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high power/amps AC to DC help.

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jesusday

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I have been spending hours on the web looking and can't find what i'm needing...

I am trying to drive a DC motor with a 110v AC wall plug in. The motor seems to pull up to 15 amps under load and is rated at 18v dc.

Is the only way to get a AC/DC ckt to put out 15 amps is through the use of a huge 15 amp transformer ("transformer sets the max amps"), going through a bridge rectifier, a filter capacitor, and then the voltage regulator?
A 15 amp transformer is huge and pricey!!

Are there better ways (AKA smaller or no transformer)... maybe PWM or something. Any help would be amazing
 
Other than a transformer linear type supply you could build or buy a SMPS type supply. Build is not easy either. The 18 volts you need while not totally uncommon is not quite easy off the shelf either. Generally motors don't require a well regulated supply, unless this is a special application. Where did this motor come from and what is your application? How was it previously powered if it was?

Yeah, transformers that will deliver what you want are large and heavy as well as costly but they are available. Building a plain linear non-regulated supply would be the easiest solution. Another solution might be to hack a welding supply?

Maybe someone else has a thought.

Ron
 
15 amps at 18 volts sounds like a common cordless drill motor rating.

What are you defining as huge and expensive?

The simplest method to make a basic power supply for something like that is to get a multi rate 6/12 volt battery charger and reconfigure the output to a full wave bridge rectifier instead of the typical half wave system they normally have.

With a full wave bridge rectifier system and a good sized capacitor the odds are you will hit something close enough to 18 VDC on one of the ranges for the motor to work.
 
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I have a power supply for a laptop. (switching power supply) It is 18V out 5 amp. Fits in the palm of my hand. Very light.
At work I have some 15V 10A switchers that are the same size.

DigiKey.com has hundreds of different types of supplies in the 15 to 18 V range with 10 to 20A output.
 
After hours of looking up what you guys have suggested, I'm liking the SMPS idea and it would be good one to learn about. Does anyone know where I could find the ckt diagram for the ~18V ~300W ckt? I'm finding good info on the SMPS but not any with high amps ckt diagrams.

And I think it might have been from a cordless drill, good call.
Oh and "huge and expensive" = more than this college student (Mechanical Engineering) wants to pay and lug around.

It's good to know that I can buy one if I needed to.
 
what are you planning to use the motor for anyway? application requirements are just as important as power supply requirements.

Most 18v cordless drill motors can pull well over 40 amps at stall so a power supply with considerable overload capacity is necessary if the motor has to do any serious load work.
 
40 AMPS!!! don't tell me that... I was going to put a pulley on it to lift a weight.
I did look up on Dewalt for a 18v drill and they give 350UWO...

"
The Power Rating
A drill’s Power Rating has been used for many years as a tool to design products. It is not until now that it will be used as new way of evaluating a drill’s performance level, and is a direct indication of how fast it will complete an application.

The drill’s Power Rating is measured by its Units Watts Out (UWO), the point where the drill’s speed and torque output are the highest. The higher a drill’s Power Rating, or UWO, the faster it will perform on the jobsite.
"

so I figured I could just gear it right to lift the weight (since speed can be varied some) while shooting for a ckt that puts out 300 to 350 watts.
 
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