I'm hoping someone who's worked at a place making appliances like a disc player can answer this question. There are countless appliances for AV stuff that are Class II (no safety ground, "earth") and are made of sheet metal and have internal PSU's. The definition across the internet is "they have plastic enclosures"..... So you see where my question comes from. I'd like to know how they're doing this so they can get the double box on the back.
Thank you
Thank you
Class II considerations
A/V electrical stuff use a Double Insulated System. That means there is no path to Earth from any secondary supply to the mains.
Mains transformers must have a separate bobbins for power in and power out. That ensures good isolation and must be flash tested to a minimum of 2000 volts for 15 Seconds.
A Class Y capacitor is normally used to drain electrical noise to the chassis etc.
Maybe you have confused Class II with Doubly Insulated.
- not to exceed 60 VDC (although they are most commonly operated at 24 VDC or 24 VAC for industrial and commercial purposes)
- load side power potential must be limited to less than 100 VA (although adhering to these limits with standard fuses or circuit breakers is not acceptable)
A/V electrical stuff use a Double Insulated System. That means there is no path to Earth from any secondary supply to the mains.
Mains transformers must have a separate bobbins for power in and power out. That ensures good isolation and must be flash tested to a minimum of 2000 volts for 15 Seconds.
A Class Y capacitor is normally used to drain electrical noise to the chassis etc.
Maybe you have confused Class II with Doubly Insulated.
I very well could have some definitions wrong. I'm solely interested in what type of precautions can be taken to allow a no-earth device. It's clear to me that it is not abnormal for appliances to exist like that and be within compliance, but as to how they are isn't very clear since everyone just likes to talk about hair dryers when asked online.
Looking up the various rules and compliance listings will confuse even the most savvy engineer.
Rule of thumb, how I interpret is, use doubly insulated power supplies and that seems to be about it for home equipment. Other than that, if the motor or amplifier/DVD/CD player has no metal parts that connect directly or indirectly to the mains supply, that just about covers it.
Hence your hair drier comment I presume.
Good luck with getting your head around the rules. It has taken me many years and as they keep moving the goal posts, I will never know any more than the basics. 🤣
Rule of thumb, how I interpret is, use doubly insulated power supplies and that seems to be about it for home equipment. Other than that, if the motor or amplifier/DVD/CD player has no metal parts that connect directly or indirectly to the mains supply, that just about covers it.
Hence your hair drier comment I presume.
Good luck with getting your head around the rules. It has taken me many years and as they keep moving the goal posts, I will never know any more than the basics. 🤣
Jon, I was also fairly convinced that Class II appliances are those which people refer to as double-insulated. Is it not class III that is low voltage?
At least with respect to IEC protection classes, anyway. There can be different bodies and terms used around the world; perhaps that is going on here.
Cheers,
Kev
At least with respect to IEC protection classes, anyway. There can be different bodies and terms used around the world; perhaps that is going on here.
Cheers,
Kev
It's pretty simple: they follow the directives of the relevant safety standard. Is is called 60065 (audio,video and similar electronic apparatus-safety requirements) for the UE market; other electrical appliances have their own safety standard, or they follow a generic standard 60335-1. If you want to put the double box sticker you need to read about 20 pages. They specify how to connect parts togheter, what test voltage to use and how must be applied, minimum distances, what should or should not be exposed whan you take the cover off and so on. It is not a quick, simple rule to follow, but rather a pretty comprehensive check list. The last appliance test report I've read was 130 pages of checklists and measures. I don't know what is the corresponding UL standard, but I guess that it would be like this.
Old superseded revisions of the 60065 standard are on the internet, and they are just fine for a hobby purpose. In the past it was required by the Italian law to have binding safety standards with legal implications such as this one available for free. Search the keyword "60065 Gazzetta Ufficiale" and you should get the download page of the full EN60065 document from the gazzettaufficiale web site. The pdf file is bilingual, english and italian. The gazzettaufficiale web site is managed by italian ministry of finances, it is the web site where the italian laws can be downloaded. The free 60065 pdf was published as supplement of the issue 226 dated 27-9-2000. You may find more recent free revisons of the standard, but I would avoid shady web sites.
I've wondered this for a long time as well.
My Denon AVR-588 has no ground pin and gives 4.3A current draw which is 516VA. Either this is simply wrong or there is a great deal of favoritism given to large companies.
My Denon AVR-588 has no ground pin and gives 4.3A current draw which is 516VA. Either this is simply wrong or there is a great deal of favoritism given to large companies.
I think jonsnell-electronic was referred to Class 2.
"Class II" and "Class 2" are two different designation.
Class II (with Roman numerals) refers to power supplies with either a double or reinforced insulation barrier between the input and the output. Class II supplies do not rely on an earth connection to protect against shock hazard.
"Class II" and "Class 2" are two different designation.
Class II (with Roman numerals) refers to power supplies with either a double or reinforced insulation barrier between the input and the output. Class II supplies do not rely on an earth connection to protect against shock hazard.
https://en.wikipedia.org/wiki/Appliance_classes
Classifying and Using Class 1, 2, and 3 Circuits
Basically if the electronic components inside the case fail & go "live" , the design is such that the outer case is still 100% safe to touch as it does not go "live". There is also a rule on that fact that any air opening etc, has to be small to stop you from placing a pen, or finger etc, into the case & touching a "live" component.
However, as the item still has live & neutral wires, you can still get what is known as "earth leakage" where there is a current difference between the live & the neutral....& in the "Class2" category which in the U.K. means "Double Insulated"......you are allowed upto 0.25mA of difference when doing P.A.T. testing...according to the EN/BS standards...
This is why you can still get "static shocks" from metal cased double insulated equipment.....as when you touch the metal case you are "grounding" the case...in fact you are "equalising the potential difference"...as the electronics are effectively "floating" relative to the planet earth & there exists a potential difference....much like when you step outside the car & then touch the metal door/roof...as you now "ground" the car to the planet as the rubber tyres insulate the car from the planet..
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