Follow these precautions when working with or near the control.

Avoid the build-up of static electricity on your body by not wearing clothing made of synthetic materials. Wear cotton or cotton-blend materials as much as possible because these do not store static electric charges as much as synthetics.

Do not remove the printed circuit board (PCB) from the control cabinet unless absolutely necessary. If you must remove the PCB from the control cabinet, follow these precautions:

Do not touch any part of the PCB except the edges. Do not touch the electrical conductors, the connectors, or the components with conductive devices or with your hands. 

When replacing a PCB, keep the new PCB in the plastic antistatic protective bag it comes in until you are ready to install it. Immediately after removing the old PCB from the control cabinet, place it in the antistatic protective bag.

Introduction

This manual provides description, operation, installation, adjustment and replacement parts information for the proportional EGB governor/actuators with hydraulic amplification systems (EGB-10P/-13P/-35P/-29P/-50P/-58P; referred to in general as an EGB-P). Certain optional auxiliary features which may be used with the actuator are included in this manual.

Description

The EGB-P is an electrically controlled, proportional output actuator with an integral backup mechanical (centrifugal) governor. It is normally used with a Woodward integrating electric control unit to form a complete governing system.

When operating on the electrical side, the actuator terminal (output) shaft assumes a position in direct proportion to the magnitude of the electrical output signal from the electric control unit. The magnitude of the input signal to the actuator is determined by the position required of the fuel or steam control to maintain the desired prime mover speed under varying conditions of load.

Applications

EGB proportional actuators are normally used on units which must continue to operate, even if the electrical governor fails. The combination of an electrically powered actuator and a mechanical ballhead governor in the same unit provides an extra aspect of reliability for control systems which must provide emergency service.

Proportional actuators are also particularly suited for use with prime movers operating in tandem to drive a common mechanical load. In these applications, a single electric control can be used for two or more proportional actuators connected in series with the output of the electrical control unit. With each actuator receiving the same current signal, the output shafts will take the same angular position and direct the same amount of fuel or steam to each prime mover. Because the EGB has droop built into the mechanical governor section it can operate these tandem units should the electrical control signal fail for any reason.

Two Controls

The EGB-P governor/actuator (Figure 1-1) is, in effect, two controls in one; an electric actuator and a mechanical governor, each independently capable of positioning the output or terminal shaft.

During normal operation, the electric section controls fuel or steam to the prime mover. The mechanical governor controls the prime mover during starting and also functions as a backup governor to prevent runaway should the electric control system fail in such a manner to call for maximum fuel. The speed of the mechanical governor is set slightly higher than the electrical governor and should the speed of the controlled unit reach this level the mechanical governor will assume and maintain control of the prime mover.

An EGB-P unit operating with droop will have the mechanical side set about five percent higher than the electrical side. If the unit is not using droop, the mechanical side may be set only one or two percent higher than the electrical side.

With standard confirmation (direct acting), the EGB-P output servo will go to minimum position should the electric control signal fail to zero volts. The EGB-P may be installed with a “reverse acting” control which will call for maximum fuel should the electric signal fail to zero volts causing the continued operation of the controlled unit by the mechanical governor side starting when the engine speed increases to the speed setting of the mechanical control.

The operating element of the electric section of the actuator is an electro hydraulic transducer. The transducer consists of a solenoid attached to the pilot valve plunger controlling oil flow to and from the power piston (see Figure 4-1).

The solenoid responds to the output of an electric control unit and moves the pilot valve plunger up or down. Through connecting linkage the servo piston moves the terminal (output) shaft of the actuator. The engine or turbine fuel linkage attaches to the actuator shaft.

Specifications

All EGB proportional actuators and governors described in this manual operate in identical fashion.

EGB-10, 13, 35, and 50 models provide operating power through a terminal shaft located in the aluminum column. The work capacities are related to the amount of hydraulic pressure available to the power cylinder.

The EGB-29 and 58 models operate with a power cylinder which has its own terminal shaft as part of the power cylinder. The EGB-29 and 58 are identical except for the difference in internal hydraulic pressures.