Description

The 4024 EPG (electrically power governor) system provides up to 4 ft-lb (5.4 J) of work to move the fuel setting of diesel or spark ignited engines. Engines with mechanical loads and generator loads are handled equally well. Generator sets which will be paralleled, however, require additional current and potential transformers and the EPG Load Sensor.

Installation of the actuator is simple because it does not require a hydraulic supply or mechanical governor drive.

Power Requirement

Most EPG systems use the same battery power as the engine installation (24 Vdc). If the engine does not have an auxiliary 24 Vdc battery system, one must be provided for the governor. Maximum steady state current is 10 A.

Return Spring

The actuator provides torque only in the increased fuel direction. A return spring is required to move toward minimum fuel. Most actuators will have the return spring installed at the factory. Actuators ordered without a return spring will require the installation of a spring conforming to the specified rate and preload.

Speed Control

An EPG is a three-component system. A magnetic pickup, speed control, and actuator are all required.

Speed controls are available for 24 volt systems with best performance between 3000 and 6000 Hz gear tooth speed.

The speed being sensed will be the number of teeth in the gear being sensed times the rpm divided by 60.

Response of the controls is different for diesel and gas turbine applications than for gasoline and gas fueled engines.

8290-147 control boxes provide the correct response for spark ignition gas or gasoline powered engines.

8290-148 control boxes provide the correct response for diesel engines or gas turbines.

Different Actuators

Two different actuators are available for use with the selected EPG control system:

Clockwise output shaft with return spring on the counterclockwise end, 8256-060. 

Counterclockwise output shaft with return spring on the clockwise end, 8256-080.

The clock-spring type of return spring provided by Woodward on EPG models will provide about 3.5 ft-lb (4.7 J) of work in the decrease fuel direction. (Torque equals 0.8 lb-ft [1.1 Nm] at minimum fuel and 8 lb-ft [10.8 Nm] at maximum fuel.) The actuator will provide about 4 ft-lb (5.4 J) of work in the increase fuel direction in addition to the work needed to overcome the return spring. (Torque equals 9 lb-ft [12.2 Nm] at the 5° minimum fuel and 3 lb-ft [4.1 Nm] at the 35° position.)

4024 EPG systems with position feedback from the actuator are described in manual 04149.

Installation

Speed Control Installation

The speed control is designed to operate within a temperature range of –40 to +75 °C (–40 to +167 °F).

Install the control box in a location with space for adjustment and wiring access. Do not expose the control to sources of radiant heat, such as exhaust manifolds or turbochargers. Choose a protected location so the control won't be damaged when moving the prime mover or when near-by equipment is moving. Mount the control close enough to the actuator and battery to meet the wire-length requirements. (See wiring instructions in this chapter.)

The control will generate a little heat and surfaces must be open to normal air movement. No special ventilation is required.

Ideally the control should be mounted flush to the metal side of a control cabinet, protected from the weather and high humidity, and close to the engine being controlled. The location should provide protection from high-voltage or high current devices, or devices which produce electro-magnetic interference. After initial adjustments are completed all functions may be selected with remote switches on the control panel. Ready access to the control will not be required for normal engine operation.

Do not install the control box directly on the engine.

Use the control for a template for the installation screws, or use the outline drawing in this chapter of the manual.

Shield Ground

Review the plant wiring diagrams in this manual and prepare to ground the shields at the control. One of the installation screws is normally used for the shield ground terminal.

Actuator Mounting and Linkage

Proper design and installation of the linkage from the actuator to the engine is necessary if the unit is to give good control.

Most installations have the actuator directly controlling the fuel flow to the engine or turbine, by moving either the fuel valve, butterfly valve, or fuel rack. Some installations have the actuator controlling the speed-setting shaft on a mechanical governor. This type of installation can give adequate control for generator sets, but may not provide control from full load to idle or shutdown.

The linkage is often connected to the shutdown lever or shaft. When this type of installation is used, the mechanical governor functions as a high-speed limit. Note that when the shutdown lever is selected for control, the emergency and safety shutdown features are often disconnected.

Linkage should be designed to provide a linear relationship between actuator movement and power from the prime mover. Most diesel engines are linear, and in this case a movement of about 4 degrees of actuator-shaft position (10% of the total movement available) should cause about a 10–15% change in the position of the fuel control shaft and the power output of the engine. Figure 2-1 shows this type of linkage between the actuator and fuel control level. (See Figure 2-5 for additional information on actuator travel.)

Carburetors and some diesel engines have non-linear fuel controls. In these cases the actuator must be linked to the engine as shown in Figure 2-2. This compensating linkage requires more actuator movement to make a change in fuel at minimum fuel than at maximum fuel.

The power output must remain linear with either type of linkage.

Study the control features of the engine being fitted with the 4024 control to determine the type of linkage required. Contact Woodward Governor Company for additional linkage information.

Incorrect matching of the actuator output and fuel-setting lever is the most common cause of unstable operation, and can cause stable operation at some fuel setting but oscillation at other fuel settings.

Manually stroke the fuel-control linkage from stop to stop, as if the actuator were moving it. The linkage must move freely, without friction, and without backlash. Lubricate or replace worn linkage or fuel control parts as required.

If a return spring is not included on the actuator a return spring must be attached to the system. The return spring may operate on the terminal lever of the actuator or directly on the engine linkage.

Make sure the actuator is capable of moving the fuel control to maximum and minimum limits. Let the fuel control limit actuator travel. Set the linkage so the actuator is just above minimum when the fuel control is at its minimum stop and so the actuator is just below maximum when the fuel control is at its maximum stop. (Some fuel systems will bind if the stops are reached. In these cases it is possible to use the maximum and minimum stops of the actuator. This will require a more precise final adjustment of the control-rod length.)

Using too little actuator rotation can cause control instability and other control problems. Too little actuator rotation will also limit the amount of droop which can be adjusted into the control system (Droop is available with the load sensor.) If it is necessary to use less than the recommended rotation adjust the linkage so the actuator approaches or reaches the maximum position at maximum fuel.

Use good rod-end connectors with as little slack as possible. Select rod ends which will not become loose and which will wear well during the nearly constant movement associated with precise speed control. Low friction, long wearing rod ends are available from Woodward.

The link connecting the actuator lever to the fuel-control lever must not be so long that if flexes when the prime mover is running. In most cases a piece of threaded rod is used for the link. Assemble the rod end and rod with jam nuts at both ends. A rod end will have to be removed from either the actuator or engine end to change the length of the rod. However, this is usually preferred over the use of a turn-buckle type of rod with left- and right-hand screws because it prevents accidental speed changes should the jam nuts work loose and because it allows both rod ends to have more common right-hand threads.

If a long connecting rod between the actuator and the engine fuel control is required, use a hollow tube to reduce weight while maintaining strength. The hollow tube will usually be less subject to vibration that will a solid connecting rod.

Actuator levers are available from Woodward which allow adjustment of the rod end location in respect to the center of the actuator shaft. The lever used must have a 0.500 inch -36 serration to fit on the actuator.

Adjust the location of the rod end on the lever to achieve the desired rotation of the actuator shaft between minimum and maximum positions. (Use as much of the 42 degrees rotation as possible, not less than 25 degrees). To increase the amount of rotation, move the rod end closer to the actuator shaft. To decrease the amount of rotation used, move the rod end farther away from the actuator shaft.

If less than 42 degrees actuator rotation is necessary, maintain about half of the unused travel at the minimum fuel direction and half of the unused travel at the maximum fuel direction. Using less than the recommended amount of rotation will often cause instability in the governor system.

Magnetic Pickup

Install the magnetic pickup to work with the selected gear through a housing or rigid bracket. Make sure the sensed gear is of magnetic material. Set the gap between the gear and the end of the magnetic pickup according to instructions which accompany the pickup.

Magnetic pickups of various sizes are available from Woodward.

The standard models of magnetic pickups require mating connectors,   MS 3102R-18-eP. The connectors can be furnished with the magnetic pickup ordered from Woodward.

Manual 82510, Magnetic Pickups and Proximity Switches for Electric Controls, contains detailed information on the installation of the sensing device.

Wiring Instructions

External wiring connections and shielding requirements for a typical control installation are shown in the plant wiring diagram (Figure 2-6). These wiring connections and shielding requirements are explained in the balance of this chapter.

Electromagnetic interference (EMI) is the undesirable interaction of electronic circuits with each other and sometimes with themselves.

Woodward has established procedures to prevent most EMI which will affect prime-mover-control circuits. Following these procedures is a slight extra effort in planning and installing electronic governing systems, but is valuable insurance over the life of the plant. Follow all of the shielding instructions to assure maximum efficiency and dependability of the electronic governing system.

Application note 50532, EMI Control for Electronic Governing Systems, has additional information on EMI causes and prevention.

Shielded Wiring

All shielded cable must be twisted conductor pairs. Do not attempt to tin the braided shield. All signal lines should be shielded to prevent picking up stray signals from adjacent equipment. Connect the shields to the control case as shown in Figure 2-6, the plant wiring diagram. Wire exposed beyond the shield should be as short as possible, not exceeding six inches. The other end of the shields must be left open and insulated from any other conductor. Do not run shielded signal wires with high voltage or high current wires.

When passing shields through connectors and terminal blocks, treat each shield as if it were a signal wire. Each shield must be given its own pin or terminal and kept insulated from nearby wires and metal conductors. Do not tin (solder) braided shields.

Use 14 AWG (2.0 mm²) or 12 AWG (3.0 mm²) wire throughout the EPG circuit. The total distance from the battery to the control and from the control to the actuator must not exceed 8 feet (2.4 m) if 14 AWG wire is used or 22 feet (6.7 m) if 12 AWG wire is used. The 8 foot limit for 14 AWG wire will make it difficult to wire most installations, and 12 AWG wire should always be used, if possible.

The fuse and switch or circuit breaker must be in the non-grounded battery lead. Use a 15 A fuse and switch for the installation. Starter relays make good EPG power switches.

The battery connection to speed control terminals 1 and 2 must be directly from the terminals, not through distribution points.