"Roger Shoaf" wrote in message
...

"Existential Angst" wrote in message
...
Awl --

How to do?

TRIACs? http://en.wikipedia.org/wiki/TRIAC
In that article they mention "alternistor". Useful? Never heard of it.

How bout PWM? http://en.wikipedia.org/wiki/Pulse-width_modulation
good
article, overview, incl. rheostats and variacs. Not clear, tho, if pwm
acts
to change the effective input frequency.

I'm guessing that, in general, speed control of 1 ph induction motors is
not so swift, given that people here are swapping out 1 ph induction for
3ph
+ VFDs.

But if it IS doable on smaller motors, it would be a big help.
The blower motor at hand (kitchen hood) is surely no more than 2-3 A, and
I'll bet about 1.5 . I've used a variac on this motor, with very
middling
results.

If 1 ph induction is freq dependent, why can't a VFD be used on a 1 ph
(220
V) induction motor?

If I need to go 3ph+VFD, Dealerselectric.com has fractional hp 3 ph
motors,
down to 1/4 hp, prices not on web.
Graingers has no 3 ph motors under 1 hp, and none of those under $250...
wow....

--
EA, PV'd



What are you trying to accomplish in the end? You can buy cheaper multi
speed motors or you can possibly make a change to the fan itself a whole
lot
easier than reinventing the wheel.

Well, speaking of wheels, I am basically going from a blower like
http://www.grainger.com/Grainger/items/1TDU8?Pid=search , oriented along the
horizontal *within* the hood, to
http://www.grainger.com/Grainger/items/1TDV4?Pid=search , where the blower
wheel diameter (suction side) is facing straight down, and re-located
*above* the hood, blowing directly out to/through the wall vent.
This greatly simplifies overall air flow.

Now, I didn't actually buy this second blower, but by removing one of the
squirrel cages on the old double blower, I basically converted the old
blower into the second grainger blower.

Now, try finding a mutli-speed small blower!
I spose I could find a multi-wound motor and mount it on a blower, but it
seems like speed control is the easier route. And, from the grainger link I
posted on the Dart controller, it appears these small motors are somewhat
amenable to speed control.

Any add'l links would be appreciated.

I will, however, monitor my old modified blower (oil cups and all) for heat,
at reduced voltage. Given that the original speed controller was just a
crappy tapped transformer on a rotary switch, my Variac is really just doing
the same thing, except better.

I am shocked by some of the prices of hoods -- the cheapest HD stuff is
$400, and it quickly goes into the thousands, $4,000 in one showroom, Broan
"Best" series. The few that turned on did not seem all that quiet or
impressive.
They were all cosmetically done well, but most are bulky, wierd, or
incompatible with my long-ish 6 burner cooktop.

So I'll be finagling away, with compound angles and air flow, for some time,
it appears.
--
EA, PV'd





--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube,
then
they come up with this striped stuff.