On Wed, 8 Oct 2008 20:30:36 -0700 (PDT), Vernon
wrote:

On Oct 8, 10:02*am, "Pete C." wrote:
"DoN. Nichols" wrote:

On 2008-10-06, Pete C. wrote:

David Lesher wrote:

* * * * [ ... ]

Get a pushbutton, a big industrial one. Allen Bradley comes to mind. They
are basically Legos; you start with the basic button and add contacts of
the type needed.

It should have 3 contacts rated for the full current of the motor. They
will be closed in OUT mode, but open when pushed in. Wire in series
with all three legs going to the motor..

Have a low current 4th contact going to the VFD shutdown connection.

This will break the power feed to your mill when hit, AND send a shutdown
to the VFD. [It may take a while to turn off, however, as compared to the
button. Maybe even as much a second or two; see what the VFD Fine Manual
says.]

This way, even if the shutdown command does not work, the power *is* off.

The shutdown pushbutton will be expensive new. There are millions surplus
but it will be tricky to mail-order same. If you have a surplus place
nearby....

The E-stop switch belongs on the power feed *to* the VFD, *not* on the
motor leads from the VFD, otherwise you just have a "VFD destruct"
button. The diagrams in the VFD manual should show the proper wiring for
an emergency stop.

* * * * Except that the VFD has a set of big capacitors in there, which
could keep it running for a second or so after the power line is cut.

While they'll keep the VFD controls running for a second or two, they
most certainly will not power the motor for any length of time.



* * * * As long as this is only to be used in a true emergency, what I
would do is set it up to drop power to the VFD (two NC contacts), and to
*short* the power from the VFD to the motor (three NO contacts) so not
only will the power be removed from the motor, but you will also have
regenerative braking.

Cutting power to the VFD and triggering the VFD's e-stop input should
allow it to do some braking during the second or two it's caps keep the
control operating.



* * * * This is likely to not damage the VFD -- because they have
circuitry to sense excess current and to shut themselves down under
those conditions -- but it is not *certain* that it would survive this.
More likely than with the high voltage spikes from opening the circuit
to the motor windings which can fry the output transistors.

* * * * Remember that it is truly an *emergency* stop button only. *When
life and limb are in danger, is the time to hit this -- not just when
you want to walk away from the machine for a while.

The best course is to follow the e-stop wiring guides provided in the
VFD manual.- Hide quoted text -

- Show quoted text -

Gentlemen. As regards properly interfacing the "instant forward -
stop - reverse" lever on the KBC mill with the VFD I have stumbled
upon the following tidbit:

"THREE-WIRE INTERFACE OPERATION"
The 3 wire interface is an industry standard motor control interface.
This function uses two inputs for momentary contact start/stop
control, and a third for selecting forward or reverse direction. To
implement the 3 wire interface, assign 20 [STA] (Start), 21 [STP]
(stop) and 22 [F/R] (Forward/Reverse) to three of the intelligent
input terminals. Use a momentary contact for Start and Stop. Use a
selector switch, such as SPST for the Forward/Reverse input. Be sure
to set the operation command selection A002=01 for input terminal
control of motor.

If you have a motor control interface that needs logic-level control
(rather than momentary pulse control), use the [FW] and [RV] inputs
instead."

(Programming table omitted).

*****

The thing is, this Hitachi VFD to my surprise and delight, yet utter
BEWILDERMENT, is far far beyond a simple "phase converter". I've come
to realize that it is a programmable automation brain. So, I'm not
sure, but out of the avalanche of programming data, I think this is
the "magic tidbit" I've been looking for.

So, to expand on advice some of you have already given, it sounds like
I need to hook the motor leads up to the VFD outputs and then re-route
all of the mill's controls (on/off switch and forward - stop - reverse
toggle lever) to the "logic input buss" terminals and then program
these as per the instructions.

Does that sound right?

Vernon


Sounds like someone hit this Vernon feller a good wack with the
Cluebyfour.

You finally got it.

Ayup..thats what you do.

Makes life somewhat simpler no?

Gunner