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Forum Index : Other Stuff : Energy efficient fan often goes wrong way
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| Georgen Guru  Joined: 13/09/2011 Location: AustraliaPosts: 462 |
I've got energy efficient 240V fan 25cm from Bunings to move air and I switch it on manually. (Uses about 4.5W ) Noticed that often it starts to go the other way. When I turn it of an on (sometimes few times) eventually it goes the right way. It has bit noisy start (it hesitates for few seconds whizzing a bit) instructions say it is normal. Problem is, I would like to put it on timer and if it starts to go wrong way it will keep going that way until I manually re-set it. Looks that I will not be able to put timer on this one. Could somebody suggest solution? George |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I'll bet its made in China. Chances are its a little induction motor. Simple induction motors, the ones without a starting coil, usually have a "Shaded-pole", that looks like a loop of thick copper wire holding the laminations together. This shorted turn is there to kick the motor in one direction only, when it starts. See http://en.wikipedia.org/wiki/Shaded-pole_motor. Some may have a odd shape in the lamination pole, again to kick it in the one direction. Quite often we see a manufacturer from China copy a common design, but leave out these added bits, possible because they didn't know what it was for, and wanted to save the manufacturing costs. An example is the extruded fibreglass blades that are a copy of the Bergy blades, but missing the ridge, see http://www.thebackshed.com/windmill/articles/ChineseBlades.a sp, the ridge was necessary. If the induction motor in your fan doesn't have these devices to kick it in the one direction, then yeah, it could start in either direction, and there sn't much you can do about it. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Take it back and get a refund. As mentioned above, most simple induction motors have features that cause them to start up in one particular direction. This one obviously lacks that, and it is a 50/50 toss up which way it will start up. I have also seen one way clutches used which cause a rotating arm on the motor shaft to hit and bounce off a fixed stop if a motor tries to start up in reverse. These can often be seen in small mechanical mains driven timers and mains powered electric clocks. It is curious with these to see the motor start, hesitate, and start again, then finally run in the correct direction after several tries. Cheers, Tony. |
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| Barry T Coles Senior Member  Joined: 30/07/2009 Location: AustraliaPosts: 109 |
Hi Georgen As said above take it back for a refund the cost of modifying a cheap motor isnt worth the hastle. I have a concrete mixer that is run from a electric motor I picked up from my favourite shop (the dum);when I first put it on the mixer it wouldnt run without spinning the fly wheel but I could get it to run in either direction by spinning the fly wheel in the direction I wanted it to go. I got one of our leccky's at work to fit a capacitor to it & now it starts up first time & only goes in the one direction without touching the fly wheel. Cheers Barry I need to learn from the mistakes of others. I dont have the time to make them all myself. |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Problem is I cannot find receipt and probably it is bit over a year now and Bunnings would probably not like to take it back. Also it was under $20, so probably not worth the hassle for this reason alone. Capacitor sounds interesting, and I have couple: One in my drawer right here: 450V~ 16uF from my now dead Flymo mower. Would it be any good? Probably not as Mower was over 1000W and this fan is under 5W George |
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