If by ‘almost too big’ it will fit, do it.
I have no idea what a chipper motor looks like, voltage, horsepower or anything else.
My experience is with HVAC, household items, pump motors, etc.
We often used what is called a ‘hard start kit’ on stiff single phase AC compressors. Basically a start cap and electronic relay that is hooked up in parallel with the run cap.
Check Graingers for your capacitor?
Grainger has the pump cap in both 370 VAC and 440 VAC. It appears to be a Grainger “house brand” made in China; the made in China part of it is just like most everybody else... Strangely, the 440 volt version is cheaper than 370 volt, but, esp. with shipping added in, still much more expensive than multiple other sources, and with less info. to boot. I would not mind the cost, but I like to support sellers who supply the best info....
I ended up ordering the biggest (dimension) non-metal can caps* in 7.5uF 450 VAC** that I could find that will squeeze in, in the hope that size translates to a little thicker film*** inside — and a little more margin in the voltage rating.
*Plural, as the price allows me to run some severe accelerated “life” tests on a cap or two.
**I found more caps @ 450 VAC than 440 VAC. So much for standardization...?
***It turns out that oil filled polypropylene capacitors are quite common as motor run or start caps. I learn something new each day. The oil helps quench tiny arcs that can occur in an overstressed capacitor.
I found some VERY interesting information on capacitor failures, which I will link to and discuss in my next post on this thread. (It will take me a bit to collect all the screen names to ping, as well as write the post, later this evening.)
That article was probably the best of all, and lead me to some interesting “directions” to take to minimize future failures. I’ll cover that in the next post, too. :-)
More soon!