Building a 24v dc power source

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Cadillac

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I'm trying to power up a 3stage vacuum motor that is 24v dc. I'm in need of sourcing,making a reliable 24 volt power source. I don't know enough about bridges and rectifiers to make my own. The motor specs say 25amps so I know it needs to handle that. Is it possible to convert 120 ac voltage easily to 24 dc? The motor is for a vacuum system I'm trying to make for my surface grinder so it will need to be able to be on for lengths of time. Any help would be appreciated.
 
Building you own would probably not be cost effective, you would need a big transformer (120Vac step down), bridge rectifier, fusing, wires, eclosure etc. It would be even more expensive to make it regulated. I would suggest buying a switching power supply which are much more compact and protected from overload.

You can get a new switching supply type 24VDC, probably something in in the 27-35 A range (600-750W). They should be able to run off of 120VAC, most are universal voltage. and are around 88% efficient. I like MeanWell power supplies, good quality and price. See HRP-600-24 below about $110, the RSP-750 is a bit more.
https://www.mouser.com/ProductDetail/MEAN-WELL/HRP-600-24?qs=l0g2inPJSHOJl3uJKxo6pw==
https://www.mouser.com/ProductDetail/MEAN-WELL/RSP-750-24?qs=sGAEpiMZZMsPs3th5F8koCgtkdmauKZkPQnGfuImKxQ=
 
I would go with the switching power supply. Keep in mind though that motor starting current usually exceeds the run current and your choice should make provisions for that. The first Mouser supply mentioned has a potential 135% overload which should be sufficient.
 
I have a stupid stiff 12V supply. Server power supply with a couple wire jumpers to enable it. Needs 220V, but can deliver 180A all day. Of course, it sounds like a jet engine.. :) I believe 24V units are available.
 
If you get really creative, you could rewind a transformer to give the 24 volts you need. The first, and most important, step would be "does it need regulated power"? It sounds like it doesn't, what scanty description you give. Like a marine or truck electrical system. Or HVAC system...... A good source for me is a high voltage transformer from a dead microwave oven. It doesn't take a lot of electrical knowledge, just a lot of work and being careful. If it must be regulated, just buy one, they're not that expensive.

Using a hacksaw, remove the high voltage winding but leave the line volage winding. Use some sort of insulating layer to protect the wiring from the core. Milk jug plastic will work. Fische paper is the correct item but may be hard to come by. Cardstock from a shoe box will do if you can't find something better. The nice thing about the microwave transformer is that if you screw up and scratch or cut the wrong wires, just chunk it and start over.

Take a piece of AWG 14 or AWG 12 and take a half dozen wraps on the core. The exact number will vary a turn or two. Read AC volts and shoot for 21 volts(+/-) or so. DC voltage will actually be somewhat higher. Now, that gets into electrical theory and does get complicated. Just shoot for a couple of volts AC less that what the desired DC is.

The "electric brick" you need is a bridge rectifier. They are available for 30 to 40 amps at 300 volts for a couple of bux. Some Chinese suppliers for less. Some US suppliers for more. Under $10 though, anywhere. About 1-1/4 inches square, 5/16" or so, thick. With four 1/4" stabs sticking up, and usually with a 5mm or 3/16" hole in the middle. A heat sink isn't necessary at your ampere rating, just a way to mount the brick. The metal is not hot.

I highly recommend you use the quick disconnects that fit. They're cheap enough... ... Look for the two connectors that have the symbol (~) on opposite corners. Connect those to the transformer. The other two, (+) and (-) are the DC lines. Sometimes there is only a corner notched or a paint splotch to indicate the (+) line.The diagonal opposite is the (-) and the two others are the AC, the two (~).

Fuse the line side about 5 amps, every one I've ever dealt with was 6 amps or better. So with 5 amps, you're safe. Rig a line cord, switch, and some sort of enclosure and you have an unregulated 24 volt supply.

Bill Hudson​
 
You said it well Bill Hudson.:encourage: I have done the same using old television transformers some of which are pretty heavy duty and still not
that hard to find. An older colored TV with tubes is where you can find these transformers. It's also environmentally friendly since
it would be recycling at it's best. A filter can be added to the supply by adding a couple hundred or more microfarad
electrolytic capacitor across the output for voltage stabilization and ripple control. To be prudent, I would mount the bridge rectifier
on a suitable heat sink to keep it safe from overheating.
 
I thank everyone for your responses. I am familiar with mouser electric thanks. I would like to learn how to build the power source. I seem to be building a lot of things that need its own power supply so I need to start sometime. I have many transformers and electronic parts. I’ve seen people make a power supply out of a computer power source. Would that have the right amperage I believe it has 24v?
The one reason why I don’t want to drop 100 bucks on the power source is that I’m still in the experimental stage of the vac system and I don’t know if the motor I have already will be sufficient for the task.
I’m gonna scrounge up some parts and see what I can do I’ll keep ya posted thanks.
 
Hi Cadillac, I too was wondering if your 24 volt motor would be suitable- maybe a 120 volt AC motor would be better- just plug it in.
mark
 
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