On Wed, 11 May 2016 10:51:19 -0700, "Bob La Londe"
wrote:

wrote in message
.. .
To all youse high speed spindle guys,
I have now a new 2.2KW VFD and matching 24000 RPM spindle motor. I am
wondering how important line and load reactors are for this setup.
Especially the line reactor because the motor/VFD combo is supposed to
be matched and because the motor wires will be short, 6 feet or so.
From looking online I have determined that a reactor rated at 12 amps,
2.5 mh, and 5% impedence is optimal. Can a reactor with a larger
current rating be used? Also, since the VFD can be connected to single
phase power and I want to use that option, I think I need to use a
reactor with a higher current rating. 18 amps instead of 12, right? I
haven't seen any single phase reactors yet on ebay which is why I am
asking. On the output side I am concerned with noise making problems
for the CNC mill (a Fadal 15XT) that the spindle will be installed in.
Will a reactor help with this sitaution? Do I really need one with
such a small (2.2 KW) motor?
Thanks,
Eric

From what I have read you DO NOT need a line reactor for short runs. Some
writers disagree about what is considered short, but most say ten feet or
less. Some users have reported no problems with slightly longer runs. I do
use a shielded high flex cable between the VFD and the motor with the shield
going to the same common ground as the VFD. I just connect to the ground
screw on the VFD. I have not noticed any significant noise problems in my
shop with multiple computers running and two CNC machines with VFDs running
at the same time. I haven't even noticed any problems when welding when I
forgot, but I typically do not weld while a CNC machine is running.

Where you need to derate is at the VFD itself. 1/3in 3out VFDs typically
must be derated by about 30% when running on single phase. This isn't even
an issue unless you will have peaks in that top 30% of rating. I am running
a couple 800kw spindles on 1/3 750Kw VFDs without issue. I plan all cuts at
.25hp or less anyway. I go for light fast cuts for most jobs. Usually in
the .11hp or less range.

On my Hurco KMB1 I am running a 5HP Leland spindle motor with a 3.7Kw
Mitsubishi VFD with no issues. I overloaded it once or twice and it just
shut down. I have my SF calculator set at 3hp for that machine now, and
have had no issues since. I would note that Hurco did not originally rate
the machine at 5HP either. You do need to be aware of load in corners of
pockets etc. Typically that peak it doesn't last long enough to be a
problem. Only sustained cutting at max load, which I don't do anymore.

Spedestar makes a line of VFDs that are rated for full label load (peaks)
with single phase input. I have debated on buying one for the Hurco, but I
really don't need to push it that hard anyway. By going with lighter cuts
and faster feeds I get better parts (in my opinion) anyway. Except for
large bit drilliing in steel I rarely get calculated loads anywhere my self
determined limit of 3HP anyway.




The run from VFD to motor is short, the run from the VFD to the
breaker panel is long, about 45 feet. All the wires in my shop run in
either metal wire ways or metal flex conduit. I don't know if this
makes any difference. The wires for powering the VFD are in the same
conduit and wire way as the wires powering the Fadal and I don't know
if this might be a problem either. I also am a little concerned about
grounding. The VFD manual says it should have its own ground, to not
share ground with anything else. For the larger machines in the shop
each has a ground wire running from the machine to the load center
ground bus bar. For some smaller machines, less than 3 HP, grounds are
shared. So there is a ground wire running through the wire way with
pigtails going to several machines. The circuit I want to run this VFD
from has this shared ground. I could pull another ground wire but it's
a real hassle to pull wire through the overhead flex conduit that the
supplies power to the side of the shop the VFD will be on. Any
thoughts on that? On your advice I bought a spindle/VFD package that
is rated about twice as powerful as the heaviest cut I plan to make.
So it looks like the derating business is taken care of. I program
virtually all inside corner milling as arcs and use cutters with a
smaller radius than the inside corner in order to reduce cutter load
and chatter.
Thanks,
Eric