The DT-2000B speed control unit is a all electronic device designed to control engine
Speed with fast and precise response to transient load changes. This closed loop control, when connected to a proportional electric actuator and supplied with a magnetic speed sensor signal,will control a wide variety of engines in a isochronous or droop mode. It is designed for high reliability and built ruggedly to withstand the engine environment.
Simplicity of installation and adjustment was formost in the design. Non-interacting performance controls allow optimum response to be easily obtained
The primary features of the DT-2000B speed control unit are the engine STARTING FUEL and SPEED RAMPING adjustments. The use of these features will minimize engine exhaust smoke experienced prior to attaining engine operating speed.
Other features include adjustable droop and idle operation, inputs for accessories used in multi-engine or special applications, protection against reverse battery voltage, transient voltages, accidental short circuit of the actuator and fail safe design in the event of loss of speed sensor signal or supply
Engine speed information for the speed control unit usually received from a magnetic
Speed sensor. Any other signal generating device may be used provided the generated frequency is proportional to engine speed and meets the voltage input and frequency range specification. The speed sensor is typically mounted in close proximity to an engine driven ferrous gear, usually the engine ring gear. As the teeth of the gear pass the magnetic sensor, a signal is generated which is proportional to engine speed.
Signal strength must be within the range of the input amplifier. An amplititude of 0.5 to 120 volts RMS is required to allow the unit to function within its design specifications. The speed signal is applied to Terminals C and D of the speed control unit. Between these terminals there is an input impedance of over 33,000 ohms. Terminal D is internally connected to Terminal E, battery negative. Only one end of the shielded cable should be connected.
When a speed sensor signal is received by the controller, the signal is amplified and shaped by an interal circuit to provide an analog speed signal. If the speed sensor monitor does not detect a speed sensor signal, the output circuit of the speed control unit will turn off all current to the actuator.
A summing circuit receives the speed sensor signal along with the speed adjust set point input. The speed range has a ratio of 8:1 and is adjusted with a 25 turn potentiometer. The output from the summing circuit is the input to the dynamic control section of the speed control unit. The dynamic control circuit, of which the gain and stability adjustments are part, has a control function that will provide isochronous and stable performance for most engine types and fuel systems.
The speed control unit circuit is influenced by the gain and stability performance adjustments. The governor system sensitivity is increased with clockwise rotation of the gain adjustment. The gain adjustment has a range of 33:1. The stability adjustment, when advanced clockwise, increases the time rate of response of the governor system to match various time constants of a wide variety of engines. The speed control unit is a PID device, the “D”,derivative portion can be varied when required.
During the engine cranking cycle, STARTING FUEL can be adjusted from an almost closed, to a nearly full fuel position. Once the engine has started, the speed control point is determined, first by the IDLE speed set point and the SPEED RAMPING circuit. After engine speed ramping has been completed, the engine will be will be at its governed engine speed , the actuator will be engergized with sufficient current to maintain the desired engine speed, independent of load（isochronous operation）.
The output circuit provides switching current at a frequency of about 500 HZ to drive the actuator. Since the switching frequency is well beyond the natural frequency of the actuator, there is no visible motion of the actuator output shaft. Switching the output transistors reduces its internal power dissipation for efficient power control. The output circuit can provide current of up to 10 amps continous at 25℃ for 12 and 24 VDC battery systems. The actuator responds to the average current to position the engine fuel control lever.
In standard operation, the speed control unit performance is isochronous. Droop governing can be selected by connecting terminals K and L and the percent of droop governing can be varied with the droop adjustment control. The droop range can be decreased by connecting Terminals G and H.
The speed control unit has several performance and protection features witch enhance the governor system. A speed anticipation circuit minimizes speed overshoot on engine start-up or when large increments of load are applied to the engine. Engine idle speed can be remotely selected and is adjustable. Accessory inputs to achieve variable speed operation and multi-engine control can be accepted by the G2R315 speed control unit from load sharing modules,automatic synchronizers, ramp generators and other accessory engine control modules. Protection against reverse battery voltage and transient voltages is provided. The design is fail-safe in the event of loss of speed sensor signal or battery supply.
Supply…………….12 or 24 VDC Battery Systems(Transient and Reverse Voltage Protected)
Actuator Current Range……Min.2.5Amps…..Max.10Amaps continuous
Speed Range Rate…………………………………………………………0.25%
Steady Ajustment Rate………………………………………………….0～5%
Operating Temperature Range…………………………………-40℃～+85℃
Relative Humidity……………………………………………….. up to 95%
Mounting………………………………………………………Any Position, Vertical Preferred
4APPLICATION AND INSTALLATION INFORMATION
The speed control unit is rugged enough to be placed in a cabinet or engine mounted
Enclosure with other delicated control equipment. If water,mist,orcondensation may come in contact with the controller, it should be mounted vertically. This will allow the fluid to drain away from the speed control unit.
Extreme heat should be avoided.
WARNING: An overspeed shut device, independent of the governor system, should be provided to prevent loss of engine control which may cause personal injury or equipment damage. Do not rely exclusively on the governor system electric actuator to prevent overspeed. A secondary shutoff device, such as a fuel solenoid must be used.
Installation outline see figure 1
FIGURE 1 Outline of the speed control unit
Basic electrical connections are illustrated in Diagram 1. actuator and battery connections
To terminals A,B,E and F should be 1.3 mm sq or larger. Long cables require an increased wire size to minimize voltage drops.
The battery positive(+)input, Terminal F,should be fused for 15 amps as illustrated.
Magnetic speed sensor connections to Terminals C and D MUST BE TWISTED AND/OR SHIELDED for their entire length. The speed sensor cable shield should be ideally connected to terminal D. the shield should be insulated to insure no other part of the shield comes in contact with engine ground, otherwise stray speed signals may be introduced to the speed control unit. With the engine stopped,adjust the gap between the magnetic speed sensor and the ring gear teeth. The gap should not be any smaller than 0.020 in.(0.45mm). usually, backing out the speed sensor 3/4 turn after touching the ring gear tooth will achieve a satisfactory air gap. The magnetic speed sensor voltage should be at least 1 VAC RMS during cranking.
Before Starting Engine
Check to insure the GAIN and STABILITY adjustments, and if applied, the external SPEED TRIM CONTROL are set to mid position.
Preset the DT-2000B as follows:
STARTING FUEL………………..FULL CW(Maximum Fuel)
SPEED RAMPING……………….FULL CCW(Fastest)
The speed control unit governed speed setting is factory set at approximately engine idle speed (1000Hz., speed sensor signal)
Crack the engine with DC power applied to the governor system. The actuator will energize to the maximum fuel position until the engine starts. The governor system should control the engine at a low idle speed. If the engine is unstable after starting, turn the GAIN and STABILITY adjustments counterclockwise until the engine is stable.
Governor Speed Setting
The governed speed set point is increased by clockwise rotation of the SPEED adjustment control. Remote speed adjustment can be obtained with an optional 5K Speed Trim control.( See Diagram 1)
Once the engine is at operating speed and at no load, the following governor performance adjustment can be made.
A . Rotate the GAIN adjustment clockwise until instability develops. Gradually move the adjustment counterclockwise until stability returns. Move the adjustment one division further counterclockwise to insure stable performance.
B. Rotate the STABILITY adjustment clockwise until instability develops. Gradually move the adjustment counterclockwise until stability returns. Move the adjustment one division further counterclockwise to insure stable performance.
C. Gain and stability adjustments may require minor changes after engine load is applied. Normally, adjustments made at no load achieve satisfactory performance. A strip chart recorder can be used to further optimize the adjustments.
Starting Fuel Adjustment
The engine’s exhaust smoke at start-up can be minimized by completing the following adjustments.
1.Place the engine in IDLE by connecting Terminals M & G.
2.Adjust the IDLE speed for as low a speed setting as the application allows.
3.Adjust the STARTING FUEL CCW until the engine speed begines to fall. Increase the STARTING FUEL slightly so that the idle speed is returned to the desired level.
4.Stop the engine.
Idle Speed Setting
If the IDLE speed setting was not adjusted as detailed in “Starting Fuel Adjustment”section , then place the optional external selector switch in the IDLE position. The idle speed set point is increased by clockwise rotation of the IDLE adjustment control. When the engine is at idle speed, the speed control unit applies droop to the governor system to insure stable operation.
Speed Droop Operation
Droop is typically used for the paralleling of engine driven generators.
Place the optional external selector switch in the DROOP position, DROOP is increased by clockwise rotation of the DROOP adjustment control. When in droop operation, the engine speed will decrease as engine load increases. The percentage of droop is based on the on the actuator current change from engine no load to full load. A wide range of droop is available with the internal control. Droop level requirements above 10% are unusual.
If droop levels experienced are higher or lower than those required, contact the factory for assistance.
After the droop level has been adjusted, the rated engine speed setting may need to be reset. Check the engine speed and adjust the speed setting accordingly.
The AUXilary Terminal N accepts input signals from load starting units, auto synchonizers, DONGFENG CUMMINS accessories are directly connected to this terminal. It is recommended that this connection from accessories be shielded as it is a sensitive input terminal.
If the auto synchronizer is used alone, not in conjunction with a load sharing module, a 3 M ohm resistor should be connected between Terminals N and P. This is required to match the voltage levels between the speed control unit and the synchronizer.
When an accessory is connected to Terminal N, the speed will decrease and the speed adjustment must reset.
When operating in the upper end of the control unit frequency range, a jumper wire or frequency trim control may be required between G and J. This increases the frequency range of the speed control to over 7000Hz.
The +10 volt regulated supply, Terminal P, can be utilized to provide power to DOFENG CUMMINS governor system accessories. Up to 20 ma of current can be drawn from this supply. Ground reference is Terminal G. Caution: a short circuit on this terminal can damage the speed control unit.
Wide Range Remote Variable Speed Operation
Simple and effective remote variable speed can be obtained with the DT2000B control unit.
A simple remote speed adjustment potentiometer can be used to adjust the engine speed continuously over a specific speed range. Select the desired speed range and the corresponding potentiometer value. (Refer to TABLE 1) if the exact range cannot be found ,select the next higher range potentiometer. An additional fixed resister may be placed across the potentiometer as shown in Diagram 2.
To maintain engine stability at the minimum speed setting , a small amount of droop can be added using the DROOP adjustment. At the maximum speed setting the governor performance will be near isochronous, regardless of the droop adjustment setting.
Connecting the factory for assistance if difficulty is experienced in obtaining the desired variable speed governing performance.
DIAGRAM 1 DT-2000B Wiring Diagram
TABLE 1. Variable Speed Range Potentiometer Value
Speed Range Potentiometer Value
900 Hz 1K
2400 Hz 5K
3000 Hz 10K
3500 Hz 25K
3700 Hz 50K
DIAGRAM 2. Slect Proper Potentiometer Value From Table 1