WOODWARD 705 DIGITAL SPEED CONTROL FOR MECHANICAL DRIVE RECI Caterpillar

Introduction

Because of the variety of installations, plus system and component tolerances, the control must be turned to each system for optimum performance.

This chapter contains information on control calibration. It includes initial prestart-up and start-up settings and adjustments.

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An improperly calibrated control could cause an engine overspeed or other damage to the engine. To prevent possible serious injury from an overspeeding engine, read this entire procedure before starting the engine.

Appendix A contains a program listing with space to write in the values used on your control.

Using The Set Point Programmer

The Set Point Programmer is a hand-held computer terminal that obtains its power from the 705 control. The terminal connects to the 20 mA Loop Serial Port on the control. To connect the terminal, slightly loosen the right hand screw in the cover over J1 and rotate the cover clockwise to expose the 9-pin connector. Then firmly seat the connector on the terminal into J1.

When power is applied to the terminal by plugging it into the control, it performs a power-up self-test. At completion of the self-test, the screen will remain blank. Press the SP (Space) key to display the part number and revision level of the software in the control. (The SP key also turns on the display backlighting.) Please refer to this number and revision level in any correspondence with Woodward Governor Company. The set points or adjustments of the control are arranged in five menus. You access these menus with the A, B, C, D, and 1 keys. Pressing the appropriate key selects the first item on each menu.

Pressing the appropriate key (A, B, C, D, 1) selects the desired menu. To step through the menu, use the left and right arrow keys. The right arrow advances through the menu and the left arrow moves backward through the menu. The menus are continuous; that is, pressing the right arrow at the last menu item takes the menu to the first item, or pressing the left arrow at the beginning of the menu takes the menu to the last item.

To adjust a set point, use the up arrow to increase the value, or the down arrow to decrease the value. Holding the up or down arrow longer than a few moments will cause the rate of change to increase. This is useful during initial setup where a value may need to be changed significantly.

On the display menu, Menu D, the up or down arrow must be pressed to update the display. Holding down the up or down arrow allows continuous updating of the display for monitoring speed, actuator output, etc.

Finally, use the "=" key to save entered values. After you are satisfied with all entries and adjustments, press the "=" key to transfer all new set point values into EEPROM memory. The EEPROM retains all set points when power is removed from the control and restores them when power is reapplied.

All other keys on the Set Point Programmer are ignored by the control.

Description Of The 705 Digital Speed Control Set Points

Menu A - Dynamics Menu

Dynamic adjustments are settings that affect the stability and transient performance of the engine. There are two sets of dynamics provided. The set being used is selected by the Alternate Dynamics contact input. The following descriptions of each menu item apply to either set. Also see Figures 5-1, 5-2, and 5-3.

1. Gain determines how fast the control responds to an error in engine speed from the speed-reference setting. The gain is set to provide stable control of the engine at light or unloaded conditions.

2. Reset compensates for the lag time and inertia of the engine and load. It adjusts the time required for the control to return the speed to zero error after a disturbance. Reset is adjusted to prevent slow hunting and to minimize speed overshoot after a load disturbance.

3. Compensation compensates for the actuator and fuel system time constant.

4. Gain Ratio is the ratio of the Gain setting at steady state to the Gain setting during transient conditions. The Gain Ratio operates in conjunction with the Window Width and Gain adjustments by multiplying the Gain set point by the Gain Ratio when the speed error is greater than the Window Width. This makes the control dynamics fast enough to minimize engine-speed overshoot on start-up and to reduce the magnitude of speed error when loads are changing. This allows a lower gain at steady state for better stability and reduced steady-state actuator linkage movement.

5. Window Width is the magnitude (in rpm) of a speed error at which the control automatically switches to fast response. The control does not use the absolute value of speed error, but "anticipated" speed error to make this switch. This method provides for quick switching to the high gain value when an offspeed occurs and early switching to the low gain value when recovering from the speed transient. This provides smoother switching than if the absolute speed error was used for the window.

6. Gain Slope changes Gain as a function of actuator output. Since actuator output is proportional to engine load, this makes gain a function of engine load. Gain Slope operates in conjunction with the Gain Breakpoint adjustment to increase (or decrease) gain when percent actuator output is greater than the breakpoint. This compensates for systems having high (or low) fuel system gain at low load levels. This allows the Gain setting to be lower at light or no load for engine stability, yet provide good control performance under loaded conditions.

7. Gain Breakpoint sets the percent output above which the Gain Slope becomes effective. It should usually be set just above the minimum load output. The Gain Breakpoint adjustment is common to both Gain 1 and Gain 2.

Menu B - Speed Setting Menu

Speed adjustments are the settings that affect the speed reference. Descriptions of each menu item follow.

1. Raise Limit is the maximum speed reference setting. It is used to limit the Raise Speed command and Remote Reference to a maximum. It normally is set at the maximum rated engine speed.

2. Lower Limit is the minimum speed reference setting. It is used to limit the Lower Speed command and Remote Reference. It normally is set at the minimum operating speed of the engine.

3. Rated Speed Reference sets the normal operating speed of the engine. It should be set at the speed at which the engine is operated at full load.

4. Idle Speed Reference sets the speed at which the engine is operated at start-up. It sometimes is used during cool down.

5. Accel Time is the time required for the control to ramp the engine speed from Idle speed to Rated speed. The ramp is started whenever the Idle/Rated switch is closed.

6. Decel Time is the time required for the control to ramp the engine speed from Rated speed to Idle speed. The ramp is started whenever the Idle/Rated switch is opened.

NOTE: Actual engine deceleration may be slower than set by the Decel Time set point. This occurs when the Decel Time set point is faster than system inertias will allow the engine to come down in speed. This condition is indicated by the control actuator output going to the minimum fuel position. See Low Idle Droop below.

7. Raise Rate 1 is the rate at which the speed reference is ramped when using the Raise Speed command as well as when the Remote Speed Setting input is changed in the increase direction and when the speed reference is between the lower limit and the rate breakpoint. A step change on the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Raise Rate 1.

8. Lower Rate 1 is the rate at which the speed reference is ramped when using the Lower Speed command as well as when the Remote Speed Setting input is changed in the decrease direction and when the speed reference is between the lower limit and the rate breakpoint. A step change on the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Lower Rate 1.

9. Raise Rate 2 is the rate at which the speed reference is ramped when using the Raise Speed command as well as when the Remote Speed Setting input is changed in the increase direction and when the speed reference is between the rate breakpoint and the high limit. A step change on the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Raise Rate 2.

10. Lower Rate 2 is the rate at which the speed reference is ramped when using the Lower Speed command as well as when the Remote Speed Setting input is changed in the decrease direction and when the speed reference is between the rate breakpoint and the high limit. A step change on the remote input does not cause an immediate change in the reference, which is ramped to the new setting at the Lower Rate 2.

11. Rate Breakpoint is the reference rpm at which the rate of change of the reference automatically switches between rates 1 and rates 2.

12. Raise Rate 3 is the rate at which the speed reference is ramped when using the Raise Speed command as well as when the Remote Speed Setting input is changed in the decrease direction and when the external Raise/Lower Rate 3 contact is also closed. This rate has priority over all other rates when this contact is closed.

13. Lower Rate 3 is the rate at which the speed reference is ramped when using the Lower Speed command as well as when the Remote Speed Setting input is changed in the increase direction and when the external Raise/Lower Rate 3 contact is also closed. This rate has priority over all other rates when this contact is closed.

NOTE: Raise and lower rates should normally be set slower than the acceleration and deceleration capabilities of the engine. This will assure that the speed control loop will always be in direct control of the fuel rack. If rates are selected that are faster than the engine's capabilities, the rates will have no effect (because the engine will accelerate/decelerate at its maximum rate).

14. 20 mA Remote Reference is the engine speed desired when 20 mA is applied to the Remote Speed Reference input.

15. 4 mA Remote Reference is the engine speed desired when 4 mA is applied to the Remote Speed Reference input.

16. 20 mA Tachometer RPM is the engine speed when the tachometer output is 20 mA.

17. 4 mA Tachometer RPM is the engine speed when the tachometer output is 4 mA.

18. Droop is based on the control output, which is proportional to engine load. The droop obtained is dependent on linkage adjustment and stroke. For example, 5% droop gives a real droop of 2.5% if the control output changes 50% from no load to full load.

19. Idle Droop is based on the control output current when it drops below the Idle Breakpoint setting (see Idle Breakpoint below). Dependencies on linkage make the Idle Droop percentage relative so large droop settings may be required to achieve the desired results.

20. Idle Breakpoint is normally set equal to the control output obtained when the engine is unloaded and at low idle. When the output of the control drops below this setting or goes to minimum fuel during rapid engine deceleration, Idle Droop, described above, will raise the speed reference. This brings the engine back under control sooner and reduces speed undershoot. Speed undershoot may occur because the time required for the control to return to the new fuel setting takes time dependent on control dynamics and linkage adjustment.

Menu C - Rack Limiters And Control Output Menu

The 705 Control provides Start, Boost Pressure, and Torque Limiters to limit the actuator output current from the control. The actuator current determines the position of the actuator and thus the rack or fuel position.

1. Rack Limit Breakpoint is the input milliamps from the turbo boost pressure sensor at which the slope of the two-slope rack limiter changes.

2. 4 mA Rack Limit determines the maximum percent actuator output current when the boost pressure input is 4 mA (1 Vdc). The control responds to inputs from 2 to 20 mA (0.5 to 5 Vdc). Inputs between 2 and 4 mA (0.5 and 1 Vdc) are treated as 4 mA (1 Vdc). The rack limit does not go below the 4 mA setting. The control interpolates the rack limit between the 4 mA Rack Limit and the Breakpoint Rack Limit set points. An input below 2 mA (0.5 Vdc) is considered failed and the control defaults to the maximum setting at 20 mA (5 Vdc) for continued operation.

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NOTICE
If you see high smoke levels during acceleration, check the boost pressure transducer to verify that it is still operating correctly.

3. Breakpoint (BP) Rack Limit is the percent actuator output current at the Rack Limit Breakpoint set above.

4. 20 mA Rack Limit determines the maximum percent actuator output current when the turbo boost pressure input is 20 mA. Straight line interpolation is made between the Breakpoint and 20 mA settings.

Figure 5-5 illustrates the breakpoint and these adjustments.

5. Torque Limit Breakpoint (BP) is the engine speed at which the slope of the torque limiter output changes.

6. Minimum Torque Limit is the maximum percent actuator output current when the engine speed is at the lower limit speed setting. The output current limit does not go below this setting even when speed may drop lower. The limiter interpolates between Minimum Torque Limit and Breakpoint Torque Limit for intermediate engine speeds.

7. Breakpoint (BP) Torque Limit is the percent actuator output current at the engine speed set by the Torque Limit Breakpoint described above.

8. Maximum Torque Limit is the maximum percent actuator output current when the engine speed is at the raise limit speed setting. The limiter interpolates between the Breakpoint Torque Limit and Maximum Torque Limit for intermediate speeds.

Figure 5-6 illustrates the breakpoint and these adjustments.

9. Start Fuel Limit sets the maximum percent actuator output during engine start-up. The limit is usually set to obtain the fuel required to start the engine reliably under all conditions. The Start Fuel Limit is independent of the Rack and Torque Limiters, so it may be set higher or lower than those limits.

10. 20mA Aux Actuator Percent is the actuator percent when the aux output is 20 mA (see Menu 1, Aux Output Configuration).

11. 4mA Aux Actuator Percent is the actuator percent when the aux output is 4 mA (see Menu 1, Aux Output Configuration).

Menu D - Display Menu

Input and output values are displayed once when each item is selected. To get a continuous update, hold down the up or down arrow. Descriptions of each menu item follow.

1. Engine Speed displays the current engine speed in rpm.

2. Speed Reference displays the current speed reference in rpm. Note that this may not be the speed the engine is currently running at due to the effect of idle droop, fuel limiters, etc.

3. Actuator Output displays the current percent of output. Maximum (100%) is 200 mA (0 mA for reverse-acting). This is useful for setup of the control fuel limiters, torque limiter, idle droop, and gain breakpoint settings.

4. Aux Output displays the milliamps on the Aux Output. This is useful for testing and system calibration.

5. Remote Input displays the milliamps currently on the Remote Speed Setting Input. This is useful for testing and system calibration.

6. Rack Limit Input displays the milliamps currently on the turbo boost pressure rack limit input. This is useful for testing and system calibration.

7. Run/Stop Switch Status displays the status of discrete input A, terminal 9. Closed indicates 24 Vdc is applied to the input selecting the run position. Open selects minimum fuel or the stop position.

8. Idle/Rated Switch Status displays the status of discrete input B, terminal 10. Closed indicates 24 Vdc is applied to the input selecting rated speed and the maximum torque limit or rack limit, whichever is lower. Open indicates idle and the start fuel limit are selected.

9. Lower Switch Status displays the status of discrete input C, terminal 11. Closed indicates 24 Vdc is applied to the input selecting lower speed (or remote speed setting if the Raise switch is also closed).

10. Raise Switch Status displays the status of discrete input D, terminal 12. Closed indicates 24 Vdc is applied to the input selecting raise speed (or remote speed setting if the Lower switch is also closed).

11. Local/Remote Switch Status displays the status of both discrete inputs C and D, terminals 11 and 12. Selecting both Raise and Lower places the control in the remote speed setting mode where the 4-20 mA Remote Speed Setting Input is used for the speed reference.

12. Alternate Dynamics Switch Status displays the status of discrete input E, terminal 13. Closed indicates 24 Vdc is applied to the input selecting the alternate dynamics (dynamics 2).

13. Raise/Lower Rate 3 Switch Status displays the status of discrete input F, terminal 14. Closed selects speed reference rate 3 for the raise or lower switch or remote reference. Open allows the reference to be changed at rates 1 or 2, depending on which side of the rate breakpoint the reference is.

14 Watchdog Status displays the status of the control CPU. The normal status displayed is CPU OK. If a CPU fault occurs, the CPU OK indicator on the front of the control will turn off, the Actuator Output and Aux Output will decrease to minimum output, and the Watchdog Status will display TIME OUT. To reset the watchdog, turn off power to the control for a minimum of 10 seconds.

15. Self Test Result displays the result of power up diagnostics performed on the microprocessor, data, and program memory. A successful test gives a result of 49. Report any other result to Woodward Governor Company when returning the control for repair.

16. ROM Check Sum is used by Woodward Governor Company during factory tests. An incorrect result will give a Self Test Result error also.

Menu 1 - Calibration/Configuration Menu

1. Calibration Key is a code which you must enter before you can change any of the set points on the calibration menu. This helps prevent accidental modification of the set points. The code is factory set to "49". Use the up and down arrow keys to select the code. Whenever the Run/Stop input is changed, the code will be reset to "0".

2. Number of Gear Teeth is the number of teeth or holes in the gear or flywheel the speed sensing device is on. If the gear is running at camshaft speed (one-half engine speed) then you must enter one-half the number of teeth on the gear. The control requires the number of teeth per engine revolution.

NOTE: Best control performance will be obtained when sensing speed from a gear rotating at full engine speed. Slower-speed gears (such as the camshaft) provide a lower sampling rate which impairs control response time.

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The number of gear teeth is used by the control to convert pulses from the speed-sensing device to engine rpm. To prevent possible serious injury from an overspeeding engine, make sure the control is properly programmed to convert the gear-tooth count into engine rpm. Improper conversion could cause engine overspeed.

3. Remote Input Calibration calibrates the 4-20 mA Remote Speed Setting input by adjusting the value of the input current as seen by the control software. This calibration is performed by Woodward Governor Company prior to shipment and should not normally require field adjustment. See the Control Test and Calibration section in Chapter 6 for proper adjustment procedure.

4. Rack Limit Calibration calibrates the 4-20 mA Rack Limit input by adjusting the value of the input current as seen by the control software. This calibration is performed by Woodward Governor Company prior to shipment and should not normally require field adjustment. See the Control Test and Calibration section in Chapter 6 for proper adjustment procedure.

5. Aux Output Configuration selects either actuator percent readout (Menu C) or tachometer readout (Menu B) for the aux output. Use the up and down arrow keys to select the desired display.

6. Aux Output Calibration is used for calibration of the 4-20 mA Tachometer output. This set point adjusts the value of the aux output current as seen by the control software. This calibration is performed by Woodward Governor Company prior to shipment and should not normally require field adjustment. See test and calibration section for proper adjustment procedure.

7. Forward/Reverse Acting Actuator sets the direction of the control actuator output to increase fuel. Forward-acting actuators require increased current to increase fuel. Reverse-acting actuators require decreased current to increase fuel. The Minimum Fuel contact must be open, engine speed must be 0, and the Calibration Key must be set to "49" to change the Forward/Reverse setting. Failure to meet any of these conditions will result in an error message being displayed on the Set Point Programmer.

8. Dynamics Map selects the mapping algorithm used to map dynamics as a function of engine speed. Figure 5-4 illustrates how dynamics vary as a function of engine speed for each map.

Map 0 is normally suitable for all medium- to high-speed engines. With Map 0, gain is proportional to engine speed and Reset and Compensation are held constant. The Gain set point may be adjusted at any engine speed, but the value is normalized to the rated speed reference. For example if gain is set to 0.1 and current engine speed is 50 percent of the maximum, then the actual gain used in the control algorithm will be 0.05, or 50 percent of the set point value. If engine speed is at rated, actual gain will be 100 percent of the set point value.

Map 1 provides additional Reset and Compensation inversely proportional to engine speed for low- to medium-speed engines. Gain for Map 1 is proportional to the square of engine speed. For example, at 50 percent of maximum speed, the actual gain will be 25 percent of the set point value and Reset and Compensation values will be two times greater than at maximum speed.

The final decision on the use of Map 0 or Map 1 depends on engine performance obtained throughout the operating speed and load range. After tuning the control for desired performance under rated speed and load conditions, performance at low speed and light loads should be evaluated. If low frequency speed oscillation occurs at low speeds using Map 0, Map 1 will provide additional stability. If performance is poor at low speed on Map 1, Map 0 will provide higher performance. Select the Map that provides the best overall performance for all operating conditions.

9. Failsafe Override is used for troubleshooting only. Turning the Failsafe Override on allows the actuator output to increase with no speed signal. The output can then be ramped up to 100% and down to 0% using the Minimum Torque Limit adjustment. This set point must be turned off during normal operation, unless the engine has a backup mechanical governor.

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To prevent possible serious injury resulting from an engine overspeed, make sure the failsafe override is off during normal operation. The failsafe override will cause the actuator to go to maximum fuel on a forward-acting control and actuator if the speed signal input is lost for any reason (such as a broken magnetic pickup wire).

Initial Prestart Settings

Menu A

Menu B

1. Raise Limit - Set to maximum engine operating speed.

2. Lower Limit - Set to minimum engine operating speed.

3. Rated Speed Reference - Set to the normal operating speed of the engine.

4. Idle Speed Reference - Set to the desired start-up speed.

5. Accel Time - Set to the time desired to ramp from idle to rated speed.

6. Decel Time - Set to the time desired to ramp from rated speed to idle speed.

7. Raise Rate 1 - Set to the rpm-per-minute rate desired to raise speed with the Raise command or with the 4 to 20 mA Remote Speed Reference, from the lower limit to the rate breakpoint.

8. Lower Rate 1 - Set to the rpm-per-minute rate desired to lower speed with the Lower command or with the 4 to 20 mA Remote Speed Reference, from the lower limit to the rate breakpoint.

9. Raise Rate 2 - Set to the rpm-per-minute rate desired to raise speed with the Raise command or with the 4 to 20 mA Remove Speed Reference, from the rate breakpoint to the high limit.

10. Lower Rate 2 - Set to the rpm-per-minute rate desired to lower speed with the Lower command or with the 4 to 20 mA Remote Speed Reference, from the rate breakpoint to the high limit.

11. Rate Breakpoint - Set the rpm at which you want the rates to change from rates 1 to rates 2.

12. Raise Rate 3 - Set to the rpm-per-minute rate desired to raise speed when the Raise/Lower Rate 3 contact on terminal 14 is closed (power applied), and with the Raise command or with the 4 to 20 mA Remote Speed Reference.

13. Lower Rate 3 - Set to the rpm-per-minute rate desired to lower speed when the Raise/Lower Rate 3 contact on terminal 14 is closed (power applied), and with the Lower command or with the 4 to 20 mA Remote Speed Reference.

14. 20 mA Remote Reference - Set to operating speed with 20 mA input. Skip if remote input is not used.

15. 4 mA Remote Reference - Set to operating speed with 4 mA input. Skip if remote input is not used.

16. 20 mA Tachometer RPM - Set to full scale rpm of your meter (if used).

17. 4 mA Tachometer RPM - Set to minimum scale rpm of your meter (if used).

18. Droop - Set to 0% for isochronous operation or to desired droop. Note that droop is dependent on the actuator stroke actually used. If actuator stroke is 50% from no load to full load, set droop at twice the desired value.

19. Idle Droop - 0%

20. Idle Breakpoint - 0%

Menu C

1. Rack Limit Breakpoint - Between 4 mA and 20 mA

2. 4mA Rack Limit - 100%

3. Breakpoint Rack Limit - 100%

4. 20mA Rack Limit - 100%

5. Torque Limit Breakpoint - Between Lower Limit and Raise Limit

6. Minimum Torque Limit - 100%

7. Breakpoint Torque Limit - 100%

8. Maximum Torque Limit - 100%

9. Start Fuel Limit - 50%

10. 20mA Aux Actuator Percent - (will be set after start-up, if used)

11. 4mA Aux Actuator Percent - (will be set after start-up, if used)

Menu 1

1. Calibration Key - 49.

2. Number of Gear Teeth - Set to number of teeth or holes in the gear where the speed sensor is mounted. If this gear is not turning at the same speed as the engine, enter the number of teeth seen by the sensor in one engine revolution.

3. Remote Input Calibration - Do not adjust (see calibration procedure in Chapter 6).

4. Rack Limit Input Calibration - Do not adjust (see calibration procedure in Chapter 6).

5. Aux Output Configuration.

Tachometer for 4-20 mA tachometer output

Actuator Percent for 4-20 mA actuator position output

6. Aux Output Calibration - Do not adjust (see calibration procedure in Chapter 6).

7. Forward/Reverse Acting Actuator

Forward for forward-acting actuators

Reverse for reverse-acting actuators

To enable the control for changing the Forward/Reverse mode, the following conditions must be met: Calibration Key must be set to "49", the Minimum Fuel contact must be open, and engine speed must be 0.

8. Dynamics Map - 0 for medium- to high-speed engines (300-2100 rpm); 1 for low-speed engines (8-300 rpm)

9. Failsafe Override - Set to "off"

At this time, we recommend saving this setup by pressing the "=" key on the Set Point Programmer. The programmer will display the message "Set Points Saved." Be sure to select a menu prior to continuing.

Start-Up Adjustments

1. Complete the installation checkout procedure in Chapter 4 and the initial prestart setting above.

2. Close the Run contact. Open the Failed Speed Override contact. Be sure the Idle/Rated contact is in Idle (Open). Apply power to the control.

3. Check the speed sensor.

Minimum voltage required from the speed sensor to operate the control is 1.0 Vrms, measured at cranking speed or the lowest controlling speed. For this test, measure the voltage while cranking, with the speed sensor connected to the control. Before cranking, be sure to prevent the engine from starting. At 5% of rated speed and 1.0 Vrms, the failed speed sensing circuit function is cleared. Verify that "Engine RPM" on Menu D displays the present actual cranking rpm (hold down the up or down arrow for continuous updates).

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TO PROTECT AGAINST POSSIBLE PERSONAL INJURY, LOSS OF LIFE, and/or PROPERTY DAMAGE WHEN STARTING THE ENGINE, BE PREPARED TO MAKE AN EMERGENCY SHUTDOWN to protect against runaway or overspeed should the mechanical-hydraulic governor(s), or electric control(s), the actuator(s), fuel control(s), the driving mechanism(s), the linkage(s), or the controlled device(s) fail.

4. Start the engine.

If there is insufficient fuel to start the engine, increase the Start Fuel Limit (Menu C). (The control will reduce fuel as required when the speed setting is reached. It requires extra fuel to accelerate the engine to idle speed.) It may take a few starts to determine the final setting of the Start Fuel Limit. If the start time is excessive, increase the Start Fuel Limit. If the start time is too fast or flooding is occurring, decrease the Start Fuel Limit. We recommend trying both hot and cold starts to determine a final setting.

5. Adjust for stable operation.

If the engine is hunting at a rapid rate, slowly decrease the Gain (Menu A) until performance is stable. If the engine is hunting at a slow rate, increase the Reset time. If increasing the Reset time does not stabilize the engine, it also may be necessary to slowly decrease the Gain OR to slowly decrease the Gain and increase the Compensation.

This completes the Start-up adjustments. We recommend saving the settings at this time by pressing the "=" key on the Set Point Programmer.

Dynamic Adjustments

The objective of the dynamic adjustments is to obtain the optimum, stable engine speed response from minimum load to full load and speed operating conditions. All adjustments apply to both sets of dynamics, 1 and 2. Use the set point with "1" following when the Alternate Dynamics contact is open and "2" when closed.

1. No-Load Adjustment

Perform this adjustment without load applied.

Slowly increase the Gain set point until the engine becomes slightly unstable, then reduce the Gain as necessary to stabilize the engine.

After acceptable performance at no load, record the Actuator Output as read on Menu D. Set the Gain Breakpoint (Menu A) to this reading.

2. Minimum Load Adjustment

Perform this adjustment at the minimum speed and load conditions at which the engine is operated. Be sure to select Rated Speed to switch to the max torque limit or rack limit. Speed may be set either with the Raise and Lower commands in local or with a 4 to 20 mA speed reference in remote.

Observe the movement of the actuator. If the activity of the actuator is excessive, reduce the Gain set point slightly to get the actuator movement to an acceptable level.

If there is a slow periodic cycling of the engine speed above and below the speed setting, there are two possible causes:

* Gain is too high and Reset is too low. Reduce the gain by 50% (i.e., if the gain was 0.02, reduce it to 0.01) and increase Reset slightly. Observe the movement of the actuator. Continue to increase Reset until the movement is acceptable but not excessive. A final value of Reset should be between 1.0 and 2.0 for most large engines. If the Reset value exceeds 2.0, but this procedure continues to improve performance, increase the Compensation set point 50% and repeat the procedure.

* Gain is too low. If the preceding procedure does not improve the slow periodic cycling of the engine speed, the control may be limiting cycling through the low gain control region set by the Window Width set point. Increase the Gain set point to minimize the cycling. If actuator movement becomes excessive, reduce the Compensation set point until movement is acceptable. In some cases, Compensation may be reduced to zero and only the Gain and Reset adjustments used. This should be done only if necessary to eliminate excessive actuator response to misfiring or other periodic disturbances. Reduce the Window Width set point until the limit cycle amplitude is acceptable without excessive rapid actuator movement.

3. Full Load Adjustment

Perform these adjustments at the speed and load ratings at which the engine is most often operated.

If operation in this range is satisfactory, no further dynamic adjustments are necessary. If during changes in speed or load, excessive speed errors occur, increase the Gain Slope adjustment until engine performance is satisfactory. If excessive actuator movement again occurs, do procedure 4, then repeat procedure 3. If the settling time after a speed or load change is too long, reduce the Reset set point slightly and increase the Gain slightly. If slow-speed hunting occurs after a load or speed change but decreases or stops in time, increase the Reset set point slightly and reduce the Gain set point. See Figure 5-3.

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The use of negative gain slope should be considered carefully. Low gain at high fuel levels will result in poor load rejection response or possible overspeed. To prevent possible serious injury from an overspeeding engine, the Maximum Torque Limit or 20mA Rack Limit (Menu C) must be set near the full load output current demand to prevent excessive integrator windup and a subsequent low gain condition.

4. When speed and load changes occur, the control should switch automatically to high gain to reduce the amplitude of the offspeeds. Reduce (or increase) the Window Width set point to just greater than the magnitude of acceptable speed error. A value of Gain ratio too high will cause the control to hunt through the low-gain region. This normally will occur only if the Window Width is too low. If necessary to decrease the Window Width to control limit cycling (identified by the engine speed slowly cycling from below to above the speed setting by the amount of Window Width), the Gain Ratio may be reduced for more stable operation.

5. Verify that performance at all speed and load conditions is satisfactory and repeat the above procedures if necessary.

6. While operating at minimum speed and load, record the Actuator Output on Menu D. Select the Idle Breakpoint on Menu B. Set at the recorded value.

7. If the Torque Limiter or Rack Limiter are being utilized, record the Actuator Output, Engine Speed, and Rack Limit Input (Menu D) while operating the engine under various speed and load conditions. These values will be used to determine the initial Torque Limit set points below.

8. If Alternate dynamics are to be used, repeat the above procedures with the Alternate Dynamics contact closed and the engine operating conditions selected for which the dynamics are required. Use the adjustments with a "2" following them.

We recommend you check the operation from both hot and cold starts to obtain the optimum stability under all conditions.

Speed Adjustments

Adjustment of the Local Speed References (Idle, Rated, Raise and Lower) should not require further setting as they are precisely determined. The Remote Speed Input and the Aux Output however involve analog circuits and may require adjustment.

1. 4 to 20 mA Remote Speed Setting Input

Apply 4 mA to the Remote Speed Setting Input. Be sure Remote is selected. Observe the operating speed of the engine as displayed on Menu D. If the engine rpm is lower or higher than desired, increase or decrease the 4 mA Remote Reference set point on Menu B to obtain the correct speed. There may be a small difference between the set point and actual speed which compensates for the inaccuracies in the analog circuits.

Now apply 20 mA to the Remote Speed Setting Input. Wait until the ramp stops. Increase or decrease the 20 mA Remote Reference set point to obtain the tach speed desired.

Repeat the above steps until the speeds at 4 mA and 20 mA are within your required range.

2. 4 to 20 mA Tachometer Output

Set engine speed to the speed desired for 4 mA output. If this is not possible, skip this step or use a signal generator into the speed input with the correct frequency corresponding to the desired rpm. Trim the 4 mA Tach rpm set point for 4 mA set point output.

Set engine speed to the speed desired for 20 mA output. Trim the 20 mA Tach rpm set point for 20 mA set point output.

Repeat the above steps until the speeds at 4 mA and 20 mA are within your required range.

3. Droop adjustment

If the control is operated isochronously, set Droop to 0%. If droop operation is required, set Rated speed to achieve the desired high idle speed. Increase load to rated, set droop to obtain the desired rated speed.

NOTE: The percent Droop is only a guide. Since droop is a function of actuator current, droop is affected by linkage, fuel system, etc.

4. Idle Droop adjustment.

If engine deceleration remains under control of the Decel Ramp or the Lower Ramp, these adjustments may not need to be performed.

Set the Idle Breakpoint to the output percent obtained previously at no load. Set engine speed to at least 25 percent above the no-load speed. Then use the Lower Speed input to call for minimum engine speed. Observe undershoot of engine speed below the no-load speed. If excessive undershoot is observed, increase the Idle Droop set point by 10% and repeat the above procedure. Proper adjustment is obtained when undershoot is within desired specification.

NOTE: The Low Idle Droop causes an increase in the speed reference when actuator current is below the Idle Breakpoint. The amount the reference is increased is dependent on linkage adjustment, reflected in the Idle Breakpoint setting, and Low Idle Droop set point. Large values of droop may be required to achieve the desired performance when small Idle Breakpoint settings are obtained. For best performance in controlling speed undershoot, the output percent at idle should be less than 25 percent. If a value greater than this is obtained, the linkage adjustment should be modified to reduce the control output to below 25 percent at idle. After adjustment of the linkage, complete fuel cutoff should be verified to occur prior to reaching the minimum stop on the actuator.

Fuel Rack Limit Adjustment

If a turbo boost pressure rack limiter is not being used, leave the set points at the 100% values set during prestart adjustment. Continue with the Torque Limiter adjustments below.

The values of the Actuator Output (Menu D) and turbo boost pressure sensor outputs obtained above provide the guide to adjustment of the rack limit set points. As a starting point, plot actuator output percent versus turbo boost pressure milliamps as show in Figure 5-5. If necessary, extrapolate the curve to include 4 and 20 mA. Plot a best-fit two-slope line 10% of the output range (maximum - minimum output values) above the curve obtained. Set the BP Rack Limit to the turbo boost pressure input current corresponding to the breakpoint in the two lines. Set the 4 mA Rack Limit, Breakpoint Rack Limit, and the 20 mA Rack Limit at the output values obtained at their respective points. Test engine performance through the speed and load range for satisfactory performance. Set point values may require readjustment from the starting values to obtain the desired result.

Torque Limiter Adjustment

If the torque limiter is not being utilized, leave the set points at the 100% values set during prestart adjustment.

The values of the Actuator Output and Engine Speed (Menu D) obtained above provide the guide to adjustment of the torque limiter set points. As a starting point, plot actuator output percent versus engine rpm as shown in Figure 5-6. Plot a best fit two-slope line 10% of the output range (maximum - minimum output values) above the curve obtained. Set the Breakpoint Torque Limit to the engine speed corresponding to the breakpoint in the two lines. Set the Minimum Torque Limit, Breakpoint Torque Limit, and the Maximum Torque Limit at the output values obtained at their respective speeds. Test engine performance through the speed and load range for satisfactory performance. If the engine accelerates too slow, or becomes overloaded for the fuel allowed, the set point values must be set higher. If acceleration is too fast or excessive smoke occurs, the set point values should be set closer to the observed data.

Aux Actuator Output Adjustment

Select 20mA Aux Actuator Percent on Menu C. Adjust to the desired actuator percentage for 20 mA output.

Select 4mA Aux Actuator Percent on Menu C. Adjust to the desired actuator percentage for 4 mA output.

For Aux Output configuration and calibration, see the calibration procedure in Chapter 6.

NOTE: If 4mA Aux Actuator Percent and 20mA Aux Actuator Percent are the same value, the Aux Output will be 0 mA.

Conclusion Of Setup Procedures

This completes the adjustment chapter. Save the set points by pressing the "=" key on the Set Point Programmer. Run through all the set points and record them for future reference. This can be useful if a replacement control is necessary or for start-up of another similar unit. Power down the control for about 10 seconds. Restore power and verify that all set points are as recorded.

Disconnect the Set Point Programmer from the control. Close the cover over J1 and retighten the retaining screw.

Figure 5-1. Control Gain as a Function of Speed Error

Figure 5-2. Control Gain as a Function of Control Output

Figure 5-3. Typical Transient Response Curves

Figure 5-4. Dynamics Map Curves

Figure 5-5. Rack Limiter Setup Example

Figure 5-6. Torque Limit Setup Example