Adding a "run" capacitor to split phase motors?

[Jeff Wisnia]

I read an article few years ago about some work done by a guy who I
think was at a US Navy research lab.

It showed how much energy could be saved by adding a "run" capacitor to
the existing fractional horsepower split phase motors used in home
appliances and light industrial applications. (Must be many millions of
those ubiquitous motors in daily use, 'eh?)

IIRC, he just put an appropriate sized motor capacitor right across the
contacts of the centrifugal starting switch so that when the switch
opened the motor operated in an erzats "capacitor run" mode.

The energy savings shown in the article were impressive, but it's such a
nuisance to get inside most motors to connect up the capacitor leads
that I don't think his idea ever got anywhere big time.

Can someone point me to references on that subject?

Thanks guys,


Jeff

 

[[email protected]]

I read an article few years ago about some work done by a guy who I
think was at a US Navy research lab.

It showed how much energy could be saved by adding a "run" capacitor to
the existing fractional horsepower split phase motors used in home
appliances and light industrial applications. (Must be many millions of
those ubiquitous motors in daily use, 'eh?)

IIRC, he just put an appropriate sized motor capacitor right across the
contacts of the centrifugal starting switch so that when the switch
opened the motor operated in an erzats "capacitor run" mode.

The energy savings shown in the article were impressive, but it's such a
nuisance to get inside most motors to connect up the capacitor leads
that I don't think his idea ever got anywhere big time.

Can someone point me to references on that subject?

Thanks guys,


Jeff

sounds like a PF correction cap - will improve the power factor of a
motor running at less than rated load, making it waste less power.
By getting current and voltage back in phase I suppose it MIGHT also
make more power from the same amount of electrical power (more
efficient).

 

[Jeff Wisnia]

sounds like a PF correction cap - will improve the power factor of a
motor running at less than rated load, making it waste less power.
By getting current and voltage back in phase I suppose it MIGHT also
make more power from the same amount of electrical power (more
efficient).

Nope, that would be connected *across* the line. It's not for power
factor correction.

I found the article I was trying to remember. It's the third "letter"
down on this page:

http://www.elecdesign.com/Articles/ArticleID/4058/4058.html

And here's the columnist's follow up:

http://www.elecdesign.com/Articles/ArticleID/3736/3736.html

Jeff