WO2005006516A1

WO2005006516A1 - Emergency electric power supply unit

Info

Publication number: WO2005006516A1
Application number: PCT/EP2003/014671
Authority: WO
Inventors: Liviano Milianti; David Martini
Original assignee: Magnetek S.P.A.
Priority date: 2003-07-14
Filing date: 2003-12-19
Publication date: 2005-01-20
Also published as: AU2003290107A1

Abstract

The device comprises an electric motor/generator (3) which is connected to an electric power supply line (1) and which, when supplied by said line, ensures rotation of a shaft (7) on which a rotating member (9) is keyed. The rotating member is an impeller (9) associated with members (13, 15, 17) for supplying a fluid so as to cause rotation of the impeller. Moreover, the supplying members are controlled so as to supply the fluid to the impeller in the event of an interruption in the electric power supply from the line, the motor/generator (3) switching from operation as a motor to operation as a generator in order to supply electric power to the user.

Description

Emergency electric power supply unit Description Technical field The present invention relates to a unit or device for ensuring the continuity in the electric power supply of a user, for example a telephone exchange or other user which is normally connected to an electric power supply line and which requires a system able to guarantee the continuity of its electric power supply even in the event of a failure in the electric mains. Background art At present, in order to ensure the continuity of the electric power supply to users who must be guaranteed continuity in the power supply, continuity units which use batteries are employed. These units have a considerable degree of autonomy, equivalent to about 1-3 hours, so as to cover even long interruptions in the power supply from the normal electric mains. In some cases, especially where high power levels are involved, an internal-combustion engine, typically a diesel engine, is combined with the batteries, said engine, once started, maintaining rotation of an alternator. The batteries, in this case, have the function of covering the transient period of the diesel engine. Battery-equipped continuity units have considerable drawbacks associated mainly with the fact that the batteries are subject to rapid wear. They must be replaced with considerable frequency, typically about every two years. The replaced batteries must be disposed of, with consequent problems of an ecological nature. In another type of continuity or emergency unit electric motors are used, said motors, when the electric power supply network is functioning, maintaining rotation of a flywheel. The flywheel constitutes an accumulator of energy in the form of kinetic energy. In the case of interruption in the electric power supply from the mains, the flywheel maintains rotation of the motor which switches to the function of a generator. The drawback of this solution consists in the fact that the flywheel has a very limited degree of autonomy, in the region of a few seconds. These emergency units are therefore useful only for covering minimum interruptions in the normal electric power supply. Objects and summary of the invention The object of the present invention is to provide an emergency electric power supply unit which overcomes the drawbacks of conventional units. In particular, an object of the present invention is to provide a continuity unit which does not use accumulator batteries and which is able to achieve an autonomy in the power supply which is greater than that ensured by flywheel systems. Essentially, the invention envisages a device comprising an electric motor/generator which is connected to an electric power supply line and which, when supplied by the line, ensures rotation of a shaft on which a rotating member is keyed. Characteristically, according to the invention, the rotating member is an impeller associated with nozzles or members for supplying a fluid which causes rotation of the impeller. Moreover, the supplying members are controlled so as to supply the fluid to the impeller in the event of interruption in the electric power supply from the line. In the event of interruption in the power supply, moreover, the motor/generator switches from operation as a motor to operation as a generator in order to supply electric power to the user. The emergency unit thus configured supplies power at least for as long as the impeller is supplied with the fluid contained in the tank or tanks with which the device is equipped. It is sufficient, therefore, to envisage a quantity of fluid which is sufficient to achieve, for example, an autonomy in the region of one or more minutes, decidedly greater than that ensured by an ordinary flywheel. As occurs in flywheel systems, the impeller is kept constantly rotating by the motor/generator for as long as the electric mains is operational. In this way, when the fluid supply nozzles are opened, the impeller is already rotating. The fluid may be advantageously a gas contained in the pressurized liquid or gaseous state in one or more tanks. In the most simple and currently preferred case, the fluid is compressed air. Alternatively, a liquid contained in a tank or a basin at a height greater than the height of the impeller may be used. In order to avoid voltage drops in the supply to the user during the operating transient of the emergency device, due mainly to the activation time of the electrovalves which control the supply of fluid to the impeller, in a particularly advantageous embodiment of the invention the device comprises at least one energy accumulator which supplies power to the user during a transient phase for initial supplying of the fluid from the nozzles to the impeller. This energy accumulator may comprise a flywheel, optionally integral with the impeller or in any case keyed onto the actual impeller shaft, or a set of supercapacitors for accumulation of electric energy, or other accumulator (other than a battery), or also a combination of two or more accumulators, also of a different nature. This accumulator may have an autonomy which may also be very limited, typically in the region of 100-300 milliseconds, which represents the opening time of the electrovalves. In order to obtain autonomy levels higher than those which can be achieved by a suitable dimensional design of the tank for the fluid intended to supply the impeller, according to a particularly advantageous embodiment of the invention it is envisaged that the device is equipped with an autogenous unit which is actuated in the event of absence of voltage on the electric power supply line. The autogenous unit may comprise an internal- combustion engine, for example a diesel engine, or alternatively and preferably, a gas turbine engine. The latter may be readily activated and therefore has transients of lesser duration compared to a reciprocating engine, such as diesel engine for example. When the device is equipped with an engine, it is able to achieve very high autonomy levels. In the most complete configuration in which an accumulator (such as a flywheel or a set of supercapacitors) is envisaged in combination with the impeller and ah internal-combustion engine, the device intervenes with the following procedure in the event of a defect in the electric mains: - the accumulator (flywheel, supercapacitors or the like) covers the first milliseconds of the transient necessary for opening the electrovalves which supply the nozzles associated with the impeller; - the fluid supplies the impeller which ensures rotation of the motor/generator which, during the operating transient covered by the accumulator, switches from operation as a motor to operation as a generator; - during a relatively long transient, covered by the impeller, the internal-combustion engine is started and, when it reaches running speed, starts to supply mechanical power to the shaft of a generator. The generator actuated by the internal-combustion engine is preferably a generator different from the motor/generator actuated by the impeller, although in principle it is also possible to use the same motor/generator, envisaging, for example, a clutch or other coupling device which connects the output of the reduction gear of the internal-combustion engine to the shaft of the motor/generator. Further characteristic features of the device according to the invention are indicated in the accompanying dependent claims. Brief description of the drawings The invention will be better understood in the light of the description which follows and the accompanying drawings which illustrate a practical non-limiting embodiment of the invention. More particularly in the drawing, where identical numbers indicate identical or corresponding parts of the device: Figs. 1 to 4 show layout diagrams of the device according to the invention; Fig. 5 shows the temporal progression of the power supplied over time by the impeller, during the operating transient; Figs. 6 to 8 show different axonometric views, partly exploded and partly with portions removed, of the impeller associated with the respective diffuser and the fluid expansion chamber which supplies the said impeller; Fig. 9 shows an exploded axonometric view of a modified embodiment of the invention, limited to the mechanical parts; and Fig. 10 shows a schematic representation of the embodiment to which the mechanical unit shown in Fig. 9 refers. Detailed description of the preferred embodiments of the invention The diagram in Fig. 1 shows a simplified illustration of a first embodiment of the invention. 1 denotes the electric power supply line or mains. The mains is connected by means of a connection 2 to a user, not shown in Fig. 1 , for example a telephone exchange or other user which must be guaranteed a continuity in the power supply. The line 1 also supplies a reversible electric motor 3, i.e. an electric machine which is able to operate as a motor/generator. By means of a reduction gear 5, for example an epicyclic reduction gear, the motor/generator 3 causes rotation of a shaft 7 on which there is keyed an impeller 9, the form of which is described and illustrated in the following figures. The impeller 9 has, associated with it, a static diffuser 11 to which a fluid, for example pressurized air, contained in a tank 13, is supplied. Basically the assembly consisting of the impeller 9 and the diffuser 11 forms a gas turbine supplied with the pressurized fluid contained in the tank 13. The pressurized fluid is supplied - when required - to the static distributor 11 via a duct 15 on which an electrovalve 17 is arranged. In practice, several ducts 15 and several electrovalves 17 supplying the pressurized fluid to the static diffuser 11 may be envisaged. Several pressurized tanks 13 may also be envisaged. The motor/generator 3 is connected to the input of an inverter 21 , the output 21 U of which is connected to the user (not shown in this figure). The operating principle of the device described hitherto is as follows. In the event of voltage being present on the normal electric power supply line 1, the user is supplied directly by the said line. This line also supplies the reversible machine, i.e. the motor/generator 3, which therefore operates as a motor. The impeller 9 is kept rotating at a high speed, in the region of 100,000 rpm by the motor 3. If, owing to a temporary blackout or voltage drop, the line 1 is no longer able to supply the user, the motor/generator 3 switches from operation as a motor to operation as a generator, while the electrovalves 17 are opened in order to supply the pressurized fluid from the tank 13 to the diffuser 11 and from the latter to the impeller 9. In this way the impeller (which was already rotating at the moment of the malfunction on the line 1) is kept rotating by the pressurized fluid, overcoming the resistance of the motor/generator 3. The voltage generated by the motor/generator 3 is converted by the inverter 21 to the desired voltage value and supplies the user until the normal power supply is restored via the mains 1. The autonomy of the device is determined by the quantity of pressurized fluid in the tank or tanks 13. The connection between line 1 and user may be effected via the same inverter 21 or separately, by means of a so-called transfer switch (not shown in this figure) which, in the event of absence of the voltage on the mains network, switches from the mains power supply to the power supply via the generator 3. The reduction gear 5 could also be dispensed with. Fig. 2 shows a diagram, similar to the diagram in Fig. 1 , of an improved embodiment of the invention. Identical numbers indicate parts which are identical or correspond to those in the embodiment according to Fig. 1. Fig. 2 shows schematically also a generic user U. Compared to the diagram in Fig. 1 , in the diagram according to Fig. 2 a set of supercapacitors 25 is envisaged at the output of the inverter 21. The supercapacitors constitute an accumulator of energy in the form of electric charges, which performs the following function. In the event of a malfunction on the line 1 and consequent drop in the mains voltage, the electrovalves 17 are opened so as to start supplying of the impeller 7. Opening of the electrovalves 17 is not instantaneous. This may result in a short voltage drop on the power supply line of the user. The presence of the supercapacitors 25 overcomes this problem. The energy stored in them covers the drop on the line 1 until the moment when the solenoid valve or valves 17 are completely open. The time interval during which intervention of the supercapacitors is required is limited to about 100-300 milliseconds. Fig. 5 shows the progression of the power supplied by the impeller 9 over time. To denotes the moment of operation of the device, with the start of opening of the solenoid valve 17. Ti denotes the moment when the solenoid valve is completely open. During the time interval T₀-T-ι, the supercapacitors 25 intervene. This diagram shows the user U connected to the mains 1 by means of the same inverter 21 which connects it to the generator 3. Fig. 3 shows a diagram which is similar to that of Fig. 2, where identical numbers indicate identical or equivalent parts. The embodiment in Fig. 3 differs from the preceding embodiment owing to the presence of an autogenous unit generically indicated by 31. In the example shown the autogenous unit 31 is a unit with a gas turbine engine, comprising a turbine 33, a compressor 35 and a combustion chamber 37 supplied with a fuel from a tank 39. The shaft of the turbine is connected, by means of a reduction gear 41 , to a generator 43 connected to the power supply line of the user U. In this embodiment the operating principle is similar to that of the device shown in the diagram according to Fig. 2 until the operating condition of the impeller 9 is reached. At this point, since the autonomy of the impeller is limited by the quantity of pressurized fluid contained in the tank or tanks 13, when the interruption in the power supply from the mains 1 is relatively long, the autogenous unit 31 is started up. Start-up is performed during the period of autonomy of the impeller 9, which stops supplying power when the autogenous unit 31 has reached its operating condition or in any case a condition such as to be able to supply the quantity of power required to the user U. Connection of the user to the mains 1 may be performed as in Fig. 2 and is not shown. Fig. 4 shows a diagram which is similar to the diagram in Fig. 3, but in which the supercapacitors 25 are omitted. Their function of storing energy in order to cover the opening transient of the electrovalves 17 is performed in this embodiment by a flywheel^' 45 keyed onto the shaft of the impeller 9 and optionally integral therewith. The flywheel 45 constitutes a mechanical accumulator of kinetic energy which keeps the shaft of the motor/generator 3 rotating for the time required for complete opening of the electrovalves 17. This figure also does not show the connection of the user U to the mains 1. In both the diagrams according to Figs. 3 and 4, the reduction gear 5 could be omitted. Figs. 6 to 8 show an exploded view arid two axonometric views, with parts removed, of the impeller, the diffuser and the chamber for expansion of the pressurized fluid. In these figures the impeller is integral with a flywheel, as described with reference to the embodiment in Fig. 4. More particularly, the impeller 9 is formed by a disk 9A integral with a hub 9B which has splinings for engagement with an input shaft of the reduction gear 5. The disk 9A has a considerable mass and therefore forms a flywheel. It also has a blading 9C which defines a series of radial ducts for discharging the fluid. The channels are closed by a flange 9D. The diffuser 11 is arranged coaxially with the impeller 9 and has a stator blading 11B which defines channels for introducing the fluid towards the radial channels of the impeller 9. The stator 11 is fixed to an expansion chamber 12 inside which the pressurized fluid is introduced by means of an inlet 14. Essentially, the chamber 12, the diffuser 11 and the impeller 9 form an air turbine supplied with compressed air (or other suitable fluid, such as for example carbon dioxide). The mass of the disk 9A forms the flywheel 45 (Fig. 4). When the impeller is used in a system without a flywheel and provided, for example, with supercapacitors 25, the disk 9A may have smaller dimensions and a smaller mass. As commented above, the autonomy of the emergency system depends, until the autogenous unit 31 (where present) starts functioning, on the quantity of compressed gas in the tank 13. In the event of successive activation, this autonomy diminishes in each case owing to the consumption of compressed gas. However, when the mains 1 functions correctly, it also supplies the motor/generator 3 which operates as a motor, so as to cause rotation of the impeller 9 and, if applicable the flywheel 45 (where present). It is also conceivable to use the power supplied by the motor 3 during regular operation of the mains 1 in order to refill the tank 13. For this purpose, it is possible to use a configuration of the type shown in Figs. 9 and 10, where Fig. 9 shows the electrical/mechanical components and Fig. 10 shows a diagram of the complete system. Identical numbers indicate parts which are identical or correspond to those of the preceding embodiments. The motor/generator can be connected by means of an electric clutch 51 to a compressor 53 which, in Fig. 9, is shown as a radial volumetric compressor, but could also be of a different type. The compressor, when it is connected by means of the clutch 51 to the motor/generator 3, supplies compressed air drawn from the environment into the tank 13 so as to bring it to the maximum filling pressure. Following which the electric clutch 51 is opened and the motor 3 continues to rotate so as to keep the impeller 9 rotating. When there is an interruption in the voltage of the mains 1 , the system functions in the manner of the system described with reference to the preceding examples of embodiment. Switching of the power supply to the user U from the mains 1 to the emergency system occurs, in this example, by means of a transfer switch 53. It must be understood, however, that the connection of the user to the mains may also be different, for example of the type shown in Fig. 2. The system according to Figs. 9 and 10 therefore allows the tank 13 to be refilled whenever it is partly or completely emptied following activation of the emergency system on one or more occasions. Refilling of the tank is performed during a normal operating period of the mains 1 by means of the mechanical power supplied by the motor/generator 3. It is understood that the drawing shows only one practical embodiment of the invention which may vary in terms of the forms and arrangements without thereby departing from the idea underlying the invention. The presence of any reference numbers in the accompanying claims merely has the function of facilitating reading thereof in the light of the text which follows and the accompanying drawings and does not limit in any way the scope of protection thereof.

Claims

CLAIMS 1. Α device for ensuring the continuity in the electric power supply of a user, comprising an electric motor/generator (3) which is connected to an electric power supply line (1) and which, when supplied by said line, ensures rotation of a shaft (7) on which a rotating member (9) is keyed, characterized in that: - said rotating member is an impeller (9) associated with members (13, 15, 17) for supplying a fluid so as to cause rotation of said impeller; - and said supplying members are controlled so as to supply the fluid to said impeller in the event of an interruption in the electric power supply from said line, the motor/generator (3) switching from operation as a motor to operation as a generator, in order to supply electric power to said user.

2. A device according to Claim 1, characterized in that it comprises at least one pressurized tank (13) for said fluid and in that said fluid flows out in the gaseous state from said pressurized tank.

3. A device according to Claim 1 or 2, characterized in that it comprises at least one energy accumulator (25; 45) which supplies energy to said user (U) during a transient phase involving initial supplying of the fluid from the supplying members to the impeller (9).

4. A device according to Claim 3, characterized in that said energy accumulator comprises a flywheel (45) for accumulating kinetic energy.

5. A device according to Claim 4, characterized in that said flywheel (45) is keyed onto the same shaft on which the impeller (9) is keyed.

6. A device according to Claim 3 or 4 or 5, characterized in that said energy accumulator comprises one or more capacitors (25) for accumulating electric energy.

7. A device according to one or more of the preceding claims, characterized in that it comprises an inverter (21) connected at its input to said motor/generator (3) and at its output to said user (U).

8. A device according to one or more of the preceding claims, characterized in that it comprises an autogenous unit (31) which is actuated in the event of absence of voltage on the electric power supply line (1).

9. A device according to Claim 8, characterized in that said autogenous unit comprises a gas turbine engine (33).

10. A device according to one or more of the preceding claims, characterized in that the flow of said fluid from said tank is regulated by valves (17), opening of which is actuated in the event of absence of voltage on said power supply line (1).

11. A device according to at least Claims 6 to 8, characterized in that said capacitors are arranged in parallel with said autogenous unit.

12. A device according to one or more of the preceding claims, characterized in that it comprises an epicyclic reduction gear (5) arranged between said impeller (9) and said motor/generator (3).

13. A device according to one or more of the preceding claims, characterized in that said impeller (9) comprises a blading (9C) defining fluid expulsion channels supplied by a static diffuser (11).

14. A device according to Claim 13, characterized in that said expulsion channels have a radial progression.

15. A device according to Claim 13 or 14, characterized in that said diffuser (11) comprises a series of channels which convey the fluid from an expansion chamber (12) to the expulsion channels of the impeller (9).

16. A device according to one or more of Claims 13 to 15, characterized in that said impeller comprises a disk (9A) which forms a flywheel and with which the blading (9C) defining the fluid expulsion channels is integral.

17. A device according to one or more of the preceding claims, characterized in that it comprises a compressor (53) which can be actuated by said motor/generator (3) during periods of normal operation of the power supply from the electric line (1), so as to accumulate said fluid for supplying the impeller.