Method for determining a coil temperature of an electric machine

• US 10,295,414 B2
• Filed: 11/04/2015
• Issued: 05/21/2019
• Est. Priority Date: 11/06/2014
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: Audi AG (Volkswagen AG)
• Inventors: Karl, Bernhard
• Primary Examiner(s): Verbitsky, Gail Kaplan
• Application Number:
  US14/932,533
• Publication Number:
  US 20160131534A1
• Time in Patent Office: 1,294 Days
• Field of Search: 374141, 374144, 374152, 374153, 374163, 374183
• CPC Class Codes: G01K 2205/00 Application of thermometers in motors, e.g. of a vehicle
• CPC Class Codes: G01K 2217/00 Temperature measurement using electric or magnetic components already present in the system to be measured
• CPC Class Codes: G01K 7/00 Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat giving results other than momentary value of temperature G01K3/00 ; Power supply therefor, e.g. using thermoelectric elements
• CPC Class Codes: G01K 7/16 using resistive elements resistive elements per se H01C, H01L

Abstract

A method for determining an actual temperature of a coil of an electric machine, includes detecting a voltage in a no-load state of the electric machine; detecting a current strength in an induced short circuit state of the electric machine; calculating an actual stator coil resistance as a function of the voltage detected during the no-load state and the current strength detected during the active short circuit” state; and calculating the actual temperature of the coil of the electric machine as a function of the actual stator coil resistance.

Claims

1. A method for determining a temperature of a stator coil of an electric machine, comprising:

measuring in a no-load state of the electric machine an open-circuit voltage across the stator coil of the electric machine;

determining from the measured open-circuit voltage a magnetic flux through the stator coil;

shorting the stator coil of the electric machine to produce an induced short circuit state and measuring in the induced short circuit state a short-circuit current strength;

calculating a stator coil resistance as a function of the magnetic flux determined during the no-load state and the short-circuit current strength measured during the induced short circuit state; and

calculating the temperature of the stator coil of the electric machine as a function of the stator coil resistance.

2. The method of claim 1, further comprising switching the electric machine into the no-load state for determining the voltage and subsequently switching the electric machine into the induced short circuit state for determining the induced current.

3. The method of claim 2, further comprising driving a vehicle with the electric machine and switching the electric machine into the no-load state and/or the short circuit state during coasting mode of the vehicle.

4. The method of claim 3, wherein the vehicle is a hybrid vehicle comprising an internal combustion engine, and wherein the method further comprises driving the vehicle with the internal combustion engine when switching into the no-load state and/or the induced short circuit state.

5. The method of claim 1, wherein the temperature of the electric machine is calculated using a model.

6. A vehicle comprising a control device configured to determine a temperature of a stator coil of an electric machine, said control device being configured to block semiconductors of a power electronics of the electric machine and measure in a no-load state of the electric machine an open-circuit voltage across the stator coil of the electric machine, to determine from the measured open-circuit voltage a magnetic flux through the stator coil, to switch the electric machine into an induced short circuit state and measure in the induced short circuit state a short-circuit current strength, to calculate a stator coil resistance as a function of the magnetic flux determined during the no-load state and the short-circuit current strength measured during the induced short circuit state, and to calculate the temperature of the coil of the electric machine as a function of the stator coil resistance.

7. The vehicle of claim 6, further comprising at least one sensor for detecting the open-circuit voltage and/or the short-circuit current strength.

8. The vehicle according to one of the claim 6, wherein the electric machine is a three-phase electric machine.