The Engineer's Place for News and Discussion®

 Previous in Forum: Elevator Motor Rating Next in Forum: MCB

### Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

### Rating Vote:

Power-User

Join Date: Jun 2008
Posts: 121

### Continuous DC Current and Peak Current

08/06/2012 10:29 AM

Hi,

I saw this statement when going through a standard for lighting equipment and i feel confused by this statement.

"Maximum output voltage does not exceed 42.4 V peak for alternating current, 60 V for continuous direct current. These products are intended primarily to providepower to low voltage, electrically operated devices"

I thought that it should be stated the other way round. ie 60V peak and 42.4V continious dc current? Please adivse ur inputs.

Thanks

__________________
"Shallow men believe in luck. Strong men believe in cause and effect." -- Ralph Waldo Emerson
Interested in this topic? By joining CR4 you can "subscribe" to

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing. Kettle's on.
Posts: 19559
#1

### Re: continious dc currrent and peak current.

08/06/2012 11:15 AM

<...thought that...>

Hint: 60/42.4≈√2, so think again.

__________________
There was a time, not long ago, when people were smarter than their phones... (tips hat to CR4 user Harley.)
Power-User

Join Date: Jun 2008
Posts: 121
#2

### Re: continious dc currrent and peak current.

08/06/2012 11:45 AM

But i thought Vp/Root 2 = Vrms?. So in this case , Dont u think the author mistakenly used Vp as 42.4 and Vrms as 60v?

__________________
"Shallow men believe in luck. Strong men believe in cause and effect." -- Ralph Waldo Emerson
Score 1 for Off Topic
Guru

Join Date: Dec 2008
Location: Long Island NY
Posts: 6991
#3

### Re: continuous dc current and peak current.

08/06/2012 11:55 AM

No, the most common method of expressing VAC is an RMS measurement. So if the RMS voltage is 42.4 VAC then what will be the peak voltage?

__________________
"A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering." Freeman Dyson
Off Topic (Score 4)
Power-User

Join Date: Jun 2008
Posts: 121
#4

### Re: continuous dc current and peak current.

08/06/2012 12:07 PM

60V?.

__________________
"Shallow men believe in luck. Strong men believe in cause and effect." -- Ralph Waldo Emerson
Off Topic (Score 5)
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#7

### Re: continuous dc current and peak current.

08/07/2012 1:27 AM

OP said 42.4VAC PEAK not RMS.

Moomoo is right.

__________________
Difficulty is not an obstacle it is merely an attribute.
Off Topic (Score 5)
Power-User

Join Date: Jun 2009
Posts: 127
#5

### Re: Continuous DC Current and Peak Current.

08/06/2012 12:14 PM

moomoo is correct.

The numbers are backwards.

Power-User

Join Date: Jun 2008
Posts: 121
#6

### Re: Continuous DC Current and Peak Current.

08/06/2012 8:57 PM

I thought so Carl, and surprisingly this is from one of the safety standards bible!

Thanks !

__________________
"Shallow men believe in luck. Strong men believe in cause and effect." -- Ralph Waldo Emerson
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#8

### Re: Continuous DC Current and Peak Current.

08/07/2012 1:29 AM

Vote "no" in the off topic for moomoo.

__________________
Difficulty is not an obstacle it is merely an attribute.
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 2672
#13

### Re: Continuous DC Current and Peak Current.

08/07/2012 9:50 AM

Done!

__________________
Teaching is a great experience, but there is no better teacher than experience.
Active Contributor

Join Date: Jul 2012
Posts: 12
#9

### Re: Continuous DC Current and Peak Current

08/07/2012 2:51 AM

thank you...nice post..

Power-User

Join Date: Oct 2009
Posts: 379
#10

### Re: Continuous DC Current and Peak Current

08/07/2012 5:24 AM

"Maximum output voltage does not exceed 42.4 V peak for alternating current, 60 V for continuous direct current."

If we are talking AC then I agree the numbers are the wrong way round, but where does the DC fit in?

Power-User

Join Date: Jan 2009
Posts: 162
#11

### Re: Continuous DC Current and Peak Current

08/07/2012 8:26 AM

Maybe what is meant is

"Maximum output voltage does not exceed 42.4 V [rms] peak ("peak" meaning an overvoltage for some limited time, not the instantaneous peak voltage) for alternating current, 60 V for continuous ("continuous" meaning "a continuously applied voltage", not necessarily a DC voltage) direct current".

It's a very confusing text anyway, probably a translation. Remember "direct current" is literally "continuous current" in other languages.

brgds

Snel

Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#12

### Re: Continuous DC Current and Peak Current

08/07/2012 8:58 AM

If moomoo is still in the vendor selection stage of this project i'd suggest that he selects to NOT buy this product.

If they can't get the documentation right then what else is wrong? Doesn't bode well for technical or any other after sales support in my experience.

Technical documentation does not tolerate poetic license. Metaphors, similes, implications and their ilk have no place here.

If you have knowledgeable folk having to have a go at paraphrasing a specification for it to make sense then the world's going to hell in a handbasket.

OP, could you tell us the country of origin for this lighting equipment please?

__________________
Difficulty is not an obstacle it is merely an attribute.
Power-User

Join Date: Jun 2008
Posts: 121
#16

### Re: Continuous DC Current and Peak Current

08/08/2012 11:17 PM

Hi Wall,

Actually this statement is written in one of the safety standards for class 2 power supplies, and i m still pulling my hair to understand what this means. I am sure they know what they are writing,but somehow it doesnt make sense to my common sense!

Regards.

__________________
"Shallow men believe in luck. Strong men believe in cause and effect." -- Ralph Waldo Emerson
Off Topic (Score 5)
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#17

### Re: Continuous DC Current and Peak Current

08/09/2012 12:27 AM

I get it.

For a power supply to be considered as class 2 then these maximum parameters can't be exceeded.

There doesn't need to be any correlation between the AC and DC values.

OR

It could still be a typo that got missed in the proof reading...

Can you contact the authors of the standard for clarification?

__________________
Difficulty is not an obstacle it is merely an attribute.
Off Topic (Score 5)
Power-User

Join Date: Apr 2012
Posts: 138
#14

### Re: Continuous DC Current and Peak Current

08/07/2012 10:57 AM

If this was a standard for lighting...why is there an output voltage at all?

Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 2371
#15

### Re: Continuous DC Current and Peak Current

08/07/2012 11:29 AM

These products are intended primarily to provide power to...

I think it is lighting control/energisation apparatus not the luminaires themselves.

__________________
Difficulty is not an obstacle it is merely an attribute.