LEM Failures On UPSB505 Uninterruptible Power Supply{4480} Caterpillar

Uninterruptible Power Supply:

UPSB505 (S/N: YTM1-UP)

Introduction

The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.

Problem

The current from AC Normal or AC Bypass, or remaining parallel UPS could be high enough to blow Input or Output fuse during IGBT failure. In such cases the LEM could also be affected due to the insufficient LEM maximum current limit to protect the LEM. The faulty LEM may not be identified during the IGBT repair process, but it could appear after some time (IGBT fail again).

This phenomenon is also applicable for the battery chopper. The LEM could also be affected in case of power fuse blown (input or output) without IGBTs failure.

Solution

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High voltage may be present. The power source must be disconnected before working on the equipment. Failure to disconnect the power source could result in injury or death. Verify that the equipment is not energized before performing any maintenance. This work must be performed by trained personnel with correct tools and procedures.

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Bodily contact with electrical potential can cause bodily injury or death. To avoid the possibility of injury or death, ensure that the main power supply has been disconnected before performing any maintenance or removing any modules.

Replace the faulty 3 LEMs from the Power Factor Correction Rectifier (PFC) or Inverter, in case of IGBT failure or fuse blown (Input or Output). Refer to the Illustrations 1 and 2.

Note: LEM has been referred as "Current transformer" in the normal schematics and as "AC and DC Current Sensors" in the French schematics.

Illustration 1	g03063897
AC normal

Illustration 2	g03063896
Inverter output

Replace both the faulty battery LEM, in case of chopper battery IGBT failure. Refer to the Illustration 3.

Illustration 3	g03063917
Battery chopper

Refer to the Schematic, UENR2160-00, "UPSB505 Uninterruptible Power Supply Electrical System (Interactive)", for complete schematics.

The LEM replacement is also applicable for the symptoms that are listed in the Table 1.

Return the failed parts to Caterpillar for failure analysis.