Three speed fan
 

I'm guessing: Do these work by having a two pole and four pole
arrangement? Switch in the two pole and get 3600- rpm, switch to four
pole and get 1800- rpm, switch in both for six poles and get 1200- rpm.
The geometry migh be somewhat screwed up in 4- and 6- pole
configuration but those are working at pretty low power.

I ask because my neighbour has one of these that only works on high
speed. I suspect the switch but before we commit surgery on it, I'd
like to understand how the thing is suposed to work. TIA

Ted

In article PbMoe.33115$wr.26609@clgrps12,
Ted Edwards wrote:
I'm guessing: Do these work by having a two pole and four pole
arrangement? Switch in the two pole and get 3600- rpm, switch to four
pole and get 1800- rpm, switch in both for six poles and get 1200- rpm.
The geometry migh be somewhat screwed up in 4- and 6- pole
configuration but those are working at pretty low power.

I ask because my neighbour has one of these that only works on high
speed. I suspect the switch but before we commit surgery on it, I'd
like to understand how the thing is suposed to work. TIA

I'm not sure about the one which you have (a window fan
perhaps?), but the multi-speed motors driving furnace squirrel cage
blowers appear to be slip limited. They are cap run motors, and the
taps simply select how much torque it can produce before it starts to
slip. More torque means higher speed. But certainly not the range that
1200-3600 RPM would cover.

The switch (if it is as I think) will probably be simply a
single pole multi-throw. Going from eix to four to two poles would
require a rather elaborate switch, I think, even if the windings were
capable of supporting all of those configurations.

Enjoy,
DoN.

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