HiPot test, but I don't think consumer PSUs must be tested individually.
I agree, which is why one shouldn't rely on these tests as the only way to ensure the product is safe.Hi Pot is not the only test to check if the product is safe, I have said this several times...but it has by far the highest priority among all of the electrical safety tests....Melted insulation is a possibility and the fuse could be on the neutral line, if it has a crappy non-polarised EU plug. The PSU would go dead and possibly the user too.If the power supply stop to work, temperature stop increasing and will not be high enough to melt thicker and reforced insulation between primary and secondary.There are other possibilities: a weak coil former (Not possible, would not pass the Hi Pot test), crappy soldering (nothing to do with insulation prmary/secondary), poor PCB mechanical support (nothing to do with insulation primary/secondary) and an unearthed metal enclosure ( this only apply to class I devices...continuity of hearting must also be tested, it is also mandatory. The present charger is a class II device, not a class I ). The tests can't catch everything and will certainly not detect poor/unsafe design/manufacturing. (poor design and unsafe design are totally different things...Standarts have a lot of details about good design, but a bad design is not necessary an unsafe design... The electric test as hi_Pot are basic and mandatory to ensure safety of the user.)The tests should supplement existing quality assurance measures. They're not a replacement and cannot guarantee the design is safe (did you even worked in an industry ? A new product is developped by engineering, a prototype is done, tested, modified, a pre-production is made, eventually some minor modifications are done, the design is then approved, and the production start...the quality control only test the units manufactured to verify if they comply with standarts and with the internal procedure of controls and tests)
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Yes, it won't test for a transient over voltage but it's "good enough" in a domestic situation ( good enough is to pass the HI-Pot test, nothing other is legally allowed...Standarts are mandatory, if it has not passed through the hig Pot test, it can't be declared beeing safe...) and it passes all the basic visual inspection: creapage clearances (impossible to verify the ferrite transformer only by visual inspection) . It certainly reduces the level of risk further. I think we forget the scope of this thread is, assisting someone to determine whether their switched mode power supply is safe, not compliance testing in a factory.Every switched mode supply must pass the High Pot test.
Class I power supplies (with earthed secondary) must pass the High Pot test at 2120Vdc between primary and (earthed ) secondary, class II (dubbel insulation) power supplies must pass the test with 4240Vdc....for power supplies with secondary not earthed, this test is absolutely essential for the safety of the user !!!
This test must be executed at the factory.
The problem is that, with no name or unknown name products, there is no way to be sure that this test has really been made or not....
For this reason, all brands fake or no name must be considered as not safe, you buy and use it at your own risks.
Don't risk your life, buy good quality products from a well known brand, not crap devices as this charger.
It's common to only do HiPot testing during design and certification phase on the entire power supply.
Then, only safety critical parts need to be tested in production, not the power supply itself.
That's to say, if a PSU with UL certified design uses safety rated PCB (with UL number on it), safety rated optocoupler, safety rated X/Y caps, safety rated fuse and safety rated transformer, then it should be allowed to bear NRTL which is has been certified for.
Also, to bear an NRTL logo, the actual OEM factory must be routinely inspected by an NRTL agency, such as UL. ISO9001 doesn't exempt a factory from NRTL factory inspection.
Since usually transformers are made in house by PSU manufacturers, you will usually see a HiPot pass label on it, but that's usually HiPot for transformer itself, not the entire PSU.
I believe some specialty PSUs, such as medical ones, require 100% individual HiPot test, but I don't think consumer PSUs must be tested individually.
If , as you said, all parts and pcb are safety rated, the transformer is High Pot tested, there is no necessity to High Pot test the entire PSU....but you speak about OEM factory , not really the kind of factory who manufactured this piece of crap you see on the pictures of this topic....
You can be sure nothing is certified, the components are of lowest quality and cost possible, the transformer has never been High Pot tested.....It can't be safe.....It only don't kill many people because not every electric chock kill you and because we have a 30mA earth fault current circuit breaker.
Class II appliances can have a metal case you know!
Weak solder joints can break, allowing loose wires/components to come into contact with things they shouldn't.
If the enclosure isn't adequately fastened together, it can come apart, leaving the user exposed to live parts.
How do you know this is the case with the original poster's SMPS?
There are different levels of risk. Forget the law for a second. The original poster is not getting this power supply mas produced. They just want to be 99% sure it won't kill them. By looking at the inside and doing a visual inspection, they've already lowered the risk somewhat. A basic electrical test, such as the one I mentioned above, would lower the risk further, even though it may not be stringent enough to satisfy the legal requirements.
QuoteClass II appliances can have a metal case you know!Yes indeed, class II (double insulation) does not require a safety connection to electrical earth (ground) of metal case, if any. Safety is usually achieved by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.
With reinforced insulation is choosed, no need of earth connection of the metal case.
Hi Pot is a test made on NEW or REPAIRED devices, it is a punctual test, not a safety warranty against abuses as transformers used in humid and salty atmosphere, transformers that have fallen,....
In normal use that meets the manufacturer's technical specifications, there can be no degradation of the insulation, except normal ones due to aging.
You are inventing something stupid that borders on ridicule.QuoteWeak solder joints can break, allowing loose wires/components to come into contact with things they shouldn't.Not possible, there is a physical separation (distance) between the primary and the secondary circuits...If it would come in contact with "things they shouldn't", it could only be "things" of the same circuit, not a safety concern.
QuoteIf the enclosure isn't adequately fastened together, it can come apart, leaving the user exposed to live parts.And the user will turn on the open device because he has not noticed that the device falls apart...you are kidding ?
QuoteHow do you know this is the case with the original poster's SMPS?Lowest tecnology possible, low quality components and PCB, no marking on transformer, no brand on PCB (RXZ does not seems to be any brand)....
QuoteThere are different levels of risk. Forget the law for a second. The original poster is not getting this power supply mas produced. They just want to be 99% sure it won't kill them. By looking at the inside and doing a visual inspection, they've already lowered the risk somewhat. A basic electrical test, such as the one I mentioned above, would lower the risk further, even though it may not be stringent enough to satisfy the legal requirements.We will never agree because your point of view is that of an amateur who knows nothing about quality control and who treats safety with lightness and unconsciousness, whereas I has been quality control manager (actually retired).
Sorry, but in a quality control department, a person like you has no place. More or less does not exist in quality control...It pass or it fails.....
QuoteHow do you know this is the case with the original poster's SMPS?Lowest tecnology possible, low quality components and PCB, no marking on transformer, no brand on PCB (RXZ does not seems to be any brand)....