On 2008-07-17, BobH wrote:
Ignoramus30183 wrote:
I wired the VFD to the lathe. Not in the best way yet, but enough to
experiment. Toshiba VF-A3 3.7 kW VFD, similar to what I sold to Pete
C, only bigger and with cracked top cover. (I have more for sale, 2.2
and 3.7 kW)
Here's one very encouraging piece of news (related to what Karl said):
switching of the speed selector lever while the motor is running does
not destroy the drive. It simply trips on a overvoltage error and lets
the lathe coast to stop.
I am very satisfied with this behavior. It is as perfect as it gets.
Sounds good.
Right now it trips when I press OFF, no doubt due to too ambitious
braking that is the default setting right now.
You probably can set a 1 second rampdown and it won't trip, or put the
braking resistor on.
I will experiment. The issue is, obviously, higher spindle speeds,
requiring longer rampdown.
The other thing I can do is this: the limit switch for tutrning the
lathe on and off, has a normally closed and normally open switch. I
obviously use the N.O switch for RUN. But I can use the N.C. switch
for RESET.
What I need to do is:
3) Place the VFD deep inside the lathe cabinet so that it would not be
a hazard or distraction. There is no need to access the drive once it
is set up. So I will put it away. This will be a single phase lathe
that would be operated with its original control and no weird wiring
outside.
The ONLY thing that I may allow to be visible outside is the FAULT
indicator shown by a LED bulb. Maybe a FAULT with RESET
pushbutton. That's all. I do not want switches, potentiometers, none
of that stuff is necessary.
Be sure to leave good air circulation, it will generate some heat.
I still need to make a shroud so that there is no direct path for chips
to fly into the unit. My VFD is up above the machine on the headstock end.
The base is very big, there is plenty of space, and also the motor is
in the providing some extra circulation. Should be fine.
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