In article ,
Charles A. Sherwood wrote:
I am considering using a static phase converter to run a 3ph 1.5HP
bench grinder and 1/2HP dust collector.

Phase a matic makes a standard and a heavy duty phase converter.
Is the standard a more robust version or are there some significant
differences. Maybe the standard just has start caps and the Heavy
duty also has run caps? There is about a 30 dollar price difference.

You've already gotten information posted on the difference
between the standard and the heavy duty.

My question is whether the dust collector will ever have to be
started while the grinder is not running. The reason is that there is
a limited range of horsepowers that these "static" converters will
handle. But -- the 1.5 HP grinder, when running, can act as a rotary
converter and this will start the dust collector with no problems.

However, also note that you will lose about 33% of the load
capability with these phase converters, compared to running on true
three phase -- including that made from single phase with a rotary
converter or a VFD (Variable Frequency Drive -- an electronic device
which synthesizes the three phase from rectified input voltage which can
be single phase.

The VFD's strong point is that it allows you to tune the speed
of the motor, if that will help you on the grinder. It does on a lathe
or a milling machine, but I'm not sure about a grinder.

The rotary converter can be built from a *used* (and therefore
cheap) three-phase motor of somewhat higher horsepower (say 2-3 HP for
this) and some means of starting (which could be the static phase
converter, or some thing which you build. You ideally should then
tune the rotary converter with capacitors to get the best balance of
voltage and current. This won't matter for something like a bench
grinder, but a well-balanced three phase yields a better surface finish
with a surface grinder.

Good Luck,
DoN.

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