JP2008099415A - Inverter device, three-phase motor, and air-conditioning machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out switching of a drive system without having to use a bidirectional switch. <P>SOLUTION: An inverter device includes a connection switch 13 that connects/disconnects the junction point WP of leg L3 and an intermediate potential point NP; an inverter controlling means 23 that controls the switching operation of the switching elements of each leg; and a switching control means 21 that controls the operation of the connection switch. The connection switch includes a parallel-connected mechanical switch SK and a semiconductor switch SH that is out of conduction or can be brought into conduction in a single direction. The switching control means causes the mechanical switch to provide/remove continuity, only when the semiconductor switch is conducting in a single direction. When the switching elements S5, S6 of leg L3 are brought out of conduction, the switching control means synchronizes the mechanical switch with transition, from a state in which the semiconductor switch SH goes out of conduction state to a state in which it is conducting in a single state. When the switching elements of leg L3 are complementarily brought into conductive state, the switching control means synchronizes the mechanical switch with transition from a state, in which the semiconductor switch SH is conducting in a single direction to a state in which it is out of conduction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control operation of an inverter device.

  In recent years, with increasing interest in the global environment, the energy saving of equipment has been emphasized, and low power consumption is also required for air conditioners.

  The compressor motor of the air conditioner can be operated at a variable speed from a low speed to a high speed, but the usage rate in an operation region lower than the rated power is high except when the operation is started. For this reason, in order to improve the annual energy consumption efficiency (APF: Annual Performance Factor), which is an index of energy saving of the air conditioner, it can be said that the efficiency of the air conditioner during low-speed operation should be increased.

  In order to achieve high efficiency during low-speed operation, for example, a drive system of an inverter device that provides a parallel circuit of a mechanical switch and a bidirectional switch and outputs a three-phase alternating current according to the operation status of the motor A technique for switching between the two has been proposed (Patent Document 1). Specifically, when the motor is operated at high speed, the inverter device is driven as a three-phase inverter, and when the motor is operated at low speed, the inverter device is driven as a two-phase inverter.

  In the above method, by providing a bidirectional switch in parallel with the mechanical switch, the influence of the bounce of the mechanical switch is eliminated, and the smooth switching of the driving method is realized.

JP 2000-350476 A

  However, since the bidirectional switch is composed of at least two or more semiconductor switch elements, the use of the bidirectional switch increases the number of peripheral circuits such as a semiconductor switch element and a driving power source for driving the semiconductor switch element. Will eventually lead to an increase in cost.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of switching the driving method without using a bidirectional switch.

  In order to solve the above problems, the invention of claim 1 is an inverter device (10), each including a first capacitor and a second capacitor having one end and the other end, and the one end of the first capacitor, A capacitor group (12) for connecting the one end of the second capacitor at an intermediate potential point (NP) and inputting a DC voltage between the other end of the first capacitor and the other end of the second capacitor; , First switching elements (S1, S3) including first to third legs (L1, L2, L3), each of the first to third legs being connected to the other end of the first capacitor. , S5) and a second switching element (S2, S4, S6) connected between the first switching element and the other end of the second capacitor, and the first to third legs The first switching element and the second switching element in each A three-phase inverter circuit (14) for outputting each of the three-phase currents from connection points (UP, VP, WP) to which are connected, and the connection point (WP) and the intermediate potential point (NP) in the third leg A connection switch (13) for conducting / non-conducting between the first switching element and an inverter control means (23) for controlling the switching operation of the first switching element and the second switching element of the first to third legs; Switching control means (21) for controlling the operation of the connection switch, the connection switch is a parallel connection between a mechanical switch (SK) and a semiconductor switch (SH) that is non-conductive or unidirectionally conductive The switching control means causes the mechanical switch to perform conduction / non-conduction only when the semiconductor switch is conductive in the unidirectional direction, and the inverter control means includes (a) the third leg The first switching element (S 5) When the operation for making both the second switching elements (S6) non-conductive is started, the operation is changed from the non-conductive state to the unidirectional conductive state. And (b) when the semiconductor switch starts the operation of complementarily conducting the first switching element (S5) and the second switching element (S6) of the third leg. The three-phase current is supplied in synchronization with the transition from the unidirectional conducting state to the non-conducting state.

  The invention of claim 2 is the inverter device (10) according to the invention of claim 1, wherein the semiconductor switch (SH) conducts in the unidirectional direction by ignition, and the switching control means (21 ) Inputs an operation switching signal (Sa) for instructing whether the three-phase inverter circuit (14) is operated as a three-phase inverter or a two-phase inverter, and the connection point in the third leg The first open / close signal (Sc) that performs the ignition of the semiconductor switch (SH) in a half cycle in which the output current output from (WP) first takes a predetermined polarity after the transition of the operation switching signal (Sa). ) And the second open / close signal (Sd) for controlling the operation of the mechanical switch (SK) are output in synchronization with each other, and the output current flows when the output current has the predetermined polarity. Is based on the connection point (WP) in the third leg. It is a direction opposite direction.

  The invention of claim 3 is the inverter device (10) according to claim 1 or claim 2, wherein the switching control means is a speed command for a three-phase load (15) that receives the three-phase current. The operation of the connection switch is controlled based on the value (30).

  The invention of claim 4 is a three-phase motor (15) driven by the inverter device (10) according to any one of claims 1 to 3.

  The invention of claim 5 is an air conditioner provided with a compressor having the three-phase motor (15) according to the invention of claim 4.

  The invention of claim 6 is the air conditioner according to the invention of claim 5, wherein the switching control means in the inverter device (10) is configured to switch the connection switch based on switching of cooling / heating operation in the air conditioner. To control the operation.

  According to the first to sixth aspects of the invention, since the mechanical switch is turned on / off only in a state where the semiconductor switch is conductive in one direction, a semiconductor switch that is conductive in both directions is employed. In addition, the influence of the bounce of the mechanical switch can be eliminated. By conducting the mechanical switch, the conduction state of the semiconductor switch can be shortened and the power loss can be reduced.

  In particular, according to the invention of claim 2, since the semiconductor switch can be ignited, the current output from the third leg can be conducted in a half cycle having a predetermined polarity, and the operation switching signal is indicated. On the other hand, the connection switch can be appropriately conducted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. First Embodiment>
<Configuration>
FIG. 1 is a conceptual diagram showing a configuration of an inverter device 10 (10A) according to the first embodiment of the present invention. FIG. 1 also shows a DC power supply 11 that supplies a DC voltage to the inverter device 10A and a three-phase load (also referred to as “three-phase motor” or “motor”) 15 that receives the three-phase current of the inverter device 10A. In addition, as a three-phase load, an induction motor, a permanent magnet type synchronous motor (IPMSM: Interior Permanent Magnet Synchronous Motor), etc. are used.

  As shown in FIG. 1, the inverter device 10 </ b> A includes a pair of input terminals 101 and 102, a set of output terminals 121 to 123, a capacitor group 12, a connection switch 13, a three-phase inverter circuit 14, a polarity determination unit 20, and switching control. A unit 21, a switching determination unit 22, and an inverter control unit 23 are provided.

  The capacitor group 12 includes a capacitor C1 having terminals 111 and 112 and a capacitor C2 having terminals 113 and 114. The terminal 111 is connected to the input terminal 101, the terminal 114 is connected to the input terminal 102, and the terminal 112 and the terminal 113 are connected to each other at a connection point (also referred to as “intermediate potential point”) NP.

  The three-phase inverter circuit 14 includes three legs L1 to L3, and the upper arm of each leg is connected to the input terminal 101, and the lower arm of each leg is connected to the input terminal 102. Each arm has switching elements S1 to S6 and diodes D1 to D6 connected to the switching elements S1 to S6 in antiparallel. Connection points UP, VP, and WP between the upper arm and the lower arm are connected to output terminals 121, 122, and 123, respectively, and three-phase currents are output from the output terminals 121, 122, and 123, respectively.

  The connection switch 13 is installed between the connection point WP and the intermediate potential point NP in the leg L3, and controls conduction / non-conduction between the connection point WP and the intermediate potential point NP. The connection switch 13 is composed of a parallel circuit of a mechanical switch SK and a semiconductor switch SH that is non-conductive or unidirectionally conductive. In the present embodiment, a case where a GTO (gate turn off thyristor) is used as the semiconductor switch SH will be described, but other self-extinguishing elements such as an insulated gate bipolar transistor (IGBT) may be used. Moreover, in this embodiment, the case where a back contact (B contact) is used as the mechanical switch SK is illustrated.

  The polarity determination unit 20 determines the polarity of the output current based on the output current output from the connection point (here, the connection point WP) to which the connection switch 13 is connected.

  Based on the speed command value 30 for the three-phase load, the switching determination unit 22 determines whether to switch the driving method of the inverter device 10A. Then, an operation switching signal Sa for instructing whether to operate as a three-phase inverter or a two-phase inverter is output. The driving method of the inverter device 10A will be described later.

  The switching control unit 21 receives the operation switching signal Sa and controls the operation of the connection switch 13. Specifically, based on the polarity of the output current, a semiconductor switch control signal (semiconductor switch open / close signal) Sc for controlling the starting and extinguishing of the semiconductor switch SH and a mechanical switch control signal for controlling the operation of the mechanical switch SK ( Machine switch open / close signal Sd.

  The inverter control unit 23 controls the switching operation of the switching elements S1 to S6 of the three-phase inverter circuit 14.

<Drive system>
Next, the driving method will be described.

  As described above, in the inverter device 10 </ b> A shown in FIG. 1, the driving method of the inverter device 10 </ b> A is switched based on the speed command value 30 of the motor 15.

  Specifically, the inverter device 10A is driven as a three-phase inverter in a high-speed operation region where the motor speed command value is larger than a predetermined threshold value, and the motor speed command value exceeds the predetermined threshold value. In the low-speed operation region, which is smaller, it is driven as a two-phase inverter.

  More specifically, in the case of high-speed operation, the connection control unit 21 is made non-conductive by the switching control unit 21, and the inverter control unit 23 performs PWM control of the six switching elements S1 to S6 so that the inverter device 10A is three-way. Drives as a phase inverter.

  On the other hand, in the case of low speed operation, the switching control unit 21 brings the connection switch 13 into a conductive state, and the inverter control unit 23 always turns off the two switching elements S5 and S6 of the phase to which the connection switch 13 is connected. To. Then, the other four switching elements S1 to S4 are PWM-controlled to drive the inverter device 10A as a two-phase (four-arm system) inverter. Since the circuit configuration when driven as a two-phase inverter is equivalent to the V-connection of the transformer, the two-phase inverter is also referred to as a V-connection inverter.

  Thus, by switching the drive method of the inverter device 10A, the conduction loss of the inverter in the low-speed operation region is reduced to about 2/3 as compared with the case of always driving as a three-phase inverter without switching the drive method. It becomes possible to reduce.

  Further, by controlling the operation of the connection switch 13 based on the motor speed command value (operation status), efficient operation according to the motor operation status becomes possible.

<Operation>
Next, the drive system switching operation will be described with reference to FIGS.

  FIG. 2 is a flowchart of the driving method switching operation, and FIG. 3 is a time chart of the switching operation.

  As shown in FIG. 2, in step SP <b> 1, it is determined based on the motor speed command value 30 whether or not to switch the driving method. If it is determined that switching is to be performed, the process proceeds to step SP2, and if it is determined that switching is not to be performed, a standby state is entered.

  In step SP2, transitions Sa1 and Sa2 of the switching signal Sa are performed (see FIG. 3).

  In step SP3, the switching timing is measured based on the current of the phase to which the connection switch 13 is connected (here, the W-phase current).

  Specifically, a state in which the W-phase current has a predetermined polarity is detected after transition of the switching signal Sa. If the predetermined polarity is detected, the process proceeds to step SP4. If not detected, the process waits until it is detected. Here, a case where the process proceeds to step SP4 by first detecting the start of a half cycle having a predetermined polarity after transition of the switching signal Sa is illustrated.

  Note that the direction in which the W-phase current flows when the W-phase current has a predetermined polarity is opposite to the unidirectional direction in which the semiconductor switch SH can conduct with respect to the connection point WP in the leg L3. Specifically, when the semiconductor switch SH that can conduct in the direction in which the current flows from the intermediate potential point NP to the connection point WP in FIG. 1 is adopted, the direction in which the W-phase current having a predetermined polarity flows is This is the direction of flow from the point WP to the motor 15.

  In step SP4, the driving method is switched. Details will be described later.

  In step SP5, it is determined whether or not to end the operation of the inverter device 10A. When the operation is terminated, the switching operation is terminated, and when the operation is continued, the operations of steps SP1 to SP5 are repeated.

  Here, step SP4 (driving method switching step) will be described in detail separately for switching from the three-phase method to the two-phase method and switching from the two-phase method to the three-phase method.

  First, in the case of switching from the three-phase type to the two-phase type, a conduction operation for switching the non-conduction state of the mechanical switch SK to the conduction state is executed, and the connection switch 13 is changed from the non-conduction state to the conduction state.

  Here, when the mechanical switch SK is completely conductive, the conduction loss is very small. However, when the mechanical switch SK is conductive / non-conductive, the bounce caused by the operating time of about 10 ms and chattering is caused. Have time. For this reason, the mechanical switch SK exhibits an unstable operation (unstable operation) FD for a certain period after the operation signal is given. However, during the period (unstable period) t3 indicating such unstable operation FD, the semiconductor switch SH connected in parallel to the mechanical switch SK is always in a conductive state, thereby avoiding the influence of the unstable operation FD. It becomes possible to do. In short, it is only necessary to execute the conduction / non-conduction operation of the mechanical switch SK only in a state where the semiconductor switch SH is conductive in a single direction.

  Therefore, in the present embodiment, the semiconductor switch control signal Sc1 and the mechanical switch control signal Sd1 are output in synchronization with the switching command signal Sb1, and the conduction operation of the mechanical switch SK is started in the conduction state of the semiconductor switch SH.

  Specifically, the switching command signal Sb1 is generated according to the optimum switching timing determined in step SP3, and the semiconductor switch control signal (semiconductor switch opening / closing signal) Sc1 output in synchronization with the switching command signal Sb1 is the semiconductor. It is given to the switch SH as a gate signal. Thereby, the semiconductor switch SH is ignited and transits from a non-conducting state to a unidirectional conducting state. The semiconductor switch control signal Sc1 is a signal having a predetermined pulse width, and the conduction state of the semiconductor switch SH is maintained in a period (also referred to as “conduction period”) t1 corresponding to the pulse width.

  The mechanical switch control signal (mechanical switch opening / closing signal) Sd1 output (transitioned) in synchronization with the switching command signal Sb1 is given to the mechanical switch SK as an operation signal. As a result, the mechanical switch SK transitions from the non-conductive state to the conductive state. In this embodiment, since the back contact is used as the mechanical switch SK, the mechanical switch control signal Sd1 output when the back contact is not operated is a signal (here, the operating voltage of the back contact). Then zero).

  Then, the output period of the semiconductor switch control signal Sc1 is adjusted (set) so that the conduction period t1 of the semiconductor switch SH is longer than the unstable period t3 of the mechanical switch SK.

  Thus, in order to avoid the unstable operation FD of the mechanical switch SK, the mechanical switch SK is transitioned from the non-conductive state to the complete conductive state in the conductive period t1 of the semiconductor switch SH, and the connection switch 13 is non-conductive. Transition from state to conduction state.

  In addition, after the predetermined period t1 has elapsed, the conduction state is maintained by the mechanical switch SK, and the semiconductor switch SH is made non-conduction, thereby reducing the power loss in the connection switch 13 in the conduction state.

  Then, the two switching elements S5 and S6 in the leg 3 are both turned off, and the inverter device 10A is driven as a two-phase (four-arm type) inverter.

  Specifically, the drive signal Se related to the two switching elements S5 and S6 in the leg L3 is synchronized with the ignition of the semiconductor switch SH, that is, the transition of the semiconductor switch SH from the non-conductive state to the unidirectional conductive state. Thus, the transition Se1 is made, and both of the two switching elements S5 and S6 are made non-conductive.

  As described above, in the case of switching from the three-phase system to the two-phase system, the ignition of the semiconductor switch SH and the switching operation of the three-phase inverter circuit 14 are performed in synchronization, so the smooth switching of the driving system is executed. It becomes possible to do.

  Next, in the case of switching from the two-phase type to the three-phase type, a non-conduction operation for switching the conduction state by the mechanical switch SK to the non-conduction state is executed, and the connection switch 13 is changed from the conduction state to the non-conduction state. Transition.

  Specifically, similarly to switching from the three-phase type to the two-phase type, in order to avoid the unstable operation FD of the mechanical switch SK, the non-switching of the mechanical switch SK is performed only when the semiconductor switch SH is conductive in one direction. The continuity operation is executed.

  Specifically, the semiconductor switch control signal Sc2 and the mechanical switch control signal Sd2 are output in synchronization with the switching command signal Sb2, and the transition operation of the mechanical switch SK to the non-conductive state is started when the semiconductor switch SH is in the conductive state. Is done.

  Then, the output period of the semiconductor switch control signal Sc2 is adjusted so that the conduction period t2 of the semiconductor switch SH is longer than the unstable period t4 of the mechanical switch SK.

  As described above, in order to avoid the unstable operation FD of the mechanical switch SK at the time of non-conduction, the conduction state is maintained by the semiconductor switch SH during a predetermined period t2 after the switching command signal Sb2 is generated, In the period t2, the non-conducting operation of the mechanical switch SK is executed. As a result, the connection switch 13 transitions from the conductive state to the non-conductive state.

  Then, the two switching elements S5 and S6 in the leg 3 are both brought into conduction, and the inverter device 10A is driven as a three-phase inverter.

  Specifically, the drive signal Se related to the two switching elements S5 and S6 in the leg L3 is synchronized with the extinction of the semiconductor switch SH, that is, the transition from the state in which the semiconductor switch SH is conductive in one direction to the non-conductive state. Transition Se1 to bring the two switching elements S5 and S6 into a conductive state in a complementary manner.

  As described above, in the case of switching from the two-phase system to the three-phase system, the arc extinguishing of the semiconductor switch SH and the switching operation of the three-phase inverter circuit 14 are performed in synchronization, so that the switching of the smooth driving system is executed. It becomes possible to do.

  As described above, in the inverter device 10A according to the present embodiment, since the mechanical switch SK performs conduction / non-conduction only in a state where the semiconductor switch SH is unidirectionally conductive, the semiconductor that is bidirectionally conductive is used. Without adopting a switch, it is possible to eliminate the influence of unstable operation such as bounce of a mechanical switch.

  In addition, when the operation of turning off both of the two switching elements S5 and S6 in the leg L3 is started, the operation is transitioned from the non-conductive state to the unidirectional conductive state of the semiconductor switch SH. In the case where an operation for complementarily conducting the two switching elements S5 and S6 is started, the operation is synchronized with the transition of the semiconductor switch SH from the unidirectional conduction state to the non-conduction state. Let According to this, it becomes possible to execute a smooth switching of the driving method.

  Further, since the semiconductor switch SH can switch between conduction in a single direction by ignition and non-conduction by self-extinguishing, the conduction / non-conduction of the connection switch 13 appropriately in response to the instruction of the switching command signal Sb. Can be executed.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described. In the first embodiment, a self-extinguishing element is used as the semiconductor switch SH. However, in the second embodiment, a semiconductor element such as an SCR (silicon controlled rectifier) having no self-extinguishing function is used as the semiconductor switch SH. Is used.

  FIG. 4 is a diagram illustrating an inverter device 10 (10B) according to the second embodiment.

  The inverter device 10B has the same configuration as the inverter device 10A of the first embodiment except that the semiconductor switch SH does not have a self-extinguishing function. Below, it demonstrates centering around difference with 1st Embodiment, about the common part, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 5 is a time chart of the switching operation in the inverter device 10B.

  In the inverter device 10B, the same switching operation as in FIG. 2 is executed except for step SP4. Below, step SP4 in the inverter apparatus 10B is demonstrated.

  As described above, the semiconductor switch SH in the inverter device 10B does not have a self-extinguishing function. For this reason, once the semiconductor switch control signal Sc synchronized with the switching command signal Sb is once applied to the semiconductor switch SH, the semiconductor switch SH maintains the conductive state until a reverse voltage is applied.

  In the case of switching from the three-phase type to the two-phase type, as in the first embodiment, in order to avoid the unstable operation FD of the mechanical switch, the machine is used only in a state where the semiconductor switch SH is conductive in one direction. The switch SK is turned on, and the connection switch 13 is changed from the non-conductive state to the conductive state.

  Specifically, a semiconductor switch control signal Sc11 and a mechanical switch control signal Sd11 that are synchronized with the switching command signal Sb11 are output, respectively.

  The semiconductor switch control signal Sc11 is output for a certain period to ignite the semiconductor switch SH. The fired semiconductor switch SH is extinguished when the current of the phase to which the connection switch 13 is connected (here, the W-phase current) becomes zero. That is, the conduction period t11 of the semiconductor switch SH is a half cycle in which the W-phase current has a predetermined polarity.

  On the other hand, the mechanical switch control signal Sd11 is given as an operation signal to the mechanical switch SK.

  Here, also in the second embodiment, the unstable operation FD of the mechanical switch SK at the time of conduction / non-conduction becomes a problem, but even when the semiconductor switch SH is configured by an element having no self-extinguishing function, It is possible to avoid the influence of the unstable operation FD. Specifically, since the W-phase current when driven as a two-phase inverter has a low frequency of about 10 Hz to 20 Hz, the half cycle of the W-phase current is 25 ms or more, and the unstable period t3 of the mechanical switch SK. , T4 is longer than about 10 ms. For this reason, even when the semiconductor switch SH is formed of an element that does not have a self-extinguishing function, the conduction periods t11 and t12 of the semiconductor switch SH are longer than the unstable periods t3 and t4 of the mechanical switch SK. It is possible to avoid the influence of the operation FD.

  As described above, the mechanical switch SK is transitioned from the non-conductive state to the complete conductive state in the conductive period t11 of the semiconductor switch SH.

  Then, the drive signal Se related to the two switching elements S5 and S6 in the leg L3 is shifted in synchronization with the ignition of the semiconductor switch SH, that is, the transition of the semiconductor switch SH from the non-conductive state to the unidirectional state. Then, both of the two switching elements S5 and S6 are made non-conductive.

  Further, in the case of switching from the two-phase type to the three-phase type, as in the first embodiment, in order to avoid the unstable operation FD of the mechanical switch, the semiconductor switch SH is in a unidirectional conduction state. Then, the non-conduction operation of the mechanical switch SK is executed, and the connection switch 13 is changed from the non-conduction state to the conduction state.

  Specifically, a semiconductor switch control signal Sc12 and a mechanical switch control signal Sc12 that are synchronized with the switching command signal Sb12 are output, respectively.

  The semiconductor switch control signal Sc12 is output for firing the semiconductor switch SH, and the fired semiconductor switch SH maintains its conduction state until the W-phase current becomes zero. That is, the conduction period t12 of the semiconductor switch SH is a half cycle in which the W-phase current has a predetermined polarity.

  On the other hand, the mechanical switch control signal Sd11 is given as an operation signal to the mechanical switch SK.

  Here, the unstable operation FD of the mechanical switch SK becomes a problem. However, as described above, since the half cycle of the W-phase current is longer than the unstable period t4 of the mechanical switch SK, the conduction period t12 of the semiconductor switch SH is longer than the unstable period t4 of the mechanical switch SK. It is possible to avoid the influence of the unstable operation FD.

  Thus, the mechanical switch SK is transitioned from the conductive state to the complete non-conductive state in the conductive period t12 of the semiconductor switch SH.

  Then, the drive signal Se related to the two switching elements S5 and S6 in the leg L3 transitions from the end of the half cycle taking the predetermined polarity of the W-phase current, that is, the state in which the semiconductor switch SH is unidirectionally conductive to the non-conductive state. In synchronism with this, the transition Se12 is set so that the two switching elements S5 and S6 can be complementarily conducted.

  As described above, in the inverter device 10B according to the second embodiment, the switching of the driving method can be realized even if an element having no self-extinguishing function is used as the semiconductor switch SH.

  In addition, since the semiconductor switch SH in the inverter device 10B can conduct in one direction by firing, the connection switch 13 can be appropriately conducted in response to the instruction of the switching command signal Sb.

  Note that the use of a self-extinguishing element as in the first embodiment is half of the W-phase current, compared to the case where an element that does not have a self-extinguishing function is used as the semiconductor switch SH as in the second embodiment. Since the semiconductor switch SH can be extinguished without waiting for the end of the cycle, it becomes possible to quickly switch the driving method.

<3. Third Embodiment>
Next, a third embodiment of the present invention will be described. In 3rd Embodiment, inverter apparatus 10A, 10B which concerns on each said embodiment is connected to the compressor for air conditioners, for example, and the said compressor is drive-controlled.

  In this case, the operation switching signal Sa may be changed based on switching of operation such as cooling and heating in the air conditioner, and the driving method of the inverter devices 10A and 10B may be switched.

  Specifically, the inverter devices 10A and 10B are driven as a two-phase inverter in the cooling operation, and are driven as a three-phase inverter in the heating operation.

  As described above, by switching the drive method of the inverter devices 10A and 10B according to the operation status such as air conditioning in the air conditioner, an efficient operation according to the operation status of the air conditioner is possible.

<Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

  For example, in the first and second embodiments, the back contact is used as the mechanical switch SK. However, the present invention is not limited to this, and a front contact (A contact) may be used.

  However, since the mechanical switch SK is used as a conduction state in low-speed operation, in an air conditioner having a high usage rate in the low-speed operation region, it is more efficient to use a back contact that is in a conduction state in a non-operation state. Can be reduced.

It is a conceptual diagram which shows the structure of the inverter apparatus which concerns on 1st Embodiment of this invention. It is a flowchart of the switching operation of a drive system. It is a time chart of the switching operation | movement of the inverter apparatus which concerns on 1st Embodiment. It is a conceptual diagram which shows the structure of the inverter apparatus which concerns on 2nd Embodiment. It is a time chart of the switching operation | movement of the inverter apparatus which concerns on 2nd Embodiment.

Explanation of symbols

10, 10A, 10B Inverter device 13 Connection switch 14 Three-phase inverter circuit 20 Polarity determination unit 21 Switching control unit 22 Switching determination unit 23 Inverter control unit 30 Speed command value FD Unstable operation NP Intermediate potential point SH Semiconductor switch SK Mechanical switch WP Connection point

Claims (6)

Each includes a first capacitor and a second capacitor having one end and the other end, the one end of the first capacitor and the one end of the second capacitor are connected at an intermediate potential point (NP), and the first capacitor A capacitor group (12) for inputting a DC voltage between the other end and the other end of the second capacitor;
First switching elements (S1, S3, L3) including first to third legs (L1, L2, L3), each of the first to third legs being connected to the other end of the first capacitor. S5) and a second switching element (S2, S4, S6) connected between the first switching element and the other end of the second capacitor, and the first to third legs A three-phase inverter circuit (14) for outputting each of three-phase currents from connection points (UP, VP, WP) at which the first switching element and the second switching element are connected to each other;
A connection switch (13) for conducting / non-conducting between the connection point (WP) and the intermediate potential point (NP) in the third leg;
Inverter control means (23) for controlling the switching operation of the first switching element and the second switching element of the first to third legs;
Switching control means (21) for controlling the operation of the connection switch,
The connection switch includes a parallel connection of a mechanical switch (SK) and a semiconductor switch (SH) capable of non-conduction or unidirectional conduction,
The switching control means causes the mechanical switch to perform conduction / non-conduction only in a state where the semiconductor switch is conductive in the unidirectional direction,
The inverter control means includes
(a) In the case where an operation for turning off both the first switching element (S5) and the second switching element (S6) of the third leg is started, the semiconductor switch is turned off. Synchronized to transition from a state to a state that conducts in one direction,
(b) In the case where an operation for complementarily conducting the first switching element (S5) and the second switching element (S6) of the third leg is started, the semiconductor switch performs the operation in the unidirectional direction. Synchronized with the transition from the conducting state to the non-conducting state,
An inverter device (10) for supplying the three-phase current. The semiconductor switch (SH) conducts in one direction by ignition,
The switching control means (21) inputs an operation switching signal (Sa) for instructing whether to operate the three-phase inverter circuit (14) as a three-phase inverter or a two-phase inverter, and The output current output from the connection point (WP) in the three legs performs the ignition of the semiconductor switch (SH) in a half cycle that first takes a predetermined polarity after the transition of the operation switching signal (Sa). A first open / close signal (Sc) and a second open / close signal (Sd) for controlling the operation of the mechanical switch (SK) are output in synchronization with each other.
The inverter apparatus according to claim 1, wherein a direction in which the output current flows when the output current has the predetermined polarity is opposite to the unidirectional direction with respect to the connection point (WP) in the third leg. (Ten). The switching control means controls the operation of the connection switch based on a speed command value (30) of a three-phase load (15) that receives the three-phase current.
The inverter device (10) according to claim 1 or claim 2.   A three-phase motor (15) driven by the inverter device (10) according to any one of claims 1 to 3.   An air conditioner comprising a compressor having the three-phase motor (15) according to claim 4. The switching control means in the inverter device (10) controls the operation of the connection switch based on switching of cooling / heating operation in the air conditioner.
The air conditioner according to claim 5.

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