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VFDs have proven their merit in
numerous WWTP applications and have become an accepted
technology. The reliability of VFDs compared to
traditional mechanical systems cannot be challenged.
Likewise, regenerative blowers are fast becoming the "preferred"
blower for WWT aeration. Regenerative blowers provide low
maintenance that only requires bearing lubrication, no
rebuilding, no expensive parts and, noise levels that are below
85 db(A) in most models.
VFDs eliminate the need for a
motor starter or control; the VFD is your starter. In
addition, the VFD can be programmed for "soft start" -
eliminating the high inrush currents of typical motors - and
reducing your power costs.
VFDs are efficient and provide a
high power factor that does not change with load
conditions. For example, the power factor on an ac
induction motor operating at 50% of load has a typical power
factor of 35-50%.
VFDs provide reliable
service. For example, a stand-by circuit can be included
with your VFD that would allow the blower to be switched to your
normal power lines while removing the VFD from the line for
maintenance.
VFDs can be switched between
multiple motors. For example, if you have two blowers for
your aeration basin, the VFD can operate one blower until it
reaches its rated 60Hz speed (3450 rpm). At that point,
that blower motor would be switched to run across-the-line at a
constant speed and
the VFD would be switched to operate the second blower motor at
variable speed.
Additional control functions can
be added to meet your needs. For example, a touch screen
(MMI) can be included to simplify system changes; recorders can
log data for archiving; process outputs can be telemeter to a
remote site; alarms can sound upon certain conditions.
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