Filter capacitors – Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control User Manual
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Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014
Chapter 3
Component Definition and Maintenance
Filter Capacitors
Filter capacitors are used on the motor side for all drives. The AFE rectifier also
includes filter capacitors on the line side (see
The filter capacitors are three-phase four-bushing units and “oil-filled”. The
three-phase capacitors are comprised of internal single-phase units that are
connected in a Y configuration. The neutral point of the Y is connected to the
fourth bushing, which is accessible and can be used for neutral point voltage
measurement or other protection/diagnostics purposes. Depending on the drive
configuration, the fourth bushing may or may not be connected to circuitry. The
metal cases of the capacitors are grounded through a stud on the capacitor
housing.
The capacitors are equipped with internal “bleeding resistors” to discharge the
capacitor and reduce its voltage below 50V in five minutes when left
disconnected. A typical three-phase capacitor is shown in
.
Figure 84 - Motor Filter Capacitor
Line Filter Capacitor (with AFE
rectifier only)
Motor Filter Capacitor
WARNING: Allow 5...10 minutes for motor capacitors to safely discharge
voltage prior to opening cabinet doors.
WARNING: Verify that the load is not turning due to the process. A
freewheeling motor can generate voltage that will be back-fed to the
equipment being worked on.