27 Apr
2005
27 Apr
'05
4:36 p.m.
All,
On 4/27/05, Kevin Handy <kth at srv.net> wrote:
[chomp]
Note that you can now buy solid state phase
converters.
I have a brother that switched to one in his wood-shop, and
it has many advantages: More efficient (cheaper to run);
more motors work with it; more power is available on
created phases; quieter; etc.
It works much better than the rotery ones he used to
use; which were designed as phase converters, not just
some large three pase motors; and his equipment
is much happier, too.
All the solid state phase converters I have come across use a three
phase H bridge to generate three phases from a common intermediate DC
rail. The incoming voltage is converted to DC, switched, PWM
synthesising a sinusoidal at the required frequency.
The PWM works pretty well for induction motors. I would expect big
iron to have some issues.
Depending on how the three phases are used for the big iron, it may be
possible for all three phases to be wired the same. That is
electrically connect all three phases together, to a single phase
supply. This can only be done if each phase is used independently of
the others (separate transformers/SMPS). If there is anything in the
machine that wants all three phases - find a nice clean sinusoidal
source.
As a couple of characters of warning, only think about running the
three phase machine from a single phase if you understand 3 phase
systems. Things have the potential to go bang (and probably will) if
you get it wrong.
Simon
--
------------------------------------------------------------------------
"Well, an engineer is not concerned with the truth; that is left to
philosophers and theologians: the prime concern of an engineer is
the utility of the final product."
Lectures on the Electrical Properties of Materials, L.Solymar, D.Walsh