# ac/dc inverter



## jjdrees (Oct 8, 2008)

So heres what I got, We have an OLD crane that ran on DC, well we havent had dc in our pplant for a number of years. Now they want there crane to work again. Ive recieved a couple quotes to change everything over to AC. this is an option but an expensive on. what Im wanting to do is set an AC to DC inverter. and just run everything the way its always run. but all of my upply houses are having a hard time coming up with an inverter that I need.
480V AC to 125V DC 100A
What Im wondering is why is it so hard for them to come up with one of these and does anyone know where to buy one??


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## wildleg (Apr 12, 2009)

I found a link for a solar one - thing is, I don't know if you can run these backwards ? http://www.solardesigntool.com/components/inverter-grid-tie-solar/Solectria/PVI%2082KW-480/specification-data-sheet.html

(I think what you need is a converter, not an inverter)

call the crane company. maybe they can help you out. (do they still exist ?)

if you can't find what you need, you could try calling a transformer company and see if they can point you in the right direction. Temco carries a lot of stuff, maybe they can help you http://www.electricmotorsale.com/


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## Skipp (May 23, 2010)

Can't you find a DC drive unit that will work?


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## brian john (Mar 11, 2007)

jjdrees said:


> So heres what I got, We have an OLD crane that ran on DC, well we havent had dc in our pplant for a number of years. Now they want there crane to work again. Ive recieved a couple quotes to change everything over to AC. this is an option but an expensive on. what Im wanting to do is set an AC to DC inverter. and just run everything the way its always run. but all of my upply houses are having a hard time coming up with an inverter that I need.
> 480V AC to 125V DC 100A
> What Im wondering is why is it so hard for them to come up with one of these and does anyone know where to buy one??


 
Well you will not find a AC to DC inverter, but you can find a AC to DC rectifier.


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## frenchelectrican (Mar 15, 2007)

Or you can go with MG { motour-Generator } that may work as well so that one of few options you can go.

Merci.
Marc


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## drsparky (Nov 13, 2008)

Look into company's that sell large battery charging systems for a rectifier. If not Marc's idea of a AC motor turning a DC generator would work well also.


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## Joshua (May 13, 2009)

You really have two options in this, the first is a transformer + rectifier (rectifier is just one-four diodes depending on if you want halfwave or fullwave - fullwave is better, cleaner DC) you will need to size the transformer and rectifier accordingly. As mentioned, there are probably circuits like that for battery charging that could be used. Another option is something akin to a switch mode power supply using thyristors (SCR's) which don't require a transformer but do require a trigger circuit. These work pretty much like a full/half wave rectifier but the conduction time can be controlled so the voltage can be stepped down without a big expensive transformer. I am sure you can find something for this as there are plenty of circuits used for battery backup systems like this and circuits like this are used for HVDC transmission lines.


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## oldtimer (Jun 10, 2010)

jjdrees said:


> So heres what I got, We have an OLD crane that ran on DC, well we havent had dc in our pplant for a number of years. Now they want there crane to work again. Ive recieved a couple quotes to change everything over to AC. this is an option but an expensive on. what Im wanting to do is set an AC to DC inverter. and just run everything the way its always run. but all of my upply houses are having a hard time coming up with an inverter that I need.
> 480V AC to 125V DC 100A
> What Im wondering is why is it so hard for them to come up with one of these and does anyone know where to buy one??



I M O the first thing to do is to determine how much D.C. amperage you need.......How many motors...and how much horsepower ? Years ago I worked on mining equipment that was fed with A.C. This equipment had a big M.G.set. As previously mentioned.. Motor Generator. This unit supplied the D.C. This can be done, but it may be costly.


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## frenchelectrican (Mar 15, 2007)

There is one compaine that it is in USA they do make M-G set up.

Volia ici link 

http://www.electricpowergenerator.com/motor-generator-sets.html


Merci.
Marc


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## Southeast Power (Jan 18, 2009)

We would have to assume that you have the transformer in place that will get you to 125 volts. 
I know that you can find the 100 amp diodes (think of a welder), how much of a tinkerer are you?

Maybe start here...
http://www.aliexpress.com/product-g...erter-3-Phase-DC-SKBPC-1600V-wholesalers.html






.


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## oldtimer (Jun 10, 2010)

jjdrees said:


> So heres what I got, We have an OLD crane that ran on DC, well we havent had dc in our pplant for a number of years. Now they want there crane to work again. Ive recieved a couple quotes to change everything over to AC. this is an option but an expensive on. what Im wanting to do is set an AC to DC inverter. and just run everything the way its always run. but all of my upply houses are having a hard time coming up with an inverter that I need.
> 480V AC to 125V DC 100A
> What Im wondering is why is it so hard for them to come up with one of these and does anyone know where to buy one??


 Try VISICOMM INDUSTRIES.


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## gold (Feb 15, 2008)

I cant imagine what a rectifier that big would look like, wouldnt it have to have really huge heat sinks to dissipate all that heat? Plus the transformer.. thats gonna eat a lot of real estate.

I'm betting changing over to an ac motor would be more economical, or as someone else said using an ac motor to turn a generator, but I think that would throw any kind of reasonable efficiancy out the window.

If its that old what kind of condition is the wiring in anyway, once you meg it you may find the lot of it needs to be replaced anyway.


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## Paulusgnome (Mar 28, 2009)

It may not be as big as you might think. At one time a couple of decades back, all telephone exchanges used big, fat linear rectifier sets which were usually so big and heavy that they had to be housed in the basement of the building. 

Then, in the late 1980's, switchmode electronics shrunk the rectifiers down to the point where they could be rack-mounted in the switchroom.

Likewise, the rectifier needed to run this crane would once have filled a whole room, but a modern switchmode design will fit in a closet-sized space.

It won't be a cheap exercise, but. Looks like a custom design.


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## nitro71 (Sep 17, 2009)

Whichever route you go as far as using DC I'd think you'll have to take into account in rush current and whether the supply gear can handle it.


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## Electric_Light (Apr 6, 2010)

Most new install elevators use three phase motor with a VFD, but plenty of existing installs still use DC motor fed from motor generator. 

You can get DC from motor-generator or a static converter, but when you're using a static converter, the mechanical load reflects directly onto power-line, because it doesn't have any reservoir. Motor generator acts like a flywheel reservoir. 

Here's a great article:
http://www.mceinc.com/DMS/Article%5CTom%5Cstatic_drives.pdf

I think your best bet is to get a used or a rebuilt MG set meant for an elevator. They don't have any 125v, but they have 480v ac to 160v DC in various sizes. Call them(or whoever you chose) and ask.
http://www.elevatormotor.com/main.htm (click on MG set)


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