I'm thinking of converting a 12vdc car radiator motor to use household outlet which is 220-240vac.

I already have the diodes to convert ac to dc.

What capacitor should I use, is 250v safe? What should be the minimum capacitance? I want to keep the cost to a minimum because this is just an experiment.

The motor has 12-segment commutator which I think must be replaced with 24-segment. Is this correct?

How to calculate the wire size and number of turns?

In case you wonder why make the conversion:
First, they run quieter than universal motor. Can be used inside the house without the wife complaining about the noise.
Second, they're easy to find because they are usually thrown away as repairing them sometimes cost as much as new units.

 

Hello,

Why not buy a 12 Volts powersupply?
https://www.makerlab-electronics.com/products/12v-12a-switching-power-supply-150w

Bertus

 

Hello,

Why not buy a 12 Volts powersupply?
https://www.makerlab-electronics.com/products/12v-12a-switching-power-supply-150w

Bertus

I already have both linear and switching.
I want to see if it's possible to eliminate power supplies and run the motor from the wall outlet.

 

Hello,

That is not an easy task.
Have a look at the links of the following page about DC motors:
http://educypedia.karadimov.info/electronics/motordc.htm

Bertus

 

Hello,

That is not an easy task.
Have a look at the links of the following page about DC motors:
http://educypedia.karadimov.info/electronics/motordc.htm

Bertus

I have some experience rewinding power tools and appliance motors mostly electric fans and washing machine motors.
I understand the basics but I'm not an engineer and the literature form the those links are far too advanced for me. Vector diagrams, sine, cosine and all those calculations are foreign language to me.

My rewinding experience is limited to re-creating the original windings but I've never done any conversions.

My understanding is that there is a limit to the amount of voltage for each commutator segment so that 220v motors have at least 24 segments.

What I'm not sure of is the exact number of turns and wire size, but looking at universal motors they have between 100 to 130 turns per coil. Wire size is something around 27 to 29 AWG. I could play around those values but at the cost of time and money.

So I'm asking for help if anyone knows how to make wire calculations instead of doing trial and error.

 

Have you tried running the Universal motor on 230vdc DC?
Maybe a lot quieter??

 

Have you tried running the Universal motor on 230vdc DC?
Maybe a lot quieter??

No, not yet. But that's a very good suggestion that I'll try.

Anyway, I still want to try the conversion because I often see these radiator motors thrown in car shop junk pile. They're sold to junk dealers for melting/recycling and it seems no one gave thought how to re-purpose them.

 

Let me make the question more simple. Let's just say I want to use a 12v motor from a car to a lorry which has 24v?

How to convert 12vdc motor to 24vdc?
How to calculate the number of turns?
What wire size to use?

 

Rewinding an armature is a very big deal because it needs to be perfectly balanced and it needs to resist the force on the windings from spinning. And you would need to replace the commutator which would be a huge effort, and rather expensive.

I am thinking that the 12 volt PM fan motor is much quieter because it is not spinning nearly as fast as most cheap universal motor spin. Certainly the automotive motor is much better quality, no question about that. What would the application be for the modified motor??

 

What would the application be for the modified motor??

If motor comes with reduction gear such as windshield wiper, can be used as winch or to power scissor jack.
Can be a substitute for Dremel rotary tool.
Can be grinding wheel or sharpening wheel

There could be more applications but that's all I could think of for now.

need to replace the commutator which would be a huge effort, and rather expensive.

Actually, the motors were thrown away due to worn-out commutators. I have 3 of them and the windings are all ok (but they are for 12 volts).

Price for a replacement 24-bar commutator is a about 3 USD.

 

Usually there is an armature segment for each commutator segment, so that would be a challenge to change. And I had no idea that commutators could be purchased that cheap.
Presently I have a serious 120 volt universal motor from a leaf blower that claimed 15,000RPM. But it has one slightly loose commutator segment. A poor quality motor it seems. It runs but on 120 volts there is spark most of the way around the comm. So the whole thing was scrapped.

 

commutators could be purchased that cheap.

https://www.aliexpress.com/item/325...ZXHphNTS&utparam-url=scene:search|query_from:

This would fit the motor for the project, although at that price the quality is questionable. But for this experiment it's good enough.

 

Usually there is an armature segment for each commutator segment, so that would be a challenge to change.

I think you mean each commutator segment corresponds to a slot.
So, yes, it's a challenge.

This one has 12 armature slots with 12 commutator segments. My idea is to split the coils, one for each segment and 2 for each slot.

The other challenge is the number of turns because converting 220ac will raise the dc voltage , which means more turns will be required. The power tools that I worked on have somewhere between 100 to 130 turns per slot for 220v. Maybe add 50% more turns will work?

 

If you want to have the same motor power when it is running,then the current will need to be 12/220 of the original current. But then I see a possible problem if the DC is filtered at all, which is that the caps will charge up to some value closer to the peak mains voltage, not the average 220 volts. So the actual voltage would be quite a bit more.

So while the greater inductance due to the much greater number of turns will tend to limit the current some, and certainly the greater resistance because of the smaller wire size will also tend to limit the current, the actual power dissipated in the motor might be too much for the insulation.

What all of those words lead up to is that there is a great deal of calculation required to determine the wire size and the number of turns per pole for rewinding this motor to run on rectified 220 volt mains power. And unfortunately for the problem, my education in electric motor design calculations is very limited. And almost all of the industrial machine designs used standard induction motors that only needed to be correctly selected for the application.

But probably another participant has either the experience or the textbook to provide the answers.

 

If motor comes with reduction gear such as windshield wiper, can be used as winch or to power scissor jack.
Can be a substitute for Dremel rotary tool.

A Dremel is principally a Universal (High RPM) motor IOW it operates in a run-away condition like practically all Universal - series field motors.
RPM governed by load !

 

the actual power dissipated in the motor might be too much for the insulation.

Now that's something I hadn't thought of, thank you!

 

A Dremel is principally a Universal (High RPM) motor IOW it operates in a run-away condition like practically all Universal - series field motors.
RPM governed by load !

Yes, but I never run it at such high speed. My rotary tool has 10 speed settings and always use #2. Never ever used it exceeding #3.

 

My understanding is that there is a limit to the amount of voltage for each commutator segment so that 220v motors have at least 24 segments.

There is no correlation between comm segments and voltage, The more segments, (poles) the smoother the rotation, e.g. High rotor pole counts are used on servo motors etc.

 

The motor in this discussion is not a universal motor. IT IS a permanent magnet DC motor. That means that the field strength does not increase with the load. It also means that there are no field coils to drop the voltage for the armature.
So once the current for the same power at 20+ times the voltage is calculated, the rewind wire size can be determined. At that time it should be possible to see if that many turns will fit in the existing armature slots. THAT could be the show-stopping issue.

 

The motor in this discussion is not a universal motor. IT IS a permanent magnet DC motor.

I was aware of that, I was referring the OP to his comments in post #10 ref: Dremel tool.