Shaded pole rings a bell. I have had motors like this that lock up on power up. It would be hard to turn. It should turn freely with no power. If nothing happens I would suspect open winding.
Well if there is power up to the motor windings then they are probably open circuit or there is a thermal fuse embedded in the windings which has gone open. You may be able to dig it out or bridge it at your risk.
More info please? How long does it run before it stops? About what speed does it run? About 3400 RPM? Does it stop abruptly or does it slow down and then stop? Does it stop when you move the various wiring bits?
Purchased ~ 4 years ago. Used extensively mostly in summer of 2011 (maybe 10 hours/day). Made strange sympathetic vibration sound, ~C#. Worked OK about 3 weeks ago. Stopped functioning altogether.
The shaft turns freely. No evidence of a heat problem. Gets 120v thru feed wires. No contacts on coil (cannot test voltage there). Just sits there and looks dumb when powered.
Can't find -any- specs on it (Model MH-20UL)
Chinee wonder mystery, probably not worth further consideration?
Thx, P
"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
Do you have continuity through the winding? If not, then there is a thermal fuse somewhere inside the motor. Usually, right under the point where the wires enter the motor. If there are terminals, look and see what size & type wire goes from them. If one is larger than the other, that will be a lead from the fuse.
--
You can't have a sense of humor, if you have no sense.
As Michael mentioned, presenting 120 V to the coil does not necessarily mean there is current through the coil.
:)
'Probably true. Please use your multimeter to measure the resistance of the switch when on, wires, connectors etc.
As Michael implies, your first - order test would be a resistance measurement from prong to prong on the unplugged A.C. connector.
If it is 'open' and the switch and power cable tested OK, you're probably not going to be able to repair the motor economically. It is your call whether you want to unwrap the winding to discover an open fuse as a matter of edification and entertainment, before you throw it away.
If you are really economical (as I can be), you can salvage a low- mileage shaded-pole motor out of a scrapped microwave oven and use that in your fan. I see four in my scrap box from where I'm sitting! :)
I doubt it. It made that sound all summer. No evidence of a burnt bearing. No play in the fan shaft.
Understood.
Such is the case.
All of that is well beyond me.
I don't even know how to properly test because I don't understand the wiring. :-(
Spare a minute? I comprehend that I can wrap wires around a conductor, apply current, and have an electromagnet. If I can time the switching of polarity, and place the em in the field of a fixed magnet, I'll have basic components of an elec. motor. No?
Alternatively, I could have + and - fields formed with the em, and have a fixed magnet as an armature (??) thus constituting a "motor".
But I'm still miles from understanding how this shaded pole motor works. It looks like it has a big fixed magnet (but with copper tubes running around it), a large winding presumably between the N and S poles, and a separate armature (with fan shaft) in the middle of the fixed magnet. This describes what I see in the pics.
If you can explain how these components relate to my miniscule understanding of the basic components of a "motor" (above), I would award you with a (virtual) "Cigar And A Beer". :-) I'm obviously missing a bunch. Hope I haven't mangled the terminology too badly.
Thanks, P
"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
Series circuit. AC hot to switch, from switch to motor, from motor to AC neutral, pretty much. That is what you see, yes?
See below. :)
Please review the results of your Internet searches WRT motors in general and shaded pole motors in particular. I expect some have very illuminating illustrations and perhaps a cartoon or two.
My understanding of these things is marginal at best, so I hereby bump your question to those more knowledgeable and articulate.
No. All I'm really familiar with is common house wiring. 3 wires, black (and maybe red), white, and bare (or green). Connect black and white to device, close circuit, device runs (if functional). 120v potential between black and white. 240v between black and red (?).
Per the pics, shaded pole is wired red, black, and blue. Where is Common?
Thx, P
"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
Its probably a tapped coil to provide two speeds. In this case, Black is "common" to both speeds (not necessarily neutral but it probably is connected to the neutral side of the cord), Red and Blue represent two speeds, fed by the switch, which in turn is fed from the mains side of the cord. Test ohms from Black to red, and from Black to blue; they should have some value other than 0 or infinity.
It has been mentioned before in this thread that the most common failure is in the brass slip bearings often used in these things. The tiniest bit of uneven wear will allow the rotor to lock to the stator. If it locks up when powered, suspect the bearing. If it spins free when powered, suspect the switch or the motor. If it spins when powered or hums, but seems to have reluctance, suspect the motor.
I ran a search on "tapped coil": wasn't much help. Howzit woik?
Unplugged. Black to red: 0. Black to blue: 0. Blue to red: 1.
Found more info:
Thermo-fuse Rot CW |--------- Black -------------------------- | | |--------- Blue (Lo) ---------- Line | | |----------Red (Hi) -----------------------
Not observed.
It just stopped running. Shaft turned freely.
I'm not really concerned about this motor. I just *hoped* to understand something of it's electromagnetic workings and how that related to the wire colors, etc.
Thx, P
"Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
"Rot CW" means it was design to rotate Clockwise. "Thermo fuse" means it has a thermal fuse that would open when it gets too hot.
Black and Red are the ends of the primary coil. The Blue wire is either "tapped" off the coil (some number of turns) short of Red end, or is wound as a smaller secondary coil. Black to Blue provides a weaker magnetic field for Low speed. From your Ohm readings it appears there is a break in the primary coil or Black wire connection, likely the thermal fuse wound into the coil.
When the sine wave of 120V Alternating Current is fed into the coil, the steel core is magnetized, reversing N-S poles at 60 Hz. The arrangement of copper "tubing" inserted the steel core provides a secondary/induced magentic field in the core, lagging behind the primary coil's sine wave. This is the "shaded pole". The phase difference in the primary sine wave and the induced shaded pole drive the rotor around.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.