Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control (PanelView 550) - Manual (Page 44)

44 Rockwell Automation Publication 7000-UM151E-EN-P - January 2013
Chapter 3 Component Definition and Maintenance
Testing Filter Capacitors
1. Isolate and lock out all power to the drive.
2. Perform visual inspection to ensure there is no oil leak or bulge in any of
the capacitors.
3. Note the location of all the cables and mark them accordingly.
4. Disconnect power cables from the capacitor terminals on all four bushings
and isolate them from the capacitor.
5. Connect a low voltage single-phase test power, for instance 110V or 220V,
across a phase and the neutral of the capacitor. Switch on the test power
and measure the test voltage and current drawn by the capacitor. Repeat
the test for all three phases and note down the test voltage and current.
6. Calculate the capacitance from the measured values of test voltage and
current. For a good capacitor, the calculated capacitance value for each of
the three readings should be within +10% of the capacitor nameplate
micro-Farad. If it is outside this range then replace the capacitor.
This example demonstrates the calculation for capacitance value.
Suppose a capacitor under test is rated at 400kVAR, 6600V, 50Hz, 29.2μF.
Assume you are using 200V, 50Hz test power with the recorded voltage and
current values for each test as shown in the table below.
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: The capacitor will charge during this test so take care to
prevent a shock or injury. When moving the test connections from one
phase to the next, wait five minutes minimum for the capacitor to
discharge.
Phase - Neutral L1-N L2-N L3-N
Test Voltage 200V 200V 200V
Measured Current 1.87A 1.866A 1.861A