238-101F

Power down and inspect KDR connections

Turn off main power and check all wiring connections between the commutating reactor (KDR) and the UVR module in the drive cabinet.

Ensure main power is OFF and wait 5 minutes for capacitor discharge before touching any connections.

Measure connection resistance

Use a multimeter to check continuity and resistance values on KDR wiring harness. Resistance should be within manufacturer specifications (typically 0.1-2 ohms).

Check for corrosion or oxidation on terminal connections which can cause high resistance readings.

Retighten and test connections

Clean and retighten all KDR connections, then power up system and monitor for alarm recurrence during drive enable sequence.

Apply dielectric grease to connections in humid environments to prevent future corrosion.

Measure KDR inductance values

Disconnect KDR from system and use an LCR meter to measure inductance values. Compare readings against nameplate specifications or service documentation.

Ensure KDR is completely isolated from power before testing.

Visual inspection of KDR

Inspect commutating reactor for signs of overheating, burnt coils, cracked ferrite cores, or physical damage that could affect inductance.

Look for discoloration around coil windings which indicates thermal stress or overcurrent conditions.

Replace KDR if damaged

If inductance readings are outside specifications or physical damage is evident, replace the commutating reactor with exact Heidenhain part number.

Always verify replacement part compatibility with your specific TNC drive model and firmware version.

Access drive parameter menu

Navigate to MOD function and access the drive parameters menu to review UVR and KDR configuration settings.

Document current parameter values before making any changes for easy rollback if needed.

Verify KDR type parameters

Check parameters related to commutating reactor type and inductance values match the installed KDR specifications from the machine documentation.

Incorrect drive parameters can cause severe damage to drive components or motors.

Reset and recalibrate UVR settings

Reset UVR parameters to default values and perform auto-configuration if available, or manually enter correct values per machine specifications.

Use the TNC's built-in drive optimization function to automatically detect and configure KDR parameters.

Swap UVR module for testing

If available, temporarily replace the UVR module with a known good unit to isolate whether the fault is in the UVR hardware or external components.

Ensure exact part number match and proper ESD precautions when handling electronic modules.

Check UVR module status LEDs

Examine status indicators on the UVR module during power-up sequence and compare LED patterns against service documentation.

LED patterns during initialization can indicate specific internal faults within the UVR module.

Replace UVR module if confirmed faulty

If testing confirms UVR module failure, replace with genuine Heidenhain part and perform complete drive recalibration procedure.

After UVR replacement, run full drive commissioning sequence to ensure proper integration with TNC system.