In article ,
says...
On Sun, 11 Sep 2005 01:09:51 -0400, Ned Simmons
wrote:

In article ,
says...

"R. O'Brian" wrote in message
news:81kUe.22811$hp.4649@lakeread08...
Make sure the VFD of choice will run on single-phase. Some have phase
loss
detection which shuts down the unit if a phase goes down.

Randy

Is that a parameter that can be changed through programming?

It's a pretty unusual feature on small (10-20HP?) VFDs. In
20+ years of building and working around industrial
machinery I've never actually run across a small VFD that
wouldn't run on single phase.

Ned Simmons

Don't all VFD's work by converting DC to synthesized 3-phase AC?

All that I'm familiar with, yes.


With rectified 3-phase there is no need to store energy because
full-wave rectified AC never goes below 86.6% of peak line voltage.
With rectified single-phase, some capacitive storage is necessary so
there is always DC available to synthesize all three phases.

The capacitance also serves to absorb energy when the drive
is decelerating the motor. Many (all?) VFDs will disable
the motor if the bus voltage goes out of range. Some can be
configured to display the bus voltage, which can be useful
when setting the accel/decel parameters and for determining
if a braking resistor may be required.


So, it would seem that any VFD should be able to run on single-phase
if sufficient capacitive storage is present.


Which is why I referred to lost phase detection as a
"feature". If a drive can detect a lost phase condition
then it seems to me that capability is intentional, not a
necessary consequence of the design.

Ned Simmons