"ignator" wrote in message
...
On Mar 3, 4:04 pm, ignator wrote:
I have two mills that I've installed VFDs on. The WELLS INDEX 645,
has a 3HP C-Face motor not inverter duty ~1968. I've used this now
for 11 years without problems. Hitachi SJ300. Also a Rockford
horizontal mill, that someone a long time ago put a overhead
conversion to drive the flat belt of this antique beast. This has a
5HP motor from some time in the 50s, this has a TECO 7200 drive. Also
put a 10HP drive on a 7.5 HP lathe motor (not inverter duty). But I
generally never push the HP envelope while machining, as I dry cut, so
slow feed and SFPM on the mills, and ceramic tooling light feeds on
the lathes. I've installed 3ph motors on my 1976 Jet 12x24 lathe,
drill press and vertical bandsaw, but these were 1HP motor with drive
kits from dealerselectric.com and were the older TECO FM100 that would
not run the motors smoothly down below 20-30Hz (the motors were
inverter duty). I recommend the sensorless vector drives, as I've had
very good luck with controlled low RPM operation.
All my wiring is short, all 240VAC single phase in. So as of yet I
have not punched through any insulation of the motors and caused
arching.
Someone here will probably beat me up over this.
ignator

Found this link
http://www1.eere.energy.gov/manufact...ployment/pdfs/
motor_tip_sheet14.pdf
This references standing waves with long cables. Maybe that's why
I've been lucky. I'm just using standard SO cord to connect the mains
to the VFD and VFD to the motor.
ignator


Informative, Thank you!

I had read in the past that putting a "non-inverter" qualified motor on a
VFD caused the motor to overheat (due to iron hysteresis and eddy current
losses) from the high frequency harmonics and bearings to fail from
circulating currents that caused current flow through the bearings. The
exception was if a "line reactor" (basically a 3 ph inductor) was added
between the VFD and motor to smooth out the high frequency content of the
drive waveform. You seem to have disproved this though. VFD technology is
rapidly changing and hard to keep up with.

I had originally posted this inquiry to news:sci.electronics.design under
thread "Soft starter or VFD" and added a bunch of links for soft starters I
had found.

Cheers - Oppie