FLO-TECH SPEED CONTROL ELECTRONIC SPEED CON Caterpillar

Introduction

Initial calibration and troubleshooting of the Flo-Tech Speed Control are identical. Many of the settings are interrelated. For this reason, if trouble is experienced, the best procedure is to follow the initial installation routine completely to see if the problem is cured by adjustment of the system.

Signal Generator

A signal generator to simulate the output of the MPU will make setup or troubleshooting of the electronic control system easier and safer, since it will allow the technician to set idle and rated speeds and check all wiring without running the engine. The wave form can be sine, square, or triangular. The signal generator must be capable of generating the frequency of the control system, not the rpm of the engine. The frequency will be the number of teeth on the sensed gear which will exposed to the MPU during one revolution of the engine times the desired rpm divided by 60 (revolutions per second).

If a signal generator is not available, all checks can be made with the engine, but overspeeds are possible.

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TO PROTECT AGAINST POSSIBLE INJURY, LOSS OF LIFE, and/or Property DAMAGE WHEN STARTING the engine, turbine, or other type of prime mover, BE PREPARED TO MAKE AN EMERGENCY SHUTDOWN to protect against runaway or overspeed should the mechanical-hydraulic governor(s), fuel control(s), the driving mechanism(s), the linkage(s), or the control device(s) fail.

Installation Checks

Do the checks in the order indicated. Terminal numbers in this chapter refer to the speed control.

1. Check that all electrical connections are correctly made and terminal screws tightened, the magnetic pickup is properly installed and the jam nut tightened, and the fuel valve and drain line are securely fastened and correctly installed.

2. Do not start the engine now. Turn on governor power. Check the battery voltage at terminals 1 (+) and 2 (-). It must be from 18 to 32 Vdc (10 to 14 Vdc for the 12-volt control).

3. If a signal generator is available: Attach the output to terminals 5 and 6, leaving the MPU connections off. Set the signal-generator output between 2 and 10 Vrms. If a signal generator is not available, proceed to step 8.

4. Set the signal-generator frequency to about half of idle speed. Close the Idle/Rated switch. Turn the signal generator and governor power on. The voltage across terminals 3 and 4 should measure about 5 Vdc (Start Fuel Limit must be fully clockwise).

5. Set the signal generator for MPU frequency at rated speed. Close the Idle/Rated switch. Set the external speed trim pot (if used) at mid position. Observe the output from terminals 3 and 4.

a. If the output is at max-fuel position (about 5 Vdc), slowly turn the rated-speed potentiometer counterclockwise until the signal just begins to move to minimum.

b. If the output is at minimum, slowly turn the rated-speed potentiometer clockwise until the signal just begins to move to maximum.

Continue to adjust the rated-speed pot very slowly, trying to stop the signal between minimum and maximum. Stop adjusting when the signal moves slowly. It will not be possible to stop the motion. The rated-speed reference is now set very close to desired speed.

6. Open the Idle/Rated switch. Set the signal generator for MPU frequency at idle speed. (Preset the idle speed only after presetting rated speed.)

a. If the signal is at maximum-fuel position, slowly turn the idle-speed potentiometer counterclockwise until the signal begins to move to minimum.

b. If the signal is at minimum, slowly turn the idle-speed potentiometer clockwise until the signal just begins to move to maximum.

7. Continue to adjust the idle-speed pot very slowly, trying to stop the signal between minimum and maximum. Stop adjusting when the signal moves slowly. It will not be possible to stop the signal. The idle-speed reference is now set very close to desired idle speed.

8. If a signal generator is not available, turn the rated speed pot fully counterclockwise. Turn the idle-speed pot fully clockwise. Remove the MPU wires from the speed control and measure between 85 and 300 Ohms resistance across the MPU wires. If the resistance is correct replace the connection.

Initial Pre-Start Settings

1. Rated Speed: If RATED SPEED was not set with a signal generator, set the RATED SPEED potentiometer to minimum (fully counterclockwise). Set the external speed trim, if used, to mid-position.

2. Stability: Set the RATED and IDLE STABILITY potentiometers to mid position.

3. Gain: Set the RATED and IDLE GAIN potentiometers to mid position.

4. Idle Speed: If IDLE SPEED was not set with a signal generator, set the IDLE SPEED potentiometer at maximum (fully clockwise).

5. Start Fuel Limit: Set the START FUEL LIMIT pot at mid point (maximum is fully clockwise).

6. Close the circuit between terminals 9 and 10 (Close for Rated).

Start-up Adjustments

1. Prepare to start the engine. Read this entire chapter before attempting to start the engine. Interrelated problems can occur, and an understanding of all possibilities is needed before using a control for the first time.

In case the newly installed Flo-Tech Speed Control does not control engine speed, be prepared to: 1) remove the power from the control with the switch between the battery and terminal 1; and 2) initiate emergency shutdown procedures including manually shutting off the fuel supply.

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TO PROTECT AGAINST POSSIBLE INJURY, LOSS OF LIFE, and/or PROPERTY DAMAGE WHEN STARTING the engine, turbine, or other type of prime mover, BE PREPARED TO MAKE AN EMERGENCY SHUTDOWN to protect against runaway or overspeed should the mechanical-hydraulic governor(s), fuel control(s), the driving mechanism(s), the linkage(s), or the control device(s) fail.

Adjust for Stable Operation

Read the following paragraphs before attempting initial engine start up. Dynamics must be quickly adjusted after initial start up.

Immediately after the initial start up, it will be necessary to adjust the governor for stable operation. Idle and Rated dynamics are completely separate. The adjustments must be made according to the dynamics selected. In most cases the idle speed has been preset at maximum (fully clockwise) and Rated Speed is selected. In many cases the selection of rated speed will not indicate a desire for rated dynamics, which will be used when the engine is loaded. Idle dynamics may be selected and adjusted while rated speed is selected.

If the engine is hunting at a rapid rate, slowly decrease the GAIN (turn the potentiometer counterclockwise) until performance is stable.

If the engine is hunting at a slow rate, increase the STABILITY (turn the potentiometer clockwise) until the engine stabilizes. If increasing the STABILITY potentiometer does not stabilize the engine, it also may be necessary to slowly decrease the GAIN (turn the potentiometer counterclockwise).

1. Start cranking the engine. If the signal from terminals 3 and 4 does not show a positive voltage (2 to 6 Vdc) check the MPU.

Minimum voltage required from the MPU to operate the electronic control is 1.0 Vrms, measured at cranking speed or the lowest controlling speed. Measure the voltage while cranking with the speed sensor connected to the control. Be sure to prevent the engine from starting. At 5 percent of the lower value of the control's speed range, the failed speed-sensing circuit is cleared. For example 150 Hz is required on the 3000 to 6000 Hz speed range.

If necessary, increase the Start Fuel Limit (turn clockwise) while cranking until the engine starts. The Start Fuel Limit must be high enough to allow the engine to reach the selected idle or rated speed.

2. If the control increases the engine speed above its cranking speed, the engine should continue to operate at the rated speed. (If the rated speed is too low, it may be necessary to increase the Rated Speed setting slightly by turning the rated-speed pot a little clockwise.) If the engine stops, it indicates a MPU problem. The MPU must produce a minimum of 1 Vac rms to activate the control. Failure to produce the minimum signal can be caused by improper MPU installation, selection of an incorrect gear, improper wiring between the MPU and the control, or a defective MPU.

3. It will be necessary to immediately adjust the control for stable operation after the engine starts. (See Adjust for Stable Operation and Dynamic Adjustment.)

4. With the engine running and stable, slowly increase the rated-speed setting with the RATED SPEED pot until the desired rated speed is reached.

Dynamic Adjustment

The object of the GAIN and STABILITY potentiometer adjustments is to obtain the optimum, or desired, stable engine-speed response (see Figure 3-1).

Increasing the setting of the GAIN potentiometer provides faster transient response (decreases the amount of speed change from a sudden change in load). To achieve the best response, slowly increase the GAIN (turn the potentiometer clockwise) until the engine becomes slightly unstable, then slowly turn the GAIN back counterclockwise as necessary to stabilize engine speed.

Step load the engine to make sure the engine returns to the proper speed with little overshoot or undershoot of the speed setting. (To reduce overshoot, increase the STABILITY setting by turning the potentiometer clockwise).

Increasing the STABILITY clockwise will require decreasing the GAIN (turning the GAIN potentiometer counterclockwise) to maintain stable operation.

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

Figure 3-1 illustrates engine starts with no ramp or capacitor connected to the control, step loadings at four different STABILITY potentiometer settings, and stable, steady-state running conditions. These are typical performance curves on a naturally-aspirated (not turbocharged) diesel engine.

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.

5. LOW IDLE SPEED ADJUSTMENT: The engine should be at rated speed with the IDLE SPEED potentiometer set at maximum (fully clockwise). Open the external CLOSE FOR RATED contact.

6. Decrease the IDLE SPEED (turn the potentiometer counterclockwise) until the desired idle speed is reached. It may be necessary to adjust the idle dynamics to maintain stability as speed is lowered.

Figure 3-1. Diesel Engine Response Curves

7. If idle dynamics were selected on initial start-up, it will now be necessary to set rated dynamics. Load the engine, then select rated dynamics. Adjust for stable but active response as was done with the idle dynamics. The idle dynamics will provide stable operation of a loaded engine, but will not provide optimum response to load changes. If the rated dynamics are set for optimum engine performance when the engine is loaded, the engine should not be stable when unloaded unless the idle dynamics are selected. Rated dynamics are normally set with the engine at operating speed.

Engine response will change as the engine warms up. It may be necessary to tune dynamics after warm-up. It may be necessary to compromise optimum control dynamics with a cold engine in order to have optimum dynamics when the engine is at operating temperature.

Start Fuel Limit

1. The START FUEL LIMIT was set at a point that allowed the cold engine to start during initial start up procedures. If START FUEL LIMIT is to be used, it should now be adjusted after engine stability and response rates are correctly adjusted.

2. Adjusting the START FUEL LIMIT counterclockwise will prevent the fuel valve from delivering a maximum amount of fuel to the injectors until the selected speed (Idle or Rated) is reached. Adjust for desired engine performance during start up. The Start Fuel Limit must be set high enough to allow the engine to reach the selected speed.

3. The Start Fuel Limit should be adjusted from counterclockwise to obtain the desired characteristics while starting the engine. NOTE: There may be differences in startup characteristics of cold and hot engines.