On Thu, 19 Jul 2018 16:34:42 -0700, Jeff Liebermann
wrote:
Maybe because the motor was paired with a compressor with a large
flywheel the pulsing torque from a single phase motor without a run
cap was not considered a problem because the flywheel would smooth
things out.

My guess(tm) is the start winding was intentionally undersized (which
is why the start cap is so large). Exactly why, I don't know.

Ok, I'm wrong. That's not the reason and nothing is wrong.
https://www.scribd.com/document/6883830/Tutorial-Motor-Basics-Lecture
See the drawing on Pg 20 of a capacitor start motor (as opposed to a
capacitor start and capacitor run motor). It has only a starting
capacitor and no run capacitor. According to the accompanying text:
- Larger single phase motors with up to about 10 HP.
- A split phase motor with the addition of a capacitor in the starting
winding.
- Capacitor sized for high starting torque.
- Very high starting torque
- Very high starting current
- Common on compressors and other hard starting equipment.

So, adding a run capacitor isn't going to do anything useful with this
type of motor. Sorry for the bad guess(tm) but I'm not familiar with
this type of motor. Everything I've seen has both capacitors.





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Jeff Liebermann
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