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Any microwave techs around...need info

bushwacker

Active Member
Jul 19, 2005
363
3
26
Northern Alberta Canada
I need some info on negative voltage power systems.
I ran into a very complicated power supply system that I had to install. This system was engineered by a guy that designed microwave systems and has alot of the components powered by a negative voltage.

The thing I could not understand is that the ground is just a reference....because of this we were some how able to connect pos 12 volt power onto this same "ground bus" as we did the 24volt negative.
The dc to ac converters in the system were powered by a negative voltage ( meaning neg power wire went to pos input on the converter)
Most of the system is powered by neg voltage...except the 12 volt side. The system does not have a negative ground, it just has a ground reference.

Does anyone have any ifo on negative voltage power supply systems?
 

They are the same as regular power supply systems except the common point, note I did not say ground I said COMMON POINT, is the positive supply rail and not the negative like we are used to seeing.We have become conditioned to thinking that the negative lead HAS to be grounded but that is not the case. Positive ground systems or dual polarity systems are in common use. Dual polarity supply systems have a + lead, a - lead and a COMMON lead.The only hard part about working on something with a negative voltage supply is rethinking current flow directions and transistor biasing. :censored:
 
They are the same as regular power supply systems except the common point, note I did not say ground I said COMMON POINT, is the positive supply rail and not the negative like we are used to seeing.We have become conditioned to thinking that the negative lead HAS to be grounded but that is not the case. Positive ground systems or dual polarity systems are in common use. Dual polarity supply systems have a + lead, a - lead and a COMMON lead.The only hard part about working on something with a negative voltage supply is rethinking current flow directions and transistor biasing. :censored:


Its a very different power supply......I've never built anything like this.
The main power souce is a -24 volts....meaning everthing has -24 volts( measured dmm) going to to the + terminals

But anyways, ground is more of a reference correct?
This enables you to connect both a -24 volt and a +12 volt to the same "ground"?

Connecting a -24 volts to the positve side of a dc to ac inverter sort of screwed me up a bit.
I guess this system lets you have 12 volts, 24 volts and if you get your reference from the right place...36 volts.

But its all about ground as being as "reference point"?
 
You talk about - ground or reference, we used to jump start old tractors or cars with these systems by making contact with their frame work and connecting the other lead to the negative post on the battery, talk about weird.
 
Its a very different power supply......I've never built anything like this.
The main power souce is a -24 volts....meaning everthing has -24 volts( measured dmm) going to to the + terminals

But anyways, ground is more of a reference correct?
This enables you to connect both a -24 volt and a +12 volt to the same "ground"?

Connecting a -24 volts to the positve side of a dc to ac inverter sort of screwed me up a bit.
I guess this system lets you have 12 volts, 24 volts and if you get your reference from the right place...36 volts.

But its all about ground as being as "reference point"?


I believe you are starting to understand it. Everything you posted here is true. (y)
 
You talk about - ground or reference, we used to jump start old tractors or cars with these systems by making contact with their frame work and connecting the other lead to the negative post on the battery, talk about weird.


I don't quite remember that far back but I have been told of lots of horror stories of when vehicles changed over from positive ground to negative ground. The problem came from not checking the two vehicles when jump starting one of them. :oops:
 
I don't quite remember that far back but I have been told of lots of horror stories of when vehicles changed over from positive ground to negative ground. The problem came from not checking the two vehicles when jump starting one of them. :oops:

Thanks for not calling me an old fart in public, Doh! there's my senility kicking in again.
 
Isn't our thinking of + and - backwards?


By that, I mean that positive has a deficit of electrons and negative has an excess?
 
Isn't our thinking of + and - backwards?


By that, I mean that positive has a deficit of electrons and negative has an excess?

DC_current.jpg
 
I did that kind of work for years, it was all 24VDC positive ground, no matter what vendor manufactured the equipment. Neary all telephone equipment is -48VDC, by the way. Sounds like you've figured it out, though.

+12VDC is only one way of doing things...


Rick
 
I did that kind of work for years, it was all 24VDC positive ground, no matter what vendor manufactured the equipment. Neary all telephone equipment is -48VDC, by the way. Sounds like you've figured it out, though.

+12VDC is only one way of doing things...


Rick

Yea...I guess the main idea behind this system is that you can get 12 volts, 24 volts and 36 volts depending on where you take the reference.

The problem is they didn't think of the Dragonwave needing -58 volts. LOL
$25,000 power system that can't power the main backhaul...LOL

I got the rack built up and found a small problem or 2...once those were correctly and redocumented the unit powered up with no probs.

Thanks for the input
 

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