On Oct 7, 10:24*pm, "DoN. Nichols" wrote:
On 2008-10-06, Vernon wrote:

Gentlemen,

I bought a Hitachi SJ200-022NFU2 model, 3 HP VFD to control my "new"
mill, which has a 2HP 3 phase motor.

This model, a "constant torque" VFD, is versatile and sophisticated,
and contains control options far beyond my needs and expertise.

* * * * Sounds like a good choice. *The 3HP rating of the VFD should
provide sufficient derating when running a 2HP motor.

I have carefully and almost completely read the owner's manual. *The
basic installation is simple enough. *You bring in the 2 legs of 220V
single phase from a 30 amp fuse or breaker, and connect these to
inputs 1 and 3.

* * * * Some have a jumper between input 2 and one of the others, but
yours is probably newer than mine, which was one of the previous batch
which were being sold off cheap to make room for the newer ones such as
what you have.

* * * * * * * * *You ground the mounted VFD and the mill motor in a
star pattern.

* * * * Actually -- you only ground the motor's *case* or frame, not the
center tap of the motor's windings. *I would be tempted to call it a Wye
(Y) instead of a star, since it is only three phase, though the other
term can apply as well.

* * * * *But* -- a Bridgeport three-phase motor is dual voltage, and you
will be using it wired for 240V, not 480V. *Wired that way, there is a
Wye which has the common point buried inside the motor, and you make a
second Wye by joining (and insulating) the proper ends of the other
wires, and the outside ends get connected in parallel with the first
Wye. *Thus you can't really get to the center point of the primary Wye,
without tearing the motor apart and probably voiding whatever warranty
is still present. *The Wye (or you could run a Delta if the motor were
designed for it) can totally float. *The ground to the frame makes the
safety ground you need.

* * * * * * * *You connect the appropriate 3 outputs from the VFD to
the motor.

* * * * Yes.

You go through an initial programming sequence, setting up certain
basic parameters. *You power up the VFD. *You verify certain that
certain pre-conditions are met and that certain LEDs are on or off on
the keypad. *You take a deep breath, make the sign of the cross, and
press START.

* * * * :-)

After that the going gets sort of tough. *Here are a couple of things
I don't understand. *I will humbly accept your guidance.

First, it is my understanding that it is possibly fatal to the VFD to
switch the motor on or off from the mill's own on-off switch, or to
otherwise control the mill (instant reverse for example) EXCEPT
through the VFD's programmable circuits.

* * * * This is generally correct. *The exception can be found when the
rating of the VFD is sufficiently larger than the motor's rating, and
there is as sufficient length of cable to act as capacitive bypass. *As
an example -- my Nichols horizontal mill (1HP motor) is across the shop
from the 7.5 HP VFD -- too far to easily run the control wires, but I
can get away with switching it at the mill end of the cable, and even
with plug reversing.

* * * * But for any reasonable rating match, you should not do this,
especially if the machine and motor are close to the VFD.

This leads to the following questions:

1) Do I remove the mill's on-off switch completely or otherwise wire
it permanently in the ON position?

* * * * No -- you wire directly from the mill's motor to the VFD --
skipping the on-off switch and the forward-reverse switch. *(Note that
some machines, such as the BOSS-3 CNC version of the Bridgeport Series-1
have a buried reversing relay (a double contactor interlocked so only
one direction can be energized at a time). *Anyway -- with the wire
going directly from the motor to the VFD, you will have bypassed this as
well -- if it exists.

* * * * Now -- rip out the wiring on the on/off switch and the
forward/reverse switch. *(Are they not all one switch on your machine --
forward/stop/reverse?) and run the switch contacts into the VFD's
command terminals, so your original switches tell the VFD to start the
motor and in which direction. *It is best to use shielded wire for this,
with the shield connected to the ground on the control logic terminals,
since electrical noise spikes could otherwise be picked up by the wires
and perhaps produce undesired activity on the motor.

* * * * You probably also want to add another small box under the
direction switch to hold a potentiometer to allow varying the speed
between whatever you have programmed as "full speed" and a dead stop.

* * * * Don't run the motor very slow for long, because you will lose
the cooling from the internal fan on the motor's shaft.

2) Do I similarly wire around the wires going to and from the mill's
FORWARD - REVERSE toggle switch and re-route these wires to the VFD's
programmable inputs/outputs?

* * * * Direct from motor to the VFD -- skipping all switches on the
machine.

* * * * Then wire the switches to tell the VFD what you want it to do.
Note that using the original switches in the original positions will
keep you reaching for the right controls, so if you are ever in a
position to use someone else's machine, your habits will be right in
case you need to stop it in a hurry.

There was previously some discussion here about whether a VFD can
adequately handle the mill's instant reverse. *However, upon careful
reading of the manual the VFD does seem to have a programmable "node"
that allows for this. *Apparently this can be tweaked a couple of
ways. *One of these involves installing additional resistors. *Another
SEEMS to provide for programming the injection of a DC current into
the motor to stop it from coasting. *I think these two things are
related but I'm not sure.

* * * * Two ways to the same end.

* * * * The resistor is to absorb power generated by the spinning motor
to slow it down more quickly.

* * * * The DC through the motor will stop it more quickly.

* * * * As soon as the motor reaches a stop, the VFD can automatically
accelerate it to the desired speed in the other direction.

I think I can get the thing installed this weekend so that it will at
least start and run. *However, my brain is a lot murkier as regards
these programmable controls.

* * * * Play with them for a while (perhaps just connected to the motor
with no mill cutting taking place) -- learn what they do -- and then
leave them set to whatever works best. *The only controls you really
need are within reach on the machine -- the forward/stop/reverse switch
and the speed control pot.

* * * * Another thing which you may or may not know -- depending on
whether you have used other Bridgeports. *When you engage the back-gear
with the lever on the right hand side of the head, the spindle direction
will reverse. *It might be worth while adding a switch in a chip-proof
housing to sense the position of the lever to reverse what your forward
and reverse switch does. *(Of course, this is the reverse of what I was
saying above to keep the action of the switches standard. :-)

* * * * Enjoy,
* * * * * * * * DoN.

--
*Email: * * | Voice (all times): (703) 938-4564
* * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---

Don. That was very very helpful. However, I bitterly regret to
inform you that my mill is not a Bridgeport. It is a common garden
variety Taiwanese bench mill. It's like a drill press on steroids.
Ironically, I bought it for two reasons: First, there were no
bidders. Second, I mistakenly thought that it was single phase and
that this would be the biggest thing to be had that WOULD operate on
single phase.

Too late, I discovered that it was 3 phase. Thus, I had to pop down
this VFD rabbit hole. Had I know in advance how wunnerful and
versatile they are, I coulda/ shoulda bought a full sized mill. But
time ain't over for me yet. So maybe there's another mill in my
future.

Best. Vernon