Hybrid Car – More Fun with Less Gas

? simple way to add PF correction run capacitors?

register ::  Login Password  :: Lost Password?
Posted by philkryder on April 7, 2011, 6:13 am
 
Our club has about 10 1/3 hp motors with very low power factor.

Is there a simple kit that we can get to add a capacitor to each of
the motors?

We want to reduce "apparent current" which is causing the breakers to
trip on our small generator.

Posted by Daniel who wants to know on April 8, 2011, 4:15 am
 

Sure, assuming the motors are wired for 120v operation. buy a case of run
caps roughly 15uf 440 volt (don't get 370 volt), some large electrical
junction boxes, a bunch of jumper wires with 1/4" push on terminals on the
ends, and a Kill-A-Watt meter.   Run a motor with it plugged in to the KAW
and put the highest normal expected load on it as the PF goes up with load.
Start connecting run caps in parallel with the motor until the PF is as high
as possible, but don't overcorrect as a leading (capacitive) PF will make
some generator's voltage regulation go nuts.

Once you figure out the needed capacitance mount the run caps securely in
the J box and wire it so that the capacitors can't ever be connected across
the generator without the motor.



Posted by philkryder on May 19, 2011, 6:21 am
 
Turns out that the units have integral switches which preclude
connecting directly to the load "easily."

Therefore, I'd like your consideration on adding 2watt 15k ohm
resistors across the caps to bleed off residual charge.

I'm looking at these:
http://www.grainger.com/Grainger/DAYTON-Resistor-2MEW2?cm_mmc=GoogleBase-=
_-Motors-_-Motor%20Supplies-_-2MEW2&ci_src=14110944&ci_sku=2MEW2

does this seem appropriate?

Also, because the individual caps have a variance of up to 10% plus or
minus, I'm considering checking them on a "bread board" before the
final installation.
Is that adequate/necessary/silly?

Finally,
the 440v caps are MUCH more expensive than the 370s.
wouldn't the 370s be more than adequate for a 120 volt system?


thanks
Phil

Posted by Mho on May 19, 2011, 4:25 pm
 Peak voltage of a 120Vac system would be 120v x root(2) = 170 volts. If the
thing was ever 180 degrees out of phase the cap may have double that or 340
volts. With any line disturbances or motor spikes you are over the voltage
rating of the cap.

--------

"philkryder"  wrote in message
Turns out that the units have integral switches which preclude
connecting directly to the load "easily."

Therefore, I'd like your consideration on adding 2watt 15k ohm
resistors across the caps to bleed off residual charge.

I'm looking at these:
http://www.grainger.com/Grainger/DAYTON-Resistor-2MEW2?cm_mmc=GoogleBase-_-Motors-_-Motor%20Supplies-_-2MEW2&ci_src 110944&ci_sku=2MEW2

does this seem appropriate?

Also, because the individual caps have a variance of up to 10% plus or
minus, I'm considering checking them on a "bread board" before the
final installation.
Is that adequate/necessary/silly?

Finally,
the 440v caps are MUCH more expensive than the 370s.
wouldn't the 370s be more than adequate for a 120 volt system?


thanks
Phil


Posted by philkryder on May 24, 2011, 7:06 am
 
anything on the appropriateness of the resistors?




This Thread
Bookmark this thread:
 
 
 
 
 
 
  •  
  • Subject
  • Author
  • Date
please rate this thread