On Mar 3, 8:36*am, "Oppie" wrote:
I have a milling machine that's starting to show its age. It has a 5 Hp,
208V, 3 Ph spindle motor that's currently on a full voltage Fwd/Rev starter.
Motor really slams when turned on and has damaged the variable speed sheaves
and keyways.

Was thinking of adding a soft start system in series with the original
starter. Considered a VFD but have heard that using one with a motor not
designed for such makes problems. Even adding a line reactor to remove
harmonic content may be required. All told, a soft starter appears to be the
best choice.

Does anybody have a favorite unit to recommend?
Ones I've seen so far have a SCR in series with two of the three legs and
control starting voltage and ramp-up time. If you keep them powered, they
can also control ramp-down time. *A contactor bypasses the reduced voltage
system after the ramp time. All fine and well but only some of the vendors
seem to rate # of starts per hour. *I would assume that this is due to heat
generation when the SCRs are carrying the load and the need to dissipate it.

Thanks in advance for any answers
Oppie

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