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Page 13 of 17 Tech Note for PSA 2012-01-001 PF7000_GEN-95

Answer #2: Testing Line Filter Capacitors

The test involves disconnecting all LFCs from the circuit, and testing each LFC 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 LFC.

Testing Steps:

Ensure there is no power to the equipment before testing the LFC.

To prevent electrical shock, ensure the main power has been disconnected

before working on the LFC. 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.

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.

1. Verify that there is no voltage present on the LFC by using a hot stick or any other appropriate voltage-measuring

device.

2. Perform visual inspection to ensure there is no oil leak or bulge in any of the LFCs.

3. Note the location of all the cables and mark them accordingly.

4. Disconnect power cables from the LFC terminals on all four bushings and isolate them from the LFC. (Refer to “Filter

Capacitor Replacement” guidelines in Classic User Manual – Component Definition and Maintenance chapter

(Chapter 6) for using proper torque when reconnecting the LFCs).

5. Connect a low voltage single-phase test power, for instance 110V or 220V, across a phase and the neutral of the

LFC. Switch on the test power and measure the test voltage and current drawn by the LFC. Repeat the test for all

three phases and record the test voltage and current.

The LFC will charge during this test so care must be taken to prevent a

shock or injury. When moving the test connections from one phase to the

next, wait for at least five minutes until the LFC is discharged. Using a hot

stick or other voltage-measuring device verify that the LFC is fully

discharged before touching it.

Rockwell Automation PowerFlex 7000 Tech Note

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