VWWall wrote:

Martin Levac wrote:
On 6/21/2011 12:56 PM, Evan wrote:
On Jun 21, 12:57 am, Martin wrote:
On 6/20/2011 11:14 PM, Evan wrote:



On Jun 20, 5:21 pm, Martin wrote:
Hello,

I have a Lasko 2155A window fan with integrated 3 speed control unit
(links at the end of this post). I want to be able to fine tune the
speed so I want a fully variable speed control unit that I would
attach
to the power cord, and control the speed from there instead.

The operator's manual states that the fan must not be used with a
solid
state speed control device. I understand that to mean that I must not
simply attempt to vary the voltage, i.e. from 120VAC to 90VAC for
example. I understand that this may cause the amperage to rise, and
all
sorts of nasty things may occur after that.

Nope, still no help at all. Get the picture?

Some small induction motors, particularly if driving a load like a fan,
can be made to run at a slower speed by simply decreasing the voltage.
As has been mentioned, the usual solid state control removes part of the
AC waveform, which may result in motor overheating.

This can be done with a tapped autotransformer or simply with a series
resistor(s). A variable resistor of sufficient power rating would give
limited stepless speed control.

I have a condenser fan on my refrigerator that the repairman replaced
with one that sounded like a jet taking off! I dropped the voltage to
about 90 volts and it's been happily and quietly running for the past
five years.

You'll never know if your particular motor behaves in this way until you
try it. It may run fine at a lower voltage, but not start. In this
case you need to insure it's always started with the higher voltage.


Virg, you're wasting your time. This is crosposted from
alt.home.repair which is full of trolls and dangerous idiots. Killfile
the loser.


--
It's easy to think outside the box, when you have a cutting torch.