Rockwell Automation 1519 MV DRIVE HARMONIC FILTER PF CORRECTION UNIT - Manual (Page 7)

1519-5.0 – May 1998
Introduction 1-3
Application Considerations (cont.) In this scheme, energizing the filter can be a permissive to allow starting the
drive or the drive can be configured to operate independently of the harmonic
filter. Similarly, a harmonic filter fault can be configured to shut down the
drive or it can be configured to create an alarm only and allow the drive to
continue to operate. The isolation switch associated with the harmonic filter
contactor can be opened to allow servicing of the filter without necessarily
affecting operation of the associated drive.
Protective Features There are a number of protective features that are incorporated in each tuned
circuit of the harmonic filter to cover the following functions:
• reactor overtemperature
• reactor/capacitor overload
• short-circuit protection for capacitors
• blown capacitor fuse detection
Reactor Overtemperature
Reactor overtemperature is implemented in the form of a normally closed
thermal switch, one of which is embedded in each of the three windings of a
particular harmonic filter reactor. The thermal switches operate at a temperature
somewhat below the maximum allowable temperature for the reactor
insulation. The three switches are wired out individually to a terminal strip on
the top of the reactor where the switches are then connected in series. These
contacts are typically configured to open a dedicated harmonic filter contactor
and/or shut down an associated drive.
Reactor/Capacitor Overload
An Allen-Bradley Bulletin 592 Thermal Overload relay is driven by window-
type current transformers which are installed on each of the phases feeding
each set of three capacitors. The heater elements are factory selected to
protect the filter reactors and capacitors from an overload condition. If there is
one capacitor per phase in a particular harmonic filter then the heater elements
are selected on the basis of the root-mean-square (rms) current rating of the
reactor in the filter. This heater element sizing also allows protecting the
capacitors against overload. If there are two identical capacitors per phase in
the harmonic filter then the heater elements are chosen based on half of the
rms current rating of the associated reactor. A contact from the 592 overload
relay is wired to either open a dedicated harmonic filter contactor and/or shut
down the associated drive.
1519-IN050B-EN-P June 2013