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

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

Reply to
janetnkansah1
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The difference is 96 volts. Is this a trick question?

Reply to
Kaz Kylheku

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:

I can't help you there. If you're only making one, Small 48V power supplies are very common and cheap:

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

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

Reply to
Sjouke Burry

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

.... Phil

Reply to
Phil Allison

Well spotted. Does seem a bit odd.

Reply to
Cursitor Doom

On Thursday, January 21, 2016 at 12:13:52 AM UTC-5, snipped-for-privacy@gmail.com wro te:

volts.

s power supply at 3A. thanks

Think of voltage as pressure. 5 pounds of pressure pushing electrons or 5 p ounds of vacuum pulling electrons is the difference between 5 volts negativ e and 5 volts positive. This is not a perfect analogy but it will get you t here. Current , amps , is the number of electrons moving. Wattage is amps t imes 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. Als o there is no such thing as a dumb question.

Reply to
John Heath

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.

Reply to
janetnkansah1

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.

Reply to
Ralph Mowery

... 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.

Reply to
Kaz Kylheku

96 Volts

Jamie

Reply to
M Philbrook

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.

Reply to
Ron D.

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.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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