Just curious how electric motors work, specifically DC motors.

[LT72884]

Just curious how electric motors work, specifically DC motors. I have some questions i would like to understand better.

do the windings of a motor determine the required voltage to power it?

Can a 110 volt ac motor be powered by a 12 volt dc battery without an inverter?

Can a 110 volt dc motor be powered by a 12 volt dc battery without an inverter? if not why? what does it do to the motor? Wont the lower voltage cause the motor to run slower? or will it actually damage the motor?

Thanks guys

 

[NobodySpecial]

AC and DC motors are fundementally different, you can't run an AC motor form DC and v.v.

The power of a motor depends on the number of loops in the winding and how much current is flowing through it, the current is determined by the resistance and the voltage applied. If you put too much voltage across the motor then too much current will flow and too much heat will be generated in the coil damaging it.
Too little voltage will mean too little current flowing and so not enough field to turn the motor

 

[LT72884]

Ok cool, the reason i ask, i am making a school project and the windshield wiper motor we have might not be able to do the job. I found a tread mill motor that is a 110 volt ac motor and was hoping i could hook it to a 12 volt car battery. But once i realized it was ac, i knew my answer. So let me ask you experts this,

If the 110 volt motor was DC, could i just hook it right up to a 12 volt battery and possibly get some turns out of it? it just needs to be enough to push 50 pounds on wheels.

Thanx

 

[NobodySpecial]

If the 110 volt motor was DC, could i just hook it right up to a 12 volt battery and possibly get some turns out of it?

Possibly but probably not - high power DC motors are a different design than low power ones and it probably wouldn't work. Also remember that voltage and power aren't the same thing. The 12V starter motor in your car is quite powerful but the 110v AC motor in a ceiling fan isn't

it just needs to be enough to push 50 pounds on wheels.

Thats a trickier question - it's not the weight of something you need to be concerned about, it's how much force you need to move it.
For example a one horsepower horse can move a 70ton canal barge on water easily if a little slowly but you probably need a few 10s of horse power to get your car moving

 

[sophiecentaur]

"would it work?"
Up to a point but the power is something like proportional to the square of the voltage - that would mean that you would only get 1% of the power - if everything else were kept proportional. That 1% might not even overcome the friction!

As a matter of fact, the treadmill motor could very possibly be an AC/DC type - with a field winding rather than a permanent magnet. You could recognise one instantly as it would have plainly visible bundles of coils of wire on the stationary part of the motor and a 'commutator', which is a set of brass 'teeth' around a cylindrical bit on one end of the inside of the motor. It should have a marking on it, in any case. Google images of ac/dc motors and you'll see what I mean.
It would do no harm to connect it up and see. It may rotate a little bit and that could make your day, possibly. Remove power if there is a dark brown smell, of course.
Good luck.

 

[Sakha]

There are many DC-AC converters designed specially to run from a 12v car battery. I find it really usefull to have 110v AC outlets in my car. It costed me around $30 for a 400W inverter.

 

[sophiecentaur]

There are many DC-AC converters designed specially to run from a 12v car battery. I find it really usefull to have 110v AC outlets in my car. It costed me around $30 for a 400W inverter.

Yes- a possible solution but 110V is introducing needless risk of shock into a simple experiment and 12V motors are readily available at that sort of price or cheaper.

 

[LT72884]

The tread mill motor has a bunch of stationary coil windings. i will check to see if it a dc type as well. Taht would be awesome if it was. might work for me project stair climber!

thanx guys

 

[sophiecentaur]

Just check to see if you can see a commutator, too.
It should say AC/DC.
OR - there may be two carbon 'brushes' in holders, which bear onto the commutator. Often there are two massive screws (pointing in, radially) holding the brushes onto the commutator.
Remember - even if it goes round, it will be incredibly weak!
Here's an image of a commutator I just found (it will be covered by the outer casing):

 

[Redbelly98]

Just curious how electric motors work, specifically DC motors. I have some questions i would like to understand better.

I don't know where you are in your studies, but I find this animation explains how a simple DC motor works pretty well:

http://www.magnet.fsu.edu/education/tutorials/java/dcmotor/index.html

Some knowledge of basic electronics and electromagnets is necessary.

 

[LT72884]

Thanx man, well, I am a lil rusty. i took electromagnetism about 2 years ago and at the time it required trig and some calc. HOWEVER, i was not even in algerbra yet so, i got lost very very easily. LUCKILY, my professor helped me out and i got an A-. I don't rememebr anything though because it was supper tough.

 

[LT72884]

Ok, that image of the rotating wire in the magnet, what's making it rotate? I want to make one of those at home so i can see what's going on.

when voltage from the battery goes through the wire, does the electric field of the voltage from the battery interact with the magnetic field and cause the rotation?

This is the first time i have ever thought about this, but what makes the motor turn? I mean, i used to look at it as everyone else does. Power makes it turn. you plug it in and it turns.. But that is so minuscule and the lazy way of thinking. This is way weird. i have never thought of how nmotors work until just this second..

""The motor features a permanent horseshoe magnet (called the stator because it’s fixed in place) and an turning coil of wire called an armature (or rotor, because it rotates). The armature, carrying current provided by the battery, is an electromagnet, because a current-carrying wire generates a magnetic field; invisible magnetic field lines are circulating all around the wire of the armature.

The key to producing motion is positioning the electromagnet within the magnetic field of the permanent magnet (its field runs from its north to south poles). The armature experiences a force described by the left hand rule. This interplay of magnetic fields and moving charged particles (the electrons in the current) results in the torque (depicted by the green arrows) that makes the armature spin. Use the Flip Battery button to see what happens when the flow of current is reversed. Take advantage of the Applet Speed slider and Pause button to visualize these forces better.""

 

[Redbelly98]

Ok, that image of the rotating wire in the magnet, what's making it rotate? I want to make one of those at home so i can see what's going on.

I've never done this myself, but to build a simple DC motor you could try following these instructions:

http://www.flinnsci.com/Documents/demoPDFs/PhysicalSci/PS10405.pdf

Here is a home-made motor in action:

when voltage from the battery goes through the wire, does the electric field of the voltage from the battery interact with the magnetic field and cause the rotation?

Not quite. The current through the wires creates a magnetic field, so the loop of wire is actually an electromagnet. That means there are really two magnets in the figure: the square loop, and the horseshoe magnet.

The north pole of the loop is attracted to the south pole of the horseshoe magnet, and the loop's south pole is attracted to the north pole of the horseshoe magnet. That's what makes the loop turn.

Once the loop's north pole is close to the horseshoe's south pole, the current in the loop reverses direction, so the magnetic poles of the loop reverse as well.

This is the first time i have ever thought about this, but what makes the motor turn?

I hope I have explained it well enough, but post again if it doesn't make sense to you yet. Studying the figure, and realizing that the current in the loop makes it into an electromagnet, are the key to understanding this.

 

[LT72884]

Thanx so much guys. Its a whole different world when you turn your brain the other direction and think about things from a different perspective. But that was the oddest moment i have had with learning. When i looked at the diagram of the turning loop and also my motor from the tread mill , it finally hit me, something is making that loop turn. i can't explain the feeling man. It was just a turning point with how i look at things i guess.

Thanx for the explanation. its starting to make sense.

the interesting thing about that video, there is no current running through the wire so it must be just the magnetic fields creating the rotation. But yet it is labeled a simple DC motor. No matter what, still an awesome video.

anyway, I am goign to try it out but I am going to add a battery to the setup and see if i can get it to rotate without my help.

 

[Redbelly98]

It's a great feeling when you're hit with a better understanding of how something works.

About that video, there is a current running through the wire, and a battery inside the box (out of view):

An easy to make DC motor.
Although not shown, there is a D-size battery inside the cardboard box. The paperclips are touching the battery so there is a current running through the loop of copper wire. The current loop in the magnetic field creates a net torque which turns the loop.

(from )

 

[brno17]

Just curious how electric motors work, specifically DC motors. I have some questions i would like to understand better.

do the windings of a motor determine the required voltage to power it?

Can a 110 volt ac motor be powered by a 12 volt dc battery without an inverter?

Can a 110 volt dc motor be powered by a 12 volt dc battery without an inverter? if not why? what does it do to the motor? Wont the lower voltage cause the motor to run slower? or will it actually damage the motor?

Thanks guys

HEY my dad has an electric motor rewind shop. Nice to know others are interested in the field too :D

The winding DOES determine the voltage. It depends on the resistance, wire size and amount of turns per coil.

The motor poles determine speed Hz*120 / # poles (120 in constant)

2) No, DC volts only travel one path. Therefore in an AC motor the motor will only "Lock" the shaft. It needs AC to travel both direction (single phase motor) so the electromagnetics change between N and S 60x a second (Frequency)

3) The motor voltage rating is dependent on how its winded. You can rewind a 575v motor to run at 115v. You just change around the wire size and amount of turns. The theory is that you need same resistance in the coil but you need to adjust the wire size to handle the amperage.

 

[LT72884]

oh ok, cool. i didnt open the video through youtube so i didnt see the explanation. but that's cool how it actually works.

i printed off the instructions so I am going to make one.

 

[LT72884]

HEY my dad has an electric motor rewind shop. Nice to know others are interested in the field too :D

The winding DOES determine the voltage. It depends on the resistance, wire size and amount of turns per coil.

The motor poles determine speed Hz*120 / # poles (120 in constant)

2) No, DC volts only travel one path. Therefore in an AC motor the motor will only "Lock" the shaft. It needs AC to travel both direction (single phase motor) so the electromagnetics change between N and S 60x a second (Frequency)

3) The motor voltage rating is dependent on how its winded. You can rewind a 575v motor to run at 115v. You just change around the wire size and amount of turns. The theory is that you need same resistance in the coil but you need to adjust the wire size to handle the amperage.

huh interesting. i have a book somewhere around here that explains it all. i just got to open it up and read it again. haha

thanx