Re: [CAD_CAM_EDM_DRO] VSD's and Line Reactors

turbulatordude wrote:

>Hi all,
>
>I'm looking for a low cost VSD for a 3/4 HP 3ph motor for use on my 9"
>lathe.
>
>AutomationDirect has a 1hp unit for under $200 but 'highly recomends' a
>Line Reactor. The Line Reactor is about the same price as the VSD.
>
>My questions are.
>
>Is a Line Reactor a good feature or not needed in a home shop. We have
>a couple computers in the house and obviously the PC as a controller on
>the CNC stuff.
>
>

Why do they "highly recommend" it? Can they give you a precise answer?
Is it because they make more money on this part?

I have never used a line reactor on a VFD (also known as VSD, although
that term
includes mechancal as well as electronic variable speed drives).
Possibly, this will
make the rectifiers last longer with single phase input, but I'm not
even convinced
of that. If their reason is conducted EMI (electronic interference) a
power line
filter salvaged from some electronic gear (or bought from Digi-Key if
you have
to) will do MUCH better than their reactor, at 1/10th the price. This I
HAVE
done on some VFD applications, where it caused interference with equipment.
I have NEVER seen any problem with off-the-shelf computer gear, as they have
a switching power supply that needs similar protection, anyway. I did have
interference in a computer monitor (just a slight fuzziness on the
screen) and my
homemade microprocessor-controlled air compressor. A salvaged line filter
box fixed the problem for free.

>Is a line reactor something that is easily obtained from a junk yard ?
>I walked past one the other day, but it was huge, at least a 18inches
>high.
>
>

Many higher-end computers and electronic gear have them built into the power
input connector. For a 1 Hp 240 V load, a filter out of a copier or laser
printer would likely be heavy enough. (It should have a current rating
listed on the part.)

Jon