Three-phase Motor

Nothing.

Then you have a stator connected to power supply without a rotor! If you are still holding it in your hands do not drop it on your feet!

A magnetic field rotates at the center and the windings warm up. Also, you may find that people who observe you doing this may find it difficult to take you seriously in the future.

Winding might burn out

do u have quations for your analysis or can u explain how is magnatic related with burn up.

You might also have the supply fuses blow, if you're lucky. What in heaven's name would possess you to do such a stupid thing? Just what is it supposed to achieve?

Wristwatch repair?

Pardon, do you have the time?

Are you making a reference to a Frank Zappa song, perhaps?

"...don't fool yourself girl......

.....

.Wristwatch!"

No, but I enjoyed the looks on peoples faces when I played Zappa and Captain Beefheart for them.

"Lets make the water turn black"

A three phase motor has nothing to do with Frank Zappa, except that Frank Zappa grew up in Lancaster, CA and there are three phase motors in Lancaster, but I don't think they're powered up with important parts taken out, but I could be wrong.

Maybe Frank can come up with a new song about Rotor and Stator madness in Lancaster! Can you hear it???

That would've a good one Frank has been dead for 2 decades.

No, Frank died...

#20

with a little modification you have a rail gun

Hmmm. I guess one of the little modification required would be addition of a rail.

I used to test 3 -phase 600 volt stators by applying 3Ph 240vac to the empty stator and putting a large ball bearing inside.

As you say,it will go round and round,but if there is a bad(open) spot,it will drop the ball or hesitate as it passes by.

Then same method will work for single phase motors,but put a bulb in series with the stator to limit the current.

A hack saw blade can also be used to check the integrity of the fields.

They make a test device based on this principle called a GROWLER,which is self powered.

"A hack saw blade can also be used to check the integrity of the fields."

I'm afraid of the answer, but I have this NEED to ask: How do you use a hacksaw blade to test field integrity of motors?

You hold the hacksaw blade close to the inside laminations of the energized stator and move it around the inside.

Of course,limit the current as described by using reduced voltage or a series load.

Hold it at a slight angle to the laminations to make it easier to move

It works on basically the same principle as a hand held Growler Tester.

You can feel the difference in pull when you cross an open or shorted section.

A piece of metal banding can also be used,but is usually too limber to get good results.

Okay, that makes a lot more sense than the image that was forming in my head of the blade curved into the cavity, chasing its tail around like some mutant baby bandsaw.

I assume a liberal amount of electrical tape it wrapped around the 'holding end' to make a non-conductive handle? I've seen a few handles that use a hacksaw blade like a keyhole saw, but those don't really look safe for this application. (having a thumbscrew/wingnut running through the hole at the end of the blade, with the screw/nut head right by the inside of the wrist if the handle were held like a probe, just feels 'wrong' on so many levels, not the least of which is the possibility of the hacksaw teeth nicking the stator insulation as the fields shift, or if it finds an existing gap in the insulation)

The hacksaw blade is used because it is a think, stiff strip of steel, no handle, just the blade, and there is no electrical connection to it. You just want something magnetic and something "springy". Could just as easily be a coat hanger bent out straight, but it's usually easier to find an old hack saw blade laying around in a motor shop than it is to find a coat hanger and sacrifice it.

"The hacksaw blade is used because it is a think, stiff strip of steel, no handle, just the blade, and there is no electrical connection to it."

As long as you don't touch the sides of the stator with it. Call me a coward, but I believe that the combining of a sharp-edged or toothed piece of metal and an electromagnet that is 'pulsing' or 'cycling' is just a Bad Idea. It's like tickling a tiger's tongue; all it takes is a moment of inattention, one missed subtle cue, and you get bit.

Get the hell out of my head..... I was going to say that too!

As an apprentice, we did the very same thing, removed the rotor, but used a 3ph variac and put thick protective plastic on the ends.

Damn didn't that ball bearing wizz round!

I looked and looked on YouTube for a video of this, couldn't find one. Of all the idiotic stunts done on YouTube, I would have though that someone would have done that one by now!

Maybe it's up to me... Now where can I get a sacrificial motor?

you would have thought someone would have made a video of it....but alas!

'.... the stator coils are essentially just a resistive load...'

.

I knew you are talking about rotor specific kind of back-EMF. However, I'd be pretty surprised if there wasn't a significant amount of inductance for most stator windings even without the rotor installed. Sure it will be less than if the rotor were installed, but not 'essentially just a resistive load'... we are talking about a very loopy current path....hundreds of turns, usually more.

Boy, you don't miss much do you?...

You're right of course, I was just keeping it simpler for the masses so-to-speak. I did hedge it a bit however, by saying the current would be at the level of the magnetic inrush, which too would be slightly tempered by mutual induction in the coils themselves. Nonetheless, the point was that the current would be extremely high if not controlled by someting, high enough to clear fuses or trip breakers. Normally that magnetic inrush is of such a short duration that protective devices hold, but without the rotor, it becomes sustained.

Probably one of the factor(no load) that worsen burn out during dry running of centrifugal pumps.

Dry running of centrifugal pumps?

The big problem here is you kill the ceramic seals in sanitary centrifugals in about 10 rotations. That squeal you hear is your profit going out the door. Very expensive error, that is only ever done once. You remember that forever.

It will become a magnetic heating element and most likely will burn up.

There will be big smoke...

Everyone in this forum fell for his trick question. He never said it was a large three phase motor, did he?

Check this out! http://www.ebay.co.uk/itm/IBM-WHEELWRITER-3-TYPEWRITER-CARRIER-MOTOR-/181205583805

I don't think you can get this motor to throw a bb very far.

Yes, he did say it is a three phase motor. In fact it's right in the thread title, which is at the top of you post...

A three phase, but not a large three phase, right?

But who would use low-voltage 3P for a motor?

At low voltage, it's easier to just use a reversible DC servo motor, or a stepper motor, fed by the usual 'chasing pulses' of DC.

....Is it star or delta connected....? but either way it will get hot, probably blow the fuse or trip the breaker, and the rotor (wherever it is) probably won't turn.

Horace, you fell for another part of the trick question. He removed the rotor, but he didn't tell you that he placed it in another motor. So, if the other motor is on, the rotor would be turning ... unless someone accidentally ran straight DC power into it. Or maybe the load on the output shaft is too high and the rotor can't turn.

Then again, if the rotor were painted with some sort of super thick lacquer paint, then dropped back in the motor wet ... or if the entire motor was dipped in shellac and let dry, the rotor probably wouldn't turn.

Autobroker #32. Your OT is a bit premature.

The OP hasn't told us anything much, and certainly nothing in response to various questions arising from possible answers, so your answer could be correct for all we know.

I once saw a demonstration of the rotating magnetic field in an AC motor. The rotor was removed from a large motor, and a ball bearing assembly was running around the inside of the stator when it was powered up, at about 2 seconds per revolution.

If stator slots are skewed(not parallel to rotor shaft) will a single phase motor rotate without capacitor or starting winding.

Nothing, as in no work.

You will open a wormhole in the time-space continuum.

Our dimension will collapse

Nothing will happen physically. When supply is given to stator, rotating magnetic field is created but as there is no conductor to cut it, there will be no induced field. Hence nothing will happen