1986/06/01 Caterpillar

Optional Load Sharing Electric Governor Changed From 2301 to 2301A Woodward Governor

Usage:

3500 Family Of Generator Sets And SI (Spark Ignited) Engines

Reference: Engine News, April 11, 1984, Page 9, "Overvoltage Protection For Woodward 2301 Governor".

Reference: Special Instruction SMHS8363, SELS0115 and Service Manual (SENR2928-01) for 2301 Governors.

Description of Change: The load sharing electric governor is an optional governor for the 3500 Family of Generator Sets and SI Engines. Formerly, the optional load sharing electric governor was a Woodward 2301 Governor. Now, this optional load sharing electric governor is a Woodward 2301A Governor. The standard 2301 Speed Control Governor (sometimes called standby control) has not changed.

The most important improvement of the 2301A Governor is the extended power supply voltage range. Thus, the 4W5391 Box Assembly (preregulator) is not required to protect the 2301A Governor from high voltage spikes and surges. See Reference Article. Other improvements are:

... The cold start relay, that is frequently required when the preregulator is used, is also not required. Special Instruction SMHS8363 covers installation of this part if needed.

... The internal power supply in the 2301A Governor is electrically isolated, eliminating the need for a high voltage selector (best battery selector). The potential for problems with grounding and governor incompatability have been reduced.

... The 2301A Governor can be adjusted for engines having much different dynamic characteristics.

... A high quality load sharing relay is not required in the load sharing lines. The 2301A Governor contains its own load sharing relay.

... A start-fuel limit feature has been added to reduce overfueling at start-up.

... Excessive contact resistance in the idle-rated switch will not affect speed.

There are many other differences between the 2301 and 2301A Governors. It is important that the people installing and adjusting the engines and switch gear be aware of these many differences and refer to the Special Instruction SELS0115, "Installation Of 2301A Load Sharing Control Group".

Adaptable To: The 7C246 Governor Control Assembly (2301A) can be used to replace the former 4W5395, 8N409, 4W5394, or 8N6728 Governor Control Assemblies (2301). The Special Instruction comes with each new governor. The instructions cover installation of the new governor in combination with either the former governor or with other new governors, or as a replacement for the former governor.

The following topics explain in more detail the differences between the two governors and cover new prestart and operation adjustments.

Differences Between 2301 And 2301A Governors

Terminal Numbers Change

The terminals used for the various interface connections have changed. These are shown in the following Chart and in the Special Instruction. Only terminals one through eleven remain the same.

Terminals That Have New Functions

The minimum fuel and defeat failsafe functions now use normally open contacts, or no connections, where normally closed contacts, or jumpers, were used previously.

Two Functions No Longer Used

The functions for former terminals 28 and 25 are not required on the 2301A Governor. However, these two terminals are still used with different functions assigned. See Chart.

Added Terminals

Load signal terminals 12 and 13 are now located on the terminal strip. Terminals 12, 22 and 27 are commom terminals to be used for shield connections. Do not use these terminals when replacing a 2301 Governor with the 2301A Governor. See Special Instruction.

Actuators In Tandem

The 2301A Governor can not be used to run actuators in tandem as shown in the Special Instruction.

NOTE: Make two changes to Sheet 3 and to Sheet 4 of the Special Instruction. Mark out the Note B and all of Detail A on both sheets.

Changes In Control Adjustments

The 2301A Governor does not have a de-droop adjustment and the stability adjustment has been replaced by a Reset Adjustment. Adjustments for Actuator Compensation and for Start-Fuel Limit have been added. The illustration shows the panels for both governors.

Comparison of Adjustments.

New Start-Up And Adjustment Procedures

Initial Prestart Settings

1. Rated Speed

A. Set the Rated Speed potentiometer to minimum (fully counterclockwise).

B. Set the external speed trim, if used, to mid-position.

2. Reset - Set at mid-position.

3. Gain - Set at mid-position.

4. Ramp Time - Set at minimum (fully counterclockwise).

5. Low Idle Speed - Set at maximum (fully clockwise).

6. Load Gain - Set at mid-position.

7. Droop - Set at minimum (fully counterclockwise).

8. Actuator Compensation.

A. Set the Actuator Compensation potentiometer at 2 on the 0 to 10 potentiometer scale for diesel, gas turbine, or fuel injected gasoline engines.

B. Set the Actuator Compensation potentiometer at 6 on the 0 to 10 potentiometer scale for carbureted gas engines.

9. Start Fuel Limit - Set at maximum (fully clockwise).

10. Be sure the actuator is connected to terminals 20 and 21.

Prestart Checks

1. Ground Checks. Measure the resistance between terminals 22 and the switch gear cabinet, and between 25 and 22. If the resistance is not infinity, remove each wire from the terminal strip until the resistance becomes infinite. Correct any wiring problems before proceeding.

NOTE: Be sure the power is not connected to 16 and 15.

2. Make sure the fuel linkage is free and does not stick or bind.

3. Check wiring and see that all screw terminals are tight.

Initial Engine Operation

Use the procedure in the 2301 Governor Service Manual (Pages 24, 25 of SENR2928-01) with the following two exceptions:

... The terminal numbers referred to have to be changed as shown in the preceding Chart or in the Special Instruction.

... The following procedures must replace Step J, "Gain And Stability Adjustment":

1. Adjust for stable operation.

If engine operation is stable, go to the following "Speed Setting Adjustment" procedure.

If the engine is hunting at a rapid rate, slowly decrease the GAIN (turn the potentiometer counterclockwise) until performance is stable. Adjusting the GAIN may cause a momentary speed change which can be minimized by turning the GAIN potentiometer slowly.

If the engine is hunting at a slow rate, increase the RESET (turn the potentiometer clockwise) until the engine stabilizes. If increasing the RESET potentiometer does not stabilize the engine, it also may be necessary to either:

... Slowly decrease the GAIN (turn the potentiometer counterclockwise) or

... Slowly decrease the GAIN and increase the ACTUATOR COMPENSATION.

2. Speed setting adjustment.

With the engine operating stably, and the external speed trim potentiometer (if used) set at mid-position, adjust the RATED SPEED potentiometer to obtain the desired operating speed.

3. Dynamic adjustment.

The object of the GAIN and RESET potentiometer adjustment is to obtain the optimum, or desired, stable speed response.

Connect a DC analog voltmeter to terminals 20 (+) and 21 (-) to monitor the actuator voltage.

NOTE: Adjusting the GAIN may cause momentary changes in speed which can be minimized by turning the GAIN potentiometer slowly.

Increasing the setting of the GAIN potentiometer provides a faster transient response because the magnitude of the speed change from a sudden change in load is reduced. To achieve optimum response, slowly increase the GAIN (turn the potentiometer clockwise) until the voltage on the voltmeter becomes slightly unstable. Then slowly turn the GAIN back counterclockwise as necessary to stabilize the meter reading. Step-load the generator, or bump the actuator terminal shaft, to make sure the prime mover returns to the correct speed with little overshoot or undershoot of the speed setting. To reduce overshoot, increase the RESET (turn the potentiometer clockwise).

When the RESET potentiometer is in the lower part of its adjustment (0 to 3 on the potentiometer scale), increasing the RESET clockwise may require decreasing the GAIN (turning the GAIN potentiometer counterclockwise) to maintain stable operation.

If the engine is slow in returning to the correct speed, decrease the RESET by turning the potentiometer counterclockwise.

NOTE: Optimum performance is not necessarily obtained with the GAIN potentiometer at the maximum stable clockwise position. In some cases, the gain must be reduced slightly to ensure stability under widely varying conditions.

4. Actuator compensation adjustment.

Normally, no adjustment is needed after making Initial Prestart Settings. A slow instability indicates the need to increase ACTUATOR COMPENSATION. A fast instability indicates the need to decrease ACTUATOR COMPENSATION. Make only small changes in ACTUATOR COMPENSATION and readjust GAIN and RESET each time compensation is changed.

5. Ramp time adjustment.

Adjust the RAMP TIME potentiometer to achieve satisfactory acceleration to rated speed with minimum overshoot. First, start at the fully clockwise (maximum RAMP TIME) position and work back in the counterclockwise direction until the unit ramps as rapidly as desired.

6. Start fuel limit adjustment.

With the engine operating at rated speed and no load, record the voltage across actuator terminals 20 (+) and 21 (-). Shut down the engine and activate the Failed Speed Signal Override by connecting a jumper wire between terminals 16 and 18. The voltage to the actuator should now be adjustable by the START FUEL LIMIT potentiometer. Set the actuator voltage approximately 30% higher than the voltage obtained at rated speed. Remove jumper wire.

Start the engine and observe the start time, overshoot of speed setting, and smoke obtained. If the engine does not start, turn the START FUEL LIMIT potentiometer slightly clockwise until the engine starts. The START FUEL LIMIT can be adjusted to make the engine start easier. The fuel limiting function is turned off automatically when the speed control takes over.

NOTE: For applications not requiring start-fuel limiting, the START FUEL LIMIT function can be eliminated by turning the potentiometer fully clockwise.

Troubleshooting The 2301A Governor

Basically, the troubleshooting published in the Service Manual (SENR2928-01) for the 2301 Governor can be used for the 2301A Governor. Of course you must use the appropriate terminal numbers and the changes in functions (where a jumper is required on the 2301A Governor to perform the function done with an open circuit on the 2301 Governor). Several places in the text need further clarification:

Page 46 - Step 5.

Diagnosis (A) - use the following when working with the 2301A: Verify supply voltage (it must be above 20 volts DC). If the supply voltage is correct, replace the 2301A.

Page 50 - Step 3, Page 63 - Step 11, Page 93 - Procedure (J).

Use the new Startup And Adjustment Procedures previously listed in this article.

Page 67 - Step 4.

Test Procedure. Do NOT simply jump the CT (Current Transformer) leads when you check the phasing of a 2301A. Do the following:

1. Disconnect wires where the CT is connected at the governor.

2. Connect these two wires together.

3. Connect a short jumper wire across the two CT terminals on the governor.

Diagnosis (A). For the 2301A, go to Step 6.

Page 71 - Step 10.

Test Procedure. A paralleling relay is not required for the 2301A. Use the circuit breaker auxiliary contact.

Diagnosis (A). Under (2b), skip Step 11 and go to Step 12.

Page 99 - Procedure (M).