Re: Question about how to set up VFD for braking resistor

Thanks Jon, I'll try the settings you suggest an see how they work
out. Is there anything else I have to tell the VFD to let it know
about the resistor or does it automaticly incorporated the external
resistance?

Thanks,
Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, "washcomp" <jeff@w...>
wrote:
> >
> >
> >>I've just installed an Omron/Yaskawa G5+ variable frequency drive
> >>
> >>
> >on
> >
> >
> >>my Bridgeport. I intend to control it from MACH3.
> >>
> >>The good news is the VFD is working like a champ (manually –
still
> >>haven't controlled it yet from MACH3). Maybe I misunderstood
about
> >>the noise, or maybe the load side reactor is doing its job
because
> >>
> >>
> >it
> >
> >
> >>sounds just like a Bridgeport 2J
> >>
> >>I've installed a breaking resistor. I'm trying to figure out
what
> >>braking mode and deceleration I should pick if I'm using a
braking
> >>resistor. Both manuals (Omron and Yaskawa) refer to it, but
> >>
> >>
> >neither
> >
> >
> >>explicitly says what function to select (DC injection braking
> >>maybe?) Any help would be appreciated on this.
> >>
> >>
> OK, first, check the RMS rating of the motor. Assume a 1 Hp, 230 V
3-phase
> motor, it will be about 3.3 A. Multiply by 1.732 (Square root of 3)
and that
> is about the worst case DC link current it should ever deliver when
> decelerating
> at a reasonable rate. So, if your braking resistor can draw 3.3 *
1.732
> = 5.7 A,
> it should be enough. At a DC link voltage of 380 V, the resistor
would be
> 66 Ohms. The Yaskawa manual should specify the minimum permitted
braking
> resistor, pick one less than 66 Ohms and more than the specified
minimum.
> You might double that calculation above, just to get more powerful
braking.
> I have my mill set up for a 0.7 S braking time (from whatever speed
to
> the point
> it cuts over to DC braking). But, when I swap motors to my Westwind
drilling
> spindle, and run it up to 400 Hz (~23000 RPM) I have to set the
braking time
> to 5 seconds or the VFD trips on overvoltage. That tiny spindle
running that
> fast can deliver a lot of energy back to the VFD. As long as you
don't
> get an
> OV fault when decelerating, everything should be fine. I actually
found
> out how
> close to the edge I was at 5 Sec, as I had a program that was
turning
> the spindle on
> and off about once a minute, and after the braking resistor got
good and
> hot I
> had an OV fault. What happened is that the resistor got hot, and
the
> resistance
> went UP, and it couldn't absorb the energy fast enough. But, I
NEVER have
> this with the standard Bridgeport motor.
>
> I have it set up to use regenerative braking down to about 10 Hz,
then
> it switches
> to DC injection braking for 1 second, at .1 times rated amps. This
works
> great.
>
> I have the same setup on my 15" Sheldon lathe, but I have a 1.5 sec
> braking time
> there, due to the massive chuck.
>
> Jon