Generator Set Load Sensor Caterpillar

Note: The potential connections for phases A, B and C should correspond to control terminals 1, 2 and 3.

1. Label all wires which are connected to terminals T4 through T9.

2. Connect a DC voltmeter to the load signal terminals T21 and T22 on the generator set load sensor. T21 is a positive terminal. T22 is a negative terminal.

3. Start the engine and fully load the generator set with a unity power factor load. Do NOT parallel the generator.

   Note: Full load is not required if complete load is not available. However, a steady load level is necessary.

4. Record the load signal voltage.

   This voltage is proportional to a percent of full load. For example, if 50 percent load is 3 DCV, then 100 percent load will be 6 DCV. See Testing And Adjusting, "Load Gain - Adjust" for this proportional adjustment.

   Note: The generator set load sensor contains internal current transformers. Due to the low impedance of the current transformers, shorting the terminals (T4 to T5, T6 to T7, T8 to T9) is not effective. The current input must be removed from the generator set load sensor and shorted externally.

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Never disconnect current transformers from the Generator Set Load Sensor when the engine is running. The current transformers can develop very high voltages when open circuited with the unit loaded. This can result in serious injury or death to personnel.

Note: Terminals 4 through 9 of the generator set load sensor are the input terminals from the current transformers.

5. Unload the engine. Stop the engine. Disconnect the lead from T5. Connect both leads from phase "A" CT to T4.

6. Start the engine. Apply the same load as described in 3. Record the load signal voltage.

   Compare this voltage reading to the reading in 4.

   1. If the voltage in 4 dropped by 1/3, Phase "A" is correct. Go to 7.

   2. If the voltage in 4 did NOT drop by 1/3, Phase "A" is not correct. Go to Testing And Adjusting, "Phasing - Adjust".

7. Unload the engine. Stop the engine. Reconnect the lead to T5 that was disconnected in 5. Now disconnect the lead from T7. Connect both leads from phase "B" CT to T6.

8. Start the engine. Apply the same load as described in 3. Record the load signal voltage.

   Compare this voltage reading to the reading in 4.

   1. If the voltage in 4 dropped by 1/3, phase "B" is correct. Go to 9.

   2. If the voltage in 4 did NOT drop by 1/3, phase "B" is not correct. Go to Testing And Adjusting, "Phasing - Adjust".

9. Unload the engine. Stop the engine. Reconnect the lead to T7 that was disconnected in 7. Now disconnect the lead from T9. Connect both leads from phase "C" CT to T8.

10. Start the engine. Apply the same load as described in 3. Record the load signal voltage.

    Compare this voltage reading to the reading in 4.

    1. If the voltage in 4 dropped by 1/3, phase "C" is correct. Unload the engine. Stop the engine. Reconnect the lead to T9 that was disconnected in 9. Go to Testing And Adjusting, "Load Gain - Adjust".

    2. If the the voltage in 4 did NOT drop by 1/3, then phase "C" is not correct. Unload the engine. Stop the engine. Reconnect the lead to "T9" that was disconnected in 9. Go to Testing And Adjusting, "Phasing - Adjust".