Title of Invention

POWER-ELECTRONIC CIRCUIT ARRANGEMENT FOR AN INDUCTION MACHINE

Abstract

A power-electronic circuit arrangement includes functional blocks (10, 20, 100) for a controllable, bi-directional exchange of energy between an induction machine with at least one strand (41, 42, 43) and an external energy storage device (30) with a positive (P) and a negative (N) pin. At least one functional block is designed as connection-compatible functional block (100) on the output side, which contains at least one internal energy storage (9), whereby this functional block shows at least one switching state, in which an output voltage (UX2) is more positive than the positive pin (P) of the external energy storage (30); and/or, in which an output voltage (UX2) is more negative than the negative pin (N) of the external energy storage (30).

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) The Patents Rules, 2003 COMPLETE SPECIFICATION [See Section 10, and rule 13) 1.TITLE OF INVENTION POWER-ELECTRONIC CIRCUIT ARRANGEMENT FOR AN INDUCTION MACHINE 2.APPLICANT(S) a) Name : RENK AKTIENGESELLSCHAFT b) Nationality : GERMAN Company c) Address : GOEGGINGER STRASSE 73, D-86159 AUGSBURG, GERMANY 3.PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - CERTIFICATION I, Samir Sachdeva, hereby certify that I am the translator of the accompanying certified official copy of the documents in respect of an application for a patent filed claiming Priority No. 10 2007 013 462.4 dated 21st March 2007 by RENK AKTIENGESELLSCHAFT and certify that the following is a true and correct translation to the best of my knowledge and belief. Dated this 15th day of March 2008. The present invention concerns a power-electronic circuit arrangement for an induction machine. Electrical drive systems with induction machines, especially with permanently-excited synchronous machines, have already reached a high level of development. Their high specific power densities enable high starting torque simultaneously with a low weight. The degrees of efficiency achieved by the entire drive system and the power densities depend, to a large extent, on the power-electronic supply. Different power-electronic circuit arrangements are already known from the in-house state of the art technology. For instance, Figure 1 shows an arrangement, in which the three strands 41-43 of a permanently-excited synchronous machine, connected to a direct-current source 30, can be controlled independent of one another with the help of power-electronic functional blocks 10. Figure 2 shows an arrangement with functional blocks 10, in which the individual strands 41-43 cannot be controlled independent of one another. Figure 3 shows here the structure of a functional block 10 from Figure 1 or Figure 2 in a two-point circuit as the so-called half-bridge circuit with two controllable electronic switches 1, 3 and two anti-parallel diodes 2, 4. Alternatively, multi-point circuits can also be used. As an example, Figure 4 shows the structure of a functional block 20 in a three-point circuit with four controllable electronic switches 1, 3, 5, 7, four anti-parallel diodes 2,4, 6,8 and two more diodes 22, 24. Such fundamental circuits enable a motor-driven operation of the synchronous machine, whereby the electrical energy from an external energy source, such as the direct-current source is converted in mechanical work, as well as also a generator-driven operation, whereby the mechanical work done on the synchronous machine is stored as electrical energy in the external energy storage device. For this, the external energy storage device, for instance can be discharged (motor-driven operation) or charged (generator-driven operation) as an accumulator battery. In this way, for instance, energy can be reclaimed in case of mechanical braking. In the same way, in hybrid systems, the time-variant difference between the power claimed by the drive system and the power provided by a fueling power machine can be compensated. A task of the present invention is to provide a power-electronic circuit arrangement for an induction machine, which enables an efficient working of the induction machine. For solving this task, a power-electronic circuit arrangement according to the generic term of claim 1 is studied further by means of its characteristic features. A power-electronic circuit arrangement according to a variant of the present invention includes one or more functional blocks for a controllable, bi-directional exchange of energy between an induction machine with at least one strand, preferably with several strands, and especially with three strands, and an external energy storage device, which has a negative and a positive pin. One or more functional blocks each can include a two-point circuit. In addition or alternative to this, one or more further functional blocks can contain multi-point circuits. At least one functional block is designed as connection-compatible functional block on the output side, which includes at least one internal energy-storage device. This connection-compatible functional block on the output side shows at least one additional switching state, in which an output voltage is more positive than the positive pin of the external energy storage. In addition or alternative to this, this connection-compatible functional block on the output side shows at least one additional switching state, in which an output voltage is more negative than the negative pin of the external energy storage. Through the internal energy storage device, which preferably has one or more unipolar storage condensers switched serially or in parallel, at least one additional switching state can be represented, in which an output voltage of the connection-compatible functional block on the output side is higher in amount than the respective pin of the energy storage device. The additional degree of freedom created through the additional switching state, in which an output voltage is more positive than the positive pin or more negative than the negative pin of the energy storage device is, clearly enables a more efficient working of the induction machine. In an especially preferred design, a connection-compatible functional block on the output side shows at least two additional switching states and, with that, at least four possible output voltage values as compared to the arrangement shown in Figure 3. Thereby, in one additional switching state an output voltage is more positive than the positive pin of the external energy storage device and in another additional switching state an output voltage is more negative than the negative pin of the energy storage device. In this way, the highly utilized permanently excited synchronous machines can be used especially efficiently. An induction machine optimized with regards to weight and/or space requirement shows only a low longitudinal inductance. This requires a high switching frequency (so-called "pulse frequency") of the power electronics or of the multi-point circuits, in order to restrict a waviness of the strand currents. In case of the arrangement described in Figure 4, the three-point circuit is often inadequate for this purpose, which increases the technical effort adversely. At the same time, a high power utilization of an induction machine - at least for a short time - requires high strand currents. As a result, despite the low longitudinal inductance, the entire voltage requirement in case of the basic frequency of the induction machine increases with reference to the active components of the voltage. This also adversely affects the degree of efficiency of the known arrangements and increases their technical effort also adversely, because accordingly a high direct current and/or a lower number of windings for the stator winding must be selected. The latter leads to undesirably high strand currents. These disadvantages can be reduced through a power-electronic circuit arrangement according to a design of the present invention. The additional degree of freedom enables a better adapted control and thus a more efficient working of such an induction machine. In the real use, sources of direct current are frequently equipped with filter condensers switched in parallel, in order to manage the high-frequency current components of power-electronics. The reduction in the degree of efficiency of known arrangements, caused by a high direct voltage and/or a reduced number of windings for the stator winding, which has been described above, represents to this extent an adverse performance factor, which, in case of known arrangements results in a higher effective current load and/or filter condensers with higher dimensions. Help can be provided in this case by means of the additional degree of freedom of a power-electronic circuit arrangement based on a design of the present invention. In the known circuit arrangements described above with reference to figures 1-4, a short-circuit of the source of the direct current 30 leads to an uncontrolled excess current in the windings of the strands 41-43. This generates high braking torques, which can put a load and damage the synchronous machine or the drive-system components coupled with it (e.g. gears, a fueling power machine, or a hybrid drive). Similar problems also occur when the voltage Ud of the direct-voltage source falls significantly below its rated voltage, for instance, owing to high loads by other consumers. It is known that these problems can be avoided by a mechanical uncoupling of induction machine. On the other hand, a power-electronic circuit arrangement based on a design of the present invention can be switched in case of faults, as explained later in detail with the help of design examples, in such a way that the problems mentioned above in case of a short-circuit can be avoided in the external energy storage device or a falling of the voltage of the external energy storage device below its rated voltage. Preferably, the external power storage device includes one or more rechargeable accumulator batteries. In addition or alternative to this, the external power storage device can have one or more fuel-cell batteries connected in series or in parallel. Similarly, the external power storage device can also include a mains supply of direct voltage. As explained in detail below with the help of different design examples, the basic structure of a known power-electronic circuit arrangement can be retained in a beneficial way, whereby, depending upon the requirement, one, more or all the functional blocks can be replaced by power-electronic, connection-compatible functional blocks, which include at least one internal power storage device and show at least one additional switching state, in which an output voltage is more positive than the positive pin of the external power storage device or more negative than the negative pin of the power storage device. Preferably, one, more or all power-electronic, connection-compatible functional blocks show at least one additional switching state, in which an output voltage is more positive than the positive pin of the external power storage device, and at least one more additional switching state, in which an output voltage is more negative than the negative pin of the power storage device. Although, according to the present invention, the connection-compatible functional blocks on the output side require a slightly higher technical effort than the known functional blocks, as shown with reference to Figure 3. On the other hand, however, such connection-compatible functional blocks on the output side open up more degree of freedom of the control or regulation and show an extended functionality, which permits a more efficient working of the induction machine. By suitably replacing one, several, or all the functional blocks of the known arrangement through connection-compatible functional blocks on the output side in accordance with the present invention, therefore, an optimum compromise can be selected between the increased technical effort caused by the replacement and the achieved improvement in the efficiency depending upon the desired extent of control. This also increases the design freedom in a beneficial way while designing the power-electronic circuit arrangement. A power-electronic circuit arrangement in accordance with a design of the present invention is used advantageously for a controllable, bi-directional exchange of energy between a permanently excited, high-utilized synchronous machine and a source of direct voltage (30). Preferably the voltage of the internal power storage device can be controlled or regulated variably depending on the speed and/ or the torque of the induction machine. For this, the power-electronic circuit arrangement can contain a suitable control device. For instance, the control device can control or regulate the voltage Uc of the internal power storage device to a reference value Uc Ref, which changes according to the speed and/or torque of the induction machine. Preferably, this reference value Uc Ref for a speed and/or torque equal to or close to zero can also essentially be equal to zero. In this case, for instance, the reference value can obey an equation of the form whereby In case of a shutdown or low speeds of the induction machine, this minimizes in a beneficial way the waviness of the current and can also make a pre-charging of the internal power storage device unnecessary. In a preferred dimensioning of the present invention, a permissible voltage of the internal power storage is selected in such a way that in case of a short-circuit and/or a low voltage of the external power storage device, no uncontrolled or excessive braking of the induction machine takes place. In this way, the loads on the induction machine described earlier and the drive elements coupled to it, such as gears, combustion engines, pumps and the like can be prevented through uncontrolled torques or persistent short-circuit currents, which appear in case of faults. In a connection-compatible functional block on the output side, in accordance with the present invention, an asymmetric blocking IGBT and/or a reverse-conducting component, especially a MOSFET and/or a Cool/MOS can be used as a controllable, electronic switch. Since this switch need not show any blocking capability in the reverse direction, the modern, loss-optimized structural elements, as the ones mentioned above, can be used advantageously. A few advantages are highlighted below once again. Firstly, a more efficient working of the induction machine is made possible. Secondly, the possible work area is extended to higher speeds with higher rotary torques. Thirdly, the operation at smaller and/or strongly fluctuating direct voltages (Ud) is improved. And fourthly, it is possible to avoid interfering braking torques in case of low voltage or short-circuit (Ud = 0) of the feed direct voltage (Ud). Further tasks, features and benefits of the present invention result from the subclaims and from the design examples described below. The figures, partly schematic, show the following: Fig.l A first, in-house known power-electronic circuit arrangement; Fig. 2 A second, in-house known power-electronic circuit arrangement; Fig. 3 a functional block of the power-electronic circuit arrangement as per Fig. 1 or Fig. 2; Fig. 4 a functional block of an in-house known modification of the power-electronic circuit arrangement as per Fig. 1 or Fig. 2; Fig. 5 a connection-compatible functional block on the output side of a power-electronic circuit arrangement according to a design of the present invention; Fig. 6 a simplified diagram for Fig. 5; Fig. 7 a power-electronic circuit arrangement according to a first design of the present invention; Fig. 8 a power-electronic circuit arrangement according to a second design of the present invention; Fig. 9 a power-electronic circuit arrangement according to a third design of the present invention; Fig. 10 a power-electronic circuit arrangement according to a fourth design of the present invention; Fig. 1 shows a first, in-house known power-electronic circuit arrangement for feeding a permanently excited synchronous machine from a source of direct voltage 30 in the form of an accumulator battery with a voltage Ud. The synchronous machine, not described in detail, includes three strands, 41, 42 and 43 respectively. Two functional blocks 10 are assigned to each strand, which are explained in more detail with reference to Fig. 3. This arrangement enables a mutually independent control of the individual strand currents. Similarly, the arrangement also allows a motor-driven as well as a generator-driven operation of the induction machine i.e. both the directions of energy flow. Fig. 2 shows a second, in-house known power-electronic circuit arrangement. With the first, in-house known power-electronic circuit arrangement in accordance with Fig. 1, elements having the same structure are identified with the same reference sign, so that below only the differences in the circuit as per Fig. 1 are discussed. In the second, in-house known power-electronic circuit arrangement, known as "three-phase pulse-controlled inverter" as per Fig. 2, only one functional block 10 is assigned to each strand 41, 42, or 43. In this way, the arrangement as per Fig. 2 no longer permits an independent control of the strand currents, but however, reduces the design effort. Fig. 3 shows a functional block 10 of the first or the second, in-house known power-electronic circuit arrangement as per Fig. 1 or 2, designed in the form of a two-point circuit. The functional block includes two controllable, electronic switches 1 and 3, and two anti-parallel diodes 2 and 4 in the interconnection shown in Fig. 3. "P" thereby identifies the positive pin of the external energy storage device 30 or a plus-connection that can be connected to it, "N" denotes the negative pin of the external energy storage 30 or a minus-connection that can be connected to it. "XI" denotes a power connection of the functional block 10, which can be connected to the connection of a strand 41,42 or 43 of the induction machine. Fig. 4 shows a modification 20 of the functional block 10 of the first or the second, in-house known power-electronic circuit arrangement as per Fig. 1 or 2. Again, elements having the same structure are identified with the same reference sign, so that below only the differences in the circuit as per Fig. 3 are discussed. The modification 20 of the function block 10, which can be used instead in the power-electronic circuit arrangement as per Fig. 1 or 2, includes four controllable electronic switches 1, 3, 5, 7, four anti-parallel diodes 2, 4, 6, 8 and two more diodes 22,24 in the interconnection shown in Fig. 4. Since these circuit arrangements and functional blocks are already known and serve only for explaining the disadvantages of the state-of-the-art technology, they will not be discussed any further. Figures 7 to 10 show power-electronic circuit arrangements partly corresponding to Fig. 1 or Fig. 2, in which, as per the invention the half (Fig. 7, 8) or all (Fig. 9,10) of the functional blocks 10 or 20 are replaced by a connection-compatible functional block 100 on the output side. As can be seen from here, the basic design of the circuit arrangement can be retained, in which case by replacing a selected number of known functional blocks 10 or 20 by connection-compatible functional blocks 100 on the output side, the functionality of the circuit arrangement can be increased in steps, and in this way, an optimum compromise between additional effort caused by further connection-compatible functional blocks 100 on the output side and the benefits achieved by this based on a higher degree of freedom can be depicted. Figures 8, 9 and 10 respectively show an induction machine with three strands 41,42 and 43. This number should be understood only as an example, a power-electronic circuit arrangement according to the present invention can equally be used for a controllable, bi-directional exchange of energy between an external energy storage device 30 and an induction machine with less or more strands. Similarly, the external energy storage device 30 is not restricted to an accumulator battery, but instead can include a fuel-cell battery and/or a direct-current supply in addition or as an alternative. In the design example, its voltage Ud lies in the range of 200 to 800 V. Fig. 5 shows a design of a connection-compatible functional block 100 on the output side, which is used in the circuit arrangements shown in figures 7, 8,9 or 10. Figure 6 shows the related simplified diagram. As can be seen from here, the connection-compatible functional block 100 on the output side includes, in the way it is used in the first (Fig. 7), second (Fig. 8), third (Fig. 9) and fourth (Fig. 10) design of the present invention, a plus-connection P, which can be connected to a positive pin of the external power storage device 30, a minus-pin N, which can be connected with a negative pin of the external energy storage device 30, and a load connection X2, which can be connected to a connection of a strand 41, 42 or 43 of the induction machine. Starting from the minus-pin N, the connection compatible functional block 100 on the output side includes four loops connected in series, each with a controllable, electronic switch 11,13,15 or 17 and a diode 12,14,16 or 18 respectively. Through its conducting direction, each diode defines the direction of orientation of the respective loop. A first loop (below in Fig. 5) with the controllable electronic switch 11 and diode 12, whose direction of orientation is mathematically positive, is connected with the minus connection N. A second loop with the controllable electronic switch 13 and diode 14, whose direction of orientation is mathematically negative, is connected with the first loop. A third loop with the controllable electronic switch 15 and diode 16, whose direction of orientation is also mathematically negative, is connected with the second loop. Finally, a fourth loop with the controllable electronic switch 17 and diode 18, whose direction of orientation is mathematically positive, is connected with the plus-connection P and the third loop. A node, in which the second and the third loops are connected with each other, is also connected with the load connection X2. Moreover, an internal energy storage 9 in the form of a uni-polar storage condenser is intended, whose connections are joined with a node, in which the first and the second, and the third and the fourth loops respectively are connected with each other. The interconnection results from the figures. Uxi denotes the output voltage of a known functional block 10 or 20 as per Figure 3 or 4, Ux2 denotes the output voltage of a connection-compatible functional block 100 as per Fig 5 or 6. These output voltages are defined respectively as reference potential against the connection N. The voltage of the internal energy storage 9 is denoted by Uc and is, as shown in Figure 5, defined positive from the node between the first and the second to the node between the third and the fourth loops. The controllable electronic switches 11, 13, 15 or 17 are designed as asymmetric blocking IGBT ("insulated-gate bipolar transistor"). The blocking voltage and the step speed of the diodes are adjusted to the values of the respective controllable electronic switches. The blocking voltage depends on the voltage Uc or Ud of the internal and the external energy storage 9 and 30 respectively and is higher than that of the diodes 2,4,6 and 8 respectively. Table 1 lists the switching states that can be represented by connection-compatible functional block 100 on the output side, which are preferably used in the normal operation. Thereby, "0" denotes the switch-off state and "1" the switch-on state of the respective controllable electronic switches 11, 13, 15 or 17. Furthermore, the output voltage Ux2 is specified for the respective switching state. Finally, Table 1 shows the resulting change dW/dt of the energy W stored in the connection-compatible functional block 100 on the output side for the case of the positive charging current i.e. iw > 0 (for negative charging current accordingly the reverse sign is applicable). Thereby, "+1" denotes an increase of this energy, "A." a decrease. "0" means that in the switching state there is no change in the energy W stored in the connection-compatible functional block 100 on the output side. TABLE 1 State Switch Output voltage Internal energy storage No. 11 13 15 17 UX2 Sign (dW/dt) 1 1 0 1 0 -Uc +1 2 1 1 0 0 0 0 3 0 1 0 1 + Uc +Ud -1 4 0 0 1 1 +ud 0 The in-house known functional block, explained earlier with reference to Fig. 3, can display only the two states "2" and "4" (whereby in table 1 the switch "11" or "13" are to be replaced by its switches "1" and "3" respectively). As can be seen from Table 1, an additional switching state "3" can be realized through the internal energy storage 9, in which the output voltage Ux2 is more positive than the positive pin of the external energy storage 30. Moreover, one more additional switching state "1" can be realized through the internal energy storage 9, in which the output voltage Ux2 is more negative than the negative pin of the external energy storage 30. This extends the number of possible output voltage values to four. This extended functionality can naturally also be achieved by another connection-compatible functional block on the output side, designed in accordance with Fig. 5. Therefore, the only essential thing for the present invention is that this functional block shows at least one additional switching state, in which its output voltage Ux2 is more positive than the positive pin of the external energy storage 30, and/or shows at least one additional switching state, in which its output voltage Ux2 is more negative than the negative pin of the external energy storage 30. This is true regardless of the polarity of the output current (strand current). For this, the connection-compatible functional block 100 on the output side includes at least one internal energy storage 9. For this reason, if a power-electronic circuit arrangement includes such a connection-compatible functional block on the output side, as per the invention, then this enables a more efficient working of the induction machine. Thus, for instance, in the first design according to Fig. 7, in which a usual, in-house known functional block 10 and a connection-compatible functional block 100 on the output side are assigned to a strand winding 41, different output voltages can be represented for each strand winding, as shown below in table 2: TABLE 2 State Switch Output voltage Internal energy storage No. 1 3 11 13 15 17 Ux1 - Ux2 Sign (dW/dt) 1 0 0 1 0 1 0 + Uc +Ud +1 2 0 1 1 1 0 0 +ud 0 3 1 1 0 1 0 1 -Uc -1 4 1 0 0 0 1 1 0 0 5 1 0 1 0 1 0 + Uc +1 6 1 1 1 1 0 0 0 0 7 0 1 0 1 0 1 - Uc -Ud -1 8 0 0 0 0 1 1 -ud 0 Table 2 thereby corresponds in structure and nomenclature to table 1, whereby (Ux1 -Ux2) denotes the output voltage of the strand 41. The number of possible output voltages clearly increases, whereby several switching states can be realized, in which the output voltage is more positive than the positive pin or more negative than the negative pin of the energy storage 30. This results in a higher degree of freedom while controlling the strand currents. The interconnection of a strand winding 41 with a usual, in-house known functional block 10 and a connection-compatible functional block 100 on the output side, shown in Figure 7, can also be implemented for the three strand windings 41, 42 and 43, as shown in Fig. 8. Thereby, the number of switching states possible for operating the induction machine increases accordingly. As mentioned earlier, by replacing a certain number of known functional blocks 10 with connection-compatible functional blocks 100 on the output side, the number of the degrees of freedom can be increased specifically, whereby an optimum compromise can be selected between the increased technical effort caused by the use of the connection-compatible functional blocks 100 on the output side and the benefits obtained by the additional degree of freedom. Thus, for instance, Fig. 10 shows a corresponding arrangement, in which all the functional blocks are designed as connection-compatible functional blocks 100 on the output side. To this extent, the arrangements as shown in Fig. 8 are preferred, in which half of the functional blocks are designed as connection-compatible functional blocks on the output side and the additional effort, therefore, is not very high. Even the arrangements as shown in Fig. 9 are to be preferred, in which although all the functional blocks are designed as connection-compatible functional blocks on the output side, but only a few of these functional blocks are used as such. The additional switching states enable a much more efficient working especially of the induction machines having a high use, especially also in case of weaker direct voltage sources, which show high voltage tolerances. In cases of faults (for instance, short-circuit of the external energy storage 30 or falling of its voltage clearly below the rated voltage), all the controllable electronic switches 11,13,15 and 17 of the connection-compatible functional blocks 100 on the output side are switched off uniformly in the first, second, third or the fourth design. In this way, uncontrolled over-currents in the strand windings 41-43 and the associated high braking torques of the induction machine can be avoided. This is true regardless of the voltage Ud of the external energy storage 30. As an advantage here, the internal energy storage 9 and the related semi-conductors 13, 14,15 or 16 are adequately dimensioned as voltage-proof, which can be fulfilled for normal voltage ranges of say 200 V to 800 V direct voltage without any significant disadvantages. The values for sign(dW/dt) are given in Tables 1 and 2 respectively. The signs are valid for the positive polarity of the strand current. The same output voltages also apply for the negative polarity, but with the reverse sign (dW/dt). The knowledge of these energy changes enables a regulation of the voltage Uc of the internal energy storage 9 to a specified reference value. In the design example, this reference value is proportional to the speed of the induction machine. As such, in case of a shutdown or at low speeds, the reference value is approximately equal to zero. This minimizes the waviness of the current in these operating states. In addition, a pre-charging of the condenser of the internal energy storage 9 becomes unnecessary. WE CLAIM: 1. Power-electronic circuit arrangement with functional blocks (10, 20, 100) for a controllable bi-directional exchange of energy between an induction machine with at least one strand (41,42,43) and an external energy storage (30) with a positive (P) and a negative (N) pin, characterized by the fact that at least one functional block is designed as connection-compatible functional block (100) on the output side, which contains at least one internal energy storage (9), whereby this functional block shows at least one additional switching state, in which an output voltage (Ux2) is more positive than the positive pin (P) of the external energy storage (30); and/or this functional block shows at least one additional switching state, in which an output voltage (Ux2) is more negative than the negative pin (N) of the external energy storage (30); 2. Power-electronic circuit arrangement as per claim 1, characterized by the fact that regardless of the polarity of an output current (strand current) the output voltage (Ux2) is more negative than the negative pin (N) of the external energy storage (30); 3. Power-electronic circuit arrangement as per claims lor 2, characterized by the fact that the external energy storage (30) includes a source of direct voltage or mains supply of direct voltage. 4. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that the external energy storage (30) includes a battery, especially a fuel-cell battery and/or an accumulator. 5. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that several, preferably at least half of all the functional blocks and especially preferably all functional blocks are designed as connection-compatible functional blocks (100) on the output side, which include at least one internal energy storage (9), whereby these function blocks show at least one additional switching state, in which an output voltage (Ux2) is more positive than the positive pin (P) of the external energy storage (30); and/or these functional blocks shows at least one additional switching state, in which an output voltage (Ux2) is more negative than the negative pin (N) of the external energy storage (30); 6. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that the induction machine is a permanently excited, preferably brushless synchronous machine. 7. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that the voltage (Uc) of the internal energy storage (3) can be controlled or regulated variably depending upon the speed and/or the rotary torque of the induction machine. 8. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that a permissible voltage of the internal energy storage (9) is selected in such a way that in case of a short-circuit and/or a low voltage of the external energy storage (30) no uncontrolled braking of the induction machine takes place. 9. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that a connection-compatible functional block (100) on the output side shows at least four possible values of the output voltage (Ux2). 10. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that the internal energy storage (9) of a connection-compatible functional block (100) on the output side contains a uni-polar storage condenser. 11. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that a connection-compatible functional block (100) as a controllable electronic switch (11, 13, 15, 17) contains an asymmetric blocking IGBT and/or a reverse-conducting structural element, especially a MOSFET and/or a CoolMOS. 12. Power-electronic circuit arrangement as per one of the claims above, characterized by the fact that a connection-compatible functional block (100) contains four loops connected in series or in parallel, with each loop having a controllable electronic switch (11; 13; 15; 17) and a diode (12; 14; 16; 18), which define a direction of orientation of the loop, whereby the directions of orientation of the first and the second loop, and of the third and the fourth loop are in the opposite direction to each other, whereby the internal energy storage is switched in parallel together with the second and/ or the third loop, and whereby the first loop can be connected with the negative pin (N) of the external energy storage (30), the fourth loop with the positive pin (P) of the external energy storage (30) and the second and/or the third loop can be connected with a strand (41; 42; 43) of the induction machine. 13. Induction machine with at least one strand (41,42,43), which is connected with an external energy storage (30) with a positive (P) and a negative (N) pin for a controllable, bi-directional energy exchange, characterized by the fact that it includes a power-electronic circuit arrangement as per one of the claims above. 14. Method for controlling a bi-directional exchange of energy between an induction machine as per claim 12 and an external energy storage (30) with a power-electronic circuit arrangement as per one of the claims 1 to 11, characterized by the fact that a voltage (Uc) of the internal energy storage (9) is regulated to a reference value (Uc Ref). 15. Method as per claim 14, characterized by the fact that the reference value (Uc Ref) is variable and changes according to the speed and/or the rotary torque, whereby the reference value is zero or approximately zero if the speed is zero or approximately zero. 16. Method as per claim 15, characterized by the fact that the reference value (Uc Ref) follows an equation of the form Uc Ref = å (ci x N1), where by N is the speed and/or the rotary torque of the induction machine and a (i=l...n) denotes constant real numbers. ABSTRACT A power-electronic circuit arrangement includes functional blocks (10, 20,100) for a controllable, bi-directional exchange of energy between an induction machine with at least one strand (41, 42, 43) and an external energy storage device (30) with a positive (P) and a negative (N) pin. At least one functional block is designed as connection-compatible functional block (100) on the output side, which contains at least one internal energy storage (9), whereby this functional block shows at least one switching state, in which an output voltage (UX2) is more positive than the positive pin (P) of the external energy storage (30); and/or, in which an output voltage (UX2) is more negative than the negative pin (N) of the external energy storage (30). To The Controller of Patents The Patent office Mumbai. (Fig- 5)

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549-MUM-2008-CORRESPONDENCE(IPO)-(23-5-2012).pdf

549-mum-2008-correspondence-received.pdf

549-mum-2008-description (complete).pdf

549-MUM-2008-DESCRIPTION(GRANTED)-(23-5-2012).pdf

549-MUM-2008-DRAWING(GRANTED)-(23-5-2012).pdf

549-mum-2008-drawings.pdf

549-mum-2008-form 1(15-5-2008).pdf

549-MUM-2008-FORM 2(GRANTED)-(23-5-2012).pdf

549-mum-2008-form 2(title page)-(complete)-(18-3-2008).pdf

549-MUM-2008-FORM 2(TITLE PAGE)-(GRANTED)-(23-5-2012).pdf

549-MUM-2008-FORM 26(23-4-2012).pdf

549-MUM-2008-FORM 3(10-1-2012).pdf

549-mum-2008-form-1.pdf

549-mum-2008-form-18.pdf

549-mum-2008-form-2.doc

549-mum-2008-form-2.pdf

549-mum-2008-form-26.pdf

549-mum-2008-form-3.pdf

549-mum-2008-form-5.pdf

549-MUM-2008-PETITION UNDER RULE 137(10-1-2012).pdf

549-MUM-2008-REPLY TO EXAMINATION REPORT(10-1-2012).pdf

549-MUM-2008-US DOCUMENT(10-1-2012).pdf