Inverter apparatus

{
  "publication_number": "US2012217795A1",
  "country": "US",
  "kind": "A1",
  "title": "Inverter apparatus",
  "abstract": "An inverter apparatus according to one embodiment includes switching elements and freewheel diodes which are connected to a direct-current power supply, a temperature detector provided near at least one of the switching elements, and a temperature estimation unit. The temperature estimation unit estimates temperatures of switching elements not provided with the temperature detector, based on an estimated-temperature increase value calculated by a loss model of the switching elements and freewheel diode and others, and a temperature of the switching element detected by the temperature detector.",
  "claims": [
    "1. An inverter apparatus comprising: a direct-current power supply; switching elements and freewheel diodes which are connected to the direct-current power supply; an unit which converts a direct current voltage into a predetermined alternating current voltage of a predetermined current and a predetermined frequency, depending on switching on/off of the switching elements; a temperature detector provided near at least one of the switching elements and a temperature estimation unit, wherein the temperature estimation unit estimates temperatures of freewheel diodes and switching elements not provided with the temperature detector, based on a loss model of the switching elements and freewheel diodes, a thermal resistance model of a module which fixes the switching elements and freewheel diodes, an estimated-temperature increase value calculated by the loss model and thermal resistance model, and a temperature of the switching element detected by the temperature detector. 2. The inverter apparatus of claim 1, wherein the temperature detector is provided for switching elements in a low-potential side, which forms part of the inverter apparatus, and includes an unit which selects and inputs the highest one among temperatures of the switching elements to the temperature estimation unit. 3. The inverter apparatus of claim 1, wherein the temperature estimation unit determined: the loss model of the switching elements as a sum of a conduction loss a and a switching loss, the conduction loss a from a polynomial expressed by a value of instantaneous current flowing through the switching element, a conductance rate thereof, and a temperature detected by the temperature detector, the switching loss from a polynomial expressed by an instantaneous current value flowing through the switching element, the direct current voltage, and the temperature of the at least one of the switching element detected by the temperature detector, the loss model of the freewheel diode as a sum of a conduction loss b and a recovery loss, the conduction loss b from a polynomial expressed by an instantaneous current value flowing through the freewheel diode, a conductance rate thereof, and the temperature detected by the temperature detector, and the recovery loss from a polynomial expressed by an instantaneous current value flowing through the freewheel diode, a current conductance rate thereof, the direct current voltage, and the temperature detected by the temperature detector. 4. The inverter apparatus of claim 3, wherein when an output frequency of an inverter is not higher than a frequency, the temperature estimation unit estimates temperatures of the switching elements and freewheel diode with use of the loss model, and when the output frequency of the inverter exceeds the frequency, the temperature estimation unit determined: the loss model of the switching elements as a sum of the conduction loss a and a switching loss, the conduction loss a from a polynomial expressed by an effective current value flowing through the switching elements and a temperature of the at least one of the switching elements detected by the temperature detector, the switching loss from a polynomial expressed by an effective current value flowing through the switching elements and freewheel diode, the direct current voltage and the temperature of the at least one of the switching elements detected by the temperature detector, the loss model of the freewheel diode as a sum of the conduction loss b and the recovery loss, the conduction loss b from a polynomial expressed by an effective current value flowing through the freewheel diode and the temperature of the at least one of the switching elements detected by the temperature detector, and the recovery loss from a polynomial expressed by the effective current value flowing through the freewheel diode, the direct current voltage, and the temperature of the at least one of the switching elements detected by the temperature detector. 5. The inverter apparatus of claim 1, wherein the temperature estimation unit determines the thermal resistance model to be caused by thermal resistance between all the switching elements and the freewheel diodes and a cooler, and by a heat interference caused between all the switching elements and the freewheel diodes each other, and expresses the thermal resistances and mutually causing heat interferences as thermal resistances and thermal capacities. 6. The inverter apparatus of claim 3, wherein the temperature of the at least one of the switching elements detected by the temperature detector, which is used in a polynomials for obtaining losses of the switching elements and freewheel diode, is taken as temperature of an switching element and a freewheel diode estimated just before. 7. The inverter apparatus of one of claims 1 to 5, wherein the inverter apparatus comprises a module mounted on a hybrid car of a sili-para system, which integrates switching elements forming an inverter for driving an electric motor for driving, and switching elements forming an inverter for a power generator driven by an engine, and the estimation unit estimates losses caused by the switching elements and freewheel diode for the inverter for the power generator, and estimates a temperature increase value in consideration of mutual influences of losses caused by the inverter for the electric motor and the inverter for the power generator."
  ],
  "description_excerpt": "Embodiments described herein relate generally to an inverter apparatus which drives an electric motor, and particularly to a technology for estimating a temperature of a switching element forming part of an inverter.\n\nAn electric motor is used in a hybrid car in combination with an engine or in an electric car which is driven only by an electric motor. When the electric motor is driven, an inverter is used to obtain desired torque and frequency. The inverter is built in a car and is demanded to achieve high power at high integration density to ensure a passenger space.\n\nDepending on driving environments of a car, an operation temperature of the inverter greatly changes. Particularly in a hybrid car, the inverter has a high temperature under influence of heat generation of an engine. Switching elements in the inverter have a risk that the temperature increases under influence of constant loss due to a current through the switching elements themselves and switching loss due to switching on/off, in addition to influence of such an environmental temperature, and a breakdown may occur when a certain temperature is exceeded.\n\nTo avoid breakdown of the switching elements, the temperatures of the switching elements need to be detected for protection. Since temperature detection can be performed with high accuracy by using an on-chip sensor in which a diode is assembled in an element, such a sensor is mounted on an inverter for a hybrid car. Since the on-chip sensor has a high electric potential, temperature information needs to be transferred to a micro-controller (hereinafter abbreviated as mi-con) through an insulating circuit.",
  "cpc": [
    "H02M 7/48",
    "B60L 3/003",
    "H02M 1/327"
  ],
  "ipc": [
    "B60L 1/00",
    "H02M 7/537",
    "H02M 7/5387"
  ],
  "assignees": [
    "Toshiba Corp"
  ],
  "inventors": [
    "Ryuta Hasegawa",
    "Hiroshi Mochikawa",
    "Masami Hirata",
    "Yukihiko Hatano"
  ],
  "filing_date": "2012-05-01",
  "publication_date": "2012-08-30",
  "priority_date": "2009-11-02",
  "application_number": "US-201213461201-A",
  "family_id": "43922048",
  "cited_by_count": 47,
  "citations": [
    "JPH07234162A",
    "US20030169611A1",
    "US20060114702A1",
    "US20090108794A1",
    "US20100080024A1"
  ]
}