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Need advice converting an AC motor to a DC motor Answered

I have a 3.5 hp AC motor I'd like to run on 12 volts.

Any potential problems forseen with this?

What changes would I need to make to the motor other than the 110 plug to a positive and negative battery hookup?

Thanks for any advice and thanks for any help.



Guys, I appreciate the insight and advice, although it's not exactly what I wanted to hear,
it's the truth and that's what I wanted to hear, so Thank you all.

In answer to a few questions, Yes, it needs to produce ALOT of power.
What I wanted to do was use my motor in conjunction with a car battery,
to mount to a gocart for my grandkids.
The cops don't like the noise of their original motor, so I thought IF it was doable,poof,
silent gocart.
On another note, Toga Dan, you said you have done it.
My email is rocket3man@rocketmail.com, could you share some specifics there?

if a motor has brushes and permanent magnets, and you are ok with less power than spec, its easy. Just swap dc for ac at the plug. see my link for circular saw fan.
If motor has brushes, and no permanent magnets, its still pretty simple. Dont expect full power at lower V, however.
hp for gas and elect motors are quite different. 1hp electric may serve the purpose of 5 hp gas. So dont consider power loss to b an automatic dealbreaker if you start with enough hp.
if its an induction motor, I dont know any method to make this work. but I hesitate to say its impossible. in fact, I think it sounds like fun to try.
there are brushless dc motors . and ive seen generators made from induction motors by drilling holes in the armature and gluing magnets there. some combination of these ideas may work.

What do you want to do with the motor? Does it need to produce much power?
Does it have brushes?

Despite those here saying simply "you can't"
I have.

And demonstrated it is not effective. Hence "You can't"

ive run an ac skilsaw motor on dc. just a test. very little speed. I didnt try cutting anything. but, again, that motor has brushes. most larger motors are induction motors. an ac current induces magnetism in an aluminum armature. no brushes. dc wont work here without getting really clever.

I just set this experiment up again. AC skillsaw on 12v cuts single ply cardboard. not much to brag about, but it does run. These motors have brushes, and will run on DC

Your 3.5 hp motor is likely an induction motor. in those, as per iceng's posts, an aluminum rotor has current induced into it by an alternating magnetic feild (from AC) this type won"t work on DC.

If you don't know if your motor has brushes, look at the sides for bulges, or threaded plastic caps which are the access to replace worn brushes.

The armatures are stacked magnetic punching laminations with the squirrel cage of injected molten aluminum or copper... Actually a transformer if you can visualize the assembly.

Be sure to click the pics to view the whole image !


some ac motors have brushes and can be used with dc. Fractional hp motors in my experience. Larger motors are brushless induction motors in mmy experience.

There are a few issues with this - first, the current draw would be enormous. Second, DC motors are made quite a bit different than AC motors. Anyone correct me if I am wrong, but AC motors don't have brushes or a control circuit - they just rely on the alternating current. DC has some sort of control circuit (or brushes) to switch the polarity to the windings. Like I said, I may be wrong, but I am pretty sure that is how it works.

Converting an AC motor to DC motor is almost impossible, and if you were really willing to do so, then it would most likely cost more to convert it than to just buy a big DC motor.

If you need some more help, let me know what the application you need a DC motor for, and I'll see if I can't help out more.


5 months ago

Suffice it to say the first two images are DC motors

To be continued if post sticks ?

DC motor.jpgArmature.jpgSQrotor3.jpgDeepbarModel1.PNG

Compare the armatures and note the solid nature of the AC armature image #3..
Then the AC wire wound field MMF coil image #4 is vastly different then the permanent magnets of the DC machine...

I think the extensive effort to shift out the AC field from the motor shell frame, to be replaced by the guts of the DC machine is far overwhelmed by the ease of simply acquiring an appropriate DC motor...
Even if you had some Secret understanding acquired over a lifelong experience with power compound machines it would no make sense to try..

Please do not equate FAKE ludicrous YouTube vids with the reality of Real the World machine conversions...

Simply put: You can't. For one thing, if it were possible, on 110V the motor will draw roughly 23A, making no allowances for losses.
On 12V, it would draw 230A.

You can't run an AC motor on DC.
And with 3.5 horse asking for proper food even a good inverter is on it's limits, not to mention the battery size to keep it running under load.
If you only have a 12V system available then use a 12V motor - if in doubt at high speed with a reduction gearbox.