pulse width modulated inverter

[malken00]

120vac to 48vdc

Hey all,

I am pretty new to doing things like this. We received a router from another location that was using -48VDC power to it. Unfortunately, we can't replace the power supply, only somehow supply -48VDC from 120VAC normal household power.

Is there a way to do this? Can I simply buy a unit that does this already, and wire it in? I'd really like to use this unit, and not just let it collect dust

Thank you all in advance!

 

[davidgrm]

negative 48vdc power supply

48 volt dc from 120 volt ac should not be a problem You need to establish how much current the router will draw and then make sure that the power supply that you purchase is rated higher than the required current.

 

[malken00]

Re: 120VAC to -48VDC?

Hey David,

Thanks for the quick reply. I actually don't need a power supply, simply a converter to be able to go from 120vac to -48vDC (it is negative 48vdc, not positive) Like I said I am brand new to this, does this just mean I can use a +48vdc and reverse the polarity?

Here is the picture of the plug in..

Beside the switch reads:
-48VDC
±20%
0.5a

and then above each post reads from left to right:

RTN ... <ground symbol> ... -48Vdc

 

[davidgrm]

Re: 120VAC to -48VDC?

you can just reverse the polarity. Are yuo sure that it is a negative sign and not an AC sign? I cannot see such detail in the picture. AC = ~. It is quite unusual for a system to specify -48 volts unless it is part of some bigger system that has other voltage levels as well

Added after 1 minutes:

just too another look at the picture - it looks like they are showing + then - then 48 volts. Perhaps the 48 volts is just a bit close to the - sign for the conector?

 

[mvs sarma]

120VAC to -48VDC?

-48V working systems are common. . The best is t0 see the spec of the equipment . Try to use 4 nos of 12V 7 ah batteries in series. Have a stepdown transformer like 120Input and 24-0-24 output, if readily availabale. you may connect bridge rectifier across 24 and 24 - not using centre tap. you are likely to get (48*1.414)- 1.4V=67V or so now you have to use Linear regulator to get 48V for the load.
Also you may have to charge the battery by sitable circuitry from the same output perhaps.

 

[jeyaraman]

Re: 120VAC to -48VDC?

Hi,

When converting from one voltage level to another, a PSU is required. In your case, the internal 48Vdc PSU will be one and the external 120Vac to 48Vdc is another.

-48Vdc is very common in telecommunication environment.

When you know current consumption at 48Vdc, find a PSU [Off Shelf] which has isolation built into it, which will avoid ground loops later. Since, it is connected to a router, i assume the connecting ports are isolated. If they are not so, it will create ground loops and spoil the weaker circuitry.

what type of battery are you planning to charge from the 120Vac PSU?

jeyaraman