21 Jan
2009
21 Jan
'09
6:52 p.m.
On 21 Jan 2009 at 21:10, Paul Koning wrote:
Again, that depends on the design. I've read
several long articles on
the subject in various on-line and paper publications. At least one of
them came with a lot of detailed testing including scope traces showing
waveforms and balance. Both were excellent. I don't have the article
at my fingertips; it probably was in Home Shop Machinist.
To be sure, there are involved designs, but the most common type (at
least in home shops, seems to be a big motor and a capacitor). The
70% figure is mostly anecdotal; certainly by tuning the design and
perhaps adding some sort of control that figure could be improved
upon.
3 phase motors certainly deliver a lot in a compact size. I recall
hooking a grinder that had been languishing in our shop because it
was 440/3 up with a large motor run cap to the 230v single-phase
line. It operated well enough until a wiseguy supervisor decided to
do it right. He had the electrical shop run in a 440/3 distribution
panel and hook the grinder up. The first guy to use it hit the
switch and turned pale. The grinder was eventually replaced with a
240v single-phase unit because no one wanted to use the over-powered
version to wire-brush thermocouple blocks.
Cheers,
Chuck