[Amps] Induction Motors was: Muffin Fans and hot exhaust

[Gary Schafer]

I have used series capacitors for speed control of blowers with good success. A
capacitor is much less critical than a resistor. It seems to provide a more
stable speed too.

On the subject of fans pulling air rather than pushing it, I think that at low
pressures either way works just about as well. As the pressure increases then
pushing will work better.
While it is true that there is a limit on how far negative a fan can operate and
no limit on positive pressure, as evidenced by a water pump only being able to
suck water from about 20 feet but able to push it to many times that height.

73
Gary  K4FMX


Jeffrey Madore wrote:

>
>
> As far as speed control on induction motors, line frequency control is the
> only way to maintain torque. And, voltage needs to be adjusted with
> frequency (volts/hertz) to keep the current within nameplate. With small
> motors, crude speed (and torque) reduction can be had by adding a capacitor
> in series with the line. Voltage adjustment alone will work to a degree, but
> torque falls off exponentially with voltage.
>
> Jeff - K1LE - CT ><>
>