# Is this practical?

I've got a 120v, 12a ac motor and ice been told that it would move with as little as 12v, but is there a practical way to run this off a 12 battery system? I took this from a near-dead vac (wasn't the motor that was going to kill it) and want to possibly turn it into a short of riding toy for my kid.

Thanks for any constructive criticism or info.

and ice been told that it would move with as little as 12v,

some one has been having you on.

is there a practical way to run this off a 12 battery system

Well I don’t know if you consider this practical but you need to build a circuit called an inverter to turn 12V DC into 120V AC with a 12Amp capacity. That is an output power of 1.44Kw.
Assuming 100% efficiency (which you won’t get ) will require a 120 Amp drain from your battery.

So no it is not very practical.

Then connect the +12V leads to your car battery and plug the 120vac plug into the outlet on your store bought inverter. People do it every day. They are used for running camping equipment and charging laptops and cell phones on campling trips where you are not supposed to bring such items. XD

Hi.

It is not practical at all.
There are fundamental differences between AC and DC motors.
The motor is an AC version, and you want to use it with the DC from a car accu.
So you'd need to create an AC out of the DC, which is possible.
But then you say the motor is 12A @ 120 Volt.
That would be 120 A @ 12 volt.
Add some 15 % conversion loss for the DC to AC conversion if you manage to do it at the most effective way available.

You need to multiply the voltage and current to get a power figure, that would be 1440 Watts in this case.
That is what your motor expects, but it is very unlikely that it can handle 120 A @ 12 volt, as there are more physical laws that need to be taken in consideration.
There is much more to be said about this, but i think you must get the point by now.

In short:
Forget it.

Lots of AC appliances use universal motors which also work with DC. You can easily identify them because they have commutators.

However I can't see a 120v motor doing much with only a 12v supply.

...R

Ohms Law
P = I x V
Prms= Irms x Vrms
= 12A x 120vac
= 1440 W rms
= 2036 W peak instantaneous

So yes you would need a 1500 W inverter and it would probably get pretty warm because the power dissipation at the peak is 2000W but it is only for a couple of mS before it decreases. You would need good ventilation for the 1500W inverter.

All this talk about running an ac motor on dc without the inverter is nonsense.
If don't believe it then stop wasting our time and just go hook it up to your car battery and report back with the results.

Robin2:
Lots of AC appliances use universal motors which also work with DC. You can easily identify them because they have commutators.

However I can't see a 120v motor doing much with only a 12v supply.

...R

Well you forget the inductance of the field windings is the main limitation of field
current, putting 120V DC across a 120V ac universal motor would be a spectacularly

But yes mains universal motors aren't very universal in practice.

So, OP, what kind of motor is it? A photo of the identification plate if it has
one would be good. If its an induction motor there's no dice at all, BTW.

MarkT:
But yes mains universal motors aren’t very universal in practice.

As far as I know all my mains electric tools have them.

…R

The "universal" tag means both AC and DC, but in practice all universal motors are
tuned to 50 or 60Hz mains and not designed to work off DC. The impedance of field
windings is the issue - for DC it must be all resistive, for AC the inductance usually
dominates.

Well you forget the inductance of the field windings is the main limitation of field
current, putting 120V DC across a 120V ac universal motor would be a spectacularly

FYI, for those non-engineers out there, 120vac doesn't actually mean the load runs on 120 V. That is only the RMS value. The actual waveform for a 120 vac wall power source is SQRT(2) * 120 vac = 169.7 V Peak or 339.4Vac Peak to Peak.
This means that the load (in this case the motor winding) would see 170V peak on the positive phase and -170 V peak on the negative phase. While putting 120V dc on a 120V ac motor might be a a spectacularly bad idea, it would not be as spectacular as putting 170 V dc
on it.

raschemmel:
While putting 120V dc on a 120V ac motor might be a a spectacularly bad idea, it would not be as spectacular as putting 170 V dc
on it.

I wonder if the experts are out-running the OP?

The original question was whether a 120vac motor (which may or may not be a universal motor) would run on 12v - probably not.

Then @Chagrin posted a link where someone claimed to run a universal motor with 60v or so.

...R

If its an induction motor its all moot - but since the forum's all searchable its still
potentially useful to someone in the future... Its a shame there isn't a way to automatically

He mentioned the motor came from a vacuum cleaner ("near-dead vac"). An induction motor would be too large, heavy, or expensive for such an application.

Chagrin:
He mentioned …

HE seems to have lost interest in the matter.

…R

This is not the first time we have beat someone senseless with logic.

I don't see how that video applies to this post since we have no information on the OP's motor .
This is all he said. You cannot say that it was a universal motor with what he told us .

I've got a 120v, 12a ac motor

Do you see any part number or datasheet or link to some specs ?

It was already covered that induction motors won’t work with DC current. But whether or not you’ll find an induction motor in a vacuum cleaner should just require a little common sense.

Point taken. Not likely. Your right. I forgot you mentioned this...

He mentioned the motor came from a vacuum cleaner ("near-dead vac").

I just didn't know what I was supposed to get out of that video since he didn't show the motor.