Re: 1/4 HP sync motor power

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-qwest-dot-net>" <broker-at-uwplatt.edu>

Terry, all

I used a 1/3 HP split-phase motor foir my SRSG.  It drew about 5A (while
the TC remained unpowered).  For grins and giggles, I added a 50uF cap
across the motor, and the current dropped to 2.3A!  After some 
experimenting, I decided that the cap reduced the overall wall-current draw
by more than adding it to the NST's PFC (total of 250uF for 15/90).  I left
it across the motor.  I'd use PFC across the Geek Group's big SRSG I 
designed, but like you said, it will interfere with John's phase controller
that we'll be using.

I can't see any reason why a motor should not have any added PFC.  The caps
merely phase shift the lagging current so that it more closely matches the
voltage sine wave, thereby lowering the apparent power drawn 
from the wall.  The power company installs PFC caps on the overhead (or
underground) "HV" lines to attempt to negate the inductive loads and power
lines.  In a large industrial setting, the PFC caps are often on sight 
next to the BIG HV transformers on their side of the power co's meter.....
In a REALLY large substation, a HUGE electric motor is often used as a
capacitor (the things I learn from a $.25 book from my alma mater....).....

Mark Broker
The Geek Group's Chief Engineer



>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
>Hi All,
>
>FYI
>
>I captured the following scope picture showing the voltage, current, and
>power into my 1/4 HP A.O Smith motor that is converted to synchronous.
>
>http://hot-streamer-dot-com/TeslaCoils/MyCoils/SmallCoil/small_power.jpg
>
>http://hot-streamer-dot-com/temp/4thHPsync.gif
>
>It draws 158 watts of real power.  494.7 VA.  I think the jaggedness in the
>current waveform may be due to the edges of the flats interacting with the
>poles as they go by.  But I am not sure of that.  I wonder if power factor
>correction would have any use for these motors or if that would cause
>problems?  For some reason I don't think PFC caps and motors are supposed
>to be used together...
>
>PFC caps would also interfere with John's controller...
>
>Cheers,
>
>	Terry
>
>
>