Power supply selection

[openthomas]

I have some equipment needs a -48v 3a isolated power supply. I am told it has 'internal Voltage Regulators to condition the internal DC voltages'.

The difference between regulated, unregulated, isolated power supplies ? Should I choose regulated over unregulated or will that be a mistake being I know it is internally regulated already ?

Why -48v ? I should reverse the polarity ?

[Bored@Work]

-48V means it is telco equipment. And it is minus, not plus, because this prevents oxidation and destruction of wires due to electrolysis.

When the manufacturer says you don't need a regulated supply, then you can use an unregulated on. Although a regulated one should not hurt. They should also have specified some limits for the unregulated supply (min and max allowed voltage).

When the manufacturer says it needs to be isolated, then get an isolated one. Which also fixes your earth reference problem "should I reverse the polarity". If the supply is isolated you just need to connect its output correctly. They hopefully have marked the polarity on the equipment correctly. If in doubt, ask them. If still in doubt, open the thing and trace the wiring and circuit.

[openthomas]

Thats helpful Thank You

[robrenz]

Wouldn't the built in regulation need a slightly higher input voltage than 48V to regulate properly? If so you don't want to feed it a regulated 48V.

[Bored@Work]

Wouldn't the built in regulation need a slightly higher input voltage than 48V to regulate properly? If so you don't want to feed it a regulated 48V.

No, there is stuff like SEPIC converters. But anyhow, just because it requires -48V externally doesn't mean it internally runs on -48V. In fact it is unlikely that any modern electronic inside will run on -48V.

[robrenz]

Thanks.  In re-reading the op I see that the 48V was the input voltage spec. not what it was regulating to internally  .