Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control - Manual (Page 100)

100 Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014
Chapter 3 Component Definition and Maintenance
Testing Filter Capacitors
There are two ways to test line filter capacitors. Rockwell Automation
recommends the first method as it reduces the chance of re-torque issues because
the capacitors are not disconnected. If the readings are unsatisfactory, the second
method is more accurate, but involves disconnecting and testing them
individually.
First Method
1. Ensure there is no power to the equipment.
2. Follow appropriate safety steps to isolate the equipment from medium
voltage.
3. Verify that there is no voltage present on the capacitor by using a hot stick
or any other appropriate voltage-measuring device.
4. Perform visual inspection to ensure there is no oil leak or bulge in any of
the capacitors.
5. Using a DMM measure the capacitance across each phase-to-neutral of
capacitors without removing any connections.
If the difference between the highest and the lowest readings is below 15%,
then all capacitors are in good condition. If the difference between the
highest and the lowest readings is off by 15% or more, then you might have
a bad capacitor. If more than one capacitor is used in the circuit, then you
would need to isolate each of them and check them separately to identify
which one is defective.
6. Before disconnecting the capacitors, note the location of all the cables and
mark them accordingly.
7. Disconnect power cables from the capacitor terminals on all four bushings
and isolate them from the capacitor (see
Replacing Filter Capacitors on
page 99 ).
ATTENTION: To prevent electrical shock, disconnect the main power before
working on the drive. Verify that all circuits are voltage-free using a hot stick or
appropriate voltage-measuring device. Failure to do so may result in injury or
death.
ATTENTION: Verify the load is not running due to process. A freewheeling
motor can generate voltage that feeds back to the equipment.
ATTENTION: Capacitors that appear bulged or are leaking oil indicate potential
problems with the internal elements. DO NOT USE. These units must be
replaced. Failure to do so may lead to personal injury or death, property
damage, or economic loss.