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Author Topic: Need help choosing spindle motor/VFD.  (Read 3105 times)

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Offline Sam

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Need help choosing spindle motor/VFD.
« on: July 18, 2010, 08:13:36 PM »
Well, I think I'm about ready to purchase a spindle motor for the mill in progress, however, I'm about as dumb as a box of rocks when it comes to choosing a motor. I'm thinking a VFD with a good 3 phase motor would be great, but I really don't know enough to make an educated decision. I've seen that I can get a new 3hp Baldor or Leeson motor for about +/- $200 delivered. I've dug up some specs on some motors, but I really don't know what I'm looking at.
2 or 4 pole? Pro's and con's? I would like to have more power at slower speeds, rather than higher, so I guess a 4 pole is more desirable?
What about VFD options to look for? Needed inputs/outputs for features that might be useful, relays, braking features, fieldbus options, etc.... I have a small bit of experience with the Danfoss drives, and I know they are quality drives, plus and I have a local supplier, so I'm kinda leaning toward those.
I know I'm asking allot, but any help at all is appreciated. Thanks!
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: Need help choosing spindle motor/VFD.
« Reply #1 on: July 19, 2010, 01:12:07 PM »
The 4 pole torque is optimum at the base speed, so with a standard motor you can go up to 120hz.
If you are buying new you could spend a bit more and look at the vector rated motors, these generally take you up higher in the rpm max range.
Also suppliers like WEG have motor/VFD combinations that offer 100% torque down to zero rpm with no cooling fan.
A nice features to have on a spindle  is up-to-speed, which would need an input into Mach, not sure if it has the option written in.
This way machining motion is delayed until the spindle is up to speed.