AU2015101570A4 - An arrangement for energising a load. - Google Patents

Abstract

Abstract: In an aspect of the invention an arrangement for energising a load is provided where said arrangement includes: a prime mover configured for variable rotational speed operation; a permanent magnet alternator operatively actuated by the prime mover, said alternator configured to generate an output voltage and frequency proportional to a speed of the prime mover; and an electric motor operatively energised by the alternator, said motor for driving the load, wherein the proportional relationship between the output voltage and frequency facilitates a constant transfer of the load to the prime mover irrespective of the rotational speed thereof. cml

Description

- 1 AN ARRANGEMENT FOR ENERGISING A LOAD. Background of the Invention 5 This invention relates to an arrangement for energising a load. Description of the Prior Art Reference in this specification to any prior publication (or information derived from it), or to 10 any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 15 There are numerous applications requiring an independent system of supplying power to a load which requires speed variation. A typical example is in the application of coal seam gas mining, where the load is a positive displacement pump inserted down a well bore. Such a pump is used to maintain groundwater at acceptable levels to allow gas to escape from a producing formation. At times, the pump speed needs to be reduced so that a bore in the 20 producing formation is not pumped dry. At other times, the pump needs to run at maximum speed to keep the groundwater at a level which allows the gas to escape from the producing formation. Figure 1 of the accompanying drawings shows an existing arrangement currently used in 25 mining applications for controlling groundwater levels. Due to the nature of such applications, it is an inherent requirement that the components form a free-standing and independent system, as external power is generally not available owing to the remoteness of such applications.

-2 Such an existing arrangement 6 generally includes an internal combustion engine 8, which is sometimes a gas-converted diesel or petrol engine due to the nature of the application and the availability of natural gas. The engine 8 is coupled to an alternator 10 and is configured to run 5 at a fixed speed by means of a governor so that the alternator 10 can supply a fixed output voltage at a fixed frequency. Such an arrangement is generally known as a stationary engine arrangement. The alternator 10 is coupled to a power electronic variable speed controller 14, which relies on power electronic principles to vary a speed of an electric motor 16, which in turn powers a pump 18. The variable speed controller 14 typically makes use of switching 10 arrangements to control the voltage and frequency levels supplied from the alternator 10 to the motor 16, to provide constant current and in turn constant torque at the pump. However, one problem associated with such an existing arrangement 6 is that the internal combustion engine 8 is typically required to be run under load. If the engine 8 is operated 15 continuously under no or limited load, its operating life can be dramatically reduced. When the pump speed is required to be reduced by the variable speed controller 14 reducing the speed of the electric motor 16, the load on the engine 8 is also reduced, as the engine 8 is running at a set speed. This set speed of the engine 8 is required so that a frequency of the output voltage of the alternator 10 is at a required level. In order to maintain a load on the engine 8, some form 20 of waste load 12 is often introduced, usually in the form of heater banks, or the like. As a result, the existing arrangement 6 is inefficient and generally requires high maintenance to ensure proper operation. Summary of the Present Invention 25 According to an aspect of the invention there is provided an arrangement for energising a load, said arrangement including: a prime mover configured for variable rotational speed operation; -3 a permanent magnet alternator operatively actuated by the prime mover, said alternator configured to generate an output voltage and frequency proportional to a speed of the prime mover; and an electric motor operatively energised by the alternator, said motor for driving the 5 load, wherein the proportional relationship between the output voltage and frequency facilitates a constant transfer of the load to the prime mover irrespective of the rotational speed thereof. Typically, the prime mover is selected from a group consisting of an internal combustion 10 engine, a windmill, a water turbine and a gas turbine engine. Typically, the prime mover is configured for variable rotational speed. Typically, the alternator is configured to generate an output voltage and a sinusoidal frequency 15 which are linearly proportional at variable rotational speed. Typically, the electric motor driving the load includes an induction motor or permanent magnet rotor motor. 20 Typically, the load includes a positive displacement pump or propeller. Typically, the arrangement is configured and adapted for use in regulating groundwater levels in a coal seam gas mining application. 25 Typically, the arrangement is configured and adapted for use in controlling a traction drive in a vehicular application. Typically, the arrangement is configured and adapted to replace sails to power a boat.

-4 Typically, the arrangement is configured and adapted for use in a wind or water powered fluid-pumping application. 5 According to a further aspect of the invention there is provided an arrangement for energising a positive displacement fluid pump for regulating groundwater levels in a coal seam gas mining application, said arrangement including: a prime mover configured for variable rotational speed operation; a permanent magnet alternator operatively actuated by the prime mover, said alternator 10 configured to generate an output voltage and frequency proportional to a speed of the prime mover; and an electric induction motor operatively energised by the alternator, said motor for driving the pump, wherein the proportional relationship between the output voltage and frequency facilitates a constant transfer of a load imposed by the pump to the prime mover 15 irrespective of the rotational speed thereof. Brief Description of the Drawings An example of the present invention will now be described with reference to the 20 accompanying drawings, in which: Figure 1 shows a prior art arrangement for energising a load in the form of a pump; and Figure 2 shows an example of an arrangement for energising a load according to the current arrangement. 25 Detailed Description of Preferred Examples -5 With reference now to Figure 2 of the accompanying drawings, there is shown an example of an arrangement 20 for energising a load 28. The arrangement 20 finds particular application in the field of regulating groundwater levels in coal seam gas mining and related applications. As such, the load 28 is typically a positive displacement fluid pump. However, the arrangement 5 20 can also be applied in other fields, as described in more detail below. In one example, the arrangement 20 includes a prime mover 22 configured for variable rotational speed operation. The prime mover 22 may include any suitable engine or machine for converting energy into useful mechanical motion, for example an internal combustion, 10 windmill, water turbine or gas turbine engine. In typical mining applications, the arrangement 20 requires an energy source for the prime mover. Such an energy source can include a diesel reservoir for a diesel engine, a supply of natural gas for a gas engine, or the like. In one example, the prime mover 22 is an internal combustion diesel engine which has been converted to run on gas. 15 The prime mover 22 is generally configured for variable rotational speed operation by including a throttle, which allows a rotational speed of the prime mover 22 to the adjusted according to requirements. This feature is an important improvement over the existing arrangement 6 shown in Figure 1, where the engine 8 is run at a constant speed irrespective of 20 load, requiring the use of waste load 12. In one example, the throttle of the prime mover 22 can be configured for remote control by means of a SCADA-type monitoring and control system according to the requirements of the load 28. For example, a number of the arrangements 20 can be used in a gas mining operation 25 and controlled by a single control system (not shown) monitoring gas output, with the speed of the respective pumps (each acting as a load 28) being controllable by such a system through varying the speed of each of the prime movers 22.

-6 The arrangement 20 also includes a permanent magnet alternator 24 which is operatively actuated by the prime mover 22. The alternator 24 is configured to generate an output voltage and frequency proportional to a rotational speed of the prime mover 22. In general, the alternator 24 is configured via suitable winding configurations to generate an output voltage 5 and a sinusoidal frequency which are linearly proportional to each other. As such, the alternator 24 is typically a permanent magnet rotor alternator able to generate an output voltage at a linearly proportional output frequency depending on a rotational speed at which the prime mover 22 actuates the alternator 24. 10 The arrangement 20 further includes an electric motor 26 which is operatively energised directly from the alternator 24. The motor 26 drives the load 28, which is a positive displacement pump in the current example. The electric motor 26 typically includes an induction motor or permanent magnet rotor motor, of which a rotational speed is determined by a number of pole pairs (i.e. the number of windings on the stator) and by the frequency of 15 the output supply of the alternator 24 being supplied to the motor 26. The amount of torque produced by said motor 26 remains constant as the change of both voltage and frequency is linear and proportional to the speed of the alternator 24. It is to be appreciated that the proportional relationship between the output voltage and 20 frequency of the permanent magnet alternator 24 allows the load 28 driven by the motor 26 to be constantly transferred to the prime mover 22 irrespective of the rotational speed of the prime mover 22. This allows the prime mover 22 to be run under constant load at a rotational speed determined by the requirements of the load 28, as the rotational speed of the prime mover 22 can be increased or decreased proportional to the requirements of the load 28. 25 In contrast, the arrangement shown in Figure 1 requires that the engine 8 is run at a constant speed with the variable speed controller 14 used to switch power to the load 18 with any excess power sent to the waste load 12. In the current example, the rotational speed of the -7 prime mover 22 is directly varied, with the proportional voltage and frequency output of the alternator 24 allowing the electric motor 26 to produce constant torque from very low speed to well above rated speed, only limited by the speed range of the prime mover 22. 5 Accordingly, the arrangement 20 finds particular application where the direct connection of an internal combustion engine to a pump is inconvenient, such as in coal seam gas mining operations. However, other examples include use in powering a drive in a vehicular application, or for powering boat or a bow or stern thruster in an aquatic application. In addition, the arrangement 20 also finds use in powering a centre pivot irrigator where mains 10 power is not available, or other applications where hydraulic motors and mechanical connections are currently used. For example, a further application of the arrangement 20 includes a wind or water powered pumping arrangement, wherein the prime mover 22 is in the form of a wind energy converter, 15 windmill or similar rotary device configured to extract energy from wind or water. In such an example, the windmill or water turbine is configured for variable rotational speed operation as dependent on a speed of wind or water to which the windmill or water turbine is exposed. The windmill or water turbine in turn actuates the permanent magnet alternator 24 which is configured to generate an output voltage and frequency proportional to a speed of the windmill 20 or water turbine. The alternator 24 then energises the electric motor 26 which drives the load 28, typically a pump. As described above, the proportional relationship between the output voltage and frequency of the alternator 24 facilitates a constant transfer of the load to the windmill or water turbine, irrespective of the rotational speed thereof. 25 It is to be appreciated that such a wind or water powered pumping arrangement allows water or other fluids to be pumped largely irrespective of a distance separating the windmill or water turbine and pump. For example, the windmill, as the prime mover 22, can be positioned on top of a hill for powering a pump located in a valley some distance away. The faster the wind -8 moves the windmill, the faster the pump will pump water out of a well, river, dam, reservoir, etc. The arrangement 20 provides numerous advantages and improvements when compared with 5 the existing arrangement shown in Figure 1. The use of the permanent magnet alternator 24 allows the electric motor 26 to produce constant torque from very low speed to well above rated speed, and the arrangement 20 keeps a constant load on the prime mover 22, as its rotational speed drops proportionately to the load speed. This constant load on the prime mover 22 also facilitates in extending an operational lifetime of the prime mover 22, not only 10 because the load on the prime mover 22 remains substantially constant, but also because the rotational speed thereof is controlled proportional to the load speed. The arrangement 20 is also more efficient because the variable speed controller 14 and waste load 12 are not necessary. This reduction of components has improvement on required 15 maintenance and cost of installation. Many modifications or variations will be apparent to those skilled in the art without departing from the scope of the present invention. All such variations and modifications should be considered to fall within the spirit and scope of the invention broadly appearing and described in more detail herein. 20 It is to be appreciated that reference to "one example" or "an example" of the invention is not made in an exclusive sense. 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 25 the overall scope of the invention in any way unless the context clearly indicates otherwise. Features that are common to the art are not explained in any detail as they are deemed to be easily understood by the skilled person. Similarly, throughout this specification, the term -9 "comprising" and its grammatical equivalents shall be taken to have an inclusive meaning, unless the context of use clearly indicates otherwise.

Claims (13)

1. An arrangement for energising a load, said arrangement including: a prime mover configured for variable rotational speed operation; 5 a permanent magnet alternator operatively actuated by the prime mover, said alternator configured to generate an output voltage and frequency proportional to a speed of the prime mover; and an electric motor operatively energised by the alternator, said motor for driving the load, wherein the proportional relationship between the output voltage and frequency 10 facilitates a constant transfer of the load to the prime mover irrespective of the rotational speed thereof.

2. The arrangement of claim 1, wherein the prime mover is selected from a group consisting of an internal combustion engine, a windmill, a water turbine and a gas turbine 15 engine.

3. The arrangement of either one of claims 1 or 2, wherein the prime mover is configured for variable rotational speed operation by means of a throttle. 20

4. The arrangement of any one of claims 1 to 3, wherein the alternator is configured to generate an output voltage and a sinusoidal frequency which are linearly proportional.

5. The arrangement of any one of claims 1 to 4, wherein the electric motor 25 includes an induction motor or permanent magnet rotor motor.

6. The arrangement of any one of claims 1 to 5, wherein the load includes a positive displacement pump. -2

7. The arrangement of any one of claims 1 to 6, which is configured and adapted for use in regulating groundwater levels in a coal seam gas mining application.

8. The arrangement of any one of claims 1 to 6, which is configured and adapted 5 for use in controlling a traction drive in a vehicular application.

9. The arrangement of any one of claims 1 to 6, which is configured and adapted for powering a boat, a bow or stern thruster in an aquatic application.

10 10. The arrangement of any one of claims 1 to 6, which is configured and adapted for use in a wind or water powered fluid-pumping application.

11. An arrangement for energising a positive displacement fluid pump for regulating groundwater levels in a coal seam gas mining application, said arrangement 15 including: a prime mover configured for variable rotational speed operation; a permanent magnet alternator operatively actuated by the prime mover, said alternator configured to generate an output voltage and frequency proportional to a speed of the prime mover; and 20 an electric motor operatively energised by the alternator, said motor for driving the pump, wherein the proportional relationship between the output voltage and frequency facilitates a constant transfer of a load imposed by the pump to the prime mover irrespective of the rotational speed thereof. 25

12. An arrangement for energising a load substantially as hereinbefore described.

13. An arrangement for energising a load substantially as hereinbefore described and illustrated with reference to the accompanying drawings.