[Milsurplus] 24 volt 40 amp switchers

[Peter Gottlieb]

Those power supplies may be difficult to get going on 120 volts single phase.  
Where I work we have a large amount of 480 volt 3 phase input VFDs and I wanted 
to make them into 400 Hz 3 phase supplies but found that while it was easy to 
bypass the missing phase detection and get them to run on single phase it was 
more difficult to get them to run on the lower voltage.  Even changing over to a 
doubler (like used in computer switchers) only gave about 350 VDC on the bus and 
that wasn't enough as they were expecting nominally twice that.  I thought at 
least I could run at reduced output power; the transistors are the limit based 
on current, but they are very compact surface mount designs and you can't get 
the schematics.  If you could trace it out, I'm sure there is some resistor 
divider to a sense circuit that could be changed.

Anyhow, a lot of time devoted to do this when a 120 volt single phase input VFD 
could be found inexpensively.  Probably the same for those switchers.  However 
if they are designed to run in current limit (not foldback or protect mode) 
continuously then they would make good candidates for battery chargers, like the 
Iota supplies.

Do you think broadcast TV has a future?  With the penetration of broadband 
digital everywhere and satellite, might the move be to reclaim the broadcast 
spectrum for more wireless digital devices?

Peter
KB2VTL


On 1/27/2019 1:17 PM, Ray Fantini wrote:
>
> I have a bunch of MGV PH1003-2440/RS 24 volt 40 Amp switching supplies from a 
> analog television transmitter that I am junking. They are adjustable from 24 
> to 31 volts and were designed for continues operation in television service.
>
> The bad news is that they were designed for three phase 340 to 460 Volts AC 
> input. Have not tried it yet but wanted to see if they will work from signal 
> phase 408 being modern switching supplies have no transformers or anything 
> like that on the input side. They just take the incoming lines and run them to 
> a huge bridge rectifier and feed that to the switching circuit. I did try one 
> on 208 but it did not start up.
>
> If anyone wants one to play with you can have one for $20 each plus shipping.
>
> Expect to have a bunch of linear regulated 24 volt supplies from a from a 
> Comark transmitter as soon as I get permission to star junking that, you may 
> be unaware of it but the television industry is going thru changes unlike 
> anything in the past where an entire fleet of analog and high channel digital 
> transmitters are all being junked. At one site I work at we have the remains 
> of the analog 60 kW transmitter all over the parking lot at another the 
> solution was to disassemble it in place and get rid of it that way.
>
>
> Ray F/KA3EKH
>
>
>
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