inducstion motor dosent work, only humms and get hot. help anyone?

[mufcwd1]

hi guys, i have just dissasembled a giant fan i had lying around that didnt work, i dissasembled it and connected it back together outside of the shell, i plugg it in the socket and when i play with the potentiometer it just humms and doesn't spin, the only ression for it that i can think of is that the capasitor is broken or somthing, do any of you know what to do?
also the stature and router get very hot in the prosses

BTW its a 240 volts, 50 Hz, rmf, three phase induction motor

[Awesome14]

Three-phase induction motors have the phase shift required to create a rotating magnetic field. Single-phase induction motors require a capacitor to shift the phase to create the rotating magnetic field. Are you running the motor on three-phase power?

[mufcwd1]

i dont really know, lol, the motor has has six diffrent cables incloding the ground cable, the cable that i plug in the sucket is a normal cable, with one hot, one neutral and ground, that cable is split into additional wires in the potentiometer, dosnet that mean that it is a three phase motor?

BTW the capasitor is a CBB61, in the multimeter its reads 5.11 microfarad, on the label its reads 5 microfarad. 

[Twoflower]

The way you ask your question sounds like you never have worked with voltages that easily can kill you. I would highly recommend that you ask someone who can help you with that in person.

[mufcwd1]

your right, and maybe i shuold stop before i kill myself, still thise problem drives me insane, if someone knows what is happening i would really like to know the answer, i start a dgree in EE this week and i want to know the solution.

[Zero999]

Are you sure it's a potentiometer? Are there set speeds or is it continuously variable?

A three phase motor will either run of three 240V to neutral phases (415V phase to phase) or 240V and have an inverter (some electronics) to generate 240V phase to phase from a 240V single phase input.

Going by your description, it sounds like the motor has different taps in the winding, which are selected by a switch to change the speed, not a potentiometer.

Most degree courses won't teach you much practical stuff like this, which is why employers invest a great deal of time and money in training new graduates.

[Twoflower]

Maybe you can do this together. That way you have the chance to learn a bit what was the problem and see how that person works. And as Hero999 mentioned: Electronics degree might not teach you how to work with high voltages or high energies (two different things, both could be harmful). But it might be a good starting point to understand how things working and supposed to work. With this knowledge you have probably an eye to things that could be dangerous to you and/or the environment.

To your problem: There many possible issues. From a burned coil, wrong or defect cabling, the capacitor might be dead... A picture of the Motor might be helpful. Also the complete technical data from the Motor (a picture from the data-plate) and the socket you're use (as there are one phase and three phase outlets).

[IanB]

You said the fan didn't work originally, before you disassembled it? So, it presumably had a fault to begin with?

If that is the case, it is not necessarily the case that you have reassembled it incorrectly, or wired it incorrectly. It may still be as faulty as when you started.

When you plug it in, does it show any signs of turning? What happens if you turn the blades by hand? Do they move freely, or are they stuck? One cause of failure in fans is that the bearings gum up and won't turn. If that is the case the fix is mechanical, not electrical. You have to lubricate the bearings, or possibly clean the gunk out of them before adding fresh oil.

[mufcwd1]

when i plugg it in, it acts like it wants to turn, and it dose turn but like 0.05% and stops, i dont want to tuch the router when its plugget in beacuse of the high voltage (240V AC in israel, dont really know if the shaft conduct ot not), but your explanation sound legit, i didnt even though of that, i'll try to oil the bearings, maybe that wil help.

Hero999 i think its a potentiometer it has three diffrent speeds, buy iam not sure.

[IanB]

Make sure you are wearing rubber soled shoes and just touch it with one hand, there is not much risk. The bigger risk is the blade chopping your fingers if it suddenly starts spinning!

However, unplug it and then try to spin the blade. Does it spin freely, or is there friction?

[mufcwd1]

lol i took the blades of, i wont let that kill me haha, when its unplugged its moves freely.
its just sits there huuming and getting really hot.

[taydin]

If it's a three phase motor, one likely reason is that one of the phases is in fault (missing)

[Zero999]

when i plugg it in, it acts like it wants to turn, and it dose turn but like 0.05% and stops, i dont want to tuch the router when its plugget in beacuse of the high voltage (240V AC in israel, dont really know if the shaft conduct ot not), but your explanation sound legit, i didnt even though of that, i'll try to oil the bearings, maybe that wil help.

Hero999 i think its a potentiometer it has three diffrent speeds, buy iam not sure.

Then it isn't a potentiometer. It's a switch. It it were a potentiometer, then it would go to s circuit board, not connected directly to different wires coming out of the motor.

Have you tested all of the speeds?

Did you visually inspect the windings? Does it look clean? Are there any signs of overheating and charring?

I suspect it's a shorted turn, in which case the motor will need to be rewound, which will probably cost more than a new fan.

[mufcwd1]

yes i have tested all the speeds and dosent work, and yeah i did checked the windings they look complete, cant i do a test of continuity with a multimeter to verify that?

[IanB]

Yes, if you can identify the endpoints of each winding you can test the resistance with a meter. Each winding should have a similar resistance.