Reported Failures Of 110-4422 Rectifiers And 110-4424 Rectifiers On 3500-Series Generator Sets Caterpillar

Reported Failures Of 110-4422 Rectifiers And 110-4424 Rectifiers On 3500-Series Generator Sets

Usage:

ELECTRIC POWER GENERATION

ENGINE

POWER MODULE

SR4 (2ED, 2SM, 3RD, 3WF, 4MD, 5ZA, 6LA, 6SA, 6WR, 8FD, 8MM, 8ZD, 8ZL),
SR4B (1BN, 1HN, 2DM, 2DN, 2FN, 2GM, 2GN, 2GZ, 2HN, 2SN, 3BM, 3EN, 3FN, 3GN, 3HN, 4DM, 4EN, 4FN, 4GN, 4WN, 5DM, 5JW, 5SN, 5WN, 6DW, 6GM, 6SN, 6ZZ, 7DN, 7GM, 7TN, 8DM, 8EZ, 8GW, 8HM, 8LZ, 8NN, 8PZ, 8TZ, 8XS, 9AZ, 9CN, 9DZ, 9EN, 9GZ, 9MZ, 9RZ, 9WZ, 9XZ, AAD, AAJ, AAR, AAY, ABH, ABM, ABY, ACA, ACP, ACX, ADD, ADL, ADR, AEB, AEZ) ELECTRIC POWER GENERATION;
3508 (23Z, PTK),
3508B (PTJ, PTN),
3512 (PTG, PTH),
3512B (4AW, 5AW, 8RM, PTF),
3516B (1NW),
G3508 (2TJ, CPS),
G3516 (CSZ),
G3516B (CSC),
G3520C (CWW) ENGINE;
PM3516 (BPD) POWER MODULE

Problem:

Caterpillar has investigated recent failures of the 110-4422 Rectifier and the 110-4424 Rectifier on 3500-Series Generator Sets. The majority (60%) of these failures occurred on 3500-Series Generator Sets that were being used in parallel applications. In parallel applications, improper droop circuits and improper paralleling procedures were found the main reason the rectifiers failed. For information on paralleling generators with utilities, refer to TIBU3345, 13JUNE2001, "Paralleling Generators to Utility Substations".

The remaining recent failures of the 110-4422 Rectifier and the 110-4424 Rectifier were found to be due to poor internal connections in the diode cube. The failed diodes (either due to external causes or quality problems) revealed a failed output post-to-base solder connection as the prevailing root cause.

Solution:

Caterpillar has worked with the supplier to improve the internal connection quality of the 110-4422 Rectifier and the 110-4424 Rectifier. The diode assembly and manufacturing processes have also been improved in order to eliminate quality issues. Because of the improved internal solder connections in the 110-4422 Rectifier and the 110-4424 Rectifier, there has been a significant failure reduction in claims for diode packs that were built after April 2000. The date code on rectifiers that were built after April 2000 is 0017 or greater.