Newbie- Purpose of Capacitor connect with Spindle Motor?

[cjchands]

Hi,
I see that there are 3 capacitors connect to Magnetic Relay in parallel with R-S, S-T, T-R terminals.
The unit is for turning spindle motor clockwise or counter clockwise thru the hand switch.
My question is WHY would you need these capacitor connect in parallel for?
Back Voltage when suddenly switch Clockwise to Counterclockwise?
Thank you
Jeff C.

[Al_The_Man]

Are they capacitors or R/C back emf snubbers? these can also come in a single unit designed to hook across three phases.
Al.

[cjchands]

Hi Al,
You are right!! It is R-C Network.
The part is RG1676-24 (1000V, 10W)
http://www.galco.com/techdoc/elcu/rg1676-16_app.pdf

I guess it is use for Back EMF in case switching FWD/REV right away to suppress surge Voltage.
According to the brochure..it is also eliminate noise too?
Would this noise be connected to MOVEMENT of X-Y-Z axis as well??

What if......
If you turn spindle CW and wait until stop, then turn CCW...I guess you don't need R-C network??
Thanks again for your helpful comments.
Jeff

[Al_The_Man]

Applying power to an induction motor while it is still turning in the opposite direction is called a plug stop.
Often these snubbers where fitted to this kind of application, now it is common to see the R/C network added to 3 phase reactors in VFD applications.
Al.