Charging system

Abstract

The present invention relates to a charging system comprising: an inverter having a DC positive terminal, a DC negative terminal, and a plurality of AC terminals, the DC positive terminal and the DC negative terminal being connected to a battery; a motor including N stator coils each having a first end connected to each of the AC ends and a second end connected to a neutral point; a power receiving terminal provided with a power receiving positive electrode end and a power receiving negative electrode end, the power receiving negative electrode end being connected to a battery negative electrode end of the battery; and a charging switch configured so as to connect the first ends of the one or more and less than N stator coils to the power-receiving positive electrode end.

Description

Technical Field

[0001] The technology of the present disclosure relates to a charging system that includes an inverter and a motor and can use the switching elements of the inverter and the stator coil of the motor as a boost circuit to charge a battery. Background Art

[0002] It is known that the circuit of the stator coil of a motor and the switching elements of an inverter can be used as a boost circuit. Japanese Unexamined Patent Application Publication No. 2023-114972 discloses a device that uses the stator coil of a motor and the lower switching elements of an inverter as a boost circuit to charge a battery using a power source with an output voltage lower than that of the battery.

[0003] In the device of Japanese Unexamined Patent Application Publication No. 2023-114972, when charging the battery, the neutral point where multiple stator coils are connected is connected to the power source. The current of the power source flows through the neutral point to the stator coils. By turning on and off the lower switching elements of the first inverter, the voltage of the power source is boosted by the stator coils. The power of the power source flows to the battery through the neutral point / stator coil / first inverter. Summary of the Invention

[0004] The electrical characteristics of the stator coil are determined based on the required performance of the motor. Therefore, the electrical characteristics of the stator coil are not necessarily the most suitable for the boost circuit. The inductance ratio of the stator coil of the motor is lower than the inductance required for the reactor of the boost circuit. If the inductance of the boost circuit is low, the AC loss becomes large. The present disclosure provides a technique for cleverly using multiple stator coils to increase the inductance of the boost circuit using the stator coil.

[0005] The charging system according to the first aspect of the present disclosure is a charging system that boosts the voltage of a power source to charge a battery, and includes: an inverter having a DC positive terminal, a DC negative terminal, and a plurality of AC terminals, the DC positive terminal and the DC negative terminal being connected to the battery; a motor having N stator coils, a first end of each of the N stator coils being connected to each of the AC terminals and a second end being connected to a neutral point, N being the number of the stator coils; a power receiving terminal having a power receiving positive terminal and a power receiving negative terminal configured to be connected to the power source, the power receiving negative terminal being connected to the battery negative terminal of the battery; and a charging switch configured to connect the first end of one or more but less than N of the stator coils to the power receiving positive terminal.

[0006] For ease of explanation, the stator coil connected to the charging switch is referred to as the upstream coil, and the other stator coils are referred to as downstream stator coils. According to the above configuration, in the current path from the power source to the battery, the upstream stator coil and the downstream stator coils are connected in series. When coils are connected in series, the total inductance increases. Since the inductance of the reactor (i.e., the series connection of the upstream stator coil and the downstream stator coils) becomes high when charging the battery using the power of the power source, the loss (AC loss) during boosting can be suppressed.

[0007] The charging system according to the first aspect of the present disclosure may further include a cooler configured to cool the stator coil using a liquid refrigerant. The charging switch may be configured to connect the first end of one of the stator coils to the power receiving positive terminal, and the stator coil connected to the charging switch may be located vertically below the other stator coils.

[0008] The charging system according to the first aspect of the present disclosure may include a direct charging switch configured to connect the power receiving positive terminal to the battery positive terminal by bypassing the stator coil.

[0009] The charging system according to the first aspect of the present disclosure may further include a sub-inverter having a DC terminal connected to the battery and an AC terminal connected to the second ends of a plurality of the stator coils.

[0010] Details and further improvements of the technology of the present disclosure will be described in the following "Detailed Description of Embodiments". BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Hereinafter, features, advantages, technology, and industrial importance of exemplary embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same components, where:

[0012] Figure 1 is a circuit diagram of the charging system of the first embodiment.

[0013] Figure 2 is a cross-sectional view of the motor included in the charging system.

[0014] Figure 3 is a circuit diagram of the charging system of the second embodiment.

[0015] Figure 4 is a circuit diagram of the charging system of the third embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0016] First Embodiment

[0017] The charging system of the embodiment will be described with reference to the drawings. Figure 1The circuit diagram of the charging system 2 of the first embodiment is shown. The charging system 2 includes an inverter 10, a motor 20, a first charging switch 31, a second charging switch 32, a direct charging switch 33, a power receiving terminal 40, and a controller 50. The controller 50 controls each switching element and each switch. The signal lines between the controller 50 and each switching element / switch are omitted from the illustration. Figure 1 In addition to depicting the charging system 2, a battery 60 and an external power source 90 are also depicted. The external power source 90 is detachable with respect to the power receiving terminal 40. The inverter 10 includes a DC positive terminal 10p, a DC negative terminal 10n, and N AC terminals (N>1).

[0018] The outline of the charging system 2 will be described. The charging system 2 can charge the battery 60 using the external power source 90 connected to the power receiving terminal 40. When charging the battery 60, the combination of the lower switching element 13 of the inverter 10 and the stator coil 21 of the motor 20 functions as a boost circuit. Therefore, the charging system 2 can charge the battery 60 using the external power source 90 whose output voltage is lower than that of the battery 60.

[0019] The charging system 2 and the battery 60 are mounted on an electric vehicle. The motor 20 is connected to an axle (not shown) of the electric vehicle, and the charging system 2 also functions as a drive system that drives the motor 20 using the power of the battery 60 to make the electric vehicle run.

[0020] The motor 20 is a three-phase AC motor and includes three stator coils 21 (a u-phase stator coil 21u, a v-phase stator coil 21v, and a w-phase stator coil 21w). One end (the first end) of each of the three stator coils 21 is connected to the AC terminal of the inverter 10. The other end (the second end) of each of the three stator coils 21 is connected to the neutral point 22. The charging system 2 can drive the motor 20 only when the external power source 90 is not connected to the power receiving terminal 40. Next, the details of the charging system 2 will be described.

[0021] The configuration of the inverter 10 will be described. The positive terminal of the battery 60 (battery positive terminal 60p) is connected to the DC positive terminal 10p of the inverter 10, and the negative terminal of the battery 60 (battery negative terminal 60n) is connected to the DC negative terminal 10n. One end of each of the three stator coils 21 is connected to each of the three AC terminals. In Figure 1 , the left end of each stator coil 21 corresponds to one end, and the right end corresponds to the other end.

[0022] The inverter 10 has three sets of series-connected bodies 11u, 11v, and 11w. The three sets of series-connected bodies 11u, 11v, and 11w are connected in parallel between the DC positive terminal 10p and the DC negative terminal 10n.

[0023] Each of the three series-connected bodies 11u, 11v, and 11w has a series-connected upper switching element 12 and a lower switching element 13. The upper switching element 12 is connected to the DC positive terminal 10p, and the lower switching element 13 is connected to the DC negative terminal 10n. The midpoints 14u, 14v, and 14w of the three series-connected bodies 11u, 11v, and 11w correspond to the AC terminals of the inverter 10. Hereinafter, the midpoints 14u, 14v, and 14w may sometimes be referred to as the AC terminals 14u, 14v, and 14w. One end of each of the three stator coils 21u, 21v, and 21w is connected to the three AC terminals 14u, 14v, and 14w, respectively.

[0024] A freewheeling diode is connected in anti-parallel to each switching element of the inverter 10. The freewheeling diode may be a component different from the switching element or a diode element included in the switching element.

[0025] If the controller 50 alternately turns on and off the upper switching element 12 and the lower switching element 13, an alternating current is output from the AC terminals 14u, 14v, and 14w.

[0026] The charging system 2 has a power receiving terminal 40. The power receiving terminal 40 has a power receiving positive terminal 40p to which the positive terminal 90p of the external power supply 90 is connected, and a power receiving negative terminal 40n to which the negative terminal 90n of the external power supply 90 is connected. The power receiving negative terminal 40n is connected to the battery negative terminal 60n.

[0027] The charging system 2 has a first charging switch 31, a second charging switch 32, and a direct charging switch 33. The first charging switch 31 connects the power receiving positive terminal 40p to one end of a stator coil (the w-phase stator coil 21w). In other words, the first charging switch 31 connects the power receiving positive terminal 40p to the AC terminal 14w. The second charging switch 32 connects the power receiving positive terminal 40p to the neutral point 22. The direct charging switch 33 bypasses the stator coil 21 and connects the power receiving positive terminal 40p to the battery positive terminal 60p.

[0028] As described above, the charging system 2 also functions as a drive system that drives the motor 20 using the power of the battery 60. In the case of driving the motor 20, the controller 50 turns on the first charging switch 31, the second charging switch 32, and the direct charging switch 33. Moreover, the controller 50 alternately turns on and off the upper switching element 12 and the lower switching element 13 of the inverter 10. An alternating current is supplied from the AC terminals 14u, 14v, and 14w of the inverter 10 to the stator coil 21, and the motor 20 rotates.

[0029] A case of charging the battery 60 using the external power supply 90 will be described. When the output voltage of the external power supply 90 is lower than the output voltage of the battery 60, the controller 50 turns off the first charging switch 31 or the second charging switch 32.

[0030] The case where the controller 50 turns off the second charging switch 32, turns on the first charging switch 31, and turns on the direct charging switch 33 will be described. If the controller 50 turns off the second charging switch 32, the positive terminal 90p of the external power supply 90 is connected to the neutral point 22. The positive terminal 90p of the external power supply 90 is connected to the positive terminal 60p of the battery through the second charging switch 32, the neutral point 22, the three stator coils 21u, 21v, 21w, and the freewheeling diode of the upper switching element 12.

[0031] The stator coil 21 and the lower switching element 13 function as a boost circuit. If the controller 50 appropriately turns on and off the three lower switching elements 13, the output voltage of the external power supply 90 is boosted by the stator coil 21. The power of the boosted external power supply 90 is supplied to the battery 60 through the stator coil 21. That is, the charging system 2 can charge the battery 60 using the external power supply 90 whose output voltage is lower than that of the battery 60. In the boost circuit when the second charging switch 32 is turned off, the three stator coils 21 are connected in parallel.

[0032] The case where the controller 50 turns off the first charging switch 31, turns on the second charging switch 32, and turns on the direct charging switch 33 will be described. If the controller 50 turns off the first charging switch 31, the positive terminal 90p of the external power supply 90 is connected to one end of the w-phase stator coil 21w. The positive terminal 90p of the external power supply 90 is connected to the positive terminal 60p of the battery through the first charging switch 31, the w-phase stator coil 21w, the neutral point 22, the u-phase stator coil 21u, the v-phase stator coil 21v, and the inverter 10.

[0033] In the boost circuit at this time, the w-phase stator coil 21w and the u-phase (v-phase) stator coil 21u (21v) are connected in series. In Figure 1 the current flow when the first charging switch 31 is turned off is indicated by thick arrow lines. The current of the external power supply 90 flows through the power receiving positive terminal 40p and the first charging switch 31 to the w-phase stator coil 21w. The current that has passed through the w-phase stator coil 21w is divided between the u-phase stator coil 21u and the v-phase stator coil 21v.

[0034] If the controller 50 appropriately turns on and off the lower switching elements 13 of the series-connected bodies 11u, 11v of the u-phase and v-phase, the output voltage of the external power supply 90 is boosted by each of the series connection of the stator coils 21w and 21u and the series connection of the stator coils 21w and 21v. The power of the boosted external power supply 90 is supplied to the battery 60 through the stator coil 21. In this case as well, the charging system 2 can charge the battery 60 using the external power supply 90 whose output voltage is lower than that of the battery 60.

[0035] The advantages of charging using the first charging switch 31 will be described. The electrical characteristics (especially the inductance) of the stator coil 21 of the motor 20 are not necessarily suitable for the reactor of the boost circuit. Since the torque output of the motor 20 is the main function, the stator coil 21 has an inductance suitable for torque output. The stator coil of the motor preferably has a low inductance in order to suppress the back electromotive force. On the other hand, in the reactor of the boost circuit, a high inductance is better. This is because if the inductance is high, a large amount of magnetic energy can be stored in the reactor. In addition, if the inductance of the reactor of the boost circuit is low, the current fluctuation becomes large and the AC loss increases.

[0036] In the boost circuit using the first charging switch 31, the w-phase stator coil 21w and the v-phase stator coil 21v are connected in series. The w-phase stator coil 21w and the u-phase stator coil 21u are also connected in series. The total inductance in the case where two coils are connected in series is higher than the total inductance in the case where two coils are connected in parallel. Therefore, the inductance of the coils of the boost circuit in the case of using the first charging switch 31 is greater than the inductance of the boost circuit in the case of using the second charging switch 32 (in this case, the three stator coils 21 are connected in parallel). Since the inductance of the reactor of the boost circuit becomes large when the first charging switch 31 is used, the AC loss during charging can be suppressed.

[0037] In the charging system 2, two of the plurality of stator coils 21 provided in the motor 20 are connected in series. The charging system 2 can implement a boost circuit including a series connection body of a plurality of coils without adding a new coil.

[0038] In the charging system 2 of the first embodiment, the current flowing through each of the stator coils 21u and 21v becomes half of the current flowing through the stator coil 21w. Therefore, the heat generation amount of the stator coil 21w is greater than the heat generation amount of each of the stator coils 21u and 21v. In view of this, in the charging system 2, the configuration of the motor 20 has been studied such that the cooling performance for the stator coil 21w is higher than the cooling performance for the stator coils 21u and 21v.

[0039] Figure 2 A longitudinal section of the motor 20 is shown. The motor 20 is configured such that its axis is aligned with the horizontal direction. In the motor 20, the w-phase stator coil 21w connected to the first charging switch 31 at one end is located at a position vertically below the other stator coils 21u and 21v.

[0040] In addition, the motor 20 of the charging system 2 includes a cooler 26. The cooler 26 uses a liquid refrigerant to cool the motor 20. The flow path 26a of the cooler 26 is connected to the upper and lower parts of the stator 25. The cooler 26 supplies the liquid refrigerant to the upper part of the stator 25. The liquid refrigerant 29 accumulates below the stator 25. The cooler 26 draws the refrigerant accumulated in the lower part of the stator 25 and returns it to the upper part of the stator 25.Figure 2 The thick arrow line indicates the flow direction of the refrigerant. Since the w-phase stator coil 21w is arranged below the other stator coils 21u and 21v, as Figure 2 shown, at least a part of the w-phase stator coil 21w is immersed in the liquid refrigerant 29 and is strongly cooled. In the charging system 2, the w-phase stator coil 21w through which a large current flows is more strongly cooled than the other stator coils 21u and 21v.

[0041] Return to Figure 1 , and continue the description of the circuit of the charging system 2. When the output voltage of the external power supply 90 is equal to the output voltage of the battery 60, the controller 50 turns on the first charging switch 31 and the second charging switch 32, and turns off the direct charging switch 33. As Figure 1 shown, the direct charging switch 33 bypasses the stator coil 21 to connect the power receiving positive terminal 40p to the battery positive terminal 60p. In other words, when the direct charging switch 33 is turned off, the current of the external power supply 90 flows to the battery positive terminal 60p bypassing the stator coil 21. When the output voltage of the external power supply 90 is equal to the output voltage of the battery 60, the charging system 2 can supply the current of the external power supply 90 to the battery 60 without passing through the stator coil 21. By bypassing the stator coil 21, the loss during charging can be suppressed.

[0042] Second Embodiment

[0043] Figure 3 The circuit diagram of the charging system 102 according to the second embodiment is shown. The charging system 102 includes a first charging switch 131 in place of the first charging switch 31 of the charging system 2. Except for the first charging switch 131, the configuration of the charging system 102 is the same as that of the charging system 2.

[0044] The first charging switch 131 includes charging sub-switches 131a and 131b. The charging sub-switch 131a connects one end of the w-phase stator coil 21w to the power receiving positive terminal 40p, and the charging sub-switch 131b connects one end of the v-phase stator coil 21v to the power receiving positive terminal 40p. The controller 50 closes or opens the two charging sub-switches 131a and 131b simultaneously.

[0045] Figure 3The thick arrow line indicates the flow of current when the first charging switch 131 is turned off. In the charging system 102, the parallel connection of the stator coils 21w and 21v is connected in series with the u-phase stator coil 21u. The currents flowing in the stator coils 21w and 21v merge and flow to the stator coil 21u. When the first charging switch 131 is turned off, the inductance of the boost circuit is higher than the inductance of the boost circuit when the second charging switch 32 is turned off (the total inductance when the three stator coils 21 are connected in parallel). Similar to the charging system 2, the charging system 102 can suppress the AC loss of the boost circuit using the lower switching element 13 and the stator coil 21.

[0046] Third Embodiment

[0047] Figure 4 The circuit diagram of the charging system 202 according to the third embodiment is shown. The charging system 202 is configured by adding a sub-inverter 80 and a plurality of neutral point switching elements 23 to the charging system 2. The DC terminal of the sub-inverter 80 is connected to the battery 60. The DC positive terminal 80p of the sub-inverter 80 is connected to the battery positive terminal 60p, and the DC negative terminal 80n is connected to the battery negative terminal 60n. The sub-inverter 80 has three AC terminals 84u, 84v, 84w, which are respectively connected to the other ends of the three stator coils 21u, 21v, 21w.

[0048] The sub-inverter 80 has three series connection bodies 81u, 81v, 81w. In each of the three series connection bodies 81u, 81v, 81w, the upper switching element 82 and the lower switching element 83 are directly connected. In each of the series connection bodies 81u, 81v, 81w, the midpoint 84u (84v, 84w) of the upper switching element 82 and the lower switching element 83 corresponds to the AC terminal of the sub-inverter 80. The circuit structure of the sub-inverter 80 is the same as the circuit structure of the inverter 10.

[0049] Each of the plurality of neutral point switching elements 23 is connected between the other ends of the plurality of stator coils 21 and the neutral point 22. If all the neutral point switching elements 23 are turned off, the other ends of the plurality of stator coils 21 are connected to the neutral point 22. If all the neutral point switching elements 23 are turned on, the other ends of the plurality of stator coils 21 are electrically disconnected from the neutral point 22.

[0050] When the external power supply 90 is not connected, if the controller 50 turns on all the neutral point switching elements 23, the inverters 10, 80 and the motor 20 become a dual-inverter type drive device. In the dual-inverter, one end of the stator coil 21 is connected to the AC terminal of the inverter 10, and the other end is connected to the AC terminal of the sub-inverter 80.

[0051] If the controller 50 appropriately turns on and off the upper and lower switching elements of the inverter 10 and the sub-inverter 80, the motor 20 outputs torque. If the motor 20 is driven by two inverters 10 and 80, a higher torque can be output than when the motor 20 is driven by a single inverter.

[0052] When charging the battery 60, the external power supply 90 is connected to the power receiving terminal 40. When charging the battery 60 by connecting three stator coils 21 in parallel, the controller 50 turns off all the neutral point switching elements 23 and connects the three stator coils 21 to the neutral point 22. The controller 50 turns off the second charging switch 32 and turns on the first charging switch 31 and the direct charging switch 33. The controller 50 turns on all the switching elements of the sub-inverter 80 and appropriately turns on and off the lower switching element 13 of the inverter 10. Similar to the charging system 2 of the first embodiment, the voltage of the external power supply 90 is boosted to charge the battery 60.

[0053] When charging the battery 60 by connecting several of the three stator coils 21 in series, the controller 50 turns off all the neutral point switching elements 23 and the first charging switch 31 and turns on the second charging switch 32 and the direct charging switch 33. The controller 50 turns on all the switching elements of the sub-inverter 80 and also turns on the upper switching element 12 and the lower switching element 13 of the series connection body 11w of the w-phase of the inverter 10. The controller 50 appropriately turns on and off the lower switching elements 13 of the series connection bodies 11u and 11v of the u-phase and v-phase. The voltage of the external power supply 90 is boosted by the series connection of the stator coils 21w and 21u and the series connection of the stator coils 21w and 21v. At this time, similar to the charging system 2 of the first embodiment, the charging system 202 can charge the battery 60 while suppressing AC loss.

[0054] As described above, the charging systems 2, 102, and 202 can increase the inductance in the boost circuit using the stator coil 21.

[0055] The features and points to note of the charging system of the embodiment are described. Here, for the sake of understanding, one end of the stator coil is hereinafter referred to as the A end, and the other end is referred to as the B end. The A ends of the plurality of stator coils 21 are connected to the AC terminals of the inverter 10, and the B ends are connected to the neutral point 22.

[0056] The charging system 2 (102, 202) of the embodiment includes three stator coils 21u, 21v, and 21w. The motor of the charging system of the present disclosure only needs to have a plurality of stator coils, and the number of stator coils is not limited to three. The motor of the charging system includes N (N>1) stator coils. The inverter has N series connection bodies and N AC terminals. The N AC terminals are respectively connected to the A ends of the N stator coils.

[0057] The first charging switches 31 and 131 connect the A terminal of at least one stator coil to the power receiving positive terminal 40p. The first charging switch 31 of the charging system 2 (202) connects the A terminal of one of the three stator coils 21u, 21v, and 21w, i.e., 21w, to the power receiving positive terminal 40p. The first charging switch 131 of the charging system 102 connects the A terminals of two of the three stator coils 21u, 21v, and 21w, i.e., 21w and 21v, to the power receiving positive terminal 40p. The charging system only needs to have a charging switch that connects the A terminals of M (1 ≤ M < N) stator coils out of N stator coils to the power receiving positive terminal 40p.

[0058] The inverter 10 includes N series-connected bodies 11 connected in parallel between the DC positive terminal 10p and the DC negative terminal 10n. Each of the N series-connected bodies 11 has a series connection of an upper switching element 12 and a lower switching element 13. The upper switching element 12 is connected to the DC positive terminal 10p, and the lower switching element 13 is connected to the DC negative terminal 10n. The midpoint of the N series-connected bodies (i.e., the midpoint between the upper switching element 12 and the lower switching element 13) corresponds to the AC terminal of the inverter 10.

[0059] When boosting the output voltage of the external power source 90 to charge the battery 60, the controller 50 performs the following processing. The controller 50 turns off the first charging switch 31 (131). For the sake of explanation, the stator coil connected to the first charging switch 31 (131) is called the upstream stator coil, and the remaining stator coils are called the downstream stator coils. In the boost circuit using the stator coil 21 and the lower switching element 13, the upstream stator coil and the downstream stator coil are connected in series.

[0060] The controller 50 turns on the upper switching element 12 and the lower switching element 13 connected to the A terminal of the upstream stator coil, and turns on and off the lower switching element 13 connected to the A terminal of the downstream stator coil. The stator coil and the lower switching element function as a boost circuit, and the voltage of the external power source 90 is boosted. The battery 60 is charged with the power of the boosted external power source 90. At this time, since the upstream stator coil and the downstream stator coil are connected in series, the total inductance of the boost circuit becomes larger.

[0061] The charging system 2 includes a cooler 26 that cools the motor 20 using a liquid refrigerant. In this case, N≥3 and M = 1. The first charging switch connects the A ends of the M stator coils to the positive power receiving terminal 40p. The motor 20 is configured such that the motor shaft faces the horizontal direction. The stator coil (upstream stator coil) connected to the first charging switch is located vertically below the other stator coils (downstream stator coils). At least a part of the upstream stator coil is immersed in the liquid refrigerant. The current flowing through the upstream stator coil is larger than the current flowing through each downstream stator coil. The heat generation amount of the upstream stator coil is larger than the heat generation amount of each downstream stator coil. However, according to the above configuration, the upstream stator coil is cooled more strongly than the downstream stator coils.

[0062] The charging system 2 (102, 202) includes a direct charging switch 33 that connects the positive power terminal 40p to the positive battery terminal 60p bypassing the stator coil 21. When the output voltage of the external power supply 90 is equal to the output voltage of the battery 60, the controller 50 turns on the first charging switch 31 (131) and the second charging switch 32 and turns off the direct charging switch 33. With this configuration, the battery 60 can be charged using the external power supply 90 without passing through the stator coil.

[0063] Other points to note about the technology described in the embodiments are described. Even without the second charging switch 32, the charging system 2 (102, 202) of the embodiments provides the above advantages.

[0064] The charging system 2 (102, 202) can drive the motor 30 using the inverter 10. Therefore, the charging system 2 (102, 202) can also be referred to as a "drive charging system".

[0065] The expression "the switching element is closed" means that the devices connected to both ends of the switching element are electrically connected. The expression "the switching element is open" means that the devices connected to both ends of the switching element are electrically separated. The expression "the switching element is closed" is equivalent to the expression "the switching element is turned on". The expression "the switching element is open" is equivalent to the expression "the switching element is turned off".

[0066] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of protection claimed in the present application. The technology described in the scope of protection claimed in the present application includes technologies obtained by various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or through various combinations, and are not limited to the combinations described in the technical solution at the time of application. In addition, the technologies illustrated in this specification or the drawings can achieve multiple purposes simultaneously, and achieving one of the purposes itself has technical usefulness.

Claims

1. A charging system that boosts the voltage of a power source to charge a battery, characterized in that, Comprising: An inverter having a DC positive terminal, a DC negative terminal, and a plurality of AC terminals, wherein the DC positive terminal and the DC negative terminal are connected to the battery; A motor having N stator coils, a first end of each of the N stator coils being connected to each of the AC terminals, and a second end being connected to a neutral point, where N is the number of the stator coils; A power receiving terminal having a power receiving positive terminal and a power receiving negative terminal configured to be connected to the power supply, the power receiving negative terminal being connected to the battery negative terminal of the battery; and A charging switch configured to connect the first end of one or more but less than N of the stator coils to the power receiving positive terminal.

2. The charging system according to claim 1, characterized in that It further includes a cooler configured to cool the stator coils using a liquid refrigerant, wherein the charging switch is configured to connect the first end of one of the stator coils to the power receiving positive terminal, and the stator coil connected to the charging switch is located at a position vertically lower than the other stator coils.

3. The charging system according to claim 1, characterized in that It further includes a direct charging switch configured to connect the power receiving positive terminal to the battery positive terminal bypassing the stator coils.

4. The charging system according to claim 1, characterized in that It further includes a sub-inverter having a DC terminal connected to the battery and an AC terminal connected to the second ends of the plurality of stator coils.

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