Inverter device

Abstract

An inverter device is provided, which can make the internal temperature of an electrolytic capacitor rise faster within the permissible range of a pulsating voltage and shorten the non-operating time. The device comprises an electrolytic capacitor (1), an inverter circuit (2), a temperature sensor (4) and a control device (3). When the ambient temperature of the electrolytic capacitor (1) detected by the temperature sensor (4) is lower than a specified temperature, the control device (3) drives a specific switching element of the inverter circuit (2) to conduct before the normal operation of a motor (5) starts, thereby performing a preheating operation while keeping the motor (5) stopped. The preheating operation causes a current to flow through the motor (5) at a specified rate of increase so that the pulsating voltage of the DC voltage can be controlled within the permissible range.

Description

Technical Field

[0001] The present invention relates to an inverter device for driving a motor by generating an AC voltage from a DC voltage smoothed by an electrolytic capacitor. Background Art

[0002] This type of conventional inverter device selectively drives three switching elements on the upper phase side and three switching elements on the lower phase side of the inverter circuit to generate three-phase voltages of U, V, and W based on a DC voltage to drive the motor. The inverter device is provided with an electrolytic capacitor for smoothing the power supply voltage of the inverter circuit.

[0003] In addition, in such inverter devices, especially vehicle-mounted inverter devices, they are sometimes used in low-temperature environments. When electrolytic capacitors are used in such environments, the internal resistance component (equivalent series resistance) of the electrolytic capacitor increases, the pulsating voltage increases, and there is a risk that the voltage applied to the electrolytic capacitor exceeds its withstand voltage or becomes a reverse voltage, causing damage.

[0004] As a method to solve this problem, although it is considered to increase the electrolytic capacitor and reduce the internal resistance component to reduce the ripple voltage, there are problems such as cost increase and large size. Therefore, as a method to reduce the internal resistance component, a method of performing a preheating mode to increase the internal temperature of the electrolytic capacitor while the motor is stopped has been developed (for example, refer to Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2012-222925 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] Here, when reducing the internal resistance component of the electrolytic capacitor to reduce the ripple voltage, it is ideal to increase the internal temperature of the electrolytic capacitor for a long time with a small current. However, in such a conventional method, there is a problem that the preheating mode time, that is, the non-operation time from the start instruction of the motor to the start of the motor rotation, becomes longer.

[0010] The present invention has been made to solve the problems of the related art, and an object of the present invention is to provide an inverter device capable of increasing the internal temperature of an electrolytic capacitor more quickly within the allowable range of a ripple voltage, thereby shortening the non-operation time.

[0011] Technical means for solving technical problems

[0012] The inverter device of the present invention is characterized in that it includes: an electrolytic capacitor that generates a DC voltage by smoothing an input voltage; an inverter circuit that generates an AC voltage based on the DC voltage to drive a motor; a temperature sensor that detects the temperature of the electrolytic capacitor or the temperature of its surroundings; and a control device that controls the driving of multiple switching elements possessed by the inverter circuit, and when the temperature detected by the temperature sensor is lower than a specified temperature, the control device drives a specific switching element selected from the multiple switching elements to conduct before the normal operation of the motor begins, thereby performing a preheating operation while keeping the motor stopped, wherein the preheating operation allows a current that can control the pulsating voltage of the DC voltage within an allowable range to flow through the motor at a specified rising rate.

[0013] The inverter device according to a second aspect of the present invention is characterized in that, in the above invention, the control device changes the rate of increase of the current flowing through the motor based on the input voltage and the temperature detected by the temperature sensor.

[0014] The inverter device according to a third aspect of the present invention is characterized in that, in the above invention, the control device changes the rate of increase of the current flowing through the motor in a decreasing direction as the input voltage is higher.

[0015] The inverter device according to a fourth aspect of the present invention is characterized in that, in the above invention, the control device changes the value of the current flowing through the motor at the start of the warm-up operation in a direction to decrease as the input voltage increases.

[0016] The inverter device according to the fifth aspect of the present invention is characterized in that, in the second to fourth aspects of the present invention, the control device changes the rate of increase of the current flowing through the motor in a decreasing direction as the temperature detected by the temperature sensor is lower.

[0017] The inverter device according to claim 6 of the present invention is characterized in that, in the above invention, the control device changes the value of the current flowing through the motor at the start of the warm-up operation in a direction to decrease as the temperature detected by the temperature sensor decreases.

[0018] The inverter device according to a seventh aspect of the present invention is characterized in that, in each of the above inventions, the control device changes the rate of increase of the current flowing through the motor in multiple stages as time passes during the warm-up operation.

[0019] An inverter device according to an eighth aspect of the present invention is characterized in that, in the above invention, the control device changes the rate of increase of the current flowing through the motor in a direction to increase as time passes after the start of the warm-up operation.

[0020] The inverter device according to a ninth aspect of the present invention is characterized in that, in each of the above inventions, the control device limits the value of the current flowing through the motor during normal operation after the warm-up operation is completed.

[0021] Effects of the Invention

[0022] The inverter device of the present invention includes: an electrolytic capacitor that generates a DC voltage by smoothing an input voltage; an inverter circuit that generates an AC voltage based on the DC voltage to drive a motor; a temperature sensor that detects the temperature of the electrolytic capacitor or the temperature of its surroundings; and a control device that controls the driving of multiple switching elements possessed by the inverter circuit. When the temperature detected by the temperature sensor is lower than a specified temperature, the control device drives a specific switching element selected from the multiple switching elements to conduct before the normal operation of the motor begins, thereby performing a preheating operation while keeping the motor stopped. The preheating operation allows a current that can control the pulsating voltage of the DC voltage within an allowable range to flow through the motor at a specified rising rate, thereby suppressing the pulsating voltage of the DC voltage within an allowable range and causing the internal temperature of the electrolytic capacitor to rise faster.

[0023] This can avoid the destruction of the electrolytic capacitor in a low-temperature environment, and can shorten the time (non-operation time) of the warm-up operation required from the start instruction to the start of the motor rotation.

[0024] In this case, since the higher the input voltage, the lower the temperature of the electrolytic capacitor, and the larger the peak value of the pulsating voltage becomes, the control device as in the second aspect of the present invention changes the rate of increase of the current flowing through the motor based on the input voltage and the temperature detected by the temperature sensor, thereby being able to more safely and effectively increase the internal temperature of the electrolytic capacitor through preheating operation.

[0025] For example, the control device according to the third aspect of the present invention changes the rate of increase of the current flowing through the motor in a decreasing direction as the input voltage increases, thereby safely and quickly raising the internal temperature of the electrolytic capacitor by the warm-up operation.

[0026] In this case, as the input voltage is higher, the control device as in the fourth aspect of the present invention changes the value of the current flowing through the motor at the start of the preheating operation in a decreasing direction, thereby more effectively avoiding damage to the electrolytic capacitor caused by the pulsating voltage of the DC voltage.

[0027] In addition, for example, the lower the temperature detected by the temperature sensor, the more the control device as in the fifth aspect of the present invention changes the rate of increase of the current flowing through the motor in a decreasing direction, thereby safely and quickly raising the internal temperature of the electrolytic capacitor through preheating operation.

[0028] In this case, the lower the temperature detected by the temperature sensor, the more the control device such as the sixth aspect of the present invention will change the value of the current flowing through the motor at the start of the preheating operation in a decreasing direction, thereby more effectively avoiding damage to the electrolytic capacitor caused by the pulsating voltage of the DC voltage.

[0029] Here, the internal resistance component of the electrolytic capacitor is extremely large at low temperatures, and tends to decrease rapidly as the internal temperature rises. Therefore, the control device as in the seventh aspect of the present invention changes the rate of increase of the current flowing through the motor in multiple stages as time passes during the preheating operation. For example, as in the eighth aspect of the present invention, the control device changes the rate of increase of the current flowing through the motor in an increasing direction as time passes from the start of the preheating operation, thereby being able to more safely and quickly raise the internal temperature of the electrolytic capacitor.

[0030] Furthermore, if the control device according to the ninth aspect of the present invention limits the current value flowing through the motor during normal operation after the warm-up operation is completed, damage to the electrolytic capacitor in a low-temperature environment can be more effectively avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic circuit diagram of an inverter device according to an embodiment of the present invention.

[0032] Figure 2 Yes Description Figure 1 Flow chart of the warm-up operation of the control device of the inverter device.

[0033] Figure 3 Yes Description Figure 2 A diagram showing the energized state of the inverter circuit during the warm-up operation.

[0034] Figure 4 It is explained in Figure 2 FIG. 1 is a diagram of the warm-up operation conditions used in the flow chart.

[0035] Figure 5 It is explained in Figure 2 A diagram showing an example of a warm-up operation performed in the flowchart of FIG.

[0036] Figure 6 It is explained in Figure 2 FIG. 2 is a diagram of another example of the warm-up operation executed in the flowchart of FIG. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Figure 11 is a circuit diagram showing a simplified structure of an inverter device IV to which an embodiment of the present invention is applied. The inverter device IV of the embodiment is an on-vehicle inverter device that is integrally provided with a compressor (not shown) constituting a vehicle air conditioning device and is mounted on a vehicle. The inverter device IV of the embodiment smoothes the input voltage HV from a battery (DC power supply) BAT mounted on the vehicle through an electrolytic capacitor 1, generates an AC voltage based on the smoothed DC voltage, and drives a motor 5 as an electric motor. The inverter device IV is configured to include an electrolytic capacitor 1, an inverter circuit 2, a control device 3, and a temperature sensor 4.

[0038] The electrolytic capacitor 1 smoothes the input voltage HV into a DC voltage and is composed of a large-capacity aluminum electrolytic capacitor. Although such an aluminum electrolytic capacitor is small and cheap, it generally has a large internal resistance component (equivalent series resistance) ESR due to the resistance of the electrolyte and the resistance of the electrolytic paper. In addition, for example, when used in a low-temperature environment, it has the following characteristics: the lower the internal temperature of the electrolytic capacitor 1, the larger the internal resistance component ESR becomes, and in particular, the lower the internal temperature becomes, the more rapidly the internal resistance component ESR increases.

[0039] An inverter circuit 2 is provided to provide a DC voltage smoothed by the electrolytic capacitor 1 as a power supply voltage. The inverter circuit 2 generates three-phase voltages Vu, Vv, and Vw from the DC voltage and provides them to a motor (three-phase brushless motor) 5 as an electric motor, and is configured to include, for example, three switching elements (IGBT) 6u, 6v, and 6w on the upper phase side and three switching elements (IGBT) 7u, 7v, and 7w on the lower phase side.

[0040] Furthermore, a control device 3 is provided in connection with the inverter circuit 2. The control device 3 is constituted by a microcomputer having a processor, and is a device for controlling the on / off driving of the six switching elements 6u to 6w, 7u to 7w of the inverter circuit 2 to properly operate the motor 5. The control device 3 is configured so that when the temperature of the electrolytic capacitor 1 is lower than a predetermined specified temperature T1, before the normal operation of the motor 5 starts, the duty ratio of the pulse width modulation (hereinafter referred to as "PWM") signal for on / off driving the switching elements 6u to 6w, 7u to 7w of the inverter circuit 2 is controlled, so that a current (phase current) that limits the pulsating voltage of the DC voltage applied to the electrolytic capacitor 1 to within an allowable range flows through the motor 5, and the motor 5 is stopped. In the above state, the Joule heat generated in the internal resistance component (equivalent series resistance) ESR of the electrolytic capacitor 1 can be directly used to implement a preheating operation to increase the temperature of the electrolytic capacitor 1.

[0041] In this case, the control device 3 causes the current to flow through the motor 5 at a predetermined rate of increase during the warm-up operation, and in the embodiment, the rate of increase is changed according to the input voltage HV from the battery BAT and the temperature around the electrolytic capacitor 1. In the embodiment, the temperature sensor 4 is provided near the electrolytic capacitor 1. The temperature sensor 4 detects the ambient temperature Tc of the electrolytic capacitor 1 (the temperature around the electrolytic capacitor 1) and outputs it to the control device 3. The temperature sensor 4 is composed of, for example, a thermocouple, a positive characteristic thermistor, or the like.

[0042] In addition, in the embodiment, the electrolytic capacitor 1 is mounted on the same substrate as the inverter circuit 2 and is housed in the same space as the inverter circuit 2, and the temperature sensor 4 is also arranged on the substrate near the electrolytic capacitor 1, but it is not limited to this, and the temperature of the electrolytic capacitor 1 itself can also be detected by the temperature sensor 4. In the embodiment, the ambient temperature Tc of the electrolytic capacitor 1 is handled as the temperature of the electrolytic capacitor 1.

[0043] In addition, the control device 3 is pre-set with Figure 4 The warm-up operation conditions of the embodiment are set based on the ambient temperature Tc of the electrolytic capacitor 1 detected by the temperature sensor 4 and the input voltage HV from the battery BAT. Figure 4 Under the preheating operation condition, only the part indicated by 10 / 10 and 5 / 10 means that the preheating operation is not performed. In addition, 10 / 10 refers to the value of the normal starting current, and 5 / 10 means half of the value.

[0044] In addition, t1 to t7 in the figure represent the energization time of the motor 5, and the fractions connected by arrows basically represent the current value at the start and the completion of the preheating operation of the motor 5, which means that the preheating operation is performed in these indicated parts. The fractions are also the magnitude of the current value relative to the normal starting current (10 / 10), for example, 2 / 10 means one fifth of the normal starting current (10 / 10).

[0045] in addition, Figure 4 The power-on time t1 to t5 in the embodiment is set to the relationship of t1<t2<t3<t4<t5. In addition, in the embodiment, the power-on time t6 and t7 are set to the relationship of t7<t6. Moreover, the longer the power-on time, the smaller the difference between the current value at the start of the preheating operation and the current value at the completion, and the lower the current rise rate becomes. The shorter the power-on time, the larger the difference between the current value at the start of the preheating operation and the current value at the completion, and the higher the current rise rate becomes.

[0046] Each energizing time t1 to t7, the current value at the start of the preheating operation and the current value at the completion (1 / 10, 2 / 10, 3 / 10, 5 / 10, 6 / 10, 7 / 10), that is, the current increase rate determined by them is the energizing time, current value, and increase rate that can suppress the pulsating voltage of the direct current in the electrolytic capacitor 1 within the allowable range under the combination conditions of each ambient temperature Tc and input voltage HV, and are determined in advance by experiments. Then, in the case of preheating operation, the control device 3 selects one of the conditions from the ambient temperature Tc and the input voltage HV when the start instruction of the motor 5 is input, and executes the preheating operation of the electrolytic capacitor 1.

[0047] Next, refer to Figure 2 The flowchart of FIG. 1 specifically illustrates the preheating operation performed by the control device 3. When there is a start instruction for the motor 5, the control device 3 first Figure 2 In step S1 of the flowchart, it is determined whether the ambient temperature Tc of the electrolytic capacitor 1 detected by the temperature sensor 4 is lower than the specified temperature T1. In the embodiment, the specified temperature T1 varies depending on the input voltage HV. That is, the higher the input voltage HV, the lower the temperature of the electrolytic capacitor 1 (the ambient temperature Tc is used in the embodiment), and the greater the peak value of the pulsating voltage of the DC voltage applied to the electrolytic capacitor 1.

[0048] Therefore, in this embodiment, when the input voltage HV is lower than 200V, the prescribed temperature T1 is set to -24°C, when the input voltage HV is 200V or higher and lower than 250V, the prescribed temperature T1 is set to -19°C, and when the input voltage HV is 250V or higher and lower than 300V, the prescribed temperature T1 is set to -14°C. Similarly, when the input voltage HV is 300V or higher and lower than 350V, the prescribed temperature T1 is set to -9°C, and when the input voltage HV is 350V or higher and lower than 400V, the prescribed temperature T1 is set to -4°C. In addition, when the input voltage HV is 400V or higher and lower than 450V, the prescribed temperature T1 is set to +1°C, and when the input voltage HV is 450V or higher and lower than 500V, the prescribed temperature T1 is set to +6°C.

[0049] When the ambient temperature Tc of the electrolytic capacitor 1 detected by the temperature sensor 4 is above the predetermined temperature T1 in step S1, the control device 3 proceeds to step S7, and starts the motor 5 with the normal starting current (10 / 10) to start normal operation. That is, the preheating operation of the electrolytic capacitor 1 is not performed before starting the normal operation of the motor 5.

[0050] On the other hand, when the ambient temperature Tc is lower than the predetermined temperature T1 in step S1, the control device proceeds to step S2 to determine whether the time tpass after the last preheating operation is shorter than the predetermined time tpass1. If the predetermined time tpass1 has elapsed since the last preheating operation is completed, the control device 3 proceeds to step S6.

[0051] If the time tpass after the last warm-up operation is completed is shorter than the predetermined time tpass1, the control device 3 proceeds to step S3 to check the input voltage HV from the battery BAT. Then, the control device 3 proceeds to step S4 to check the input voltage HV based on the ambient temperature Tc and the input voltage HV. Figure 4 Among the preheating operation conditions, select and determine any one of the preheating operation conditions to start the preheating operation of the electrolytic capacitor 1.

[0052] In the preheating operation, the control device 3 calculates the duty ratio of the PWM signal based on the determined preheating operation conditions. Then, the PWM signal with the calculated duty ratio drives the upper phase side of the inverter circuit 2, such as the switching element 6u, and drives the lower phase side, such as the switching elements 7v and 7w, to turn on. Figure 3 As indicated by the thick solid line, in the inverter circuit 2 and the motor 5, a current determined to satisfy the preheating operation condition in which the ripple voltage of the DC voltage is within the allowable range flows, and the preheating operation is performed.

[0053] In this case, the switching elements of the inverter circuit 2 that are turned on are fixed to the upper phase side, for example, the switching element 6u, and the lower phase side, for example, the switching elements 7v and 7w, so the motor 5 remains stopped. Thus, while the current is flowing to the motor 5, the electrolytic capacitor 1 is heated by the Joule heat generated in its internal resistance component ESR and the temperature rises.

[0054] (1) Preheating operation (Part 1)

[0055] Next, the following is based on Figure 4 As described above, the higher the input voltage HV is, the lower the temperature of the electrolytic capacitor 1 (the ambient temperature Tc is used in the embodiment), and the greater the peak value of the pulsating voltage of the DC voltage applied to the electrolytic capacitor 1 becomes. Therefore, when the ambient temperature Tc of the electrolytic capacitor 1 is above -24°C and below -20°C, and the input voltage HV is above 200V and below 300V, the control device 3 sets the current value flowing through the motor 5 to 5 / 10 (fixed value). This is half the current value of the normal starting current (10 / 10).

[0056] In the case where the ambient temperature Tc is between -19°C and -15°C, even when the input voltage HV is between 250V and less than 350V, the current value flowing through the motor 5 is set to 5 / 10. In the case where the ambient temperature Tc is between -14°C and -10°C, even when the input voltage HV is between 300V and less than 400V, the current value flowing through the motor 5 is set to 5 / 10. In the case where the ambient temperature Tc is between -9°C and -5°C, even when the input voltage HV is between 350V and less than 450V, the current value flowing through the motor 5 is set to 5 / 10. In the case where the ambient temperature Tc is between -4°C and 0°C, even when the input voltage HV is between 400V and less than 500V, the current value flowing through the motor 5 is set to 5 / 10. Furthermore, when the ambient temperature Tc is between +1°C and +5°C, even when the input voltage HV is between 450V and less than 500V, the current value flowing through the motor 5 is similarly set to 5 / 10.

[0057] Thus, when the ambient temperature Tc is relatively high, the lower the input voltage HV is, the lower the ambient temperature Tc is, or the higher the input voltage HV is, the higher the ambient temperature Tc is, a fixed current (5 / 10) of half the normal starting current (10 / 10) flows through the motor 5, thereby controlling the pulsating voltage of the DC voltage applied to the electrolytic capacitor 1 within an allowable range and implementing a preheating operation of the electrolytic capacitor 1.

[0058] (2) Preheating operation (Part 2)

[0059] Then, if Figure 4 As shown, when the input voltage HV is lower than 300V when the ambient temperature Tc is below -25°C, when the input voltage HV is above 300V and lower than 350V when the ambient temperature Tc is above -24°C and below -20°C, when the input voltage HV is above 350V and lower than 400V when the ambient temperature Tc is above -19°C and below -15°C, when the input voltage HV is above 400V and lower than 450V when the ambient temperature Tc is above -14°C and below -10°C, and when the input voltage HV is above 450V and lower than 500V when the ambient temperature Tc is above -9°C and below -5°C, the control device 3 implements a preheating operation in which the current flowing through the motor 5 increases at a specified increase rate.

[0060] For example, when the input voltage HV is lower than 200V under the condition of ambient temperature Tc being above -29℃ and below -25℃, the current value at the start of the preheating operation is set to 3 / 10 (three tenths of the normal starting current), the current value at the completion is set to 7 / 10 (seven tenths of the normal starting current), and the power-on time is set to t1. Figure 5 As shown in FIG. 1 , the current flows through the motor 5 at a rate of increase from 3 / 10 to 7 / 10 during the time t1. In this case, the pulsating voltage of the DC voltage in the electrolytic capacitor 1 increases from the start of the warm-up operation, but since the internal temperature of the electrolytic capacitor 1 increases and the internal resistance component ESR decreases, it reaches MAX (maximum value) at a certain moment, and then gradually decreases even if the current increases. In addition, by making the current flowing through the motor 5 as Figure 5 The increase rate shown increases, and the internal temperature of the electrolytic capacitor 1 can be increased earlier than when a fixed current flows.

[0061] On the other hand, similarly, even when the input voltage HV is lower than 200V, the current value at the start of the preheating operation is set to 2 / 10 (two tenths of the normal starting current), the current value at the completion is set to 6 / 10 (six tenths of the normal starting current), and the power-on time is set to t2 when the ambient temperature Tc is above -39°C and below -35°C. In this case, the difference between the current value 2 / 10 at the start of the preheating operation and the current value 6 / 10 at the completion is the same as the difference when the ambient temperature Tc is above -29°C and below -25°C (the difference between 3 / 10 and 7 / 10), but as described above, the power-on time t2 is longer than t1, so the current increase rate from the start of the preheating operation to the completion is lower than the current increase rate when the ambient temperature Tc is above -29°C and below -25°C. That is, even if the input voltage HV is the same, the lower the ambient temperature Tc is, the more the control device 3 changes the current increase rate in the preheating operation in the direction of decreasing.

[0062] Furthermore, when the ambient temperature is between -39°C and -35°C, the current value flowing through the motor 5 at the start of the preheating operation is reduced to 2 / 10, compared to 3 / 10 when the ambient temperature Tc is between -29°C and -25°C. That is, even if the input voltage HV is the same, the lower the ambient temperature Tc, the more the control device 3 changes the current value at the start of the preheating operation in a decreasing direction.

[0063] Similarly, even when the ambient temperature Tc is above -29°C and below -25°C, for example, when the input voltage HV is above 450V and below 500V, the current value at the start of the preheating operation is set to 1 / 10 (one tenth of the normal starting current), the current value at the completion is set to 5 / 10 (five tenths of the normal starting current), and the power-on time is set to t5. In this case, the difference between the current value 1 / 10 at the start of the preheating operation and the current value 5 / 10 at the completion is the same as the difference when the input voltage HV is below 200V (the difference between 3 / 10 and 7 / 10), but as described above, the power-on time t5 is longer than t1, so the current increase rate from the start of the preheating operation to the completion is lower than when the input voltage HV is below 200V. That is, even at the same ambient temperature Tc, the higher the input voltage HV, the more the control device 3 changes the current increase rate in the preheating operation in a decreasing direction.

[0064] Furthermore, when the input voltage HV is 450 V or more and less than 500 V, the current value flowing through the motor 5 at the start of the preheating operation is reduced to 1 / 10, compared to 3 / 10 when the input voltage HV is less than 200 V. That is, even at the same ambient temperature Tc, the higher the input voltage HV, the more the control device 3 changes the current value at the start of the preheating operation in a decreasing direction.

[0065] Figure 4 The preheating operation conditions in other ambient temperatures Tc and input voltages HV also have the same tendency. Even at the same input voltage HV, the lower the ambient temperature Tc, the more the control device 3 changes the current value at the start of the preheating operation in a decreasing direction. Even at the same ambient temperature Tc, the higher the input voltage HV, the more the control device 3 changes the current value at the start of the preheating operation in a decreasing direction.

[0066] When the preheating operation Figure 2 When the preheating operation is completed in step S5, the control device 3 proceeds to step S6 and drives the motor 5 with a starting current of 5 / 10, which is half of the normal starting current (10 / 10), to start normal operation. That is, after the preheating operation is completed, the control device 3 limits the value (5 / 10) of the current flowing through the motor 5 by the normal value (10 / 10).

[0067] As described above, when the ambient temperature Tc detected by the temperature sensor 4 is lower than the prescribed temperature T1, the control device 3 drives on specific switching elements 6u, 7v, 7w selected from a plurality of switching elements 6u~6w, 7u~7w before starting the normal operation of the motor 5, thereby performing a preheating operation in which a current that can control the pulsating voltage of the DC voltage within an allowable range flows through the motor 5 at a prescribed rising rate while keeping the motor 5 stopped. This allows the internal temperature of the electrolytic capacitor 1 to rise faster while suppressing the pulsating voltage of the DC voltage within an allowable range.

[0068] This can avoid the destruction of the electrolytic capacitor 1 in a low-temperature environment, and shorten the warm-up operation time (non-operation time) required from the start instruction until the motor 5 starts rotating.

[0069] In the embodiment, the control device 3 changes the rate of increase of the current flowing through the motor 5 based on the input voltage HV and the ambient temperature Tc detected by the temperature sensor 4. Therefore, the internal temperature of the electrolytic capacitor 1 can be increased more safely and efficiently by the warm-up operation.

[0070] In this case, in the embodiment, the control device 3 changes the rate of increase of the current flowing through the motor 5 to a lower direction as the input voltage HV is higher, so the internal temperature of the electrolytic capacitor 1 can be safely and quickly increased by the warm-up operation.

[0071] In the embodiment, the control device 3 changes the value of the current flowing through the motor 5 to a lower value when the warm-up operation starts as the input voltage HV increases, thereby more effectively avoiding damage to the electrolytic capacitor 1 caused by the pulsating voltage of the DC voltage.

[0072] In the embodiment, the control device 3 changes the rate of increase of the current flowing through the motor 5 to decrease as the ambient temperature Tc detected by the temperature sensor 4 decreases. Therefore, the internal temperature of the electrolytic capacitor 1 can be safely and quickly increased by the warm-up operation.

[0073] In this case, in the embodiment, the lower the ambient temperature Tc detected by the temperature sensor 4 is, the lower the control device 3 changes the value of the current flowing through the motor 5 when the preheating operation starts, thereby more effectively avoiding damage to the electrolytic capacitor 1 caused by the pulsating voltage of the DC voltage.

[0074] Furthermore, in the embodiment, since the control device 3 limits the value of the current flowing through the motor 5 in the normal operation after the warm-up operation is completed, it is possible to more effectively avoid damage to the electrolytic capacitor 1 in a low-temperature environment.

[0075] (3) Preheating operation (Part 3)

[0076] In an extremely severe environment, that is, when the ambient temperature Tc is extremely low and the input voltage HV is also extremely high, the control device 3 changes the rate of increase of the current during the preheating operation step by step according to the passage of time. This example is represented as Figure 4 That is, when the ambient temperature Tc of the electrolytic capacitor 1 detected by the temperature sensor 4 is below -30°C and the input voltage HV from the battery BAT is above 450V and below 500V, the control device 3 Figure 2 In the preheating operation started in step S4, first, the current value at the start of the preheating operation is set to 1 / 10 (one tenth of the normal starting current), and the current value at the time t6 after the start is set to 2 / 10 (two tenths of the normal starting current), and then the motor 5 is energized. Then, the state is switched to a state in which the current value at the time of completion of the preheating operation after the time t7 after the time t6 has passed is set to 5 / 10 (five tenths of the normal starting current) to energize.

[0077] Therefore, if Figure 6 As shown, in the motor 5, from the start of the warm-up operation to the time t6, the current flows at a rising rate of 1 / 10 to 2 / 10 during the power-on time t6, and from the moment of the time t6 to the time t7, the current flows at a rising rate of 2 / 10 to 5 / 10 during the power-on time t7. Here, as described above, in the embodiment, the power-on time t6 is longer than t7, and the current difference from the time t6 to the time t7 is larger than the current difference from the start to the time t6, so the current rising rate from the start to the time t6 is low, and then the current rising rate to the time t7 becomes high. In addition, it is sufficient to ensure the change of the related step-like rising rate, and the magnitude relationship between the power-on times t6 and t7 is not limited to the embodiment.

[0078] Here, the internal resistance component ESR of the electrolytic capacitor 1 is extremely large at low temperatures and tends to decrease rapidly as the internal temperature rises. Figure 6 From the start of the preheating operation, the pulsating voltage of the DC voltage in the electrolytic capacitor 1 increases, but the rising rate of the current until the time t6 is small, the internal temperature of the electrolytic capacitor 1 increases, and the internal resistance component ESR also drops sharply, so the MAX1 (maximum value 1) of the pulsating voltage is relatively low within the allowable range.

[0079] In addition, the rate of increase of the current from time t6 to time t7 until the preheating operation is completed becomes higher, but at this moment, the internal resistance component ESR of the electrolytic capacitor 1 decreases significantly, so the ripple voltage is less than another MAX2 (maximum value 2) within the allowable range, and then it will slowly decrease even if the current increases. As described above, in an environment where the ambient temperature Tc and the input voltage HV are extremely severe, the control device 3 changes the rate of increase of the current flowing through the motor 5 in a multi-stage (two-stage in the embodiment) manner according to the passage of time during the preheating operation, and changes the rate of increase of the current flowing through the motor 5 in a higher direction as time passes from the start of the preheating operation, so that the internal temperature of the electrolytic capacitor 1 can be raised more safely and quickly.

[0080] in addition, Figure 6 The time axis shown is not fixed, and the portion at the power-on time t6 is reduced and the portion at the power-on time t7 is expanded to exaggerate the image. In addition, the current axis is also displayed larger than the actual value as the current axis increases.

[0081] In addition, Figure 4 In the embodiment of the present invention, the preheating operation condition is set based on the input voltage HV and the ambient temperature Tc (the temperature of the electrolytic capacitor 1), but the present invention is not limited thereto, and the preheating operation condition may be set based on only the input voltage HV, or conversely, may be set based on only the ambient temperature Tc. However, by performing the preheating operation based on both the input voltage HV and the ambient temperature Tc as in the embodiment, more accurate control can be performed.

[0082] Furthermore, in the warm-up operation of (3) above, the rate of increase of the current is changed in two stages, but it may be changed more finely in a plurality of stages of three or more stages.

[0083] In addition, in the embodiment, a three-phase inverter circuit 2 is described, but the present invention is not limited to this. The inverter circuit 2 may have any number of phases, such as four phases, and may be appropriately set according to the number of phases of the applied motor 5 (electric motor).

[0084] The inverter device IV is not limited to the vehicle-mounted inverter device of the embodiment, but can be applied to various electrical equipment such as a general air conditioner.

[0085] Description of symbols

[0086] 1 Electrolytic capacitor

[0087] 2 Inverter Circuit

[0088] 3. Control Device

[0089] 4 Temperature Sensor

[0090] 5. Motor (electric motor)

[0091] 6u~6w、7u~7w switching elements

[0092] BAT Battery

[0093] ESR Internal resistance component

[0094] IV Inverter unit.

Claims

1. An inverter device, characterized in that: include: an electrolytic capacitor that smoothes the input voltage to generate a DC voltage; an inverter circuit for generating an AC voltage according to the DC voltage to drive the motor; A temperature sensor, which detects the temperature of the electrolytic capacitor or the temperature of its surroundings; as well as a control device for controlling driving of a plurality of switching elements included in the inverter circuit, When the temperature detected by the temperature sensor is lower than a specified temperature, the control device drives a specific switching element selected from the plurality of switching elements to be turned on before the normal operation of the motor begins, thereby performing a preheating operation while keeping the motor stopped. The preheating operation allows a current to flow through the motor at a specified rising rate so as to control the pulsating voltage of the DC voltage applied to the electrolytic capacitor within an allowable range.

2. The inverter device according to claim 1, characterized in that: The control device changes a rate of increase of a current flowing through the motor based on the input voltage and the temperature detected by the temperature sensor.

3. The inverter device according to claim 2, characterized in that: The control device changes the rate of increase of the current flowing through the motor in a decreasing direction as the input voltage increases.

4. The inverter device according to claim 3, characterized in that: The control device changes the value of the current flowing through the electric motor when the warm-up operation is started in a direction to decrease as the input voltage increases.

5. The inverter device according to any one of claims 2 to 4, characterized in that: The control device changes the rate of increase of the current flowing through the electric motor in a decreasing direction as the temperature detected by the temperature sensor is lower.

6. The inverter device according to claim 5, characterized in that: The control device changes the value of the current flowing through the electric motor at the start of the warm-up operation in a direction to decrease the lower the temperature detected by the temperature sensor.

7. The inverter device according to any one of claims 1 to 4, characterized in that: The control device changes the rate of increase of the current flowing through the electric motor in multiple stages as time passes during the warm-up operation.

8. The inverter device according to claim 7, characterized in that: The control device changes the rate of increase of the current flowing through the electric motor in a direction to increase as time passes after the warm-up operation is started.

9. The inverter device according to any one of claims 1 to 4, characterized in that: The control device limits a value of a current flowing through the electric motor during the normal operation after the warm-up operation is completed.

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