New Personality Modules For 3412 Generator Set Engines{1902} Caterpillar

Introduction

New personality modules have been released to update and upgrade 3412 Generator Set Engine parameters. These new personality modules replace former canceled modules.

NOTE: Electronic Technician (ET) version 1.4 or later must be used to access these parameters.

Refer to Chart A for a list of new and canceled part numbers.

General Accessing And Programming

The following parameters are accessed using Electronic Technician (ET) version 1.4 or later service tool with the software for commercial engines or for truck and commercial engines.

Schematic to configure the system before starting the ET program.

* Connect the 7X-1688 Adapter Cable Group between the personal computer and the 7X-1700 Electronic Tool Group.

* Connect the 7X-1412 Adapter Cable Assembly between the 7X-1700 Electronic Tool Group and the Electronic Control Module (ECM) of the engine.

* Start the ET program.

* Select the Configuration menu.

* Scroll through the available parameters listing until the specific programmable parameter is found.

* To change a parameter value, highlight the current value and press the change button at the lower left portion of the screen.

* Type the new value in the dialog box that appears, then select OK.

Low Idle

An expanded low idle range is now programmable. The original range for the low idle was 1200 to 1350 rpm. The new range is 600 to 1800 rpm. This greatly expanded range has been added in order to support several applications using a non-Caterpillar generator.

NOTE: The idle should not be set below 1200 rpm when used with a Caterpillar generator due to possible generator voltage regulator shutoff if the unit operates at lower rpm for an extended period of time.

High Idle

High idle is the top engine speed with 100 percent throttle (90 percent PWM duty cycle). A new high idle range is now programmable. The original high idle was fixed and not programmable. The new range is 1500 to 2010 rpm for the 50 Hz engines and 1800 to 2412 rpm for the 60 Hz engines. The default value is 1621 rpm for the 50 Hz engines and 1945 rpm for the 60 Hz engines. If the high idle is used with 4P-0319 Governor Control Assembly, the default value MUST be used for proper operation.

New Throttle Control Mode (SW IP 1)

A new Throttle Control Mode selectable with AUX CKT (SW IP 1) (Pin 20) customer connector J17) is now available to allow a desired speed input from the programmed low speed to the programmed high idle speed. The default (open or not grounded Pin 20/J17) allows the duty cycle of the PWM signal to the Primary Throttle input (Pin 9/J17) to control the engine speed. The PWM duty cycle will allow the speed to be controlled from 1369 rpm (low idle) to 1945 rpm (high idle) for 60 Hz units, or from 1141 rpm (low idle) to 1621 rpm (high idle) for 50 Hz units.

If Pin 20/J17 is grounded, the control will allow the PWM signal to operate the engine speed from the programmed low idle to the programmed high idle. However, if the Idle/Rated Switch input is open (Pin 7/J17) for idle speed operation, then the engine speed will be the programmed low idle speed.

NOTE: If the programmed adjustment range from Low Idle to High Idle is used, then Pin 20/J17 must be grounded.

Governor Gain Parameters

The new adjustable Governor Gain parameters are:

* Proportional Gain

* Proportional Offset

* Stability Min Gain

* Stability Max Gain

* Compensation Gain

The programmable parameters for all of the gains range from 1 to 65534.

NOTE: These gain values are numbers with no engineering units associated with them.

NOTE: This wide programmable range may not be fully used on any system. In addition, if programmed to 0 or 65535, the system will revert back to the factory default value.

Gain Explanations

Proportional Gain/Proportional Offset

The Proportional Gain is applied to the speed error and then sent to the rack. The Proportional Offset is applied directly to the rack without looking at the speed error.

For the Proportional Gain a form of droop is inherent. However, if the engine is running at exactly the desired speed, there is no speed error and Proportional Gain is not contributing to change the rack.

* If the Proportional Gain value is too large, the engine can overshoot the desired speed. The overshoot is caused by the time delay between the rack movement and the burning of fuel.

* If the Proportional Gain value is too small, the rack movement necessary to accelerate the engine to the desired speed must be obtained by ramping the stability accumulator to a higher value. This process is time consuming so, as a result, the engine is slow to respond.

The Proportional Offset is used to apply a constant amount of rack signal to help offset losses in the engine. These losses are from friction, dead band in the fuel system, and to keep the stability accumulator in the middle of its range under steady state conditions. If the Proportional Offset is adjusted, it should be adjusted approximately the same percentage as any change to the Proportional Gain.

Stability Minimum Gain/Stability Maximum Gain

The Stability Gain terms work to eliminate a steady state speed error by multiplying the speed error by the gain value and adding this result to an accumulator. The value of the accumulator is then added to the desired rack position. For example, if the engine is operating 3 rpm below the desired speed, the governor will multiply the end by the Stability Min Gain value and add the result to the accumulator to increase the rack position. Then, because the engine has received a small fuel increase, it will accelerate slightly and move toward the desired speed.

If either the Stability Min Gain or the Stability Max Gain is set too high, the governor will provide more fuel than is necessary to bring the error to zero. The additional fuel will cause the engine speed to overshoot and ring. If set too low, the engine will take too long to arrive at a steady state speed.

* If the error is greater than 30 rpm and the error is increasing, then the Stability Max Gain is functioning.

* If the error is less than 30 rpm, then the Stability Min Gain is used. This function allows the use of a high gain that would otherwise cause the engine to be unstable when the engine is operating near the desired speed.

Compensation Gain

Compensation Gain helps the engine respond to sudden changes by reacting to a change before the full effects of the change are realized. For example, if a sudden load is applied, the engine speed will start to decrease.

* If the control takes no action, the engine would stabilize at some lower speed than the original speed. The Compensation Gain portion of the control reacts to the initial deceleration and responds to increase the rack.

* If the Compensation Gain is too high, the governor will over respond to very small speed changes (less than 1 rpm), and cause the engine speed to hunt.

* If the Compensation Gain is too low, the governor will allow the error to become excessively large before the stability and proportional terms correct for the condition.