Inrush Current ratings of Hosptial Circuit breakers 1

[Huggie]

I wish to "daisy chain" AC/DC switching power supplies in a hospital environment and need to know how many I can link in a chain. I would prefer to do this without any extra components, such as relays and momentary switches.

What is the inrush current rating of a common hospital 120V outlet's circuit breaker?

Each supply is drawing 0.5A, with an inrush rating of about 25A.

Thanks.

 

[itsmoked]

I can't say much on the incredibly sparse info you have dribbled out.

I would promptly switch to parallelable soft-start power supplies which usually have power factor correction included, which helps with harmonics mitigation in hospital environments to boot.

Often you can just parallel them. Sometimes you need just a diode. Check with the manufacturer.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Huggie]

Do you have a pointer to a parallelable soft-start power supply? (yes, i'm googling as i wait.)

I thought that "What is the inrush current rating of a common hospital 120V outlet's circuit breaker?" was rather specific dribble...

This is in a hospital environment, but not medical equipment.

 

[dpc]

These little molded case circuit breaker have a wide tolerance band on the instantaneous pickup. I would try to stay under about 6 times the breaker rating. So for a typical 20A breaker, that's 120 A. You should also assume that the instantaneous element will respond to the peak asymmetrical current, not rms.

 

[waross]

"Daisy Chaining" often implies a series connection, or the output of one into the input of the next and so on.
What do you mean by "Daisy Chaining" power supplies?
Code restrictions in hospitals usually effectively rule out any unique or imaginative circuits and equipment arrangements.
yours

 

[Huggie]

waross:
The way I'm using the term 'daisy chaining' here is that there is only one AC connection from the wall to the first unit, then every other downstream units plug into the upstream's AC out connector.

So, sorry for the confusion, the ac/dc converters are actually connected to the AC in parallel. The product has 'daisy chained' power chords, I guess.

dpc:
This was exactly the answer I was looking for. Thanks. I'll have to make sure I'm looking at peak asymmetrical current.

The worst case senario is that someone unplugs and replugs the first unit, and all of the downstream, parallel, units turn on at the same time, summing the inrush current. If I want to allow more than the 6x that dpc states, I have to do something...

thanks.

 

[waross]

Thanks for the feedback. Don't forget to give dpc a star.
Respectfully

 

[dpc]

Huggie,

As I'm sure you know, the inrush into the power supply will vary somewhat randomly depending on the voltage phase angle when the switch is closed. For a purely inductive load, the worst case is closing at V=0. So if you start getting reports of "random" breaker tripping, you'll know what to do.....

 

[Huggie]

dpc,
Yeah, I read the

http://www.allaboutcircuits.com

page on the subject, but all I'm going on is the inrush spec in the AC/DC datasheet. I don't know if they know what we know.

Your previous information is a helpful decision point: if we want <=6 in the chain (for a 20A breaker), then nothing special needs to be done, if we want >6 in the chain, then we must do something to limit the inrush. The latter is more interesting from a design point of view I guess.