Electronic Modular Control Panel II+ (EMCP II+) for EUI Engines Caterpillar

Illustration 1	g00633979
System Schematic For AC Transformer Box + (ATB+)

Show/hide table

When the engine-generator, or any source to which the engine-generator is synchronized to, is operating, voltages up to 600V are present in the control panel. Do not short these terminal with line voltage to ground with any part of the body or any conductive material. Loss of life or injury could result from electrical shock or injury from molten metal.

The engine is running. The load is connected. One of the AC phases on the GSC+ is showing 0 volts or 0 amperes.

If there is a problem with AC voltage, begin troubleshooting at Step 1.

If there is a problem with AC current, begin troubleshooting at Step 4.

1. Check the fuses.

   1. Check the three fuses on the AC transformer box (ATB+).

      The fuses should not be blown.

      Expected Result: The fuses should not be blown.

      Results:

      • OK: Fuses are OK. Proceed to Step 2.

      • NOT OK: One or more of the fuses are blown. Check for a shorted component or wiring error. Troubleshoot the fault and repair the fault. See the "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics and Wiring Diagram". STOP.

2. Check the generator output.

   1. Run the engine. Open the circuit breaker or remove the load. Measure the voltage between all three fuses on the ATB+.

      Expected Result: The line to line voltage is correct for all three phases.

      Results:

      • OK: The voltages are correct and the problem remains. Proceed to Step 3.

      • NOT OK: One or more of the voltages are NOT correct. The wiring is faulty or connections are faulty. Check the wiring between the ATB+ and the generator's bus. See the "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics And Wiring Diagram". Also check the electrical connections at the ATB+ terminal. See Testing And Adjusting, "Electrical Connector Inspection". STOP.

3. Check the connections.

   1. Stop the engine.

   2. Check the harness connector and crimp terminals of the ATB+.

   3. Check the GSC+ harness connector. See Testing And Adjusting, "Electrical Connector - Inspect".

   4. Check for one or more broken wires between the ATB+ and the GSC+. See "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics And Wiring Diagrams".

      Expected Result: All connectors are OK and the problem is no longer present.

      Results:

      • OK: All connectors are OK and the problem is no longer present. This procedure has fixed the fault. STOP.

      • NOT OK: The AC voltage still has a problem. It is unlikely that the GSC+ is faulty. Replace the ATB+. If the problem persists, then replace the GSC+. STOP.

      • NOT OK: The AC current still has a problem. Proceed to Step 4.

4. Check the current transformers.

   1. Stop the engine.

   2. At terminals 51, 52 and 53 of the ATB+, disconnect only the wires that lead away from the ATB+. These disconnected wires go to the current transformers (CT1, CT2, and CT3).

   3. Measure the resistance from terminal 50 to each of the disconnected wires.

      Expected Result: The resistance should be less than 5 ohms.

      Results:

      • OK: The resistance is correct. Therefore, the current transformers are good. Proceed to Step 5.

      • NOT OK: One or more of the resistance measurements are NOT correct. A current transformer or related wire is open. Check for an open CT or wiring. See "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics And Wiring Diagrams". STOP.

5. Check the ATB+.

   1. Stop the engine.

   2. Remove the harness connector from the GSC+.

   3. At the GSC+ harness connector, measure the resistance: contact 4 to contact 16, contact 5 to contact 16 and contact 6 to contact 16. Allow each measurement to stabilize.

      Expected Result: Each of the three resistances should be 120 ± 20 ohms.

      Results:

      • OK: Proceed to Step 6.

      • NOT OK: One or more of the resistance measurements at the GSC+ harness connector is NOT correct. Therefore, the ATB+ or the related wiring is faulty. Check for an open or short in the wiring from the GSC+ harness connector to the ATB+ harness connector. See "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics And Wiring Diagram". Check the electrical connections at the GSC+ and ATB+ harness connectors and at the ATB+ terminal strip. See Testing And Adjusting, "Electrical Connector - Inspect". If necessary, repair the wiring or replace the wiring. If the fault is not found, replace the GSC+. STOP.

6. Check the ATB+.

   The wires that were disconnected in step 4 remain disconnected. The only wires that are connected to these terminals should lead into the ATB+.

   1. At the terminal strip of the ATB+, measure the resistance: terminal 51 to 50, terminal 52 to 50 and terminal 53 to 50.

      Expected Result: All resistances should be less than 1 ohm.

      Results:

      • OK: All resistances are correct. The ATB+ is OK. The fault is in the GSC+ or the GSC+ harness connector. Check the GSC+ harness connector. See "Generator Set Wiring Diagram" in Testing And Adjusting, "Schematics and Wiring Diagram". If the connector is good and the fault remains, then replace the GSC+. See Testing And Adjusting, "EMCP Electronic Control (Generator Set) - Replace". STOP.

      • NOT OK: One or more of the resistance measurements are NOT correct. The ATB+ is faulty. Replace the ATB+. STOP.