AU2022204061B2 - Efficiency improvements for electromechanical system for driving a pump - Google Patents

Abstract

An electromechanical system 10 comprising an internal combustion engine 12 having a controllable mechanical output and measurable instantaneous fuel consumption. System 10 also includes an electrical generator 14, such as an alternator, which is mechanically coupled to the engine's mechanical output and operatively generates electrical power. The generator 14 includes a controllable excitation system, such as a voltage regulator 22, whereby generator voltage output is controllable. System 10 also includes an asynchronous motor 16 which is operatively supplied with electrical power from the electrical generator 14, and a pump 18 driven by the asynchronous motor 16 for operatively displacing fluid and having at least one user-selectable pump operating characteristic. System 10 further includes a controller 20 which is programmed with a speed-torque relationship of both the engine 12 and asynchronous motor 16 and a performance curve of the pump 18, the controller configured to continuously monitor operating characteristics of the engine 12, generator 14, motor 16 and pump 18 whilst automatically and dynamically controlling the engine's mechanical output and generator's excitation system 22 in order to dynamically and continuously correlate the speed-torque relationships and the pump performance curve to facilitate optimal energy transfer efficiency through the system 10 while maintaining the user selectable pump operating characteristic for a steady-state of operation. In addition, once such a steady-state of operation is established, the controller 20 is configured to adjust the excitation system 22 to improve a power factor of the electrical power according to the instantaneous engine fuel consumption. 1/5 E p Q-Q 0 0 '-4 (N CNU 0t C)C w0 (N (N

Description

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(N (N EFFICIENCY IMPROVEMENTS FOR ELECTROMECHANICAL SYSTEM FOR DRIVING A PUMP TECHNICAL FIELD

[0001] This invention broadly relates to the field of

electrical engineering, in general, and more particularly to an

electromechanical system for operatively driving a load, such as

a pump, and an associated controller for such an

electromechanical system.

BACKGROUND ART

[0002] The following discussion of the background art is

intended to facilitate an understanding of the present invention

only. The discussion is not an acknowledgement or admission that

any of the material referred to is or was part of the common

general knowledge as at the priority date of the application.

[0003] Applicant has developed an electrical system and

associated controller for operatively driving a pump which are

described in Australian Patent Application No. 2017213531, the contents of which are incorporated herein by reference.

[0004] There are millions of electrical motors in use in

industry and offices around the world. Such motors may operate

a variety of loads, such as mining dewatering pumps, sewage and

irrigation pumps, milking machines and ski lifts, paper machines

and power-plant fans, sawmill conveyors and hospital ventilation

systems, to name just a few examples. It has been estimated that

in the vicinity of sixty-five percent or more of industrial

electrical energy is consumed by electrical motors.

[0005] In many cases, these electrical motors operate at a

constant speed while supplied by a static frequency and voltage

electrical supply. In other cases, these electrical motors are

required to operate at variable speed supplied by dynamic

frequency and voltage. The later method generally uses solid

state switching methodologies for starting and controlling such

motors, e.g. pulse width modulation, etc. Such practices are

generally inefficient from an energy point of view.

[0006] For example, a solid-state motor soft starter is a

device used with alternating current (AC) electrical motors to

temporarily reduce the voltage amplitude which consequently

reduce the current applied to the motor during start-up. This

can reduce the associated mechanical and electrodynamic stresses

and extend the lifespan of the system. In general, starting an

induction motor is accompanied by inrush currents up to 7-10

times higher than operating current, and starting torque up to

3 times higher than running torque. The increased torque results

in sudden mechanical stress on the machine which leads to a

reduced service life. Moreover, the high inrush current stresses

the power supply, which may lead to voltage dips. As a result,

lifespan of sensitive equipment may be reduced.

[0007] Accordingly, solid-state devices can be used to

control the voltage applied to a motor, but to accommodate the

large currents and voltages involved at start-up, these solid

state starters must generally be designed with a much higher

electrical rating than required for normal operation, and the

generator must be much higher rated than a motor which it drives,

typically in the order of a 250% rating increase. Such nameplate

capacity increases generally mean more expensive equipment able

to cater for such larger currents and voltages involved at start

up. Applicant's system, as described in Australian Patent

Application No. 2017213531, seeks to ameliorate this shortcoming

in the art.

[0008] Application of these systems driving a load, such as

a pump in industrial pumping arrangements, for example as part

of mining water management, particularly dewatering applications

such as in an open pit or an underground mine where below-surface

water management is a critical operation, often occurs in

geographically distant or isolated areas, such as at mine sites

located in the Pilbara region of Western Australia, or the like.

[0009] Typically, in such applications, an internal

combustion engine functions as prime mover and even a relatively

small efficiency increase can mean thousands of dollars in

savings over a prolonged period of time. Such savings typically

result from fuel savings, including cost and transport of fuel

to remote locations, as well as capital expenditure for

equipment. As such, any efficiency improvements or operating

optimisations may lead to significant savings over the lifetime

of such a system, making even minor incremental efficiency

increases very attractive.

[0010] The present invention was conceived with this goal in

mind.

SUMMARY OF THE INVENTION

[0011] The skilled addressee is to appreciate that the

present invention is described as driving a pump; however, any

suitable load driven by the electromechanical system is apposite. For example, a fan, a compressor, or the like may

comprise a suitable load, and may be substituted accordingly,

with required variations made as will be within the understanding

of the skilled addressee.

[0012] Additionally, as known in the art of electrical

engineering, reference herein to a 'motor' generally refers to

an induction motor or asynchronous motor, broadly being an AC

electric motor in which an electric current in a rotor needed to

produce torque is obtained by electromagnetic induction from a

magnetic field of a stator winding. In such asynchronous motors, 'slip' is defined as the difference between synchronous speed

and operating speed, at the same frequency, typically expressed

in RPM or as a percentage or ratio of synchronous speed. Slip,

which varies from zero at synchronous speed and one when the

rotor is stalled, generally determines the motor's torque.

[0013] Similarly, an induction or asynchronous motor

inherently presents an inductive electrical load, which reduces

an electrical system's power factor. As is known in the art, the

power factor of an AC power system is defined as the ratio of

the real power absorbed by the load to the apparent power flowing

in the circuit, and is a dimensionless number in the closed

interval of -1 to 1. A power factor of less than one indicates

that voltage and current are not in phase, reducing the average

product of the two, i.e. real power useable to perform work. In

an electrical system, a load with a low power factor draws more

current than a load with a high power factor for the same amount

of useful power transferred. These higher currents increase the

energy lost in the system and a low power factor typically wastes

energy via excessive heating of equipment, i.e. lost energy

provided by an energy source which is not used to perform work.

[0014] According to one aspect of the present invention there

is provided an electromechanical system for operatively driving

a pump, said system comprising: an internal combustion engine having a controllable mechanical output and a measurable instantaneous fuel consumption; an electrical generator mechanically coupled to said mechanical output for operatively generating electrical power, said generator having a controllable excitation system whereby generator voltage output is controllable; an asynchronous motor operatively supplied with such electrical power from the electrical generator; a pump driven by the asynchronous motor and having at least one user-selectable pump operating characteristic; and a controller programmed with a speed-torque relationship of both the engine and asynchronous motor and a performance curve of the pump, said controller configured to: i) continuously monitor operating characteristics of the engine, generator, motor and pump whilst automatically and dynamically controlling the engine's mechanical output and generator's excitation system in order to dynamically and continuously correlate the speed torque relationships and the pump performance curve to facilitate optimal energy transfer efficiency through the system while maintaining the user-selectable pump operating characteristic to establish a steady-state of operation; and ii) once such steady-state operation is established, adjust the excitation system to improve a power factor of the electrical power according to the instantaneous measured engine fuel consumption.

[0015] The skilled addressee will appreciate that optimal

energy transfer efficiency through the system generally refers

to a maximum ratio of energy provided as input to the system to

energy applied to perform useable work output from the system, i.e. quantum of energy derived from fuel powering the engine converted to useable energy able to displace fluid by the pump.

Such optimal energy transfer efficiency will minimise loss of

energy via waste, such as heat, friction, noise, or the like.

[0016] The skilled addressee will further appreciate that a

speed-torque relationship of either the engine or the

asynchronous motor may vary depending on engine or motor design

and is generally indicative of desired operating ranges for a

specific engine or motor at which said engine or motor has

increased power efficiency. It is also to be appreciated that

the performance curve of a pump provides an indication of

producible pressure relational to producible fluid flow rate and

a desired operating range delivering maximised efficiency for

such variables. Such speed-torque relationships and performance

curves are inherent to a design of a component and are often

reflected in an operating specification from a manufacturer of

the component.

[0017] In light hereof, by dynamically correlating such

speed-torque relationships and performance curves whilst

maintaining the user-selectable pump operating characteristic,

i.e. the controller individually operating individual components

at specific operating levels along such specific speed-torque

relationships and performance curves while maintaining a desired

outcome or user-selectable pump operating characteristic,

generally facilitates efficient energy transfer through the

system as such components are operated at complementary and

reciprocal levels depending on requirements. As an energy source

for the system typically comprises a fuel source for the engine,

such energy efficiency generally allows for minimised fuel use

or improved fuel efficiency.

[0018] Additionally, the skilled addressee will appreciate

that the controller generally performs its functions as broadly

described herein by means of executing suitable programming

instructions, algorithms and/or software which has been

configured to enable such controller functionality and

performance. Specifics of such instructions or algorithms are

function-dependent and variable according to controller type,

hence such instructions, software or algorithms are variable in

execution and may be implemented in a variety of manners, as is

well-known and understood in the art of electrical, computer and

control engineering. Accordingly, due to such variability of

implementation, specific details and minutiae of such software

implementation are not described in detail herein as it will be

within the grasp and understanding of the skilled addressee.

[0019] Typically, the engine operating characteristics

continuously monitored by the controller are selectable from a

non-exclusive group consisting of oil pressure, oil temperature,

oil level, coolant level, coolant temperature, inlet air

pressure, inlet air temperature, fuel level, fuel pressure,

output rotational speed, output torque, cylinder temperature,

exhaust temperature, and atmospheric pressure.

[0020] Typically, the engine includes an engine control unit

(ECU) via which the mechanical output is controllable and the

engine operating characteristics are monitorable.

[0021] Typically, the controller is configured to control the

mechanical output of the engine by varying any of the suitable

operating characteristics, e.g. fuel consumption, inlet air,

etc.

[0022] Typically, the electrical generator comprises a

synchronous three-phase AC alternator.

[0023] Typically, the electrical generator operating

characteristics continuously monitored by the controller are

selectable from a non-exclusive group consisting of voltage

output, current output, excitation system voltage, excitation

system current, winding temperature, magnetic field status, air

intake and air discharge.

[0024] Typically, the controller is configured to control the

excitation system of the generator by varying any of the suitable

operating characteristics of the electrical generator, e.g.

excitation system voltage.

[0025] Preferably, the controllable excitation system

comprises a voltage regulator whereby the controller is able to

control generator voltage output.

[0026] In an embodiment, the controller, via the voltage

regulator, is configured to control the generator output voltage

by controlling the excitation system through pulse-width

modulation.

[0027] Typically, the system includes switchgear electrically

coupling the generator and the asynchronous motor, said

switchgear having a circuit breaker monitored and controlled by

the controller for selectively decoupling the generator and the

motor, as required, as a safety feature.

[0028] Typically, the asynchronous motor operating

characteristics continuously monitored by the controller are

selectable from a non-exclusive group consisting of nominal voltage, nominal current, a frequency range, lock rotor current, power factor and operating efficiency.

[0029] Typically, the at least one user-selectable pump

operating characteristic is selectable from a non-exclusive

group consisting of a fluid flow rate, a fluid pressure at an

inlet and/or at an outlet, a fluid level, a pump temperature

and/or pump speed.

[0030] Typically, the pump is selected from a non-exclusive

group consisting of a centrifugal pump, a reciprocating pump, a

centrifugal fan, a blower and a compressor, or the like.

[0031] Typically, the pump operating characteristics

continuously monitored by the controller are selectable from a

non-exclusive group consisting of fluid flow rate, fluid

pressure, fluid level, pump acceleration and deceleration time,

pump frequency, pump rotational speed ranges, and overall pump

hydraulic performance.

[0032] Typically, the controller is configured to improve the

power factor by increasing or decreasing an excitation voltage

of the excitation system to decrease or increase, respectively,

the power factor, as required, whilst the desired steady-state

of operation is maintained.

[0033] In an embodiment, the controller is configured to

improve the power factor by measuring a first instantaneous

engine fuel consumption, incrementally adjusting the excitation

system to change the power factor, and taking a second

instantaneous engine fuel consumption, comparison of said first

and second instantaneous engine fuel consumption values used to

maximise fuel efficiency.

[0034] Typically, the controller is configured, once the

steady-state of operation changes via changes to the at least

one user-selectable pump operating characteristic and/or changes

to any relevant operating characteristics of the engine, generator, motor and/or pump, to return to step i) in order to

re-establish a steady-state of operation, after which step ii)

is performed.

[0035] According to a further aspect of the invention there

is provided a controller for an electromechanical system for

operatively driving a pump, the system having an internal

combustion engine having a controllable mechanical output and

measurable instantaneous fuel consumption, an electrical

generator mechanically coupled to said mechanical output and

operatively generating electrical power and having a

controllable excitation system whereby generator voltage output

is controllable, an asynchronous motor operatively supplied with

electrical power from the electrical generator, and a pump driven

by the asynchronous motor for operatively displacing fluid and

having at least one user-selectable pump operating

characteristic, wherein the controller is programmed with a

speed-torque relationship of both the engine and asynchronous

motor and a performance curve of the pump, wherein the controller

is configured to:

i) continuously monitor operating characteristics of the

engine, generator, motor and pump whilst automatically

and dynamically controlling the engine's mechanical

output and generator's excitation system in order to

dynamically and continuously correlate the speed

torque relationships and the pump performance curve to

facilitate optimal energy transfer efficiency through

the system while maintaining the user-selectable pump operating characteristic for a steady-state of operation; and ii) once such steady-state operation is established, adjust the excitation system to improve a power factor of the electrical power according to the instantaneous engine fuel consumption.

[0036] Typically, the controller comprises a programmable

logic controller (PLC).

[0037] Typically, the controller comprises an interface via

which a user is able to interface with the controller, including

a local and/or remote monitoring interface for remotely

monitoring and/or controlling the system.

[0038] Typically, the engine operating characteristics

continuously monitored by the controller are selectable from a

non-exclusive group consisting of oil pressure, oil temperature,

oil level, coolant level, coolant temperature, inlet air

pressure, inlet air temperature, fuel level, fuel pressure,

output rotational speed, output torque, cylinder temperature,

exhaust temperature, and atmospheric pressure.

[0039] Typically, the engine includes an engine control unit

(ECU) via which the mechanical output is controllable and the

engine operating characteristics is monitorable.

[0040] Typically, the controller is configured to control the

mechanical output of the engine by varying any of the suitable

operating characteristics, e.g. fuel consumption, inlet air,

etc.

[0041] Typically, the electrical generator comprises a

synchronous three-phase AC alternator.

[0042] Typically, the electrical generator operating

characteristics continuously monitored by the controller are

selectable from a non-exclusive group consisting of voltage

output, current output, excitation system voltage, excitation

system current, winding temperature, magnetic field status, air

intake and air discharge.

[0043] Typically, the controller is configured to control the

excitation system of the generator by varying any of the suitable

operating characteristics of the electrical generator, e.g.

excitation system voltage.

[0044] Preferably, the controllable excitation system

comprises a voltage regulator whereby the controller is able to

control generator voltage output.

[0045] In an embodiment, the controller, via the voltage

regulator, is configured to control the generator output voltage

by controlling the excitation system through pulse-width

modulation.

[0046] Typically, the asynchronous motor operating

characteristics continuously monitored by the controller are

selectable from a non-exclusive group consisting of nominal

voltage, nominal current, a frequency range, lock rotor current,

power factor and operating efficiency.

[0047] Typically, the at least one user-selectable pump

operating characteristic is selectable from a non-exclusive

group consisting of a fluid flow rate, a fluid pressure at an inlet and/or at an outlet, a fluid level, a pump temperature and/or pump speed.

[0048] Typically, the pump is selected from a non-exclusive

group consisting of a centrifugal pump, a reciprocating pump, a

centrifugal fan, a blower and a compressor, or the like.

[0049] Typically, the pump operating characteristics

continuously monitored by the controller are selectable from a

non-exclusive group consisting of fluid flow rate, fluid

pressure, fluid level, pump acceleration and deceleration time,

pump frequency, pump rotational speed ranges, and overall pump

hydraulic performance.

[0050] Typically, the controller is configured to improve the

power factor by increasing or decreasing an excitation voltage

of the excitation system to decrease or increase, respectively,

the power factor, as required, whilst the desired steady-state

of operation is maintained.

[0051] In an embodiment, the controller is configured to

improve the power factor by measuring a first instantaneous

engine fuel consumption, incrementally adjusting the excitation

system to change the power factor, and taking a second

instantaneous engine fuel consumption, comparison of said first

and second instantaneous engine fuel consumption values used to

maximise fuel efficiency.

[0052] Typically, the controller is configured, once the

steady-state of operation changes via changes to the at least

one user-selectable pump operating characteristic and/or changes

to any relevant operating characteristics of the engine, generator, motor and/or pump, to return to step i) in order to re-establish a steady-state of operation, after which step ii) is again performed.

[0053] According to a further aspect of the invention there

is provided a method for operatively driving a pump, said method

using an electromechanical system or a controller in accordance

with aspects of the invention above.

[0054] According to a yet further aspect of the invention

there is provided an electromechanical system or a controller,

substantially as herein described and/or illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be made with reference to the accompanying

drawing in which:

Figure 1 is a diagrammatical representation of one

embodiment of an electromechanical system for operatively

driving a pump, in accordance with an aspect of the invention;

Figure 2 is a diagrammatic overview representation of broad

method steps for driving a load, such as a pump, using the

electromechanical system of Figure 1;

Figure 3 is diagrammatic representation of a graph showing

a relationship between torque and speed for components of the

system of Figure 1;

Figure 4 is a diagrammatic representation of a graph showing

a relationship between efficiency/power factor, current and load

of the components of the system of Figure 1; and

Figure 5 is a diagrammatic graphical representation showing

a relationship between torque and slip of the relevant components

of the system of Figure 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0055] Further features of the present invention are more

fully described in the following description of several non

limiting embodiments thereof. This description is included

solely for the purposes of exemplifying the present invention to

the skilled addressee. It should not be understood as a

restriction on the broad summary, disclosure or description of

the invention as set out above.

[0056] In the figures, incorporated to illustrate features of

the example embodiment or embodiments, like reference numerals

are used to identify like parts throughout. Additionally,

features, mechanisms and aspects well-known and understood in

the art will not be described in detail, as such features,

mechanisms and aspects will be within the understanding of the

skilled addressee.

[0057] Broadly, the present invention provides for an

electromechanical system 10 for operatively driving a load 18,

such as a pump. In particular, while incorporating operating

improvements similar as those described in Australian Patent

Application No. 2017213531 to the same Applicant, the system 10

introduces additional efficiency improvements as described

herein.

[0058] In a broad example, the system 10 comprises an internal

combustion engine 12 having a controllable mechanical output and

measurable instantaneous fuel consumption. System 10 also includes an electrical generator 14, such as an alternator, which is mechanically coupled to the engine's mechanical output and operatively generates electrical power. The generator 14 includes a controllable excitation system, such as a voltage regulator 22, whereby generator voltage output is controllable.

[0059] System 10 also includes an asynchronous motor 16 which

is operatively supplied with electrical power from the

electrical generator 14, and a pump 18 driven by the asynchronous

motor 16 for operatively displacing fluid and having at least

one user-selectable pump operating characteristic, i.e. a

process variable which is desired to be controlled.

[0060] Importantly, system 10 includes a controller 20 which

is programmed with a speed-torque relationship of both the engine

12 and asynchronous motor 16 and a performance curve of the pump

18, the controller configured to continuously monitor operating

characteristics of the engine 12, generator 14, motor 16 and

pump 18 whilst automatically and dynamically controlling the

engine's mechanical output and generator's excitation system 22

in order to dynamically and continuously correlate the speed

torque relationships and the pump performance curve with each

other to facilitate optimal energy transfer efficiency through

the system 10 while maintaining the user-selectable pump

operating characteristic for a steady-state of operation. In

addition, once such a steady-state of operation is established,

the controller 20 is configured to adjust the excitation system

22 to improve a power factor of the electrical power according

to the instantaneous engine fuel consumption.

[0061] The system 10 finds typical, yet non-limiting,

application in mining water management, particularly dewatering

applications, such as in an open pit or an underground mine.

Below surface water management is a critical operation, utilised

extensively in the mining industry to remove or lower aquifer

water levels in a controllable manner, by pumping the water out

using purposely build pumps generally driven by three-phase

induction motors directly coupled to a pump. Other related

application includes injecting an amount of water into the ground

into purposely drilled holes called wellbores. Another

application is where the pump is above-ground, such as in a

transfer station, to maintain a desired flow, pressure, temperature or level.

[0062] These pumps generally require three-phase electrical

power to drive them and in typical installation locations, mains

grid power is not available. It is known that electrical

generators provide electrical power at a frequency of 50Hz or

Hz, depending on the applicable local regulation. In a steady

state operation, at the supplied frequency, a pump will deliver

a relatively stable flow, pressure or temperature.

[0063] If any of the pump operating characteristics require

variation, then at least one of the process parameters, being

operating characteristics of the components driving the pump,

has to change in a controllable manner. Typically, the most

important parameter or characteristic of a pump that needs to be

changed is fluid flow rate, and this parameter can be changed in

multiple ways: by throttling a flow control valve, by controlling

the pump delivery rate via limiting or controlling the power and

frequency supplied thereto, etc.

[0064] Operating characteristics of the pump 18 generally

comprise a measurable fluid flow rate, fluid pressure and fluid

level, but may also include a pump speed, pump temperature, etc.

The motor 16 and pump 18 generally form part of a pumping package

36 as a wellbore or transfer station pumping installation. Such

an installation typically includes so-called headworks

influenced by pump operating characteristics of fluid flow rate,

pressure, temperature, etc. These operating characteristics are

generally measured or monitored by a controller 20 of the system

, typically via control feedback into a suitable interface

panel, such as a junction box 30, or the like. Variations hereon

are possible and expected and within the scope of the present

invention.

[0065] The controller 20 of the system 10 is programmed with

a speed-torque relationship of both the engine 12 as prime mover

and induction motor 16, as well as a performance curve of the

pump 18. The controller 20 is then configured to continuously

monitor the operating characteristics of the engine 12, the

electrical generator 14, the induction motor 16 and the pump 18,

and to automatically and dynamically control the engine output

and excitation system 22 in order to dynamically and continuously

match the speed-torque relationship of the engine 12 to that of

the induction motor 16 and the pump performance curve. In this

manner, optimal energy transfer efficiency through the system 10

can be facilitated whilst user-selectable pump operating

characteristics, such as fluid flow rate, fluid pressure and/or

fluid level are maintainable when displacing fluid via the pump

18.

[0066] In light hereof, by dynamically matching such speed

torque relationships and performance curves whilst maintaining

the user-selectable pump operating characteristics, allows for

efficient energy transfer through the system 10. As an energy

source for the system 10 typically comprises a fuel source for

the engine 12, such energy efficiency generally allows for

minimised fuel use, resulting in overall cost-saving.

[0067] The engine 12 typically comprises an internal

combustion engine, such as a diesel engine, but other types of

engines may also be used. For example, any reciprocating internal

combustion engine can be used fuelled by diesel, natural gas,

propane, LPG, ethanol, etc. Also, other types of prime movers

can be used, such as external combustion engines, diesel and gas

turbines, water propelled turbines, wind turbines, solar power,

etc. The skilled addressee will appreciate that such alternative

prime movers will typically require slightly different

controller configurations, as is known in the art.

[0068] Typically, the prime mover or engine 12 operating

characteristics continuously monitored by the controller are

selectable from a group consisting of oil pressure, oil

temperature, oil level, coolant level, coolant temperature,

inlet air pressure, inlet air temperature, fuel level, fuel

consumption, fuel, pressure, output rotational speed, output

torque, cylinder temperature, exhaust temperature, and

atmospheric pressure.

[0069] The controller 20 is configured to control the

mechanical output of the engine by varying any of the suitable

operating characteristics. In one example, the prime mover 12

comprises a diesel engine with a governor or engine control unit

(ECU) 28 which can interface with a large number of sensors

within the engine 12. In this manner, the controller 20 has the

ability to monitor and control the rotational speed, torque and

other operating characteristics or parameter set points of the

engine via a digital physical communication layer, such as CAN,

RS232 or RS484, as is known in the art.

[0070] In one example, communication between ECU 28 and the

controller 20 is typically via a CAN bus utilizing various

protocols, such as VP, MTU, J1939, J 1850, KWP2000, J1962, etc.

To control and monitor the engine 12, multiple parameters and

commands are generally received and sent from the controller 20

at a very high speed, minimizing substantially the wiring

requirements, system efficiency, and reliability, and maximizing

the uptime. CAN bus communication between controller 20 and

engine 12 impose a clear and distinctive advantage in controlling

the engine rotational speed, torque and fuel consumption, the

ultimate goal being overall system efficiency.

[0071] Applicant has identified some examples of known

engines with which the controller 20 can communicate via CAN or

Modbus protocol, as described above, including: Standard 1939,

VOLVO EDC3, VOLVO EDC4, VOLVO EMS2, SCANIA, IVECO, IVECO VECTOR,

JOHN DEERE HPCR, JOHN DEERE 4045, 6068, CATERPILLAR (series

3000), CATERPILLAR (other series), PERKINS 2300/2800, PERKINS

1100, MTU 304, MTU 303, MTU 302, MTU 201, MTU ADEC, DEUTZ EMR2,

CUMMINS, CUMMINS/2, CUMMINS/485.Such engine generally include a

suitable ECU 28.

[0072] The electrical generator 14 typically comprises a

synchronous three-phase AC alternator with a 2/3 pitch winding

configuration and is directly coupled to the prime mover

mechanical output. Other winding configurations can be

accommodated depending on the numbers of alternators pole. The

electrical generator operating characteristics continuously

monitored by the controller 20 are selectable from a group

consisting of voltage output, current output, excitation system

voltage, excitation system current, winding temperature,

magnetic field status, air intake and air discharge.

[0073] The controller 20 is generally configured to control

the excitation system of the generator 14 by varying any of the

suitable operating characteristics of the electrical generator,

such as excitation voltage. The controllable excitation system

typically comprises a voltage regulator 22 via which the

controller 20 is able to control generator voltage output. The

controller 20, via the voltage regulator 22, is typically

configured to control the generator output voltage by

controlling the excitation system through pulse-width

modulation, or the like. Such voltage regulators are also known

as automatic voltage regulators (AVR) and are known in the art.

The AVR may be a distinct component, or may be implemented within

the controller 20.

[0074] In a preferred embodiment, the system 10 generally

includes switchgear electrically coupling the generator 14 and

the induction motor 16. The switchgear also generally has a

circuit breaker monitored and controlled by the controller 20

for selectively decoupling the generator 14 and the induction

motor 16, as required, as a safety feature.

[0075] In one example, the system 10 uses a synchronous three

phase alternator without sliprings and revolving field brushes

as the generator 14, directly coupled to the engine 12. The

preferred windings for the alternator are 2/3 pitch optimized

for a required voltage and frequency, having insulation class H,

rated for a temperature rise of 125°K and an excitation system

permanent magnet generator (PMG) which impose a short-circuit

capacity of 3 times the nominal current for 10 seconds.

Additional temperature sensing elements are utilised to monitor

the winding temperature, air intake and discharge as performance

monitoring parameters, as temperature represent one of the

critical parameters of alternator functionality and performance.

[0076] The alternator voltage can be adjusted via the

excitation system closely controlled by the voltage regulator

(VR) or AVR with a closed control loop regulating an external

controller voltage set point from the controller 20. Depending

on requirements, the rated output voltage can be 400VAC, 480VAC,

690VAC, 2600VAC, 3300VAC, 4100VAC, 4800VAC, etc. For example,

the engine 12 and alternator can be coupled directly or via a

transfer gearbox to a variety of synchronous alternators, some

manufacturers including LeroySomer, AVK, TOYO, MeccAlte,

Stamford, WEG, LINZ, ABB, etc.

[0077] It is to be appreciated that the primary function of

the voltage regulator or AVR 22 is to maintain a constant voltage

at the alternator terminals by precisely controlling the

excitation utilising PWM as the most effective control system.

The voltage regulator 22 is generally able to monitor the

alternator exciter inductor field, exciter armature, EMC

varistor status, diode block and main field performance. An

important control parameter in the system 10 is the ability to

precisely control the excitation level which directly controls

the alternator voltage output which influences the induction

motor speed and torque characteristics which further influence

the controlled process value. Examples of voltage regulator

manufacturers include Basler DECS-150, DECS-200, DEIF DVC 310,

Leroy-Somer D510, etc.

[0078] The electrical switchgear between the generator 14 and

motor 16 are utilised to protect the load and power source

(alternator) by disconnecting them form each other, using a

circuit breaker, manually operated or automatic with a motor

mechanism, air or vacuum type, magnetic and/or thermal, or

electronic, with protection setting for rated voltage, rated current, tripping current level and overload and short-circuit current breaking characteristics, along with current imbalance, earth fault level, etc. The circuit breaker is externally monitored and controlled by the controller 20 to connect or disconnect the induction motor load in accordance with a desired operating condition.

[0079] The electrical induction motor 16 generally comprises

a squirrel-cage winding configuration. The electrical motor

operating characteristics continuously monitored by the

controller are selectable from a group consisting of nominal

voltage, nominal current, a frequency range, lock rotor current,

power factor and operating efficiency.

[0080] The pump can be selected from a group consisting of a

centrifugal pump, a reciprocating pump, a centrifugal fan, a

blower and a compressor, but other types of fluid movers may

also be used. Typically, the pump operating characteristics

continuously monitored by the controller are selectable from a

group consisting of fluid flow rate, fluid pressure, fluid level,

pump acceleration and deceleration time, pump frequency, pump

rotational speed ranges, and overall pump hydraulic performance.

The controller 20 generally takes into consideration the

acceleration and deceleration time, pump process values,

frequency or rotational speed ranges and the overall pump

hydraulic performance.

[0081] The controller 20 can comprise any suitable central

processing unit having electronic circuitry configured to

perform arithmetic, logical, control and/or input/output (I/0)

operations as specified by a set of instructions. Typically, the

controller comprises a programmable logic controller (PLC). The

controller 20 generally also comprises a local and or remote monitoring interface 26 for remotely monitoring and/or controlling the system 10.

[0082] In one example, the controller 20 is based on a SICES

generator controller DST4602 Evolution with colour screen human

machine interface (HMI) with programmable logic control logic

(PLC) included. There are also additional RTD, thermocouple,

voltage and current inputs via additional CAN bus modules. The

controller 20 has the native ability to be remote controlled for

extra flexibility via ModBus communication protocol over RS232,

rs485 and TCP/IP physical layer, where it can be integrated into

a SCADA, as is known in the art.

[0083] The voltage output of the generator 14 is generally

precisely controlled to deliver the desired electrical power and

protect the engine 12 from stall, in the event of load being

more than the maximum deliverable power from the alternator 14.

The controller 20 controls the engine parameters and its

performance by continually adjusting the rotational speed based

on the primary control parameter of the headworks 30 (level,

flow, pressure or frequency) and is achieved, depending on the

selected engine, by adjusting the throttle on mechanical engine

or by requesting a particular speed or torque, on electronic

engines, as a command over the CANbus to the ECU 28.

[0084] An important feature of the system 10, being a clear

and distinct difference between conventional variable speed or

soft start systems, are at start-up. When the system 10 is

required to start, the engine 12 generally starts with the load

18 connected and circuit breaker closed, without excitation

(starting); after the system 10 is started, it runs for a period

of time at a desired engine idle speed, typically between 750 to

900rpm, for a warmup (idle run); after the idle run time, the alternator excitation is engaged and output voltage is increased proportional to the rotational speed of the load, without exceeding the maximum power delivered by the engine in accordance with its power curve and without exceeding the synchronous alternator overcurrent level, as the current level.

[0085] The induction motor 16 coupled to the pump 18 achieves

minimum speed typically less than three seconds under full

operational load. This starting phase is operationally similar

to conventional soft starter systems, with the exception that

the delivered power in the system 10 is at variable speed and is

identical with an external variable speed drive or variable

frequency drive which delivers power to the load at variable

frequency and voltage, with the exception the power system is

not affected by the harmonics generated by Soft Starter or VSD,

resulting into a much smoother operation, reduces copper loses,

reduces cable temperature; as the power supplied to the induction

motor is a pure sine-ware without any distortions. The final

speed is then determined by the functional mode selected.

[0086] From a process perspective, the pump temperature is

monitored and if above a typical 600C, the system 10 will

initiate a warning and above 700C will initiate an alarm. The

difference between warning and alarm is that the system 10 will

signal a warning if a parameter is outside of normal operation

value but the system will continue to function; and an alarm is

a situation where the system 10 will signal an outside warning

limit value and will shut down the system. As designed, there

are two types of alarm use in system 10: one which will trip the

system e.g. low bore level, electrical faults, pump temperature

and critical mechanical faults; and process alarms which will

not trip the system 10 but will inhibit operation e.g. stop bore

level, low flow, high flow, pump low pressure, pump high pressure, discharge low pressure, discharge high pressure and remote inhibit.

[0087] The controller 20 generally monitors and displays the

following process instruments: pump temperature, Input: RTD

(PTC, NTC), slope indicator (level transmitter), Input: 4-20mA,

flow transmitter; Input: 4-20mA, pulse, PWM, pump discharge

pressure, Input: 4-20mA, PNP, NPN, discharge pressure, Input: 4

mA, PNP, NPN, instrument failure. It also controls user defined

operation parameters: level start (m) - System starts, Level

Stop (m) - System stops, Minimum bore level (m) - System trips

due dangerously low bore level, Pump temperature warning and

alarm(°C) - pump protection, Flow Levels, minimum and maximum

(Vs) - pump cooling and pipework protection, Pump pressure (kPa)

- pump protection and efficiency, pipework protection, Starting

interval - pump and generator protection.

[0088] The system 10 can also display the system efficiency:

fuel consumption, 1/hr, water pumped per litre of diesel

consumed, kL/L, water totalizer, m3 and able to monitor and

control optional equipment: pipework water temperature, Input:

RTD (PTC, NTC), external fuel tank monitoring and protections,

pump type automatic detection, additional 4-2OmA input and

outputs, alarm beacon, user selectable colour, radio

communication equipment, etc.

[0089] The system 10 generally includes a number of

selectable operational modes, such as: Generator - this mode of

operation includes all the details specified and functions as

generic power generator suppling desired frequency, 50 or 60Hz.

In this mode all the process conditions are ignored and if the

induction motor is connected to the system, prohibits the

generator starting and trips the circuit breaker.

[0090] Operational mode soft starter - this mode of operation

controls the pump power by applying the voltage gradually to the

desired frequency (from 30 to 60Hz), Start/Stop manually or

automatic by the level transmitter, monitors the pump

connection, monitors earth continuity, monitors alternator.

[0091] Operational mode level control - this mode of

operation controls the bore water level, controls the pump power

by varying the frequency (30 to 60Hz) to maintain a desired water

level, Start/Stop manually or automatic by the level

transmitter, monitors the pump connection, monitors earth

continuity, monitors alternator winding temperature, monitors

the pump temperature, monitors flow, monitors pump pressure

upstream and downstream.

[0092] Operational mode flow control - this mode of operation

controls the bore water flow, controls the pump power by varying

the frequency (30 to 60Hz) to maintain a desired water flow,

Start/Stop manually or automatic by the level transmitter,

monitors the pump connection, monitors earth continuity,

monitors alternator winding temperature, monitors the pump

temperature, monitors pump pressure upstream and downstream.

[0093] Operational mode pressure mode - this mode of

operation controls the pressure, controls the pump power by

varying the frequency (30 to 60Hz) to maintain a desired water

pressure, Start/Stop manually or automatic by the level

transmitter, monitors the pump connection, monitors earth

continuity, monitors alternator winding temperature, monitors

the pump temperature, monitors flow.

[0094] Importantly, as described above, once the system 10

reaches a steady state of operation according to the at least

one user-selectable pump operating characteristic with the

controller 20 individually monitoring and controlling the engine

12, alternator 14, motor 16 and load 18 in accordance with

preferred operating characteristics to achieve maximum energy

efficiency, the controller 20 is also configured to improve the

power factor by increasing or decreasing an excitation voltage

of the excitation system 22 to decrease or increase,

respectively, the power factor, as required, whilst the steady

state of operation is maintained.

[0095] As shown in Figure 2, power generation typically

starts with the circuit breaker closed, and the engine 12 runs

to idle for a few seconds, after which the engine 12 ramps-up to

a desired speed while the alternator 12 is excited to produce a

desired torque for the desired speed. Such an approach is

referred to as a scalar variant of motor control. The controller

monitors and controls the engine 12 and alternator 14

operating characteristics or parameters within the prescribed

limits as determined by the relevant speed-torque relationships

and performance curves, as well as user-selectable pump

operating characteristics.

[0096] As soon as a steady-state of operation has been

achieved, e.g. desired speed, pressure, flow, level, etc.

reached, the controller 20 evaluates the efficiency of the system

and optimises the power factor by manipulating the excitation

to the alternator 12, while monitoring the current to the motor

16, as a function directly controlled by the engine's

instantaneous fuel consumption.

[0097] For example, in one embodiment, the controller 20 is

configured to improve the power factor by measuring a first

instantaneous engine fuel consumption, incrementally adjusting

the excitation system to change the power factor, and taking a

second instantaneous engine fuel consumption. These first and

second instantaneous engine fuel consumption values are

continually compared with each other by the controller 20 and is

used to maximise fuel efficiency.

[0098] As described, the controller 20 is programmed or has

embedded the pump performance curve and speed-torque

relationships which can be used as reference for theoretical

operational performance of the system 10. While in operation, at

a particular steady-state of operation, if there is a difference

between such theoretical values (as determined by the pump

performance curve and speed-torque relationships) and monitored

values, the controller 20 can measure the instantaneous fuel

consumption at that point in time. Following that, the controller

controls the system output to minimise any difference between

the theoretical and measured value and performs another fuel

consumption reading. The controller 10 generally adjusts the

excitation voltage level in small increments and this cycle of

small adjustments with intermittent fuel consumption

measurements followed by further adjustment can be continuously

performed at a steady-state of operation to maximise fuel

efficiency.

[0099] In generally, increasing the excitation voltage will

determine extra current draw which adds an additional electrical

load on any connecting cables and increase induction motor slip

while the power factor decreases. Inversely, decreasing the

excitation voltage will have an opposite effect on current, motor

slip and less load on all components, while the power factor increases. Such an approach is referred to as a vector variant of motor control as it is an adaptive control method determined by the fuel consumption of the system. This method of vector control should not allow voltage changes greater than 10% (±5%) when compared with the above scalar control method.

[00100] As described, the controller 20 evaluates at the

steady-state the most efficient method to control the load based

on the load curve, alternator curve, engine curve and associated

desired operating characteristics or operational (desired)

limits, driving the system 10 to the most optimal and efficient

state. If a change in the load occurs, the controller 20 re

evaluates the control approach and reverts to scalar control to

achieve a new steady-state of operation which, once achieved,

the controller 20 again applies the vector control approach to

further tweak the power factor and further improve system

efficiency.

[00101] Such a combination of scalar and vector control is

generally able to dynamically compensate for any parasitic or

undesired capacitance and induction in the system, e.g.

connections or cables between components, such as between the

alternator 14 and the motor 16 by evaluating the power factor

and current load as close as possible to a desired power factor

able to improve system efficiency. Such evaluation of efficiency

is typically performed based on the instantaneous measured

engine fuel consumption as compared to a monitored pump operating

characteristic, such as flow, pressure, level, etc.

[00102] With reference to Figure 3, in use, the controller 20

typically receives as feedback the voltage, current and

alternator temperature and the desired operating characteristic

or process values (flow, pressure, level, pump temperature, etc.). The controller 20 then evaluates these feedback values and compares them with the programmed motor power curve and engine power curve to drive or control the load 18 in close proximity below the engine power curve, as shown.

[00103] In this dynamic scenario, the load 18 is typically

controlled by a fixed generator excitation level determined by

a position on the graph towards a steady-state of operation

dictated by the primary operating characteristic or process

control value. Subsequent evaluation by the controller 20 of the

power factor and associated induction motor slip is not possible

until the system 10 achieves a steady-state of operation, as the

position of the load on the graph shown in Figure 5 is generally

unstable and usually in position A or slightly to the left. By

manipulation of operation in this region, the excitation voltage

level, i.e. excitation of the alternator 14, can make the

torque/slip relationship unpredictable if it is driven outside

of the typical torque control, as per Figure 3.

[00104] As soon as a steady state of operation is achieved,

the power factor control correction function of the controller

, i.e. vector control, starts evaluating the position of the

load on Figure 5 and drives the load towards the stability region

of the system by correcting the excitation level to the

alternator towards a power factor zone close to the induction

motor's optimal value, as provided by a manufacturer's

specification or routine test report which has been programmed

into controller 20, as described. In this manner, the controller

is able to improve the steady state operation position process

value as determined by the instantaneous engine fuel consumption

while maintaining the same level of torque within the operating

characteristic limits imposed, i.e. point B in Figure 5 moves

towards point C.

[00105] Applicant believes it particularly advantageous that

the system 10 allows for such vector control manipulation of the

power factor, which has a direct result of reducing heat

dissipation in the system (induction motor, cables, switch gear,

alternator, engine, etc.). By improving the system's power

factor, thermal losses can be minimised, which translates into

improved fuel efficiency for powering the system 10 as required.

[00106] Optional embodiments of the present invention may also

be said to broadly consist in the parts, elements and features

referred to or indicated herein, individually or collectively,

in any or all combinations of two or more of the parts, elements

or features, and wherein specific integers are mentioned herein

which have known equivalents in the art to which the invention

relates, such known equivalents are deemed to be incorporated

herein as if individually set forth. In the example embodiments,

well-known processes, well-known device structures, and well

known technologies are not described in detail, as such will be

readily understood by the skilled addressee.

[00107] The use of the terms "a", "an", "said", "the", and/or

similar referents in the context of describing various

embodiments (especially in the context of the claimed subject

matter) are to be construed to cover both the singular and the

plural, unless otherwise indicated herein or clearly

contradicted by context. The terms "comprising," "having,"

"including," and "containing" are to be construed as open-ended

terms (i.e., meaning "including, but not limited to,") unless

otherwise noted. As used herein, the term "and/or" includes any

and all combinations of one or more of the associated listed

items. No language in the specification should be construed as indicating any non-claimed subject matter as essential to the practice of the claimed subject matter.

[00108] It is to be appreciated that reference to "one

example" or "an example" of the invention, or similar exemplary

language (e.g., "such as") herein, is not made in an exclusive

sense. Various substantially and specifically practical and

useful exemplary embodiments of the claimed subject matter are

described herein, textually and/or graphically, for carrying out

the claimed subject matter.

[00109] Accordingly, one example may exemplify certain aspects

of the invention, whilst other aspects are exemplified in a

different example. These examples are intended to assist the

skilled person in performing the invention and are not intended

to limit the overall scope of the invention in any way unless

the context clearly indicates otherwise. Variations (e.g. modifications and/or enhancements) of one or more embodiments

described herein might become apparent to those of ordinary skill

in the art upon reading this application. The inventor(s) expects

skilled artisans to employ such variations as appropriate, and

the inventor(s) intends for the claimed subject matter to be

practiced other than as specifically described herein.

Claims (17)

1. An electromechanical system for operatively driving

a pump, said system comprising:

an internal combustion engine having a controllable

mechanical output and a measurable instantaneous fuel

consumption;

an electrical generator mechanically coupled to said

mechanical output for operatively generating electrical power,

said generator having a controllable excitation system whereby

generator voltage output is controllable;

an asynchronous motor operatively supplied with such

electrical power from the electrical generator;

a pump driven by the asynchronous motor and having at

least one user-selectable pump operating characteristic; and

a controller programmed with a speed-torque relationship

of both the engine and asynchronous motor and a performance

curve of the pump, said controller configured to:

i) continuously monitor operating characteristics of

the engine, generator, motor and pump whilst

automatically and dynamically controlling the

engine's mechanical output and generator's

excitation system in order to dynamically and

continuously correlate the speed-torque

relationships and the pump performance curve to

facilitate optimal energy transfer efficiency

through the system while maintaining the user

selectable pump operating characteristic to

establish a steady-state of operation; and

ii) once such steady-state operation is established,

dynamically adjust the excitation system to improve

a power factor of the electrical power according to the instantaneous measured engine fuel consumption by: increasing or decreasing an excitation voltage of the excitation system to decrease or increase, respectively, the power factor, as required, whilst the desired steady-state of operation is maintained; measuring a first instantaneous engine fuel consumption and incrementally adjusting the excitation system to change the power factor; measuring a second instantaneous engine fuel consumption; and comparing such first and second instantaneous engine fuel consumption values and using such comparison to maximise fuel efficiency at the desired steady-state of operation.

2. The system of claim 1, wherein the controller is

configured, once the steady-state of operation changes via

changes to the at least one user-selectable pump operating

characteristic and/or changes to any relevant operating

characteristics of the engine, generator, motor and/or pump,

to return to step i) in order to re-establish a steady-state

of operation, after which step ii) is again performed.

3. The system of either of claims 1 or 2, wherein the engine

includes an engine control unit (ECU) via which themechanical

output is controllable and the engine operating

characteristics are monitorable.

4. The system of any of claims 1 to 3, wherein the engine

operating characteristics continuously monitored by the

controller are selectable from a non-exclusive group

consisting of oil pressure, oil temperature, oil level, coolant level, coolant temperature, inlet air pressure, inlet air temperature, fuel level, fuel pressure, output rotational speed, output torque, cylinder temperature, exhaust temperature, and atmospheric pressure.

5. The system of claim 4, wherein the controller is

configured to control the mechanical output of the engine by

varying any of the suitable operating characteristics, such as

fuel consumption and/or inlet air.

6. The system of any of claims 1 to 5, wherein the electrical

generator comprises a synchronous three-phase AC alternator.

7. The system of any of claims 1 to 6, wherein the electrical

generator operating characteristics continuously monitored by

the controller are selectable from a non-exclusive group

consisting of voltage output, current output, excitation

system voltage, excitation system current, winding

temperature, magnetic field status, air intake and air

discharge.

8. The system of claim 7, wherein the controller is

configured to control the excitation system of the generator

by varying any of the suitable operating characteristics of

the electrical generator, such as excitation system voltage.

9. The system of any of claims 1 to 8, wherein the

controllable excitation system comprises a voltage regulator

whereby the controller is able to control generator voltage

output.

10. The system of claim 9, wherein the controller, via the

voltage regulator, is configured to control the generator output voltage by controlling the excitation system through pulse-width modulation.

11. The system of any of claims 1 to 10, which includes

switchgear electrically coupling the generator and the

asynchronous motor, said switchgear having a circuit breaker

monitored and controlled by the controller for selectively

decoupling the generator and the motor, as required, as a

safety feature.

12. The system of any of claims 1 to 11, wherein the

asynchronous motor operating characteristics continuously

monitored by the controller are selectable from a non-exclusive

group consisting of nominal voltage, nominal current, a

frequency range, lock rotor current, power factor and operating

efficiency.

13. The system of any of claims 1 to 12, wherein the at least

one user-selectable pump operating characteristic is

selectable from a non-exclusive group consisting of a fluid

flow rate, a fluid pressure at an inlet and/or at an outlet,

a fluid level, a pump temperature and/or pump speed.

14. The system of any of claims 1 to 13, wherein the pump is

selected from a non-exclusive group consisting of a centrifugal

pump, a reciprocating pump, a centrifugal fan, a blower and a

compressor.

15. The system of any of claims 1 to 14, wherein the pump

operating characteristics continuously monitored by the

controller are selectable from a non-exclusive group

consisting of fluid flow rate, fluid pressure, fluid level,

pump acceleration and deceleration time, pump frequency, pump rotational speed ranges, and overall pump hydraulic performance.

16. A controller for an electromechanical system for

operatively driving a pump, the system having an internal

combustion engine having a controllable mechanical output and

measurable instantaneous fuel consumption, an electrical

generator mechanically coupled to said mechanical output and

operatively generating electrical power and having a

controllable excitation system whereby generator voltage

output is controllable, an asynchronous motor operatively

supplied with electrical power from the electrical generator,

and a pump driven by the asynchronous motor for operatively

displacing fluid and having at least one user-selectable pump

operating characteristic, wherein the controller is programmed

with a speed-torque relationship of both the engine and

asynchronous motor and a performance curve of the pump, wherein

the controller is configured to:

i) continuously monitor operating characteristics of

the engine, generator, motor and pump whilst

automatically and dynamically controlling the

engine's mechanical output and generator's

excitation system in order to dynamically and

continuously correlate the speed-torque

relationships and the pump performance curve to

facilitate optimal energy transfer efficiency

through the system while maintaining the user

selectable pump operating characteristic for a

steady-state of operation; and

ii) once such steady-state operation is established,

adjust the excitation system to improve a power

factor of the electrical power according to the

instantaneous engine fuel consumption by: increasing or decreasing an excitation voltage of the excitation system to decrease or increase, respectively, the power factor, as required, whilst the desired steady-state of operation is maintained; measuring a first instantaneous engine fuel consumption and incrementally adjusting the excitation system to change the power factor; measuring a second instantaneous engine fuel consumption; and comparing such first and second instantaneous engine fuel consumption values and using such a comparison to maximise fuel efficiency at the desired steady-state of operation.

17. The controller of claim 16, which is configured, once the

steady-state of operation changes via changes to the at least

one user-selectable pump operating characteristic and/or

changes to any relevant operating characteristics of the

engine, generator, motor and/or pump, to return to step i) in

order to re-establish a steady-state of operation, after which

step ii) is again performed.

12 14 16 18

Engine Generator Motor Pump

28 22

ECU AVR 1/5

Controller Feedback

20 26 30 Interface

Figure 1.