Thread: DC or AC motor?
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Old 04-14-2020, 08:14 PM
R K R K is offline
Join Date: Apr 2011
Location: Kimberly Idaho USA
Posts: 4
208 3ph with VFD

For many years, I used a 2HP DC Baldor on my knife grinder.. Now I use a 3hp, 3ph 208V AC motor with a VFD (Variable Freq Drive)
The AC motor with a VFD is light years ahead of the DC motor/controller.
The DC only has full power at full speed, as you decrease speed you decrease power because you are decreasing speed by decreasing voltage.
The AC motor speed is controlled by varying the 3 phase frequency, thus you loose very little if any power as you decrease speed.
I have two knife grinders in my shop and both use the 208V AC motors with the VFD controllers. I can't imagine ever going back to DC.
A couple years ago, I found seven Baldor DC controllers and two 2HP Baldor motors at the dump, as it turns out, a packing plant near here was retrofitting with the new 208V AC units. Now I use the DC units on my disc sanders.
IMHO, I wouldn't even consider a DC motor for a grinder now!
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