Question about wall wart "transformer class" - Electronic Circuits Projects Diagrams Free

Torben · 18th August 2008, 07:52 AM

Hi all,

I've been looking at wall warts recently and noticing that some are marked "Class 2" or "Plug in Class 2 Transformer" or similar.

What are the class designations for wall warts? I imagine this is all explained somewhere but I'm not able to put together good search terms for it at the moment, apparently. :/

Do these markings refer to some performance characteristic of the wall wart as a whole or do they just refer to the transformer inside?

Thanks,

Torben

eblc1388 · 18th August 2008, 08:20 AM

The magic search phrase is:

"Appliance classes" and here is a Wiki link: Appliance classes

Torben · 18th August 2008, 08:28 AM

Quote:

Originally Posted by eblc1388

The magic search phrase is:

"Appliance classes" and here is a Wiki link: Appliance classes

Thank you! I was hoping that "Class 2" on a wall wart would mean that it could be depended upon to provide a certain level of rectification and smoothing, but it appears that I'm not so lucky this time.

You always seem to have a concise, informative, and correct answer.

Torben

Mikebits · 18th August 2008, 08:34 AM

Quote:

Originally Posted by eblc1388

The magic search phrase is:

"Appliance classes" and here is a Wiki link: Appliance classes

Good job, I searched UL and NEC with no luck.

k7elp60 · 18th August 2008, 02:27 PM

Here is some more information that I found recently.

What is a Class II Transformer?
A Class II transformer is used to supply Class II circuits. Class II transformers have a maximum VA (Volt-Ampere) rating of less than 100 and a maximum secondary output of 30 VAC. The maximum VA generally offered is 75 and the most common secondary voltage is 24 VAC. All Class II transformers are either inherently or non-inherently limited. This means that the maximum output current of the transformer is limited, either by the intrinsic coil impedance or by a fuse or circuit breaker. These transformers are designed to meet the requirements of U.L. 1585.
Inherently Energy Limited Transformers - Class II transformers up to 50 VA are "Inherently Limited" which means that the transformer, if overloaded, will short itself out and fail safely, not requiring a fuse.
Non-Inherently Energy Limited Transformers - 60 thru 75 VA Class II transformers are generally protected by a resettable circuit breaker or a fuse within the transformer secondary. Without this overload protection, the transformer would not satisfy the safety requirements for a Class II circuit.

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18th August 2008, 07:52 AM	(permalink)
Torben	Question about wall wart "transformer class" Hi all, I've been looking at wall warts recently and noticing that some are marked "Class 2" or "Plug in Class 2 Transformer" or similar. What are the class designations for wall warts? I imagine this is all explained somewhere but I'm not able to put together good search terms for it at the moment, apparently. :/ Do these markings refer to some performance characteristic of the wall wart as a whole or do they just refer to the transformer inside? Thanks, Torben __________________ Curiosity was framed. Ignorance killed the cat.

18th August 2008, 08:20 AM	(permalink)
eblc1388	The magic search phrase is: "Appliance classes" and here is a Wiki link: Appliance classes __________________ L.Chung

18th August 2008, 02:27 PM	(permalink)
k7elp60	Here is some more information that I found recently. What is a Class II Transformer? A Class II transformer is used to supply Class II circuits. Class II transformers have a maximum VA (Volt-Ampere) rating of less than 100 and a maximum secondary output of 30 VAC. The maximum VA generally offered is 75 and the most common secondary voltage is 24 VAC. All Class II transformers are either inherently or non-inherently limited. This means that the maximum output current of the transformer is limited, either by the intrinsic coil impedance or by a fuse or circuit breaker. These transformers are designed to meet the requirements of U.L. 1585. Inherently Energy Limited Transformers - Class II transformers up to 50 VA are "Inherently Limited" which means that the transformer, if overloaded, will short itself out and fail safely, not requiring a fuse. Non-Inherently Energy Limited Transformers - 60 thru 75 VA Class II transformers are generally protected by a resettable circuit breaker or a fuse within the transformer secondary. Without this overload protection, the transformer would not satisfy the safety requirements for a Class II circuit. __________________ The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best. Show me a different way. I have an open mind.