Re: VFD question

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Marv Frankel"
><Dcdziner@p...> wrote:
> Guys,
> The VFD I have feeding power to my Enco mill, is wired directly
> into the original switch, which has 2-speeds forward, and 2-speeds
>in
> reverse. I hardly ever touch the speed controller on the VFD, and
> this setup has been running like that for about 1 1/2 years.
>
> Marv Frankel
> Los Angeles
>

This is a definte NO NO.
The power to the motor MUST NOT be removed whilst the invertor is
running. If you need to switch speed outside the invertor then you
must stop it first then restart.
It's like running a stereo without speakers and load resistors , the
power has to go somewhere.
All the makers books tell you this and they are right. I supply and
fit around 20 new invertors every month to mixing machines.
The failure rate is very very low, they either don't work out the box
or they fail because of motor / wiring problems.

Reversing on a FVD is quite simply you feed a signal to the terminal
marked REV instead of the one marked FWD. Far less trouble than a
three pole change over switch and a damn sight safer as the signal
voltage is around 10 to 24v and 20 or so milliamps depending on make
of invertor.
You can place a pendant style control anywhere you need it with
start, stop, reverse, jog and speed control running off a simple
length of multicore signal wire with no hazard problems.

John S.

John S.

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>

wrote:

> >
> >
> > metlmunchr wrote:
> >
> > >Obviously if you're feeding in single phase power, the reversing
> > >starter would have to be on the leaving side of the VFD. Where
> > >should it be if you're feeding the VFD with 3 phase power?
> > >
> > >
> > No, you don't need any reversing starter, and the VFD makers
> strongly
> > discourage using one. Any VFD can generate the 3-phases in

forward

> > or reverse sequence, thereby reversing the motor electronically.
> >
> > Most modern VFD's under 100 Hp don't care about the phase sequence
> > of the input power. They just turn it to DC, and then create the

3-

> phase
> > output from that.
> >
> > Jon