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-48V DC vs. 48V DC vs. +48V DC

R

Randy Day

Jan 1, 1970
0
Caiser said:
Can somebody tell me what difference is between -48V DC, +48V, and
48VDC DC input power supplies?

Example of -48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id=2426

Example of 48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id=3842

Example of +48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id=3851

I think the titles are a not-so-good way to group
the supplies for their catalog software.

They have different rated capacities in amperes, one
has a 3.3v output, the three have different dimensions
(L/W/H) and mounting hardware. One's for PS/2 pc's,
one's ATX, and one seems to be a generic supply.
 
C

Caiser

Jan 1, 1970
0
I know that all 3 of these power supplies are differrent but I am look
more specifically at the input voltage, what is the difference between
-48V DC, +48V, and 48VDC?
 
G

Gordon reeder

Jan 1, 1970
0
Can somebody tell me what difference is between -48V DC, +48V, and
48VDC DC input power supplies?

Example of -48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id= 2426

Example of 48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id= 3842

Example of +48VDC power supply:
http://store.orbitmicro.com/commerce/catalog/product.jsp?product_id= 3851

Anytime you have a signed voltage it implies that there is a referance
to some ground point. So -48VDC implies that you need to have the (+)
side of your input voltage tied to ground (or there is an internal
connection of the (+) to ground).

By the same token, +48 would indicate that the (-) side of your input
supply should be at ground (or perhaps there is an internal connection
of the (-) to ground).

It then follows that the unsigned 48VDC input has no particular
preferance for which end is grounded.
 
K

Kitchen Man

Jan 1, 1970
0
I know that all 3 of these power supplies are differrent but I am look
more specifically at the input voltage, what is the difference between
-48V DC, +48V, and 48VDC?

The chassis reference is the most likely reason for the input polarity
designation. Usually, with no sign given, the assumption is a
negative chassis reference, or "+" voltage. The reason for indicating
a difference is in application; if you are working comm gear,
typically with a -48V power source, and you connect a +48V input
supply (observing correct polarity), everything will be fine until you
mount the +48V supply to a rack that is referenced to the other
equipment. Now you've shorted out the facility power supply, with
both the "+" and "-" output terminals connected to the ground
reference.
 
J

Jasen Betts

Jan 1, 1970
0
Can somebody tell me what difference is between -48V DC, +48V, and
48VDC DC input power supplies?

probably which side of the output is connected to ground.
internally.


Bye.
Jasen
 
R

Rich Grise

Jan 1, 1970
0
probably which side of the output is connected to ground.
internally.

Input, which you'd have seen if you'd looked at the links.

Probably the first one is to run off the Telco batteries,
which are positive ground because of the electrolysis problem
with buried cables.

And frankly, it looks like the other two don't care, since
they're open frame - the difference between the second and
third is only in the nomenclature, because the spec is the
same.

Cheers!
Rich
 
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