CHAPTER 9
ELECTROHYDRAULIC LOAD-SENSING
SPEED GOVERNORS
An electrohydraulic governor may be operated as
This chapter contains a discussion about the
an isochronous governor; that is, at constant speed
operation and maintenance of electrohydraulic
load-sensing speed governors. If you do not have a
regardless of load, provided the load does not exceed
thorough understanding of solid state circuitry,
An isochromous
the limits of the prime mover.
components, or terms, review the Navy Electricity and
governor may also be used with speed droop; that is, as
Electronics Training Series (NEETS). The modules
the load increases, the speed of the prime mover
that deal with solid state circuitry include the following:
decreases. Speed droop permits paralleling with other
generators that have dissimilar governors or paralleling
Module 6, NAVEDTRA 172-06-00-92
with an inifinite bus (such as shore power).
Module 7, NAVEDTRA 172-07-00-92
The operation of a typical electrohydraulic
Module 8, NAVEDTRA 172-08-087
load-sensing governoring system may be generally
described as follows:
Module 9, NAVEDTRA 172-09-00-85
1. The throttle that controls the prime mover fuel
medium is operated by an electrohydraulic
LEARNING OBJECTIVES
actuator.
Upon completion of this chapter, you should be able
2. This electrohydraulic actuator responds to the
to do the following:
output of an electronic amplifier.
1. I d e n t i f y s o m e o f t h e c h a r a c t e r i s t i c s o f
3. Generator speed and load signals are fed into the
electrohydraulic load-sensing speed governors.
electronic amplifier.
2. Identify the function of various components in
4. The electronic amplifier produces a power
an electrohydraulic load-sensing speed
output that operates the electrohydraulic
governor.
actuator.
3. Identify the sequence of operation of EG-M
5. The electrohydraulic actuator correctly
load-sensing speed governor through speed
positions the steam valve or throttle.
changes.
The speed signal is usually provided by a small
4. Identify the sequence of operation of the EG-R
permanent magnet generator (PMG) or a permanent
hydraulic actuator through speed changes.
magnet alternator (PMA). The PMG or PMA are driven
5. Identify the sequence of operation EGB-2P
from the shaft of the prime mover controlled by the
electohydraulic load-sensing speed governor
governor. When used to control a ship's service
during speed changes.
generator, the speed signal is sometimes obtained by
6. I d e n t i f y t h e m i n i m u m m a i n t e n a n c e
sensing the output frequency of the generator.
requirements for maintaining electrohydraulic
However, a loss of signal, which could be caused by a
load-sensing speed governors.
short circuit on the generator, is a disadvantage of this
Electrohydraulic load-sensing speed governors
The speed signal is applied to a
method.
have been developed for the ship's service generators in
frequency-sensitive and reference circuit in the
electrical systems that require closer frequency
governor control unit. The output of this circuit is a net
regulation than that provided by mechanical-type
error signal if there is any deviation from the set speed.
governors. Electrohydraulic governors have been used
Stability of the prime mover is obtained by the use
successfully on steam turbine, gas turbine, and
of electrical feedback circuits.
diesel-driven generators.
9-1
