Method for drying inside of hermetic compressor and method for manufacturing hermetic compressor

Abstract

To provide a method for drying the inside of a hermetic compressor capable of accurately acquiring temperature of each winding phase of a stator winding during energization, sufficiently improving temperature of the stator winding, and shortening time required for a drying process of the hermetic compressor.SOLUTION: With a method for drying the inside of a hermetic compressor, a rotary electric machine accommodated in the hermetic compressor dries the inside of the hermetic compressor by selectively switching connection between each terminal of each winding phase of a stator winding configured by two or more winding phases and an external power supply provided outside of the hermetic compressor. The method includes: a winding phase information acquisition step of acquiring winding phase information including at least one of winding phase temperature of each winding phase of the stator winding or a winding phase resistance value of each winding phase independently of other phases for each phase; and an energization switching step of selectively switching connection between each terminal of each winding phase and an external power supply in accordance with the acquired winding phase information to perform energization.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for drying the inside of a hermetic compressor and a method for manufacturing a hermetic compressor. [Background technology]

[0002] In a hermetic compressor, if moisture remains inside the compressor, the moisture reacts with the refrigerant to generate chlorine, which then freezes in the refrigeration cycle, reducing the compressor's performance. To prevent this, a drying process is performed in the manufacturing process of a hermetic compressor after the assembly process, in which the inside of the hermetic compressor is dried.

[0003] One method for drying the inside of a hermetic compressor is to pass current through the stator winding of a rotating electric machine housed inside the hermetic compressor. The Joule heat generated by passing current through the stator winding raises the temperature of the rotating electric machine and the compressor, while simultaneously reducing the pressure inside the hermetic compressor, thereby drying the inside of the hermetic compressor. Note that moisture is particularly likely to remain in the insulating coating applied to the stator winding and the varnish that secures the stator winding. The above-mentioned method directly heats the winding, making it possible to efficiently dry the inside of the hermetic compressor.

[0004] Patent Document 1 discloses a method for drying the inside of a hermetic compressor, which efficiently dries the inside of the hermetic compressor by selectively switching the connection between the stator winding of a rotating electric machine housed inside the hermetic compressor and an external power source to pass electricity.

[0005] When using the above-described method of energizing the stator winding, it is necessary to pay attention to the heat resistance temperature of the insulating coating applied to the stator winding. This is because the heat resistance temperature of each insulating coating is determined depending on the type of insulating coating, and the insulating coating deteriorates if the heat resistance temperature is exceeded. For this reason, when drying the inside of a hermetic compressor using the above-described method, it is necessary to ensure that the temperature of the energized stator winding does not exceed the heat resistance temperature.

[0006] However, hermetic compressors often lack a temperature sensor for measuring the stator winding temperature. In such cases, the stator winding temperature must be measured indirectly. One method for indirectly measuring the temperature is to use the winding resistance. This method involves measuring the resistance of the stator winding during the drying process, and then determining the temperature of the stator winding during the current-carrying period from the change in the stator winding resistance from the resistance before the current was applied. The stator windings of the rotating electric machines housed inside hermetic compressors are typically three-phase, and there are two types of connection methods: Y-connection and Delta-connection. In the case of a Y-connection, there is generally no connection terminal at the neutral point. Therefore, when current is applied to the stator winding, it is either a two-phase series or three-phase series-parallel connection; it is not possible to apply current to only one phase. In the case of a Delta-connection, it is a three-phase series-parallel connection; it is also impossible to apply current to only one phase. Therefore, the stator winding resistance can only be measured as a two-phase series or three-phase series-parallel connection. However, since the winding resistance of each winding phase of the stator winding varies, it is not possible to accurately measure the resistance of each winding phase of the stator winding, and therefore it is not possible to accurately obtain the temperature of each winding phase of the stator winding. In other words, with the above-mentioned temperature obtaining method, it is necessary to pass current through the stator winding under conditions that allow a margin above the heat-resistant temperature. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3869132 Summary of the Invention [Problem to be solved by the invention]

[0008] In the method for drying the inside of a hermetic compressor described in Patent Document 1, when a conventional method for acquiring the temperature of a stator winding is used, it is not possible to accurately acquire the temperature of each winding phase of the stator winding while it is energized, so it is necessary to energize the stator winding under conditions that allow a margin above the heat-resistant temperature. As a result, it is not possible to sufficiently increase the temperature of the stator winding, which causes the problem of the drying process taking a long time.

[0009] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a method for drying the inside of a hermetic compressor that can accurately obtain the temperature of each winding phase of a current-carrying stator winding, sufficiently increase the temperature of the stator winding, and shorten the time required for the drying process of the hermetic compressor. [Means for solving the problem]

[0010] The method for drying the inside of a hermetic compressor according to the present disclosure is a method for drying the inside of a hermetic compressor by selectively switching the connection between each terminal of each winding phase of a stator winding, which is composed of two or more winding phases of a rotating electric machine housed inside the hermetic compressor, and an external power source provided outside the hermetic compressor to pass current through the connection, and includes a winding phase information acquisition step for acquiring winding phase information for each phase independently of other phases, the winding phase information including at least one of the winding phase temperature of each winding phase of the stator winding or the winding phase resistance value of each winding phase, and a current switching step for selectively switching the connection between each terminal of each winding phase and the external power source to pass current through the connection in accordance with the acquired winding phase information. [Effects of the Invention]

[0011] According to the method for drying the inside of a hermetic compressor of the present disclosure, the temperature of each winding phase of the stator winding while it is energized can be accurately obtained, thereby making it possible to sufficiently increase the temperature of the stator winding and shorten the time required for the drying process of the hermetic compressor. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing the configuration of a drying device inside a hermetic compressor according to a first embodiment. [Figure 2] 3 is a schematic diagram showing a switching section of a drying device inside the hermetic compressor according to the first embodiment. FIG. [Figure 3] 2 is a schematic diagram showing an example of a current path in a drying device inside the hermetic compressor according to the first embodiment. FIG. [Figure 4]2 is a schematic diagram showing an example of a current path in a drying device inside the hermetic compressor according to the first embodiment. FIG. [Figure 5] 3 is a schematic diagram showing an example of the configuration of a winding phase information acquisition unit of the drying device inside the hermetic compressor according to the first embodiment. FIG. [Figure 6] 4 is a flowchart showing an example of the procedure of a method for drying the inside of the hermetic compressor according to the first embodiment. [Figure 7] 1 is a schematic diagram showing a stator winding inside the hermetic compressor according to the first embodiment. [Figure 8] 4 is a graph showing changes in winding phase temperature of each winding phase of the stator winding in the method for drying the inside of the hermetic compressor according to the first embodiment. [Figure 9] FIG. 4 is a schematic diagram showing a stator winding inside a hermetic compressor according to a modified example of the first embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a drying device inside a hermetic compressor according to a second embodiment. [Figure 11] FIG. 10 is a schematic diagram showing the configuration of a drying device inside a hermetic compressor according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiment 1 A method for drying the inside of a hermetic compressor according to embodiment 1 will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a drying device 100 inside a hermetic compressor that realizes the method for drying the inside of a hermetic compressor according to embodiment 1. First, the drying device 100 inside a hermetic compressor will be described with reference to Fig. 1.

[0014] As shown in FIG. 1, the drying device 100 includes an external power supply 1, a switching unit 2, a winding phase information acquisition unit 3, a control unit 4, and a vacuum pump 50.

[0015] 1, the drying device 100 is connected to a stator winding 63 of a stator 62 of a rotating electric machine 61 housed inside a hermetic compressor 60. Details will be described later.

[0016] First, the stator winding 63 connected to the drying apparatus 100 will be described. The stator winding 63 is composed of two or more winding phases. In this embodiment, the stator winding 63 is composed of three winding phases. Specifically, the stator winding 63 is composed of three winding phases: winding phase U, winding phase V, and winding phase W. Terminals of each winding phase are drawn to the outside of the hermetic compressor 60 via airtight terminals 65 provided in a casing 64 of the hermetic compressor 60. As shown in FIG. 1 , in this embodiment, the three-phase windings of the stator winding 63 are connected in a Y-connection. In the case of a Y-connection, a connection terminal is often not provided at the neutral point of the Y-connection. In the following description, it is assumed that the three-phase windings of the stator winding 63 are connected in a Y-connection and that a connection terminal is not provided at the neutral point of the Y-connection.

[0017] Next, the detailed structure of the drying device 100 will be described. The external power supply 1 is provided outside the hermetic compressor 60. The external power supply 1 has a function of increasing the temperature of each winding phase of the stator winding 63 by using Joule heat. Furthermore, in this embodiment, the external power supply 1 has a function of passing a current through the stator winding 63 in order to measure the inter-terminal resistance value, which will be described later. Note that it is desirable to use a DC power supply as the external power supply 1 so as not to be affected by inductance when measuring the inter-terminal resistance value, which will be described later.

[0018] The switching unit 2 is disposed between the external power source 1 and the stator winding 63. The switching unit 2 selectively switches the connection between each terminal of each winding phase of the stator winding 63 and the external power source 1 to allow current to flow. As shown in FIG. 1 , in this embodiment, the switching unit 2 selectively switches the connection between each terminal of winding phase U, winding phase V, and winding phase W and the external power source 1 to allow current to flow. FIG. 2 shows an example of the internal wiring of the switching unit 2. In this embodiment, the switching unit 2 is configured as a three-phase H-bridge circuit, with an input terminal 22 connected to the external power source 1 and a three-phase output terminal 23 connected to each terminal of each winding phase of the stator winding 63. By switching the switch 21 of the switching unit 2, the current output from the external power source 1 can be directed to any current path. In this embodiment, current can be passed through a two-phase series circuit or a three-phase series-parallel circuit. Examples of current paths are shown in FIGS. 3 and 4. 3 shows a two-phase series configuration in which current is applied to winding phase U and winding phase V, while FIG. 4 shows a three-phase series-parallel configuration in which winding phase V and winding phase W are connected in parallel and winding phase U is connected in series. Note that in this embodiment, mechanical switches 21 are used as the switches 21 that make up the H-bridge, but semiconductor elements such as FETs and IGBTs may also be used as the switches 21. Note that each switch 21 operates in response to a command from the control unit 4.

[0019] The winding phase information acquisition unit 3 acquires winding phase information for each phase, including at least one of the temperature and resistance of each winding phase of the stator winding 63, independently of the other phases. In the following description, the temperature of each winding phase will be referred to as the "winding phase temperature" of that winding phase, and the resistance of that winding phase will be referred to as the "winding phase resistance" of that winding phase. As shown in FIG. 1, in this embodiment, the winding phase information acquisition unit 3 is built into the control unit 4, but it may also be provided outside the control unit 4. In this embodiment, both the winding phase temperature and the winding phase resistance of each winding phase are acquired as the winding phase information. FIG. 5 shows the winding phase information acquisition unit 3 of this embodiment. 5, in order to acquire the winding phase resistance values, the winding phase information acquisition unit 3 of this embodiment includes an inter-terminal resistance value acquisition unit 31 that acquires the inter-terminal resistance values ​​between each terminal of each winding phase, and a winding phase resistance value calculation unit 32 that calculates the winding phase resistance value of each winding phase independently of the other phases from the inter-terminal resistance values ​​between each terminal acquired from the inter-terminal resistance value acquisition unit 31. Also, as shown in FIG. 5, the winding phase information acquisition unit 3 of this embodiment further includes a winding phase temperature calculation unit 33 that calculates the winding phase temperature of each winding phase from the winding phase resistance value of each winding phase calculated by the winding phase resistance value calculation unit 32. Details will be described later.

[0020] As shown in FIG. 5 , the terminal-to-terminal resistance value acquiring unit 31 of this embodiment includes a current value measuring unit 311 that measures the current value of the current output from the external power supply 1 and a terminal-to-terminal voltage value measuring unit 312 that measures the terminal-to-terminal voltage value between each terminal of each winding phase in order to acquire the terminal-to-terminal resistance value. The terminal-to-terminal resistance value acquiring unit 31 acquires the terminal-to-terminal resistance value between each terminal of each winding phase from the current value measured by the current value measuring unit 311 and the terminal voltage value measured by the terminal voltage value measuring unit 312. In this embodiment, as shown in FIG. 1 , the current value measuring unit 311 is disposed between the external power supply 1 and the switching unit 2. The current value measuring unit 311 may be independent or may be built into the external power supply 1. The current value measuring unit 311 may also be, for example, an ammeter. Furthermore, a terminal-to-terminal voltage value measuring unit 312 that measures the terminal voltage value is connected to each terminal of each winding phase. 1, a plurality of inter-terminal voltage value measuring units 312 may be individually arranged between the terminals of each winding phase to measure the inter-terminal voltage value between each terminal, or only one inter-terminal voltage value measuring unit 312 may be arranged and a switching circuit such as the switching unit 2 may be used to switch the connection between any terminals to measure the inter-terminal voltage value between each terminal. As described above, the inter-terminal resistance value acquiring unit 31 of this embodiment can acquire the inter-terminal resistance value using the measurement results measured by the inter-terminal voltage value measuring unit 312 and the current value measuring unit 311.

[0021] The control unit 4 controls the switching of the switching unit 2 and the ON / OFF, voltage, and current of the external power source 1. First, the switching control of the switching unit 2 will be described. As described above, the control unit 4 controls the switching of the switching unit 2 by operating each switch 21 of the switching unit 2 in response to a command from the control unit 4. The control unit 4 controls the switch 21 of the switching unit 2 in accordance with winding phase information including at least one of the winding phase temperature and the winding phase resistance of each winding phase, which is acquired from the winding phase information acquisition unit 3. Furthermore, in this embodiment, the control unit 4 controls the switch 21 of the switching unit 2 to pass current through an arbitrary current path in order to measure the inter-terminal resistance. A detailed control method will be described later. Next, the control of the external power source 1 will be described. The control unit 4 controls the current to each winding phase of the stator winding 63 by controlling the ON / OFF, voltage, and current of the external power source 1. A detailed control method will be described later. The control unit 4 may have a CPU 41 that executes the above control, and may further have a memory 42 that stores a control program and transfers the stored control program to the CPU 41 when the above control is executed by the CPU 41. The control unit 4 may also control the start and stop of operation of a vacuum pump 50, which will be described later.

[0022] The vacuum pump 50 is connected to a refrigerant connection pipe 66 provided in a casing 64 of the hermetic compressor 60. The vacuum pump 50 lowers the air pressure inside the hermetic compressor 60 and reduces the saturated vapor pressure while the stator winding 63 is energized. This is called vacuuming the inside of the hermetic compressor. This promotes the removal of moisture inside the hermetic compressor 60.

[0023] As described above, the drying device 100 inside the hermetic compressor of this embodiment is configured.

[0024] Next, an example of a method for drying the inside of a hermetic compressor using the drying device 100 for the inside of the hermetic compressor will be described with reference to FIG. 6. FIG. 6 is a flowchart showing an example of the steps of the method for drying the inside of a hermetic compressor according to this embodiment. The method for drying the inside of a hermetic compressor includes a winding phase information acquisition process and a current switching process. The winding phase information acquisition process of this embodiment includes a terminal-to-terminal resistance acquisition process, a winding phase resistance calculation process, and a winding phase temperature acquisition process. The terminal-to-terminal resistance acquisition process of this embodiment also includes a current value measurement process and a terminal-to-terminal voltage value measurement process. Note that the process of evacuating the inside of the hermetic compressor using a vacuum pump is conventional and will not be described here.

[0025] In step 1, a certain winding phase temperature of the stator winding 63 is set as a reference temperature, and an initial value of the winding phase resistance value of each winding phase of the stator winding 63 at the reference temperature is acquired. Step 1 is a winding phase initial resistance value acquisition step. In this embodiment, the winding phase temperature of each winding phase of the stator winding 63 before current is applied is set as the reference temperature. For example, the initial values ​​of the winding phase resistance values ​​may be acquired by measuring the winding phase resistance values ​​of each winding phase of the stator winding 63 before current is applied before the hermetic compressor is assembled. The initial values ​​of the winding phase resistance values ​​of each winding phase acquired in the winding phase initial resistance value acquisition step are used in the winding phase temperature calculation step, which will be described later.

[0026] In step 2, the control unit 4 turns on the external power supply 1, thereby starting the supply of current to the stator winding 63. In this embodiment, the current is supplied in two phases in series as shown in FIG.

[0027] In step 3, the control unit 4 determines whether a predetermined time has elapsed since the start of power supply. The predetermined time is set by estimating in advance the time required to remove moisture from inside the hermetic compressor 60 for each model of the hermetic compressor 60. Alternatively, a sensor may be provided to detect the amount of moisture inside the hermetic compressor 60, and in step 3 the control unit 4 may determine whether the amount of moisture inside the hermetic compressor 60 is equal to or less than a certain value.

[0028] If it is determined in step 3 that the time since the start of energization has not yet elapsed the predetermined time, the external power supply 1 is left ON, and energization to the stator winding 63 continues, and the process proceeds to step 4. In step 4, the inter-terminal resistance values ​​are acquired and the winding phase resistance values ​​of each winding phase are calculated. Step 4 includes an inter-terminal resistance value acquisition step and a winding phase resistance value calculation step. First, in the inter-terminal resistance value acquisition step, the inter-terminal resistance value acquisition unit 31 acquires the inter-terminal resistance values ​​between each terminal of each winding phase, which is a combined resistance value composed of the winding phase resistance values ​​of two or more phases. In this embodiment, to acquire the inter-terminal resistance values, the current value measurement step measures the current value of the current output from the external power supply 1 by the current value measurement unit 311, and the inter-terminal voltage value measurement step measures the inter-terminal voltage value between each terminal of each winding phase by the terminal voltage value measurement unit 312. Next, the inter-terminal resistance values ​​between each terminal of each winding phase are acquired from the current value measured in the current value measurement step and the inter-terminal voltage value measured in the terminal voltage value measurement step. In this embodiment, the winding phases of the stator winding 63 are connected in a Y-connection, forming a two-phase serial current path. Therefore, in the inter-terminal resistance value acquisition process, the two-phase serial terminal resistance value is acquired. In other words, a combined resistance value consisting of the two-phase winding phase resistance values ​​is acquired. Here, the control unit 4 controls the ON / OFF switching of the switch 21 of the switching unit 2 in a short time, thereby sequentially changing the two-phase serial current path and measuring the inter-terminal voltage values ​​between the UV terminals, VW terminals, and WU terminals. Therefore, the inter-terminal resistance values ​​between the UV terminals, VW terminals, and WU terminals can be acquired in a short time from the current values ​​and the inter-terminal voltage values ​​between each terminal.

[0029] Next, in the winding phase resistance value calculation step, the winding phase resistance value calculation unit 32 calculates the winding phase resistance value of each winding phase independently from the other phases from the inter-terminal resistance values ​​between each terminal acquired in the inter-terminal resistance value acquisition step. FIG. 7 shows the stator winding 63 inside the hermetic compressor 60 of this embodiment. As shown in FIG. 7, the inter-terminal resistance values ​​between the U, V, and WU terminals acquired by the inter-terminal resistance value acquisition unit 31 are denoted as Ruv, Rvw, and Rwu, respectively. Meanwhile, the winding phase resistance values ​​of the winding phase U, winding phase V, and winding phase W are denoted as Ru, Rv, and Rw, respectively. In the case of a Y-connection, the inter-terminal resistance values ​​between each terminal can be expressed by the following equations. As shown in the following equations, the inter-terminal resistance value between each terminal is a combined resistance value composed of the winding phase resistance values ​​of the two phases. Ruv=Ru+Rv Rvw=Rv+Rw Rwu=Rw+Ru By solving the above simultaneous equations, the winding phase resistance values ​​Ru, Rv, and Rw of each winding phase can be obtained.

[0030] In step 5, the winding phase temperature of each winding phase is calculated using the initial winding phase resistance value acquired in the winding phase initial resistance value acquisition step in step 1. Step 5 includes a winding phase temperature calculation step. In the winding phase temperature calculation step, the winding phase temperature calculation unit 33 calculates the winding phase temperature of each winding phase of the stator winding 63 for each phase independently of the other phases. Copper or aluminum is generally used as the conductor that constitutes the stator winding 63, and the resistance temperature coefficient of the conductor is determined depending on the material. The winding phase temperature of each winding phase is calculated using the temperature coefficient of the conductor. The change in the winding phase resistance can be calculated by comparing the initial winding phase resistance value of each winding phase at the reference temperature acquired in step 1 with the winding phase resistance value calculated in step 5. The temperature change from the reference temperature can be determined using the calculated change in the winding phase resistance value and the temperature coefficient of the conductor, and the winding phase temperature of the winding phase during current flow can be calculated from the temperature change. If the winding phase temperature of each winding phase before the start of energization is taken as the reference temperature, the temperature change amount from the winding phase temperature of each winding phase before the start of energization can be calculated. Therefore, it is desirable to obtain the initial values ​​of the winding phase temperatures before the start of energization in advance, along with the initial values ​​of the winding phase resistances before the start of energization in step 1.

[0031] The winding phase information acquisition process, including the inter-terminal resistance value acquisition process, the winding phase resistance value calculation process, and the winding phase temperature calculation process, are performed as needed while current is being supplied to the stator winding 63. This allows the winding phase resistance value and winding phase temperature of each winding phase to be accurately determined in real time.

[0032] In steps 6 and 7, it is determined whether the winding phase temperature of a certain phase has reached a threshold value, and if it has reached the threshold value, current is switched so that current is passed to the two phases with lower winding phase temperatures. If the threshold value has not been reached, the process returns to step 3 and current continues to be passed through the same current path. Steps 6 and 7 comprise a current switching step. In this current switching step, the control unit 4 selectively switches the connections between each terminal of each winding phase and the external power supply 1 to pass current, depending on the winding phase temperature of each winding phase acquired in the winding phase information acquisition step, which includes the winding phase temperature calculation step.

[0033] In this embodiment, the current switching process is performed by conducting two-phase series current. The controller 4 compares the winding phase temperature of each winding phase acquired in the winding phase information acquisition process, which includes the winding phase temperature calculation process, with a threshold value set based on the heat resistance temperature of the insulating coating applied to the stator winding 63. Based on the comparison result, the controller 4 selectively switches the connections between the terminals of each winding phase and the external power source 1 to conduct current. Specifically, the controller 4 selectively switches the connections between the terminals of each winding phase and the external power source 1 to conduct current to one winding phase that has reached the threshold value set based on the heat resistance temperature. In other words, the controller 4 selectively switches the connections between the terminals of each winding phase and the external power source 1 to conduct current to the two winding phases with lower winding phase temperatures. FIG. 8 shows the change in winding phase temperature of each winding phase after the start of current conduction when the current switching process is performed. In FIG. 8, the winding phase U is indicated by a solid line, the winding phase V by a dashed line, and the winding phase W by a dashed line. It should be noted that time 0 to T1 is UV series current application, time T1 to T2 is VW series current application, time T2 to T3 is UW series current application, and time T3 to T4 is UV series current application.

[0034] As shown in Figure 8, when current begins to flow in UV series, the winding phase temperatures of winding phase U and winding phase V rise, but differences in the temperature rise between the two phases occur due to variations in winding phase resistance values ​​and variations in thermal resistance of the heat dissipation paths. Here, it is assumed that winding phase U rises in temperature more easily. At this time, no current is flowing through winding phase W, but the entire stator winding 63 is heated by the current flow through winding phases U and V, which causes the winding phase temperature of winding phase W to also rise. Furthermore, if the rotating electric machine 61 has distributed windings, the winding phase temperatures also rise due to heat transfer between the winding phases at the coil ends where the winding phases overlap.

[0035] As shown in FIG. 8, when the winding phase temperature of winding phase U reaches the threshold value set based on the heat-resistant temperature at time T1, the control unit 4 controls the switching unit 2 to switch the current path from UV series to VW series. That is, the current path is switched to stop the current flow to winding phase U, which has reached the threshold value set based on the heat-resistant temperature. When the current path is switched to VW series, the winding phase temperatures of winding phases V and W rise, and the winding phase temperature of winding phase U gradually decreases. Next, when the winding phase temperature of winding phase V reaches the threshold value set based on the heat-resistant temperature at time T2, the control unit 4 controls the switching unit 2 to switch the current path from VW series to WU series. That is, the current path is switched to stop the current flow to winding phase V, which has reached the threshold value set based on the heat-resistant temperature. Thereafter, by switching the switching unit 2 so as to stop the current supply to one of the winding phases that has reached a threshold value set based on the heat resistance temperature, it is possible to prevent the current supply to the stator winding 63 from being interrupted and to prevent the winding phase temperature of each winding phase from exceeding the upper limit.

[0036] The winding phase information acquisition process, including the inter-terminal resistance acquisition process, winding phase resistance calculation process, and winding phase temperature calculation process, and the current switching process are performed until it is determined in step 3 that a predetermined time has elapsed since the start of current supply. When the control unit 4 determines in step 3 that the predetermined time has elapsed since the start of current supply, the control unit 4 turns off the external power supply 1. This stops the supply of current to the stator winding 63, and the drying of the inside of the hermetic compressor is completed.

[0037] The inside of the hermetic compressor 60 is dried using the method for drying the inside of the hermetic compressor described above. According to the method for drying the inside of the hermetic compressor of this embodiment, the winding phase resistance value and the winding phase temperature of each winding phase of the energized stator winding 63 can be obtained for each phase independently of the other phases. Therefore, even if there is variation in the winding phase temperatures of the winding phases of the stator winding 63, the winding phase temperature of each winding phase can be accurately determined. This makes it possible to sufficiently increase the temperature of the stator winding 63 and shorten the time required for the drying process of the hermetic compressor 60.

[0038] Furthermore, in a drying method such as the drying method of this embodiment, in which the temperature of the stator winding 63 is increased by passing current through the stator winding 63 inside the hermetic compressor 60, there is an upper limit to the current value that can be passed depending on the conductor diameter of the winding, so it is effective to reduce the time during which current is stopped in order to quickly increase the temperature of the stator winding 63. According to the drying method of the inside of a hermetic compressor of this embodiment, the winding phase temperature of each winding phase can be accurately determined, so that switching control of the switching unit 2 can be performed more appropriately than in the prior art. Furthermore, switching control of the switching unit 2 can be performed without interrupting the passage of current to the entire stator winding 63, so that the time required for the drying process of the hermetic compressor 60 can be further reduced.

[0039] In the above description, the inter-terminal resistance value acquisition process includes a current value measurement process and a terminal voltage value measurement process, and the inter-terminal resistance value between each terminal is acquired from the current value output from the external power supply 1 and the inter-terminal voltage value between each terminal. However, the current value measurement process and the inter-terminal voltage value measurement process may be omitted, and the inter-terminal resistance value may be acquired directly. For example, a resistance meter may be used to directly acquire the inter-terminal resistance value. The inter-terminal resistance value between each terminal can be acquired by temporarily stopping the supply of current to the stator winding 63 and using the resistance meter during this period. Note that, because the time for temporarily stopping the supply of current to the stator winding 63 is very short, even when the inter-terminal resistance value is acquired using the resistance meter, the time required for the drying process of the hermetic compressor 60 can be shortened compared to the prior art.

[0040] In the above description, the winding phase information acquisition process includes a terminal-to-terminal resistance acquisition process, a winding phase resistance calculation process, and a winding phase temperature calculation process. The winding phase resistance of each winding phase of the stator winding 63 is calculated, and the winding phase temperature of each winding phase is calculated from the calculated winding phase resistance. However, it is sufficient to acquire at least one piece of winding phase information, either the winding phase temperature or the winding phase resistance. That is, the winding phase information acquisition process may omit any of the terminal-to-terminal resistance acquisition process, the winding phase resistance calculation process, or the winding phase temperature calculation process. For example, the terminal-to-terminal resistance acquisition process and the winding phase resistance calculation process may be omitted, and the winding phase temperature may be acquired directly. For example, to directly acquire the winding phase temperature, a temperature sensor 71 may be provided for each winding phase. This allows the winding phase temperature of each winding phase to be directly acquired independently of the other phases.

[0041] In the above description, the current switching step is performed by selectively switching the connections between the terminals of each winding phase and the external power source 1 so as to stop current flow through one of the winding phases whose winding phase temperature has reached a threshold value set based on the heat-resistant temperature. However, current may be passed through a three-phase series-parallel configuration as shown in Fig. 4, and the control unit 4 may selectively switch the connections between the terminals of each winding phase and the external power source 1 so as to suppress the value of current flowing through one of the winding phases whose winding phase temperature has reached a threshold value set based on the heat-resistant temperature. For example, as shown in Fig. 4, when a three-phase series-parallel current path is formed in which winding phase V and winding phase W are connected in parallel and winding phase U are connected in series, and the winding phase temperature of winding phase U reaches a threshold value set based on the heat-resistant temperature, the switching unit 2 may switch the current path to a three-phase series-parallel current path in which winding phase U is connected in parallel and winding phase W is connected in series. This makes it possible to suppress the value of the current flowing through winding phase U. Furthermore, current may be passed through a combination of two-phase series current paths and three-phase series-parallel current paths as appropriate depending on the winding phase temperature of each winding phase.

[0042] In the above description, the control unit 4 selectively switches the connection between each terminal of each winding phase and the external power source 1 to energize the winding phase in accordance with the winding phase temperature of each winding phase calculated in the winding phase temperature calculation step. However, the winding phase temperature calculation step may be omitted, and the control unit 4 may selectively switch the connection between each terminal of each winding phase and the external power source 1 to energize the winding phase in accordance with the winding phase resistance calculated in the winding phase resistance calculation step. For example, the winding phase resistance of each winding phase may be compared with a threshold value set based on the heat-resistant temperature of the insulating coating applied to the stator winding 63, and the connection between each terminal of each winding phase and the external power source 1 may be selectively switched to energize the winding phase. In this case, the threshold value may be set based on the winding phase resistance at the heat-resistant temperature, and the winding phase resistance value during energization may be compared with the set threshold value to perform energization switching in the same manner as when the threshold value is set based on the winding phase temperature.

[0043] In the above description, the energization switching step compares the winding phase information acquired in the winding phase information acquisition step with a threshold value set based on the heat resistance temperature of the stator winding 63, and selectively switches the connection between each terminal of each winding phase and the external power source 1 to energize the stator winding 63. However, energization may also be performed by selectively switching the connection between each terminal of each winding phase and the external power source 1 so as to increase the value of current supplied to a winding phase having a lower value of winding phase information. For example, a lower limit threshold different from the upper limit threshold set based on the heat resistance temperature may be set, and energization may be performed by selectively switching the connection between each terminal of each winding phase and the external power source 1 so as to increase the value of current supplied to a winding phase having a value of winding phase information that has reached the lower limit threshold.

[0044] In the above description, the energization switching step selectively switches the connection between each terminal of each winding phase and the external power supply 1 to energize the winding phase in accordance with the winding phase information including at least one of the winding phase temperature and the winding phase resistance value of each winding phase acquired in the winding phase information acquisition step. However, the connection between each terminal of each winding phase and the external power supply 1 may be selectively switched to energize the winding phase in accordance with the amount of change in the winding phase temperature and the winding phase resistance value, rather than the absolute values ​​of the winding phase temperature and the winding phase resistance value. In this case, the threshold value used for the switching control of the switching unit 2 in the energization switching step may also be set to the value of the amount of change in the winding phase temperature and the winding phase resistance value.

[0045] In the above-described winding phase initial resistance value obtaining step of this embodiment, the winding phase temperature of each winding phase of the stator winding 63 before current is applied is used as a reference temperature, and the winding phase resistance value of each winding phase of the stator winding 63 before current is applied is measured in advance before the hermetic compressor is assembled to obtain the initial value of the winding phase resistance value. However, as in the inter-terminal resistance value obtaining step and the winding phase resistance value calculating step described above, a method may be used in which the control unit 4 controls the ON / OFF switching of the switch 21 of the switching unit 2 in a short time to sequentially change the two-phase series current path, measure the inter-terminal voltage value between each terminal, obtain the inter-terminal resistance value between each terminal from the current value and the inter-terminal voltage value between each terminal, and calculate the winding phase resistance value of each winding phase from the inter-terminal resistance value between each terminal independently of the other phases. Therefore, in the winding phase initial resistance value acquisition process, the winding phase temperature of each winding phase of the stator winding 63 immediately after the start of current flow may be used as the reference temperature, and the winding phase resistance value of each winding phase of the stator winding 63 immediately after the start of current flow may be used as the initial value of the winding phase resistance value of each winding phase of the stator winding 63.

[0046] Furthermore, in the method for drying the inside of the hermetic compressor of this embodiment, Joule heat generated by energizing the stator winding 63 is used as the heat source, but a heat source from outside the hermetic compressor 60 may also be used in addition to this. For example, a contact heater may be placed in contact with the outside of the hermetic compressor 60, infrared rays may be irradiated from the outside of the hermetic compressor 60, or the hermetic compressor 60 may be placed in a heating furnace. This makes it possible to further heat the inside of the hermetic compressor 60, thereby shortening the time required for the process of drying the inside of the hermetic compressor.

[0047] Next, a method for manufacturing the hermetic compressor 60 including a drying process using a method for drying the inside of the hermetic compressor will be described. The method for manufacturing the hermetic compressor 60 includes an assembly process, a drying process, and a lubricating oil filling process.

[0048] In the assembly process, the hermetic compressor 60 is assembled. The assembly process includes a welding process for the casing 64 of the hermetic compressor 60. Various inspection processes are carried out before the drying process.

[0049] In the drying step, the inside of the assembled hermetic compressor 60 is dried. The inside of the hermetic compressor 60 is dried using the method for drying the inside of the hermetic compressor described above.

[0050] In the lubricating oil filling step, lubricating oil is filled into the dried hermetic compressor 60. Specifically, the compression mechanism, bearings, and the like inside the hermetic compressor 60 are filled with lubricating oil.

[0051] Generally, the hermetic compressor 60 is not filled with lubricating oil during the drying process. One example of a drying method for the drying process is to continuously drive the rotating electric machine 61 at high speed to dry the interior of the hermetic compressor 60. This drying method can increase the winding phase temperature of each winding phase while also reducing the temperature difference between the winding phases. However, as described above, since the hermetic compressor 60 is not filled with lubricating oil during the drying process, using the drying method described above would require the rotating electric machine 61 to rotate multiple times, which could damage the compression mechanism and bearings. For the reasons described above, the drying process of this embodiment does not use a drying method that continuously drives the rotating electric machine 61 at high speed. Instead, it uses a drying method that minimizes the switching of the current path to the stator winding 63 to minimize the operation of the rotating electric machine 61. Therefore, the drying process using the drying method for the hermetic compressor interior of this embodiment can dry the interior of the hermetic compressor 60 without damaging the compression mechanism and bearings.

[0052] Next, a modification of the first embodiment will be described. FIG. 9 shows the stator winding 63 inside the hermetic compressor 60 according to the first embodiment. The configuration of the drying device 100 is the same as that of the first embodiment, and is therefore omitted. In the first modification, the winding phases of the stator winding 63 incorporated inside the hermetic compressor 60 are connected in a delta connection. Similar to the Y connection, the delta connection also prevents current from flowing through each winding phase individually, making it impossible to directly measure the winding phase resistance of each winding phase. Therefore, in the delta connection of the modification, similar to the Y connection described in the first embodiment, the inter-terminal resistance between each terminal of each winding phase, which is a combined resistance value composed of the winding phase resistances of two or more phases, is acquired in the inter-terminal resistance acquisition step. Then, in the winding phase resistance calculation step, the winding phase resistance of each winding phase is calculated for each phase independently from the inter-terminal resistance between each terminal acquired in the inter-terminal resistance acquisition step. In the first modification, the winding phases of the stator winding 63 are connected in a delta connection, resulting in a three-phase series-parallel current path. Therefore, in the inter-terminal resistance value acquisition step, three-phase series-parallel inter-terminal resistance values ​​are acquired, that is, a combined resistance value formed from the winding phase resistance values ​​of the three phases is acquired.

[0053] As shown in Figure 9, the inter-terminal resistance values ​​between the XY terminals, YZ terminals, and ZX terminals acquired in the inter-terminal resistance value acquisition process are Rxy, Ryz, and Rzx, respectively, and the winding phase resistance values ​​of winding phase U, winding phase V, and winding phase W are Ru, Rv, and Rw, respectively. In the case of a Δ connection, the inter-terminal resistance values ​​between each terminal can be expressed by the following equations. As shown in the equations below, the inter-terminal resistance value between each terminal is a combined resistance value made up of the winding phase resistance values ​​of the three phases. Rxy = Ru(Rv+Rw) / (Ru+Rv+Rw) Ryz = Rv (Rw + Ru) / (Ru + Rv + Rw) Rzu = Rw (Ru + Rv) / (Ru + Rv + Rw) By solving the simultaneous equations described above, the winding phase resistance values ​​Ru, Rv, and Rw of the winding phases can be found in the case of a Δ connection as well as in the case of a Y connection.

[0054] Embodiment 2 A method for drying the inside of a hermetic compressor according to the second embodiment will be described with reference to FIG. 10 . A drying device 200 for realizing the method for drying the inside of a hermetic compressor according to the second embodiment is similar to the drying device 100 according to the first embodiment in terms of the external power supply 1, the switching unit 2, etc., but differs from the drying device 100 according to the first embodiment in that a thermometer 70 is further provided. The thermometer 70 measures the surface temperature of the hermetic compressor 60 and may be of a contact or non-contact type. As shown in FIG. 10 , the thermometer 70 is provided near the location of the rotating electrical machine 61 inside the hermetic compressor 60, and measures the surface temperature of the hermetic compressor 60 at that location. Although only one thermometer 70 is provided in FIG. 10 , multiple thermometers 70 may be provided. The thermometer 70 is primarily used to measure the initial surface temperature of the hermetic compressor 60.

[0055] In the method for drying the inside of a hermetic compressor according to the present invention, when the winding phase temperature of each winding phase is indirectly acquired, the winding phase temperature of each winding phase is calculated from the amount of change in the winding phase resistance of each winding phase. To improve the accuracy of the calculation of the winding phase temperature of each winding phase, it is necessary to accurately determine the initial value of the winding phase resistance of each winding phase at the reference temperature of the winding phase in step 1 described above. However, as described above, in the manufacturing process of the hermetic compressor 60, the drying process is the final process, and almost all assembly processes, such as assembling the hermetic compressor 60 and welding the casing 64 of the hermetic compressor 60, as well as various inspection processes, are performed before the drying process. Therefore, when the hermetic compressor 60 reaches the drying process, the surface temperature of the hermetic compressor 60 does not necessarily match the ambient temperature during the drying process. Therefore, by comparing the ambient temperature during the drying process with the initial surface temperature of the hermetic compressor 60 measured using the thermometer 70 to determine a temperature correction value, and applying the temperature correction value to the reference temperature of the winding phase temperature of each winding phase, the reference temperature of the winding phase temperature of each winding phase can be accurately estimated. Therefore, in the winding phase temperature calculation process in step 5 described above, the winding phase temperature of each winding phase during current application can be calculated more accurately. This further improves the temperature of each winding phase of the stator winding 63, thereby further shortening the time required for the drying process of the hermetic compressor 60.

[0056] As described above, in the method for drying the inside of a hermetic compressor according to the second embodiment, in addition to the same effects as those of the first embodiment, the temperature of each winding phase of the stator winding 63 can be further increased compared to that of the first embodiment, and therefore the time required for the drying process of the hermetic compressor 60 can be shortened.

[0057] Embodiment 3 A method for drying the inside of a hermetic compressor according to the third embodiment will be described with reference to Fig. 11. A drying device 300 that realizes the method for drying the inside of a hermetic compressor according to the third embodiment has the same external power supply 1 and switching unit 2 as those of the first embodiment, but differs from the drying device 100 according to the first embodiment in that a temperature sensor 71 is further provided in addition to the configuration of the drying device 100. As shown in Fig. 11, the temperature sensor 71 is provided inside the hermetic compressor 60. Also, as shown in Fig. 11, wiring extending from the temperature sensor 71 is connected to the outside of the hermetic compressor 60 via an airtight terminal 65 provided in the casing 64 of the hermetic compressor 60, similar to the stator winding 63.

[0058] Note that some hermetic compressors 60 are provided with a temperature sensor 71 such as a thermistor in advance on the stator winding 63 inside the hermetic compressor 60. The temperature sensor 71 is provided inside the hermetic compressor 60 for the purpose of detecting whether the stator winding 63 is overheated during operation of the hermetic compressor 60. However, typically, the temperature sensor 71 is not provided for each winding phase of the stator winding 63, but is provided for one of the winding phases. This is because, during normal operation of the hermetic compressor 60, an equal amount of current flows through each winding phase, and the temperature difference between the winding phases is not large, so there is no need to provide an individual temperature sensor 71 for each winding phase. In a drying method such as the method for drying the inside of a hermetic compressor of the present invention, which controls the operation of the rotating electric machine 61 by minimizing switching of the current path to the stator winding 63, it is inevitable that a temperature difference will occur between the winding phases during current flow, and therefore the winding phase temperature of each winding phase cannot be accurately obtained using only the temperature sensor 71 provided in one of the winding phases. Therefore, when using the above drying method, the output value of the temperature sensor 71 provided in one of the winding phases alone is insufficient, and it is necessary to obtain the winding phase temperature of each winding phase independently of the other phases.

[0059] FIG. 11 shows a drying device 300 for implementing a method for drying the inside of a hermetic compressor, in which a temperature sensor 71 is provided in advance for one of the winding phases. In the third embodiment, the output value of the temperature sensor 71 is also input to the winding phase temperature calculation unit 33 of the winding phase information acquisition unit 3. The temperature sensor 71 measures the temperature of one of the winding phases for which the temperature sensor 71 is provided. A temperature correction value is calculated by comparing the reference winding phase temperature of each winding phase with the winding phase temperature measured by the temperature sensor 71, and the temperature correction value is applied to the reference winding phase temperature of each winding phase. This allows the reference winding phase temperature of each winding phase to be accurately determined, thereby enabling the winding phase temperature of each energized winding phase to be more accurately calculated in the winding phase temperature calculation step in step 5 described above. Furthermore, in step 5 described above, the winding phase temperatures of the winding phases provided with temperature sensors among the winding phase temperatures calculated in the winding phase temperature calculation step are compared with the winding phase temperature output from temperature sensor 71 to obtain a temperature correction value, and the temperature correction value is applied to the winding phase temperatures of the winding phases, thereby making it possible to more accurately calculate the winding phase temperatures of the energized winding phases in the winding phase temperature calculation step. This further improves the temperatures of the winding phases of stator winding 63, thereby further shortening the time required for the drying step of hermetic compressor 60.

[0060] As described above, in the method for drying the inside of a hermetic compressor according to the third embodiment, in addition to the same effects as those of the first embodiment, the temperature of each winding phase of the stator winding 63 can be further increased compared to that of the first embodiment, and therefore the time required for the drying process of the hermetic compressor 60 can be shortened.

[0061] The configurations shown in the above embodiments are merely examples of the contents of the present disclosure, and may be combined with other known technologies. Also, embodiments may be combined with each other. Furthermore, a portion of the configuration may be omitted or modified without departing from the gist of the present disclosure. [Explanation of symbols]

[0062] 100, 200, 300 Drying device, 1 External power supply, 2 Switching unit, 3 Winding phase information acquisition unit, 31 Terminal resistance value acquisition unit, 32 Winding phase resistance value calculation unit, 33 Winding phase temperature calculation unit, 311 Current value measurement unit, 312 Terminal voltage value measurement unit, 4 Control unit, 60 Hermetic compressor, 61 Rotating electric machine, 62 Stator, 63 Stator winding, U, V, W winding phase

Claims

1. A method for drying the inside of a hermetic compressor by selectively switching connections between terminals of each winding phase of a stator winding, which is composed of two or more winding phases of a rotating electric machine housed inside the hermetic compressor, and an external power supply provided outside the hermetic compressor, and energizing the terminals, a winding phase information acquiring step of acquiring winding phase information for each phase independently of other phases, the winding phase information including at least one of a winding phase temperature of each winding phase of the stator winding and a winding phase resistance value of each winding phase; and a current switching step of selectively switching connections between the terminals of the winding phases and the external power source in accordance with the acquired winding phase information to pass current therethrough.

2. The winding phase information acquisition step includes: an inter-terminal resistance value acquisition step of acquiring an inter-terminal resistance value between each of the terminals, which is a combined resistance value composed of winding phase resistance values ​​of two or more phases; and a winding phase resistance value calculating step of calculating a winding phase resistance value of each of the winding phases independently of other phases from the inter-terminal resistance values ​​between the terminals acquired in the inter-terminal resistance value acquiring step.

3. The inter-terminal resistance value acquisition step includes: a current value measuring step of measuring a current value of a current output from the external power supply; a terminal voltage value measuring step of measuring a terminal voltage value between the terminals, 3. The method for drying the inside of a hermetic compressor according to claim 2, wherein the inter-terminal resistance value acquisition step acquires the resistance value between each of the terminals from the current value measured in the current value measurement step and the inter-terminal voltage value measured in the inter-terminal voltage value measurement step.

4. 2. The method for drying the inside of a hermetic compressor according to claim 1, wherein the winding phase information acquisition step acquires the winding phase temperature of each of the winding phases independently of the other phases using a temperature sensor provided in each of the winding phases.

5. 5. The method for drying the inside of a hermetic compressor according to claim 1, wherein the current switching step compares the winding phase information acquired in the winding phase information acquisition step with a threshold value set based on a heat resistance temperature of the stator winding, and selectively switches connections between the terminals of each winding phase and the external power supply based on the comparison result to apply current.

6. 6. The method for drying the inside of a hermetic compressor according to claim 5, wherein the energization switching step selectively switches connections between the terminals of the winding phases and the external power source to stop energization of one phase among the winding phases when the value of the winding phase information has reached a threshold value set based on the heat resistance temperature.

7. 6. The method for drying the inside of a hermetic compressor according to claim 5, wherein the current switching step selectively switches connections between the terminals of each of the winding phases and the external power source to supply current to one of the winding phases when the value of the winding phase information has reached a threshold value set based on the heat resistance temperature, thereby suppressing a current value to be supplied to that phase.

8. 5. The method for drying the inside of a hermetic compressor according to claim 1, wherein the current switching step selectively switches connections between the terminals of each of the winding phases and the external power source to energize a winding phase having a lower value of the winding phase information among the winding phases.

9. The winding phase information acquisition step includes: a winding phase initial resistance value acquisition step of acquiring an initial value of the winding phase resistance value of each of the winding phases at a reference temperature of the winding phase temperature of each of the winding phases; 4. The method for drying the inside of a hermetic compressor according to claim 2, further comprising: a winding phase temperature calculating step of calculating a temperature change of the winding phase temperature of each winding phase from the reference temperature, the temperature change being calculated by comparing the winding phase resistance of each winding phase calculated in the winding phase resistance calculating step with the initial winding phase resistance of each winding phase acquired in the winding phase initial resistance acquiring step, and calculating the winding phase temperature of each winding phase during current application from the temperature change.

10. measuring an initial temperature of the hermetic compressor surface; 10. The method for drying the inside of a hermetic compressor according to claim 9, further comprising the steps of: determining a temperature correction value from an initial temperature of a surface of the hermetic compressor; and applying the temperature correction value to the reference temperature of the winding phase temperature of each of the winding phases.

11. measuring a temperature of any one of the winding phases with a temperature sensor; determining a temperature correction value from the winding phase temperature measured by the temperature sensor, and applying the temperature correction value to the reference temperature of the winding phase temperature of each winding phase; 10. The method for drying an inside of a hermetic compressor according to claim 9, further comprising: a step of comparing the winding phase temperatures of each winding phase calculated in the winding phase temperature calculating step with the winding phase temperatures measured by the temperature sensors to obtain a temperature correction value; and applying the temperature correction value to the winding phase temperatures of each winding phase.

12. A method for manufacturing a hermetic compressor, comprising a drying step using the method for drying the inside of a hermetic compressor according to any one of claims 1 to 4, an assembly process for assembling a hermetic compressor; a drying step of drying the inside of the assembled hermetic compressor; and a lubricating oil filling step of filling the inside of the dried hermetic compressor with lubricating oil.

Images