Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) - Manual (Page 284)

5-42
Component Definition and Maintenance
7000A-RM001A-EN-P – January 2011 7000 “A” Frame
Testing Filter Capacitors
Two methods of testing/checking the capacitors are explained below. The
first method is simple, easy, and takes least amount of time to check the
capacitors. In this method, you would need a digital multimeter (DMM)
to measure the capacitance in micro-Farad (µF) across each phase-to-
neutral of the capacitors. It is recommended that you should use this
method since it avoids the chance of creating re-torque issues because you
don’t have to disconnect the capacitors unless the readings are off by 15%
or more. For accurate measurements, Rockwell recommends that you
should use one of the DMMs shown in Figure 5.35.
The second method involves disconnecting all capacitors from the circuit,
and testing each capacitor individually by applying 120V across each
phase-to-neutral and measuring the current in each phase. This method is
most accurate and can be used to confirm the integrity of the capacitor
when the readings from the first method appear to be unsatisfactory.
First Method
1.
Ensure there is no power to the equipment before testing the
capacitor.
A T T E N T I O N A T T E N T I O N To prevent electrical shock ensure the main power
has been disconnected before working on the
capacitor. 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.
A T T E N T I O N A T T E N T I O N Verify the load is not running due to process. A
freewheeling motor can generate voltage that will
be back-fed to the equipment being worked on.
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.
D.C. Link / Fan / Control
Components (cont.)