JP6093683B2 - AC motor drive device - Google Patents

Description

  The present invention relates to an AC motor driving device that drives an AC motor.

  In an AC motor drive device for a high voltage (for example, 3 kV or higher) motor, a multi-stage inverter in which single-phase cell inverters are connected in series is used to increase the capacity of the inverter and improve the output waveform.

  A twin drive inverter control system is known in which two high-voltage direct inverter devices that drive a high-voltage, large-capacity motor at a variable speed are used to directly drive the mechanical axes of two motors (for example, see Non-Patent Document 1). .

Hitachi review January 2008, p039-p040

  For example, when a machine having a relatively large capacity is driven, there is a case where one machine is driven by two high-voltage motors instead of a configuration in which the machine is driven by one high-voltage motor.

  In this case, two high-voltage motor drive devices for operating the high-voltage motor are required.

  FIG. 10 is a block diagram showing a configuration of a conventional AC motor driving device.

  The AC motor drive device 100 shown in FIG. 10 includes, for example, a plurality of unit inverters 11ar, 11as, and 11at connected in multiple stages to form one set (multistage connected inverter 11a), and such multistage connected inverters 11a, 11b, and 11c. Are provided with a three-phase inverter 110 that outputs three phases and three-phase inverter 120.

  The AC motor driving apparatus 100 also includes an input transformer 201 in which the primary winding 200 is connected to the three-phase AC power source 3 and the secondary winding groups 220a, b, and c are connected to the three-phase inverter 110, and the primary winding. The line 200 is connected to the three-phase AC power source 3, and the secondary winding groups 220 a, b and c are provided with the input transformer 202 connected to the three-phase inverter 120. The secondary winding group 220a and the like include secondary windings 220ar, 220as, and 220at. The primary winding 200, the secondary windings 220ar, 220as, and the like are respectively connected to the iron cores 230 of the input transformers 201 and 202. 220at etc. are wound.

  In the AC motor driving apparatus 100, the three-phase inverter 110 is connected to the AC motor 41, and the three-phase inverter 120 is connected to the AC motor 42. With the configuration as described above, the AC motor drive device 100 drives the machine 5 to be loaded by operating the AC motor 41 and the AC motor 42.

  In the case of driving one machine 5 as in the AC motor driving device 100 shown in FIG. 10, in the configuration in which the two AC motors 41 and the AC motor 42 are operated, two three-phase inverters 110 and 120, Two input transformers 201 and 202 connected to the two inverters were required.

  In the configuration as described above, since there are two input transformers for two three-phase inverters, the ratio of the installation area of the input transformer at the place where the AC motor driving device is installed is also large. In addition, the input transformer having two units was also affected by the harmonic current on the input side (primary side).

  The problem to be solved by the present invention is to provide an AC motor drive device that can save space for an input transformer and suppress harmonic current on the input side.

In order to solve the above problems, an AC motor driving device according to the present invention includes an input transformer connected to an AC power source and a plurality of three-phase inverters for operating one or a plurality of AC motors. . The three-phase inverter rectifies the three-phase AC output from the input transformer, converts it into DC power, and reversely converts it into a single-phase AC. The output side of the unit inverter is N stages (N is an integer of 2 or more). There are three-phase connection inverters for one phase connected to each other, the input transformer has a primary winding connected to the AC power source, and a secondary winding is one phase of the plurality of three-phase inverters N corresponding to the input of the multi-stage connection inverter is divided into 6 groups, and each group is connected to the multi-stage connection inverter for one phase, and the 1 of the secondary winding The secondary windings are wound by a common iron core so that the phase difference in voltage between the N secondary windings in the group is 360 ° / (6 × N), and the input transformer is The N secondary windings connected to the two three-phase inverters are grouped together. A total of 6 groups, a first group of 3 groups connected to the input of one of the three-phase inverters, and a first group of 3 connected to the input of the other one of the three-phase inverters Each of the secondary windings is divided into a second group that is three groups other than the group, and further, the secondary windings are divided into three groups of the secondary windings divided into the first group and the second group. the phase difference between the voltage between the three groups, characterized that you and 360 ° to each other / (6 × 2 × N) .

  According to the AC motor driving device of the present invention, the input transformer can be saved in space and the harmonic current on the input side can be suppressed.

The block diagram which shows the structure of 1st Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of the unit inverter of FIG. The block diagram which shows the structure of 2nd Embodiment of the AC motor drive device which concerns on this invention. The block diagram which shows the structure of 3rd Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of 4th Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of 5th Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of 6th Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of 7th Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of 8th Embodiment of the alternating current motor drive device which concerns on this invention. The block diagram which shows the structure of the alternating current motor drive device by a prior art example.

  Hereinafter, an AC motor drive device according to an embodiment of the present invention will be specifically described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted. Each of the following embodiments described here will be described by taking an example of an AC motor drive device that controls a three-phase AC motor.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a first embodiment of an AC motor driving device according to the present invention. FIG. 2 is a block diagram showing a configuration of the unit inverter shown in FIG.

  FIG. 1 shows a system for driving AC electric motors 41 and 42 having a machine (Load) 5 as a load. In the system shown in FIG. 1, a three-phase AC power source 3 that supplies alternating current at a predetermined frequency, an AC motor drive device 1 that converts alternating current supplied from the three-phase AC power source 3 into alternating current at a driving frequency, and a load are connected. AC motors 41 and 42 are provided.

  Furthermore, the AC motor drive device 1 includes an input transformer 2 and three-phase inverters 11 and 12 as shown in FIG. In the configuration of the AC motor driving device 1 shown in FIG. 1, one input transformer 2 is provided.

  The input transformer 2 includes a primary winding 20 whose primary side is connected to the three-phase AC power source 3, secondary winding groups 21a to 21c and 22a to 22c whose secondary side is connected to the three-phase inverters 11 and 12, It is composed of an iron core 23.

  Further, the secondary winding group 21a includes secondary windings 21ar, 21as, and 21at. Secondary winding group 21b includes secondary windings 21br, 21bs, and 21bt. The secondary winding group 21c includes secondary windings 21cr, 21cs, and 21ct.

  Similarly, the secondary winding group 22a includes secondary windings 22ar, 22as, and 22at. The secondary winding group 22b includes secondary windings 22br, 22bs, and 22bt. The secondary winding group 22c includes secondary windings 22cr, 22cs, and 22ct.

  As described above, the secondary windings of the input transformer 2 are composed of six groups of secondary winding groups 21a to 21c and secondary winding groups 22a to 22c. Details of the configuration of the six groups of secondary windings will be described later.

  A primary winding 20 and secondary windings constituting the secondary winding groups 21a and 22a are wound around the iron core 23. The iron core 23 is a common iron core for the secondary winding groups 21a and 22a. For example, the primary winding 20 is wound around the iron core 23 by Y connection, and the secondary windings in the secondary winding groups 21a and 22a are wound by Δ connection or the like.

  The secondary windings 21ar, 21as, and 21at of the secondary winding group 21a are, for example, three unit inverters 11ar (N units, N is a positive integer, FIG. 1 shows an example of N = 3) connected in multiple stages in series. , 11as and 11at are three sets (N sets) corresponding to the inputs. As for the secondary windings of the other secondary winding groups 21b and 21c and the secondary winding groups 22a to 22c, as shown in FIG. 1, three sets corresponding to the inputs of the corresponding unit inverters ( N sets).

  As described above, the input transformer 2 includes a single transformer.

  The three-phase inverters 11 and 12 convert alternating current input / output via the input transformer 2 into alternating current with a driving frequency.

  The AC motor 41 is operated by the three-phase inverter 11. The AC motor 42 is operated by the three-phase inverter 12. That is, the AC motor driving apparatus 1 operates the two AC motors 41 and 42 using the two three-phase inverters 11 and 12.

  The machine 5 is a load (Load shown in FIG. 1) driven by two AC motors 41 and 42.

  The power transmission mechanism by the AC motors 41 and 42 is configured to be connected to, for example, a coupling shaft with the machine 5. Thereby, the AC motors 41 and 42 operated by the AC motor driving device 1 drive the machine 5.

  Next, the three-phase inverters 11 and 12 will be described with reference to FIGS. 1 and 2.

  Three-phase inverters 11 and 12 are installed between input transformer 2 and AC motors 41 and 42.

  The three-phase inverter 11 is, for example, connected in series with the outputs of three unit inverters 11ar, 11as, and 11at in series (when N = 3), and this is used as a multi-stage inverter 11a for one phase. Three sets (multi-stage inverters 11a, 11b and 11c) of this one phase are provided.

  Further, for example, the three-phase inverter 12 connects the outputs of the unit inverters 12ar, 12as, and 12at in multiple stages in series to form a multi-phase connected inverter 12a for one phase. Connection inverters 12a, 12b and 12c) are provided.

  Each of the unit inverters 11ar, 11as, and 11at converts a three-phase alternating current into a direct current, and reverse-converts the direct current to output a single-phase alternating current. The same applies to the other unit inverters 11br, 11bs and 11bt, 11cr, 11cs and 11ct, and 12ar to 12ct.

  Regarding the connection between the three-phase inverter 11 and the AC motor 41, the output of the multistage connection inverter 11a is connected to the U phase of the AC motor 41, the output of the multistage connection inverter 11b is connected to the V phase, and the output of the multistage connection inverter 11c is Connected to W phase.

  As for the connection between the three-phase inverter 12 and the AC motor 42, the output of the multistage connection inverter 12a is connected to the U phase of the AC motor 42, the output of the multistage connection inverter 12b is connected to the V phase, and the multistage connection inverter 12c The output is connected to the W phase.

  Three-phase inverters 11 and 12 convert alternating current with a predetermined frequency into alternating current with an arbitrary drive frequency (inverter frequency).

  FIG. 2 shows the configuration of the unit inverter 11ar as a representative of the unit inverters 11ar, 11as, 11at, and the like.

  As shown in FIG. 2, the unit inverter 11ar includes, for example, a diode 16a as a rectifier unit that converts alternating current into direct current, a capacitor 16b that smoothes the rectified direct current, and an inverter that reversely converts the smoothed direct current into alternating current. The part includes a self-extinguishing power element (for example, IGBT) 16c to which a diode 16d is connected in antiparallel.

  As the connection of the secondary winding, three units constituting one phase of the three-phase inverter, for example, unit inverters 11ar, 11as and 11at are composed of three sets of secondary winding group 21a, secondary windings 21ar, 21as and 21at. Connected to.

Furthermore, unit inverters 11br, 11bs and 11bt are connected to three sets of secondary winding group 21b and secondary windings 21br, 21bs and 21bt. Unit inverters 11cr, 11cs, and 11ct are connected to three sets of secondary winding group 21c and secondary windings 21cr, 21cs, and 21ct.
Similarly, as the secondary winding connection, the unit inverter shown in FIG. 1 is connected to three sets of secondary windings for each of the secondary winding groups 22a to 22c.

  For example, the three sets of secondary windings in the secondary winding group 21a have a phase difference of, for example, an output voltage of 20 ° (360 ° / (6 × N), in this example, N = 3). It is wound to hold. When the phase of the output voltage at the secondary winding 21as is 0 ° as a reference, the phase difference between the reference 0 ° and the output voltage at the secondary winding 21ar is + 20 °, and the reference 0 ° and the output at the secondary winding 21at are output. The voltage phase difference is set to -20 °.

  These phase relationships are the same for the secondary winding groups 21b and 21c and the secondary winding groups 22a to 22c.

When one phase of the three-phase inverters 11 and 12 is composed of, for example, three unit inverters 11ar, 11as, and 11at, a rectification method called 18-pulse rectification is used. Theoretically, the input transformer 2 The harmonics of the input current are
Other than the (18 m ± 1) order harmonics are eliminated, and the influence of harmonics on the power supply side can be suppressed. Note that m is a positive integer.

  By adopting the configuration of the secondary winding as described above, harmonics of the input current of the input transformer 2 can be suppressed.

In the above description, the unit inverter for one phase of the three-phase inverter has been described as three units. However, in the case of the N unit configuration, 6N pulse rectification is performed, and the harmonic current is theoretically
((6N × m) ± 1) Other than the next harmonic will be deleted.

  As described above, according to the first embodiment, the input transformer is also composed of one unit for two three-phase inverters, and the apparatus is more than the configuration using two input transformers. Cost can be reduced. Moreover, the ratio of the installation area of the input transformer in the installation place of an AC motor drive device can also be made small. Furthermore, the harmonic current on the input side of the input transformer can be reduced by the configuration in which the output voltages of the secondary windings of the input transformer have a predetermined phase difference.

[Second Embodiment]
FIG. 3 is a block diagram showing the configuration of the second embodiment of the AC motor driving device according to the present invention.

  In the AC motor drive device 1x shown in FIG. 3, the secondary winding of the input transformer 2 having the configuration of the AC motor drive device 1 shown in FIG. 1 is divided into secondary winding groups 21a, 21b and 21c, and the secondary winding. The configuration is replaced with a group 22xa, 22xb, and 22xc.

  Hereinafter, the configuration of the six groups of secondary windings illustrated in FIG. 3 will be described.

  In the input transformer 2x, a total of 6 groups including N secondary windings connected to the two three-phase inverters 11 and 12 as one group, and three groups connected to the input of the three-phase inverter 11; Are divided into a first group and a second group which is three groups other than the three groups of the first group connected to the input of the three-phase inverter 12.

  The first group includes secondary winding groups 21a, 21b and 21c. The second group includes secondary winding groups 22xa, 22xb, and 22xc.

  For example, three sets of secondary windings 21ar, 21as, and 21at in the secondary winding group 21a have positive output numbers of 20 ° (360 ° / (6 × N), for example, N = 3 in this example. ) So as to have a phase difference of. When the phase of the output voltage at the secondary winding 21as is 0 ° as a reference, the phase difference between the reference 0 ° and the output voltage at the secondary winding 21ar is + 20 °, and the reference 0 ° and the output at the secondary winding 21at are output. The voltage phase difference is set to -20 °. These phase relationships are the same for the secondary winding groups 21b and 21c.

  Three sets of secondary windings 22xar, 22xas, and 22xat in the secondary winding group 22xa have, for example, output voltages of 20 ° (360 ° / (6 × N), in this example, a positive number of N = 3). It is wound so as to have a phase difference.

  Further, the second embodiment differs from the first embodiment in the output voltage of the secondary winding of the secondary winding group 21a and the output voltage of the corresponding secondary winding of the secondary winding group 22xa. For example, the phase difference is 10 ° (360 ° / (6 × 2 × N), where N is a positive integer).

  Specifically, in the example shown in FIG. 3, the phase of the output voltage at the secondary winding 21as is set to 0 °, and the phase difference between the reference 0 ° and the output voltage at the secondary winding 22xar is + 10 °. The phase difference between the reference 0 ° and the output voltage at the secondary winding 22xas is −10 °, and the phase difference between the reference 0 ° and the output voltage at the secondary winding 22xat is −30 °.

  The phase relationship between the secondary winding group 21b and the secondary winding group 22xb and the phase relationship between the secondary winding group 21c and the secondary winding group 22xc are the same.

In the case of the input transformer 2x described above, the rectification method is called 36-pulse rectification, and theoretically, the harmonic of the input current of the input transformer 2x is
Other than the (36 m ± 1) order harmonics are eliminated, and the influence of harmonics on the power supply side can be further suppressed. Note that m is a positive integer.

In the description here, three unit inverters for one phase of the three-phase inverter are now described. However, when N (positive integer) units are used, 12N pulse rectification is performed, and the harmonic current is Theoretically,
((12N × m) ± 1) Other than the next harmonic will be deleted.

  According to the second embodiment, as in the first embodiment, the input transformer is also configured for one three-phase inverter, and the configuration using two input transformers is more than that. It becomes economical in price, and the installation area can be reduced.

[Third Embodiment]
FIG. 4 is a block diagram showing a configuration of the third embodiment of the AC motor driving device according to the present invention.

  In the configuration of the AC motor driving device 1 shown in FIG. 1, one machine 5 is driven by using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12. The AC motor drive device 1 drives separate machines 6 and 7 using an AC motor 41 and a three-phase inverter 11, and an AC motor 42 and a three-phase inverter 12.

  According to the third embodiment, the same effects as those of the first embodiment can be obtained as long as the two machines have the same amount of load. Even when the load amounts of the two units are different, the input side of each three-phase inverter has an 18-pulse configuration, and the effect of the 18-pulse configuration can be obtained with respect to the input harmonic current of the input transformer. Can do.

[Fourth Embodiment]
FIG. 5 is a block diagram showing the configuration of the fourth embodiment of the AC motor driving device according to the present invention.

  In the AC motor drive device 1x shown in FIG. 3, one machine 5 is driven using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12, but the AC motor shown in FIG. The drive device 1x drives separate machines 6 and 7 using the AC motor 41 and the three-phase inverter 11, and the AC motor 42 and the three-phase inverter 12.

  According to the fourth embodiment, the same effect as in the second embodiment can be obtained as long as the two machines have the same amount of load.

  Even when the load amounts of the two units are different, the input side of each three-phase inverter has an 18-pulse configuration, and the effect of the 18-pulse configuration can be obtained with respect to the input harmonic current of the input transformer. Can do.

[Fifth Embodiment]
FIG. 6 is a block diagram showing a configuration of the fifth embodiment of the AC motor driving device according to the present invention.

  In the AC motor driving apparatus 1 shown in FIG. 1, one machine 5 is driven by using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12, but the AC motor shown in FIG. The drive device 1 b drives the machine 5 using one AC motor 43 and two three-phase inverters 11 and 12.

  The AC motor 43 shown in FIG. 6 is an AC motor having a larger output than the AC motor 41 shown in FIG. In order to be able to drive a high-capacity output AC motor, the AC motor drive device 1b includes the outputs U-phase, V-phase and W of the three-phase inverters 11 and 12 in addition to the configuration of the AC motor drive device 1 shown in FIG. Each phase is provided with a reactor, and is connected to the AC motor 43 from the midpoint (the midpoint of the reactors 8a, 8b and 8c shown in FIG. 6) where the reactors are connected to each other.

  With the configuration as described above, the AC motor drive device 1b can supply power to one AC motor 43 by the two three-phase inverters 11 and 12 via the reactors 8a, 8b and 8c. Can handle large output.

  According to the fifth embodiment, in addition to the same effects as those of the first embodiment, it is possible to drive a high-capacity output AC motor.

[Sixth Embodiment]
FIG. 7 is a block diagram showing the configuration of the sixth embodiment of the AC motor driving device according to the present invention.

  In the AC motor driving device 1x shown in FIG. 3, one machine 5 is driven by using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12, but the AC motor shown in FIG. The drive device 1xb drives the machine 5 using one AC motor 43 and two three-phase inverters 11 and 12.

  The AC motor 43 shown in FIG. 7 is an AC motor having a larger output than the AC motor 41 shown in FIG. 3, for example. In order to be able to drive a high-capacity output AC motor, the AC motor drive device 1xb includes the outputs U-phase, V-phase and W of the three-phase inverters 11 and 12 in addition to the configuration of the AC motor drive device 1x shown in FIG. Each phase is provided with a reactor, and is connected to the AC motor 43 from the middle point (the middle point of the reactors 8a, 8b and 8c shown in FIG. 7) where the reactors are connected to each other.

  That is, in the sixth embodiment, in the input transformer 2x shown in FIG. 7, the voltage phase difference on the secondary winding side of the input transformer 2 shown in FIG. 6 is changed.

  With the configuration as described above, the AC motor drive device 1xb can supply power to one AC motor 43 by the two three-phase inverters 11 and 12 via the reactors 8a, 8b, and 8c. Can handle large output.

  According to the sixth embodiment, in addition to the same effects as those of the second embodiment, it is possible to drive a high-capacity output AC motor.

[Seventh Embodiment]
FIG. 8 is a block diagram showing a configuration of the seventh embodiment of the AC motor driving device according to the present invention.

  In the AC motor driving apparatus 1 shown in FIG. 1, one machine 5 is driven by using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12, but the AC motor shown in FIG. The drive device 1c drives the machine 5 using one AC motor 44 and two three-phase inverters 11 and 12.

  The AC motor 44 shown in FIG. 8 has a larger output than the AC motor 41 shown in FIG. 1, for example, and is a multi-winding AC motor. The AC motor 44 is, for example, a two-winding AC motor in which the stator winding includes two sets of three-phase windings.

  In the AC motor drive device 1c shown in FIG. 8, in order to drive a two-winding AC motor (AC motor 44), the outputs of the two three-phase inverters 11 and 12 are respectively connected to the respective winding systems (2 Winding configuration). The three-phase outputs of the two three-phase inverters 11 and 12 are separately connected to one system and the other system of the two-winding configuration of the AC motor 44. That is, the three-phase inverter 11 is connected to one set of three-phase windings (one system) of the AC motor 44, and the three-phase inverter 12 is connected to the other set of three-phase windings (other system). .

  With the configuration as described above, the AC motor driving device 1c can drive the multi-winding AC motor.

  According to the seventh embodiment, in addition to the same effects as those of the first embodiment, a large-capacity output multi-winding AC motor can be driven.

[Eighth Embodiment]
FIG. 9 is a block diagram showing a configuration of the eighth embodiment of the AC motor driving device according to the present invention.

  In the AC motor driving device 1x shown in FIG. 3, one machine 5 is driven by using two AC electric machines 41 and 42 and two three-phase inverters 11 and 12, but the AC motor shown in FIG. The drive device 1xc drives the machine 5 using one AC motor 44 and two three-phase inverters 11 and 12.

  That is, in the eighth embodiment, in the input transformer 2x shown in FIG. 9, the voltage phase difference on the secondary winding side of the input transformer 2 shown in FIG. 8 is changed.

  With the configuration as described above, the AC motor driving device 1xc can drive the multi-winding AC motor.

  According to the eighth embodiment, in addition to the same effects as those of the second embodiment, a large-capacity output multi-winding AC motor can be driven.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, the AC motor driving device may control a multiphase (two or more phases) AC motor. For example, the features of the embodiments may be combined. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  DESCRIPTION OF SYMBOLS 1, 1b, 1c, 1x, 1xb, 1xc, 100 ... AC motor drive device, 2, 2x, 201, 202 ... Input transformer, 3 ... Three-phase AC power supply, 5, 6, 7 ... Machine (Load), 11 , 12, 110, 120 ... three-phase inverter, 8a, 8b, 8c ... reactor, 11ar, 11as, 11at, 11br, 11bs, 11bt, 11cr, 11cs, 11ct, 12ar, 12as, 12at, 12br, 12bs, 12bt, 12cr , 12cs, 12ct ... unit inverter, 11a, 11b, 11c, 12a, 12b, 12c ... multi-stage inverter, 16a, 16d ... diode, 16b ... capacitor, 16c ... self-extinguishing power element, 20, 200 ... primary winding , 21a, 21b, 21c, 22a, 22b, 22c, 22xa, 22xb, 22xc 220a, 220b, 220c ... secondary winding group, 21ar, 21as, 21at, 21br, 21bs, 21bt, 21cr, 21cs, 21ct, 22ar, 22as, 22at, 22br, 22bs, 22bt, 22cr, 22cs, 22ct, 22xar, 22xas, 22xat, 22xbr, 22xbs, 22xbt, 22xcr, 22xcs, 22xct, 220ar, 220as, 220at, 220br, 220bs, 220bt, 220cr, 220cs, 220ct ... secondary winding, 23, 230 ... iron core, 41, 42, 43 44 ... AC motor

Claims (5)

In an AC motor drive device comprising an input transformer connected to an AC power source and a plurality of three-phase inverters for operating one or more AC motors,
The three-phase inverter rectifies the three-phase AC output from the input transformer, converts it into DC power, and reversely converts it into a single-phase AC. The output side of the unit inverter is N stages (N is an integer of 2 or more). It has a multi-phase connection inverter for three phases connected to one phase,
In the input transformer, the primary winding is connected to the AC power source, and the secondary winding is a group of N pieces corresponding to the input of the multistage connection inverter for one phase of the plurality of three-phase inverters. The phase difference of the voltage between the N secondary windings in the one group of the secondary windings is divided into groups and connected to the multi-stage connection inverter for the one phase for each group. The secondary winding is wound by a common iron core so as to be mutually 360 ° / (6 × N) ,
The input transformer is configured to connect a total of six groups including the N secondary windings connected to the two three-phase inverters to one input of the three-phase inverter. A first group as a group and a second group as a third group other than the three groups of the first group connected to the input of the other one of the three-phase inverters, and The voltage phase difference between the three groups of the secondary windings divided into the first group and the three groups of the secondary windings divided into the second group is 360 ° / (6 X 2 x N) . An AC motor driving device. The machine is driven by using the two AC motors and the two three-phase inverters when a single machine is a load driven by the AC motor. AC motor drive device described in 1. When two independent machines that are loads driven by the AC motor are used, each of the machines is driven using one AC motor and one three-phase inverter.
The AC motor drive device according to claim 1 , wherein: When the AC motor is one, the same phase of the three-phase outputs of the two three-phase inverters are connected to each other via a reactor, and the midpoint of each of the reactors is connected to the AC motor, Operate the AC motor using the two three-phase inverters
The AC motor drive device according to claim 1 , wherein: When the AC motor has a two-winding configuration and one unit, the three-phase outputs of the two three-phase inverters are separated into one system and the other system of the two-winding configuration of the AC motor. Connected, and the AC motor is operated using the two three-phase inverters.
The AC motor drive device according to claim 1 , wherein:

Images