Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 273)

TROUBLESHOOTING 10-31
1557-UM050F-EN-P – June 2013
Replacing Snubber Capacitors
Snubber capacitors in both the machine side converter and line side converter assemblies can be
replaced without having to remove the heatsink assemblies from the drive. For 4160 volt drives it may be
necessary to remove the small snubber resistor and capacitor assembly so that there is sufficient room to
remove the capacitor.
In the machine side converter assembly, remove the M8 bolt at the front of the capacitor. Remove the ¼”
nuts which fasten the snubber diode copper link to the heatsink. The snubber diode can now be removed
complete with its clamp and links. Rotate the capacitor counter-clockwise by hand so that the capacitor
can be removed. Note the M8 hardware at the back of the capacitor is locked in place with adhesive
because of its access difficulty.
Install the new capacitor by threading it onto the M8 bolt by hand. Replace all the links described in the
removal procedure.
In the line side converter assembly, remove the M8 bolt at the front of the capacitor. Rotate the capacitor
counter-clockwise by hand so that the capacitor can be removed. Note the M8 hardware at the back of the
capacitor is locked in place with adhesive because of its access difficulty. Install the new capacitor by
threading it onto the M8 bolt by hand. Reassemble the front M8 bolt and leads.
Replacing Snubber Resistors
Snubber resistors are mounted on vertical glass polyester channels. The channels should not be removed
from the drive because they form part of its internal support structure.
Replacing DI/DT Reactors
Di/Dt reactors ( air core chokes ) are located behind the insulation barriers of the machine side converter
section. They are designed to be removed with front access, however; if rear access is available; it is
easier.
In the case of rear access, remove the rear cabinet covers and access is available to the mounting
hardware and links of the reactors.
In the case of front access, the machine side converter heatsink assemblies must be removed as
described previously in REPLACEMENT OF THYRISTORS
– MACHINE SIDE CONVERTER. The
snubber resistor assemblies on the right hand side of the machine side converter section must be
removed. Remove the mounting hardware of the large barrier at the back of the machine side converter
section. After removal of the barrier, mounting hardware of the reactors is now accessible.
Ensure that the polarity marks of the reactor are in the correct position when the new reactor is installed.