Re: The Answers: Question on VFD line rectors

For those that are interested:

Short form: Your motor will run fine on a VFD without them. Unless
it is a motor specificly designed for variable speed, it not last as
long.

Long form:

I got a hold of an applications engineer at MTE who had nothing to
do but give me the parameters on what makes a good line reactor:

A proper size reactor on the line side of a VFD blocks harmonics in
both directions. It also acts as an inertial damper and and smooths
over voltage fluctuations and spikes. Apparently a Corcom EFI
filter can/should also be put on this side of the VFD. In shot, it
protects the dirve.

A proper size reactor on the load side of a VFD smooths out the wave
form. Especially in the case of a motor which was not designed for
variable speed, it will reduce the heating of the motor's coils and
greatly extend its life. It also quiets down the sound the motor
makes. Capacitors, if properly tuned to the reactors (apparently
not trivial to do) will make an even better sine wave.

The optimal % reactance is apparently about 5%. The reactor's rated
inductance is reduced by the proportion of the operating voltage
compared to the rated voltage. It is also reduced by the percentace
of the motor current as a proportion to the rated current of the
reactor.

A too small reactor will protect the drive somewhat against voltage
fluctuations, but will not filter harmonics significantly. If the
load side reactor is too small, it has little benefit.

Regards,
Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "washcomp" <jeff@w...> wrote:
> I'm planning on adding a VFD to my Bridgeport (varying the speed
> from my CNC controller). They recommend the use of a line reactor
> on both the input and the output sides.
>
> Locally, I have 208V 3 phase A.C. 60Hz.
> I have a 1.5 HP motor on my Bridgeport
>
> I came across this and was wondering if it would be the proper one
> my application:
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?
> ViewItem&category=42881&item=2570523396
>
> Thanks and regards,
> Jeff