stations in municipal sewage systems are an application that often
need a phase converter. They are commonly placed in residential
areas where three-phase power is not readily
installation consists of
redundant pumps with one of the pumps
acting as a backup if the other pump fails or the volume to be
pumped exceeds the capacity of the other pump.
The only type of static converter that should be used
with these installations is a specialized type that uses
auto-transformers along with the capacitors in the converter.
The converter is a dual converter that is essentially two converters
in one, since a static converter can be
used on only one motor load. The
three-phase voltage balance is tuned to the load by adding and
subtracting capacitors and by changing taps on the transformers.
The voltage balance is good as long as the load does not change, but
even modest changes in the load result in serious voltage imbalance
for a motor operating at its rated capacity.
converters are not a good solution for dual lift stations.
Because the load changes dramatically as the pumps switch on and
off, voltage balance is a problem.
inefficiency of the converter is a major drawback since the
converter is likely to be running most of the time, and
configuring a system
to turn the rotary converter on and off also complicate the
converting VFDs can be used in these installations with a separate
VFD for each pump. Since a VFD cannot be used as a power supply,
standard control panels for dual lift stations cannot be used. The
VFD must be wired directly to the motor leads, not to the input of a
standard pump panel.
phase converter can power one or both pumps with perfect voltage
balance. It can be used as a power supply, providing power to the
standard pump panel. A digital phase converter can remain
constantly powered, using very little power when on standby, or can
easily be configured to turn on and off automatically.