Running 110v ac motor on 220v

Thread Starter

Ronon_Dex

Joined Jan 9, 2024
3
Hi. I was wandering if you can run an AC induction motor designed for 110v , on 220v.
Pls correct me if I'm wrong butI 'm thinking that it should be fine as the speed of the motor isn't really affected by voltage but by frequency so I assume that feeding it double voltage will result in it using half the current.
Staying below max KW limit should ensure that the steel core doesn't saturate and if the enamel on the wires is not absolute garbage , then should handle the higher voltage.

Thanks in advance
 

MaxHeadRoom

Joined Jul 18, 2013
28,670
Double the voltage double the current, You are thinking of a motor that is Designed for 240v when you quote 'half the current'.
If what you think is true, then there would be no need for dual winding motors to cater for dual voltage.!
 

MisterBill2

Joined Jan 23, 2018
18,442
The motor will start and run and then overheat and burn up. All in less than a minute. Unlike a load connected to a higher CURRENT RATED power source, a higher voltage power source will certainly force much more current to flow. And if the over-current is enough to saturate the magnetic material then only the resistance will limit the current and so it will be quite a bit more than twice the input power.
I have seen this happen when co-workers ignored the sign on an extension cord that said "240 volts". First they burned up a shop vac in less than a minute, then destroyed an electric drill in about 2 minutes.
 

Reloadron

Joined Jan 15, 2015
7,514
I have seen this happen when co-workers ignored the sign on an extension cord that said "240 volts". First they burned up a shop vac in less than a minute, then destroyed an electric drill in about 2 minutes.
So someone actually used a sign to indicate that a 120 VAC socket was actually a 240 VAC socket? Gee and I thought we had a 120 volt socket design for a reason and a 240 volt socket design for a reason. I wonder who left more to be desired, the person who placed the sign or the employee who failed to read the sign? Hard to say but I would venture OSHA might have a say. :)

Yes, as has been already said, the motor will burn up. That or trip a breaker.

Ron
 

Thread Starter

Ronon_Dex

Joined Jan 9, 2024
3
Double the voltage double the current, You are thinking of a motor that is Designed for 240v when you quote 'half the current'.
If what you think is true, then there would be no need for dual winding motors to cater for dual voltage.!

”Double the voltage double the current" That applies to resistors and other kinds of motors though like brushed or DC motors. I'm talking about an AC induction motor that always stays at the same RPM no matter the load and draws current proportionally to the torque or lag of the rotor. I don't have an 110v motor so this is purely academic question.
BUT I hooked up a 220v motor to my Variac which was connected to a watt meter and when I decrease the volts , the current goes UP so at 110v it was drawing almost double the current (and not half as a resistor obeying ohm's law would) . So it was trying to draw around 300 watts no matter the voltage coz that's the power it needs to spin without a load I guess.
I can't bump upp the voltage to test it coz the Variac only do so by maybe 10v as it shows 240 max
 

schmitt trigger

Joined Jul 12, 2010
889
You are correct, an electric motor is not a resistor. A motor is a magnetic device which uses ferromagnetic materials. These materials have a maximum flux density, exceed it and it will saturate, and as such the magnetizing current will skyrocket. Literally.

For reasons of cost optimization, the magnetic material is always operated very close to saturation at the nominal plate voltage. Increase that voltage and the high magnetizing current will burn the motor as sure as the sun rises every morning.

Don’t believe it? Go ahead, make the experiment yourself.
 

dendad

Joined Feb 20, 2016
4,471
Not only are motors often designed to run at close to the limits, transformers may be too. I recall watching a transformer cook many years ago. It was a 60Hz rated one. When run on the correct voltage, but at 50Hz, the core saturated and let the smoke out. The inductance is very handy to limit the current but when that "goes away", all that is left is the resistance and that is usually as low as possible for best efficiency.
 

MaxHeadRoom

Joined Jul 18, 2013
28,670
Hi. I was wandering if you can run an AC induction motor designed for 110v , on 220v.
Pls correct me if I'm wrong butI 'm thinking that it should be fine as the speed of the motor isn't really affected by voltage but by frequency so I assume that feeding it double voltage will result in it using half the current.
”Double the voltage double the current" That applies to resistors and other kinds of motors though like brushed or DC motors. I'm talking about an AC induction motor that always stays at the same RPM no matter the load and draws current proportionally to the torque or lag of the rotor. I don't have an 110v motor so this is purely academic question.
BUT I hooked up a 220v motor to my Variac which was connected to a watt meter and when I decrease the volts , the current goes UP so at 110v it was drawing almost double the current (and not half as a resistor obeying ohm's law would) . So it was trying to draw around 300 watts no matter the voltage coz that's the power it needs to spin without a load I guess.
I can't bump upp the voltage to test it coz the Variac only do so by maybe 10v as it shows 240 max
Well you ask a question, you appear to know the answer to. :(
An AC motor current is governed by the inductive reactance of the windings. A 120v-240v motor has two sets of run windings, on 240v, they are placed in series.
Thus increasing the inductive reactance and halving the current.
On a motor where the speed is reduced by just lowering voltage, the slip will be affected and there will be higher current in the rotor which is reflecting in the run windings.




Two winding, double voltage motor:

1704880220777.png
 

Thread Starter

Ronon_Dex

Joined Jan 9, 2024
3
Oh so it's like a transformer then. Not only there's a max power it can handle but also a voltage it saturates at , didn't think about that. Well thanks guys , I was mostly interested in the specifics of why it can't work :)

I don't have a 110 motor but I hooked a 24v-220v transformer to the variac (with a 10 amp fuse) and the watts spiked after about 30v like falling up? a cliff. It went up from 10w to almost 300w by increasing only couple volts
 

MisterBill2

Joined Jan 23, 2018
18,442
OK, so now we have well detailed descriptions of why what some of us explained without enough details.
Just because not everybody can explain something does not mean it is not true. Likewise, just because somebody is unable to understand an explanation does not mean it is incorrect.
 

MaxHeadRoom

Joined Jul 18, 2013
28,670
Oh so it's like a transformer then. Not only there's a max power it can handle but also a voltage it saturates at ,
A induction motor at the point of switch on, appears as a transformer with a shorted turn secondary, it has a Squirrel cage (shorted turns) rotor .
The current in these (squirrel-cage) turns, decreases as RPM increase.

Typical 1ph, dual winding, dual voltage motor.

1704903979581.png
 

MisterBill2

Joined Jan 23, 2018
18,442
Note that many induction motors do not include a capacitor. The addition of the capacitor appears to be to improve efficiency, but the legacy motors mostly do not seem to include capacitors. So there are a great many fractional horsepower motors with a starter switch and no capacitor. They also serve as a transformer as far as operating conditions.
 

dendad

Joined Feb 20, 2016
4,471
The only ways I'm aware of, that a single-phase motor can start without a capacitor is a repulsion-induction type that uses a brush commutator to start, or small shaded-pole types.
Do you know of other ways?
Single phase motors without capacitors have an extra start winding that is switched out of circuit when the motor gets spinning. This is done with a centrifugal switch. Often this can be heard clicking as it starts up and also as it spins down when the motor is turned off.
 
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MaxHeadRoom

Joined Jul 18, 2013
28,670
The commutation of a AC induction motor requires a separate source providing a phase shift to the main/principle winding due to 180° alternating phase which on its own, results in zero rotation.
 

MaxHeadRoom

Joined Jul 18, 2013
28,670
Single phase motors without capacitors have an extra start winding that is switched out of circuit when the motor gets spinning. This is done with a centrifugal switch.
Also done with with a second winding always in circuit providing a phase shift. Mostly seen on smaller motors.
 

petec

Joined Jan 2, 2019
10
I have seen motors that can be rewired for either voltage. Typically open up where the power goes in and see if there is a diagram that shows how to wire it.
 

crutschow

Joined Mar 14, 2008
34,393
Single phase motors without capacitors have an extra start winding that is switched out of circuit when the motor gets spinning. This is done with a centrifugal switch. Often this can be heard clicking as it starts up and also as it spins down when the motor is turned off.
I understand they have an extra winding.
But I believe that extra winding needs a capacitor in series to provide the required phase-shift.
 
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