JP2011097668A - Refrigeration unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce common mode noise in a refrigeration unit having multiple compressors provided with a motor. <P>SOLUTION: Power conversion devices (42a, 42b) that supply predetermined power are provided for each motor (27). A control unit (48) is provided to control switching at the power conversion devices (42a, 42b), based on a carrier signal (C) and the like. Coils (50) are provided for grounding the capacitance (Co) formed in each motor (27). These coils (50) are wound in phase on a ferrite core (51). The timing of switching is controlled by the control unit (48) so that rise or fall of common mode voltages is synchronized between the power conversion devices (42a, 42b) at least once in one cycle of the carrier signal (C). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus having a plurality of compressors driven by a motor.

  In a refrigeration apparatus such as an air conditioner, a power converter is generally used to supply AC power to a motor that drives a compressor. This power conversion device includes a converter circuit that converts alternating current to direct current and an inverter circuit that converts direct current to alternating current. For example, in an inverter circuit, an input direct current is switched by a switching element. There is one that can obtain the desired alternating current.

  In a refrigeration apparatus equipped with such an inverter circuit, when the switching element performs switching, a so-called common mode voltage is generated, and a steep voltage change occurs in the capacitance formed between the winding of the motor and the ground, Due to the voltage change, a high-frequency current (leakage current) may flow to the ground via the capacitance. Such a leakage current or a noise terminal voltage generated thereby can be a cause of malfunction of other devices, and is regulated to a certain level or less. For this reason, some power conversion devices include a noise filter for suppressing noise in a power line on the input side of the power conversion device (see, for example, Patent Document 1).

JP 2006-136058 A

  However, some refrigeration apparatuses such as an air conditioner include a plurality of compressors and motors. In such a refrigeration apparatus, the high-frequency current is larger than that in the case of a single motor (compressor). When the high-frequency current increases, for example, even if a plurality of power converters share a noise filter to reduce the size of the entire power converter, it is necessary to increase the size of the noise filter components. It is thought that it will hinder the transformation.

  The present invention has been made paying attention to the above problem, and an object of the present invention is to reduce common mode noise in a refrigeration apparatus including a plurality of compressors having a motor.

In order to solve the above problems, the first invention is
A refrigeration apparatus comprising a plurality of compressors (22) having a motor (27), and performing a refrigeration cycle by circulating refrigerant in a refrigerant circuit (21),
Power converters (42a, 42b) that are provided for each motor (27), switch the input power to convert it into output power, and supply the output power to the corresponding motor (27),
A control unit (48) for controlling the switching in each power converter (42a, 42b) in synchronization with the periodically changing carrier signal (C);
A coil (50) provided for each motor (27) and grounding a capacitance (Co) formed in the corresponding motor (27);
A magnetic core (51) in which each coil (50) is wound in the same phase;
With
The control unit (48) is configured such that, between the respective power conversion devices (42a, 42b), rising timings or falling timings of the common mode voltage due to the switching are at least during one cycle of the carrier signal (C). The switching timing is controlled to synchronize once.

  In this configuration, when each power conversion device (42a, 42b) performs switching by the control unit (48), each power conversion device (42a, 42b) performs predetermined input power (for example, single-phase AC power) by switching. Output power (for example, three-phase alternating current) and supply it to the corresponding motor (27). Thus, when switching is performed in each power converter (42a, 42b), a common mode voltage is generated, and a steep voltage change occurs in the capacitance (Co) formed in the motor (27). Along with this voltage change, a high-frequency current (leakage current) flows through the capacitance (Co), and this leakage current is connected to the ground wire (49) via the coil (50) connected to each motor (27). Will flow into.

  In the present invention, the control unit (48) includes at least the common mode voltage rising or falling timings between the power converters (42a, 42b) during one cycle of the carrier signal (C). It is controlled to synchronize once. As described above, when the timing of voltage change in the same direction (hereinafter referred to as voltage change timing) is synchronized, in the present invention, each coil (50) is wound around one magnetic core (51). (50) generates magnetic flux in the same direction. Thereby, the magnetic flux generated by a certain coil (50) enters another coil (50). Thus, when the magnetic flux from another coil (50) enters, the coil (50) functions as a coil having a larger inductance (L) than when it is wound around the magnetic core (51) alone.

In addition, the second invention,
In the refrigeration apparatus of the first invention,
The control unit (48)
A first switching control unit (48a) that controls switching in any one of the power conversion devices (42a) and outputs a timing signal (S2) indicating the timing of the switching;
Using the timing signal (S2), a second switching control unit (48b) for controlling switching timing in another power converter (42b);
It is characterized by having.

  In this configuration, the switching timing of the other power conversion device (42b) is controlled on the basis of the switching timing in the power conversion device (42a) controlled by the first switching control unit (48a).

In addition, the third invention,
In the refrigeration apparatus of the second invention,
It has a detection unit (71) that detects the current change timing at which the current flowing into each coil (50) rises or falls,
The second switching control unit (48b) corrects the switching timing so as to reduce a shift in the current change timing.

  In this configuration, in the power conversion device (42b) controlled by the second switching control unit (48b), the switching timing is corrected based on the current change timing in each coil (50), and the synchronization shift is prevented. .

In addition, the fourth invention is
In the refrigeration apparatus of the first invention,
The control unit (81) outputs a common control signal (Gup,..., Gwn) to each power converter (42a, 42b) to control switching in each power converter (42a, 42b). It has the part (81a), It is characterized by the above-mentioned.

  In this configuration, a common control signal (Gup,..., Gwn) is output to each power converter (42a, 42b) by one switching control unit (81a). Thereby, each power converter device (42a, 42b) performs the same operation | movement, while being controlled by the control part (81). That is, according to the present invention, it is possible to always switch the power converters (42a, 42b) in synchronization.

In addition, the fifth invention,
In any one of the first to fourth aspects of the refrigeration apparatus,
Each motor (27) is electrically insulated from a pipe (28) constituting the refrigerant circuit (21).

  In this configuration, since the motor (27) is electrically insulated from the pipe (28), it is possible to prevent the leakage current from flowing through a path other than the ground such as the pipe.

  According to the first invention, when the rising timings or the falling timings of the common mode voltage are synchronized between the power converters (42a, 42b), each coil (50) is used more than when used alone. Also functions as a coil with a large inductance (L). Thereby, in this refrigeration apparatus, it becomes possible to reduce the level of leakage current (common mode noise) flowing into the ground wire (49) via the respective coils (50).

  According to the second invention, the timing signal (S2) facilitates the synchronization of the switching timing between the power converters (42a, 42b).

  In addition, according to the third invention, since the synchronization shift is prevented, the level of the common mode noise is surely reduced even when the impedance of the motor (27) or the wiring is varied, for example. It becomes possible.

  In addition, according to the fourth invention, the power converters (42a, 42b) can always be switched in synchronization, so that the level of common mode noise can be reduced more effectively. It becomes possible.

  In addition, according to the fifth aspect, it is possible to prevent leakage current from flowing to other than the coil (50), so it is possible to more effectively reduce the level of common mode noise.

FIG. 1 is a refrigerant piping system diagram of a refrigeration apparatus according to Embodiment 1 of the present invention. 2A is a block diagram showing the configuration of the power supply unit, and FIG. 2B is a diagram for explaining the capacitance formed in each motor. FIG. 3 is a block diagram illustrating a configuration example of the first and second power conversion devices. FIG. 4 is a diagram illustrating the waveform of the gate signal applied to the gate of each switching element on the upper arm side in each inverter circuit. FIG. 5 is a diagram illustrating an example of waveforms of the common mode voltage and the leakage current. FIG. 6 is a circuit diagram modeling the power supply unit and the motor according to the first embodiment. FIG. 7 is a diagram illustrating a waveform of a common mode voltage generated from each power source in the simulation circuit. FIG. 8 is a diagram illustrating a simulation result of the level of common mode noise. FIG. 9 is a block diagram illustrating a configuration of a power supply unit according to a modification of the first embodiment. FIG. 10 is a block diagram illustrating a configuration of a power supply unit according to the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
"Overview"
As a first embodiment of the present invention, an example of a refrigeration apparatus including two compressors will be described. FIG. 1 is a refrigerant piping system diagram of a refrigeration apparatus (1) according to Embodiment 1 of the present invention. The refrigeration apparatus (1) includes an outdoor unit (2), an indoor unit (3), and a power supply unit (4). In the outdoor unit (2) and the indoor unit (3), an outdoor side and indoor side refrigerant circuit (21a, 21b) through which the refrigerant circulates are formed, respectively, and the outdoor side refrigerant circuit (21a) and the indoor side refrigerant circuit ( 21b) are connected to each other by a connecting pipe (21c). Hereinafter, the outdoor refrigerant circuit (21a), the indoor refrigerant circuit (21b), and the connecting pipe (21c) are collectively referred to as a refrigerant circuit (21). Next, each component of the refrigeration apparatus (1) will be described.

<Configuration of outdoor unit (2) and indoor unit (3)>
The outdoor unit (2) has a casing (20), and the casing (20) accommodates an outdoor refrigerant circuit (21a) and a power supply unit (4). As shown in FIG. 1, the outdoor refrigerant circuit (21a) includes two compressors (22), a heat exchanger (23), an expansion valve (24), two closing valves (25), and an insulating member. (26)

  Each compressor (22) has a motor (27). These motors (27) are motors driven by three-phase AC, and AC power corresponding to the capability that the refrigeration apparatus (1) should exhibit is supplied from the power supply unit (4). Each compressor (22) is housed in the casing (20) while being electrically insulated from the casing (20).

  The insulating member (26) is a member for electrically insulating each compressor (22) (that is, each motor (27)) from the pipe (28) without blocking the refrigerant flow path. Is formed. As a material of the insulating member (26), for example, glass, ceramic, resin, or the like can be adopted. In this outdoor refrigerant circuit (21a), one closing valve (25) (gas side closing valve), insulating member (26), compressor (22), insulating member (26), heat exchanger (23) The expansion valve (24) and the other closing valve (25) (liquid side closing valve) are connected to each other by a pipe (28) in this order. In this example, the two compressors (22) are connected in parallel to each other as shown in FIG.

  On the other hand, the indoor unit (3) has a heat exchanger (31), and this heat exchanger (31) constitutes an indoor refrigerant circuit (21b) together with a predetermined pipe (28). The indoor refrigerant circuit (21b) is connected to the outdoor refrigerant circuit (21a) via the connecting pipe (21c). In FIG. 1, only one indoor unit (3) is shown, but a plurality of indoor units (3) may be connected to the refrigerant circuit (21).

<Configuration of power supply unit (4)>
FIG. 2A is a block diagram illustrating a configuration of the power supply unit (4). The power supply unit (4) converts the input power into predetermined output power and supplies it to each motor (27). Specifically, the power supply unit (4) includes a noise filter (41), first and second power converters (42a, 42b), a carrier signal generation unit (47), a control unit (48), and a ground wire (49 ) And a coil (50), and converts the alternating current supplied from the alternating current power source (5) into a predetermined output alternating current. The AC power source (5) in this example is a single-phase AC power source. In the AC power supply (5), capacitors (C1, C2) connected in series are connected between output terminals, and the midpoint between these capacitors (C1, C2) is grounded (see FIG. 2).

<First and second power converters (42a, 42b)>
The first and second power conversion devices (42a, 42b) convert input power into predetermined power by switching. In this embodiment, each power converter device (42a, 42b) converts single phase alternating current into three phase alternating current. In this example, the first power converter (42a) and the second power converter (42b) have the same configuration, and both include a converter circuit and an inverter circuit. Hereinafter, the converter circuit and the inverter circuit in the first power converter (42a) are referred to as the first converter circuit (43) and the first inverter circuit (45), respectively, and the converter circuit in the second power converter (42b), And the inverter circuit are referred to as a second converter circuit (44) and a second inverter circuit (46), respectively.

-First and second converter circuits (43, 44)-
These converter circuits (43, 44) are connected to an AC power source (5) via a noise filter (41), respectively, and rectify and output the AC output from the AC power source (5) to DC. FIG. 3 is a block diagram showing a configuration example of the first and second converter circuits (43, 44). As shown in FIG. 3, both converter circuits (43, 44) include four diodes (D1,..., D4) connected in a bridge, a reactor (43a), and a smoothing capacitor (43b). Is full-wave rectified.

  As shown in FIG. 3, the noise filter (41) includes a combination of four capacitors (C3, C4, C5, C6) and two coils (L1, L2). In this example, the noise filter (41) is shared by the first and second power converters (42a, 42b).

-First and second inverter circuits (45,46)-
The first inverter circuit (45) is paired with the first converter circuit (43) and switches the direct current output from the first converter circuit (43) to convert it into alternating current. Similarly, the second inverter circuit (46) is paired with the second converter circuit (44), and switches the direct current output from the second converter circuit (44) to convert it into alternating current. Each inverter circuit (45, 46) has a one-to-one correspondence with the motor (27), and supplies the output AC to the corresponding motor (27).

  As shown in FIG. 3, each inverter circuit (45, 46) of the present embodiment includes three switching elements (Sup, Svp, Swp) and three free-wheeling diodes (Dup, Dvp, Dwp) constituting the upper arm, Three switching elements (Sun, Svn, Swn) and three free-wheeling diodes (Dun, Dvn, Dwn) constituting the lower arm are provided. These inverter circuits (45, 46) are provided with a pair of positive and negative DC buses (P, N). These DC buses (P, N) have a pair of converter circuits (43, 43). , 44) is supplied.

  In these inverter circuits (45, 46), the upper arm switching elements (Sup, Svp, Swp) and the lower arm switching elements (Sun, Svn, Swn) are connected in series in a one-to-one correspondence. Has been. Hereinafter, a pair of switching elements (Sup,..., Swn) connected in series is referred to as a switching leg. In this example, a switching leg (leg1) formed by a pair of a switching element (Sup) and a switching element (Sun), a switching leg (leg2) formed by a pair of a switching element (Svp) and a switching element (Svn), There is a switching leg (leg 3) formed by a pair of a switching element (Swp) and a switching element (Swn).

  These switching legs (leg1, leg2, leg3) are connected between a positive DC bus (P) and a negative DC bus (N), respectively. Also, each intermediate point (M1, M2, M3) of each switching leg (leg1, leg2, leg3) is the phase voltage (Vu, Vv, Vw) of each phase (U phase, V phase, W phase) of output AC The intermediate points (M1, M2, M3) are respectively connected to the respective phases of the motor (27). In each inverter circuit (45, 46), these switching elements (Sup,..., Swn) are switched on and off to perform inverter control. The on / off control of these switching elements (Sup,..., Swn) is performed by the corresponding switching control units (48a, 48b).

<Carrier signal generator (47)>
The carrier signal generator (47) generates a periodically changing carrier signal (C) and supplies it to the first and second switching controllers (48a, 48b). The carrier signal (C) is a signal that becomes a reference when the inverter circuits (45, 46) are inverter-controlled. That is, each inverter circuit (45, 46) operates in synchronization with the common carrier signal (C). In this example, the inverter control performed in each inverter circuit (45, 46) is PWM control (PWM: Pulse Width Modulation), and the carrier signal (C) is a triangular wave having a predetermined frequency.

<Control part (48)>
The control unit (48) of the present embodiment includes first and second switching control units (48a, 48b). The first switching control unit (48a) controls switching of each switching element (Sup,..., Swn) in the first inverter circuit (45), and the second switching control unit (48b) includes the second inverter circuit (46 ) Controls switching of each switching element (Sup,..., Swn). More specifically, the control unit (48), between the respective power converters (42a, 42b), the rise timings or the fall timings of the common mode voltage (described later) due to switching of each inverter circuit (45, 46). Each inverter circuit (45, 46) is PWM-controlled so that (the timings at which the voltages change in the same direction) are synchronized at least once during one cycle of the carrier signal (C).

  Specifically, the first switching control unit (48a) generates gate signals (Gup,..., Gwn) to be applied to the gates of the switching elements (Sup,..., Swn) of the first inverter circuit (45). Control these on and off. At this time, the first switching control unit (48a) determines the gate signal (Gup,..., Gwn) based on the magnitude relationship between the voltage command signal (S1) that determines the output AC voltage and the carrier signal (C). Control the pulse width. The voltage command signal (S1) may be given from outside the control unit (48) or may be generated by the control unit (48).

 The first switching control unit (48a) outputs a timing signal (S2) indicating the switching timing in the first inverter circuit (45) to the second switching control unit (48b). As an example of the timing signal (S2), a gate signal (Gup, Gvp, Gwp) to be given to the switching element (Sup, Svp, Swp) of the upper arm can be considered.

  Similarly to the first switching control unit (48a), the second switching control unit (48b) generates gate signals (Gup,..., Gwn) to be applied to the gates of the switching elements (Sup,..., Swn). Control these on and off. The second switching control unit (48b) is also based on the magnitude relationship between the voltage command signal (S3) and the carrier signal (C) that determines the output AC voltage output from the second inverter circuit (46). Controls the pulse width of (Gup, ..., Gwn). This voltage command signal (S3) is a separate signal from the voltage command signal (S1) given to the first switching control unit (48a). Depending on the operating state of the refrigeration system (1), these voltage command signals (S1, S3) may indicate the same voltage, or may indicate different voltages. The voltage command signal (S3) may be given from the outside of the control unit (48) or may be generated by the control unit (48).

  The second switching control unit (48b) determines that the switching timing in the second inverter circuit (46) is at least once during one cycle of the carrier signal (C) based on the timing signal (S2). The switching timing in the second inverter circuit (46) is controlled so as to be synchronized with the switching timing in the first inverter circuit (45). That is, in this refrigeration apparatus (1), the first switching control unit (48a) outputs the timing signal (S2), and the second switching control unit (48b) uses the timing signal (S2) to generate the second inverter. By outputting a gate signal to the circuit (46), the switching timings of both inverter circuits (45, 46) are synchronized.

<Ground wire (49)>
Between the windings (Lu, Lv, Lw) of each phase of the motor (27) and the stator core (for example, casing) of the motor (27), as shown in FIG. Is formed. The ground wire (49) is a wiring for grounding one end of the capacitance (Co), and is provided in each motor (27).

<Coil (50)>
The coil (50) is provided for each motor (27). That is, in this example, there are two coils (50). In this embodiment, each coil (50) is obtained by winding a ground wire (49) connected to each motor (27) around a common ferrite core (51) (magnetic core) so as to be in phase with each other. is there. The coupling coefficient of the two coils (50) is preferably as close to 1 as possible.

<Operation of refrigeration system (1)>
In the refrigeration apparatus (1), one or both motors (27) are operated, and the refrigerant circulates in the refrigerant circuit (21) to perform a refrigeration cycle (specifically, for example, indoor cooling or heating). Is called. In this refrigeration cycle, the operating state (number of rotations) of each motor (27) is controlled according to the ability that the refrigeration apparatus (1) should exhibit. Specifically, inverter control is performed in the first and second inverter circuits (45, 46), respectively, and AC power corresponding to the required capacity is supplied to each motor (27).

<Inverter control in refrigeration system (1)>
In the inverter control, each switching control unit (48a, 48b) controls switching in each inverter circuit (45, 46). FIG. 4 is a diagram for explaining the waveforms of the gate signals (Gup, Gvp, Gwp) given to the gates of the switching elements (Sup, Svp, Swp) on the upper arm side in the inverter circuits (45, 46). In this figure, when the gate signal (Gup, Gvp, Gwp) is displayed at a high level, the switching element on the upper arm side corresponding to the signal is turned on, and the switching element on the lower arm side that is paired with it is turned on. Indicates that it is off. Conversely, when the gate signal (Gup, Gvp, Gwp) is displayed at a low level, the switching element on the upper arm side corresponding to the gate signal is off, and the switching element on the lower arm side that is paired with the switching element is on the lower arm side. Indicates that it is on. In the example of FIG. 4, the switching state of the first inverter circuit (45) is changed at t1, t2, t3, t5, t6, and t7 in one cycle of the carrier signal (C). As a result, in the first and second inverter circuits (45, 46), the common mode voltage changes six times during one cycle of the carrier signal (C).

  The pulse widths of the gate signals (Gup, Gvp, Gwp) given to the first and second inverter circuits (45, 46) are determined according to the magnitude of the current to be passed through each motor (27). Therefore, in this refrigeration system (1), each inverter circuit (45, 46) may be controlled so that the same current flows in both motors (27), or the refrigeration system (1) exhibits. Depending on the power, the motor (27) may be controlled so that different currents flow. FIG. 4 shows that the first and second switching control units (48a, 48b) control the first and second inverter circuits (45, 46) so that different currents flow through the motors (27). This is an example. In this example, a gate signal (Gup,..., Gwn) having a pulse width larger than that of the second inverter circuit (46) is given to the first inverter circuit (45).

<Synchronization of switching timing>
In the present embodiment, the first switching control unit (48a) outputs the timing signal (S2) to the second switching control unit (48b). Therefore, the second switching control unit (48b) can know the switching timing in the first inverter circuit (45). And a 2nd switching control part (48b) controls the switching timing in a 2nd inverter circuit (46) based on a timing signal (S2). In the example of FIG. 4, the second switching control unit (48b) generates the gate signal at the timing (t2) when the first switching control unit (48a) outputs the gate signal (Gvp) based on the timing signal (S2). (Gup) is output. That is, the switching timing of the first inverter circuit (45) and the second inverter circuit (46) is synchronized at t2. When the first and second inverter circuits (45, 46) are controlled to have the same output, the switching of both is performed in all six common mode voltage changes that occur during one cycle of the carrier signal (C). Will be synchronized.

<Common mode noise in refrigeration equipment (1)>
In the refrigeration apparatus (1), each motor (27) has a capacitance (Co) formed between a winding (not shown) and ground. When switching is performed in each inverter circuit (45, 46) in this state, a pulse is generated at the switching timing in the inverter circuit (45, 46) connected to the capacitance (Co) of each motor (27). Voltage (i.e., common mode voltage) is generated. Specifically, in each inverter circuit (45, 46), the common mode voltage changes six times during one cycle of the carrier signal (C), and as shown in FIG. 4, the capacitance of each motor (27). In (Co), a pulsed voltage that rises or falls at each switching timing is generated. As the common mode voltage changes sharply, a high-frequency current (hereinafter also referred to as a leakage current) flows through the capacitance (Co) as shown in FIG. Since each motor (27) is electrically insulated from the pipe (28) and the casing (20) as described above, the leakage current from each motor (27) is the so-called common mode noise. It flows to the ground through the coil (50) connected to the motor (27) and the ground wire (49).

  In this case, since the switching timing of each inverter circuit (45, 46) is synchronized at least once during one period of the carrier signal (C) as described above, in each inverter circuit (45, 46). The rising timings or falling timings of the common mode voltage are synchronized at least once in one cycle of the carrier signal (C). In the example shown in FIG. 4, the switching timing of the first and second inverter circuits (45, 46) is synchronized at t2, and the rising timing of the common mode voltage is synchronized at t2.

<< Effect in this embodiment >>
In this embodiment, since each coil (50) is wound around one ferrite core (51) in the same phase, when the switching timing is synchronized as described above, a magnetic flux in the same direction is generated in each coil (50). . As a result, the magnetic flux generated by one winding enters the other winding. When the magnetic flux enters in this way, the coil (50) functions as a coil having a larger inductance (L) than when the coil (50) is wound alone on the ferrite core (51). Thus, if a larger inductance (L) can be obtained, it is possible to reduce the level of common mode noise flowing into the ground wire (49) via the respective coils (50).

  The inventor of the present application verified the effect of reducing common mode noise by simulation. FIG. 6 is a circuit diagram modeling the power supply unit (4) and the motor (27) of the present embodiment. In this model, each motor (27) is represented by a coil of 500 μH and a resistance of 250Ω. Further, a capacitance (Co) having a capacitance of 1000 pF is provided as a capacitance (Co) between the motor (27) and the ground. The power supplies (60, 61) correspond to the first and second inverter circuits (45, 46), respectively.

  In this simulation, each inverter circuit (45, 46) is controlled so that the same current flows in both motors (27), and the same common mode voltage is generated by these inverter circuits (45, 46). Assumes that. FIG. 7 is a diagram showing a waveform of a common mode voltage generated from each power supply (60, 61) in this simulation circuit. In this model, the voltage between the motor (27) and the ground is detected by the voltmeter (62) as the common mode noise level.

  The inventor of the present application performed a simulation for each case where the coupling coefficient (K) of both coils (50) is 0 and 1 in the above model. The simulation in the case where the value of the coupling coefficient (K) is 0 corresponds to the case where the coil (50) is used independently, for example, by being wound around a separate ferrite core. The simulation when the value of the coupling coefficient (K) is 1 corresponds to the case where both coils (50) are wound in the same phase around the same ferrite core (51). In the actual coil, the coupling coefficient (K) is smaller than 1, but here, the simulation is performed with 1 which is an ideal value in terms of confirmation of the effect. Of course, in the design and manufacture of the power supply unit (4), it is preferable that the coupling coefficient (K) be as close to 1 as possible. FIG. 8 is a diagram illustrating a simulation result of the level of common mode noise in the above model. In FIG. 8, the level of common mode noise is shown in time series. As shown in the figure, when the coupling coefficient (K) is 1, it can be seen that the level of common mode noise is reduced. As described above, according to the present embodiment, common mode noise can be reduced. Therefore, for example, even if the noise filter (41) is shared by the power converters (42a, 42b), it is not necessary to increase the size of the noise filter (41).

<< Modification of Embodiment 1 >>
FIG. 9 is a block diagram illustrating a configuration of a power supply unit (70) according to a modification of the first embodiment. The power supply unit (70) is obtained by adding a detection unit (71) to the power supply unit (4) of the first embodiment and changing a part of the configuration of the second switching control unit (48b). .

  The detection unit (71) detects the rising timing of the leakage current flowing into each coil (50). Further, the second switching control unit (48b) of the present modification corrects the switching timing based on the timing signal (S2) so as to reduce the mutual deviation of the rising timing.

  For example, if there is impedance variation in the motor (27) or the wiring, the switching timing may be shifted, and the rising or falling timing of the common mode voltage may be shifted. On the other hand, in this modification, for example, the rise timing of the leakage current from the motor (27) driven by the second inverter circuit (46) is higher than the rise timing of the leakage current from the other motor (27). If it is early, the second inverter circuit (46) performs switching at a timing later than the timing indicated by the timing signal (S2). By correcting the switching timing in this way, each coil (50) is at least once in one cycle of the carrier signal (C) even if the impedance of the motor (27) or wiring varies as described above. ), The leakage current rising timing can be reliably synchronized. That is, in this modification, it is possible to reliably reduce the level of common mode noise even when there is a variation in the impedance of the motor (27) or wiring.

  The detection unit (71) may detect the falling timing of the leakage current. In this case, the second switching control unit (48b) corrects the switching timing based on the timing signal (S2) so as to reduce the mutual shift of the falling timing.

<< Embodiment 2 of the Invention >>
FIG. 10 is a block diagram showing a configuration of the power supply unit (80) according to the second embodiment of the present invention. The power supply unit (80) is different from the first embodiment in the configuration of the control unit.

  The control unit (81) of the present embodiment has a switching control unit (81a) common to the first and second inverter circuits (45, 46), and both inverters are used in the switching control unit (81a). Controls the switching of the circuits (45, 46). Specifically, the switching control unit (81a) outputs a common gate signal (Gup,..., Gwn) (switching control signal) to each inverter circuit (45, 46).

  Specifically, in the switching control unit (81a), a common voltage command signal (S4) is input to the first and second inverter circuits (45, 46). This voltage command signal (S4) is also a signal for determining the output AC voltage, and may be given from the outside of the control unit (81) or generated by the control unit (81). The switching control unit (81a) then uses the same gate for both the first and second inverter circuits (45, 46) based on the magnitude relationship between the voltage command signal (S4) and the carrier signal (C). Output signals (Gup, ..., Gwn). That is, the first and second inverter circuits (45, 46) of this embodiment perform switching at the same timing. Therefore, in this embodiment, both the first and second inverter circuits (45, 46) can be synchronized with respect to all six common mode voltage fluctuations performed during one cycle of the carrier signal (C). become. Thereby, in this embodiment, it becomes possible to reduce common mode noise more effectively.

<< Other Embodiments >>
In addition, the number of motors (compressors) shown in each of the above embodiments and modifications is an example. Furthermore, the present invention can be applied to a refrigeration apparatus including a large number of motors (compressors).

  The configuration of the power conversion device is also an example, and for example, a matrix converter or the like may be employed.

  The circuit configurations of the inverter circuits (45, 46) and the converter circuits (43, 44) are also illustrated. Similarly, the inverter control method performed in each inverter circuit (45, 46) is also an example. The present invention can be applied to other types of inverter control.

  The present invention is useful as a refrigeration apparatus having a plurality of compressors driven by a motor.

DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 21 Refrigerant circuit 22 Compressor 27 Motor 28 Piping 42a 1st power converter (power converter)
42b 2nd power converter device (power converter device)
48 control unit 48a first switching control unit 48b second switching control unit 50 coil 51 ferrite core (magnetic core)
71 Detection unit 81 Control unit 81a Switching control unit S2 Timing signal

Claims (5)

A refrigeration apparatus comprising a plurality of compressors (22) having a motor (27), and performing a refrigeration cycle by circulating refrigerant in a refrigerant circuit (21),
Power converters (42a, 42b) that are provided for each motor (27), switch the input power to convert it into output power, and supply the output power to the corresponding motor (27),
A control unit (48) for controlling the switching in each power converter (42a, 42b) in synchronization with the periodically changing carrier signal (C);
A coil (50) provided for each motor (27) and grounding a capacitance (Co) formed in the corresponding motor (27);
A magnetic core (51) in which each coil (50) is wound in the same phase;
With
The control unit (48) is configured such that, between the respective power conversion devices (42a, 42b), rising timings or falling timings of the common mode voltage due to the switching are at least during one cycle of the carrier signal (C). The refrigeration apparatus, wherein the switching timing is controlled so as to be synchronized once. The refrigeration apparatus of claim 1,
The control unit (48)
A first switching control unit (48a) that controls switching in any one of the power conversion devices (42a) and outputs a timing signal (S2) indicating the timing of the switching;
Using the timing signal (S2), a second switching control unit (48b) for controlling switching timing in another power converter (42b);
A refrigeration apparatus comprising: The refrigeration apparatus of claim 2,
It has a detection unit (71) that detects the current change timing at which the current flowing into each coil (50) rises or falls,
The refrigeration apparatus, wherein the second switching control unit (48b) corrects the switching timing so that a shift in the current change timing is reduced. The refrigeration apparatus of claim 1,
The control unit (81) outputs a common control signal (Gup,..., Gwn) to each power converter (42a, 42b) to control switching in each power converter (42a, 42b). A refrigeration apparatus comprising the portion (81a). In any one freezing apparatus in Claim 1-4,
Each motor (27) is electrically insulated from piping (28) which constitutes the refrigerant circuit (21).

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