what is the difference btn -48volts and 48volts power supply?

[janetn...@gmail.com]

l wish to know the difference between negative 48 volts and the normal 48 volts.
Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks

[Kaz Kylheku]

On 2016-01-21, janetn...@gmail.com <janetn...@gmail.com> wrote:
> l wish to know the difference between negative 48 volts and the normal
> 48 volts.

The difference is 96 volts. Is this a trick question?

[Jeff Liebermann]

On Wed, 20 Jan 2016 21:13:48 -0800 (PST), janetn...@gmail.com
wrote:

>l wish to know the difference between negative 48 volts and the normal 48 volts.

Telecom power is postive ground or -48VDC. A "normal" 48V power
supply has both the - and + terminals floating from ground. You can
ground the + terminal and it will possibly make a suitable -48V
telecom power supply:
<http://www.sinrace.com.cn/en/knowledge-base/636-why-telecom-power-supply-has-48vdc-power-supply.html>
<http://www.erlang.com/forum/erlang/thread.htx?thread=927>

>Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks

I can't help you there. If you're only making one, Small 48V power
supplies are very common and cheap:
<http://www.mpja.com/48-Volt-Power-Supply/products/544/>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Sjouke Burry]

On 21.01.16 6:13, janetn...@gmail.com wrote:
> l wish to know the difference between negative 48 volts and the normal 48 volts.
> Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks
>

Study electronics for a year or two, an the answer will
come to you.

[Phil Allison]

** Those two requests ought not be in the same post from the same person.



.... Phil

[Cursitor Doom]

Well spotted. Does seem a bit odd.

[John Heath]

On Thursday, January 21, 2016 at 12:13:52 AM UTC-5, janetn...@gmail.com wrote:
> l wish to know the difference between negative 48 volts and the normal 48 volts.
> Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks

Think of voltage as pressure. 5 pounds of pressure pushing electrons or 5 pounds of vacuum pulling electrons is the difference between 5 volts negative and 5 volts positive. This is not a perfect analogy but it will get you there. Current , amps , is the number of electrons moving. Wattage is amps times voltage so a voltage of 48 at 3 amps , full throttle , is 48 V times 3 A for 144 watts. Write this down and memorize it and Bob's your uncle. Also there is no such thing as a dumb question.

[janetn...@gmail.com]

On Wednesday, January 20, 2016 at 9:13:52 PM UTC-8, janetn...@gmail.com wrote:
> l wish to know the difference between negative 48 volts and the normal 48 volts.
> Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks

Thanks a lot Jeff you've actually given me a good understanding. so I can build a normal 48 volts supply and ground the positive terminal instead.

[Ralph Mowery]

<janetn...@gmail.com> wrote in message
news:1fd0baa9-59c9-42d1...@googlegroups.com...

That is right. Just build any power supply that will meet your needs and do
not ground any of the components in it. That isolates it from the chassies.
The ground the positive output instead of the negative output.

While not usually as high as 48 volts the 3 terminal regulators are made for
the negative as well as the positive output. The leads are sometimes in
different places and most of the diodes and capacitors are just reversed.
That is often the way unregulated supplies are made.

[Kaz Kylheku]

On 2016-01-21, John Heath <heath...@gmail.com> wrote:
> On Thursday, January 21, 2016 at 12:13:52 AM UTC-5, janetn...@gmail.com wrote:
>> l wish to know the difference between negative 48 volts and the normal 48 volts.
>> Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks
>
> Think of voltage as pressure.

... and as you gradually ease into thinking of voltage as pressure,
relax and concentrate on supressing that strange feeling that makes you
want the schematic for a "regulated power supply", even though you don't
know WTF that means.

[M Philbrook]

In article <b4ffde5b-2847-4ff5...@googlegroups.com>,
janetn...@gmail.com says...

>
> l wish to know the difference between negative 48 volts and the normal 48 volts.
> Also l will be glad if a could have a circuit for a regulated -ve 48 volts power supply at 3A. thanks

96 Volts

Jamie

[Ron D.]

It turns out that -48 V is less corrosive. that's why it's used.

the voltage is "relative". Lots of wall warts might have a coaxial power connector. Some may have center positive and others the outside positive.
How you hook it up depends on the circuit.

A -48 supply may indeed have the positive side grounded, but it may not.

A +-12 V supply has a common point and when you measure to that common point you get the +12 and -12 voltage. But that common point may not yet been grounded.

An isolated 48 V supply can generally be connected either way.

[Jeff Liebermann]

On Thu, 21 Jan 2016 09:32:53 -0800 (PST), janetn...@gmail.com
wrote:

Yes, that will work. However, when specifying a power supply, you
also need to deal with over-current limiting, fold back power
dissipation, transient response, stability with various loads, line
ripple, power line isolation, and EMI/RFI emissions. Any or all of
these might be important for running your unspecified device.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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