The scope of the blower VFD upgrade was to replace obsolete reduced-voltage starters with new variable frequency drive (VFD).  With the existing starter circuit, the blowers were run at full speed and the air volume was controlled with inlet dampers on each blower.  The VFD replacement allows air volume to be controlled by modulating the blower speed.  This reduces wear on the motor and blower bearings and has reduced the electrical consumption by an average of 25-30%.


The VFDs were to be installed in the existing motor control center enclosure.  Only one blower could be out of operation during the installation.  The main supply power bus had to remain energized throughout the equipment installation.  Ventilation had to be added to each motor control enclosure to ensure adequate cooling of the drive.  The drives had to operate in conjunction with the existing blower control panels and the plant-wide SCADA system.


Toric removed the existing reduced voltage equipment and moved the main control circuit breaker to allow installation of the variable frequency drive (VFD).  A dv/dt filter was also added to the load side of the drive to provide additional filtering for the existing motors.  The 700 Amp power wiring was installed utilizing flexible insulated busbar.  The control wiring was connected to the existing PLC and SCADA system and each blower was back in service within 48 hours.