OPERATING METHOD AND POWER ELECTRONICS FOR AN ELECTRIC MOTOR

Abstract

A method for operating an electric motor is provided which includes power electronics of a drive system operating an electric motor of the drive system using clock signals, as well as power electronics for a drive system and a vehicle.

Claims

1. A method for operating an electric motor, comprising: operating, by power electronics of a drive system, an electric motor of the drive system using clock signals; and selectively operating the electric motor, at each operating point of the electric motor using the clock signals.

2. The method according to claim 1, wherein the power electronics provides the clock signals for an operating point with a power of the electric motor below a maximum power of the electric motor.

3. The method according to claim 1, wherein the power electronics provide the clock signals for an operating point with a power of the electric motor below a limit power rating of the electric motor for pulse width modulation instead of pulse width modulation.

4. The method according to claim 1, wherein the power electronics provide the clock signals for an operating point with a power of the electric motor above a limit power rating of the electric motor for pulse width modulation instead of overmodulation.

5. The method according to claim 1, wherein the power electronics heat a rotor and/or a stator of the electric motor using the clock signals.

6. The method according to claim 5, wherein at least one flux harmonic of the clock signals in a d/q reference system rotating with the rotor has a d component.

7. The method according to claim 5, wherein the rotor and/or the stator heats an oil arranged in the electric motor and flowing around the rotor and/or the stator for heating a traction battery of an electrically drivable vehicle.

8. The method according to claim 1, wherein a permanently excited synchronous motor, a synchronous reluctance motor, or an externally excited synchronous motor is operated as the electric motor.

9. A power electronics system for a drive system configured to operate an electric motor of the drive system in a method including: operating, by the power electronics system, the electric motor using clock signals; and selectively operating the electric motor, at each operating point of the electric motor, using the clock signals.

10. A vehicle with an electric drive system, comprising: a traction battery; an electric motor; and the power electronics system according to claim 9.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0032] Embodiments are schematically illustrated in the drawings.

[0033] FIG. 1 shows a vehicle according to one embodiment in a partial block diagram.

[0034] FIG. 2 shows a bar graph of a power range of the electric motor shown in FIG. 1.

[0035] FIG. 3 shows a spectral diagram of clock signals provided by the power electronics shown in FIG. 1.

DETAILED DESCRIPTION

[0036] FIG. 1 shows a vehicle 1 according to one embodiment in a partial block diagram. The vehicle 1 is electrically drivable and comprises an electric drive system 10 having a traction battery 102, an electric motor 101, and power electronics 100. The electric motor 101 comprises a rotor 1010 and a stator 1011 and may be configured as a permanently excited synchronous motor, a synchronous reluctance motor, or an externally excited synchronous motor. The rotor 1010 and the stator 1011 may have an oil 2 flowing around them.

[0037] The power electronics 100 are suitable for the drive system 10 and configured to operate the electric motor 101 in a method as described herein.

[0038] The power electronics 100 of the drive system 10 operate the electric motor 101 of the drive system 10 by means of clock signals 4.

[0039] FIG. 2 shows a bar graph of a power range 3 of the electric motor 101 shown in FIG. 1. The power range 3 comprises a maximum power 31 of the electric motor 101 and a limit power rating 30 of the electric motor 101, which is lower than the maximum power 31.

[0040] At the maximum power 31, the power electronics 100 operate the electric motor 101 with the clock signals 4. Below the limit power rating 30, the power electronics 100 may provide pulse width modulation as a timing of the alternating current voltage for normal operation of the electric motor 101. Above the limit power rating 30, the power electronics 100 may provide overmodulation as a timing of the alternating current voltage for normal operation of the electric motor 101.

[0041] The electric motor 101 is selectively operated by means of the clock signals 4, by the power electronics 100 at each operating point 32 of the electric motor 101.

[0042] Thus, the power electronics 100 may provide the clock signals 4 for an operating point 32 with a power of the electric motor 101 below the maximum power 31 of the electric motor 101.

[0043] The power electronics 100 may further provide the clock signals 4 for an operating point 32 with a power of the electric motor 101 below the limit power rating 30 of the electric motor 101 for one pulse width modulation instead of the pulse width modulation.

[0044] Further, the power electronics 100 may provide the clock signals 4 for an operating point 32 with a power 3 of the electric motor 101 above a limit power rating 30 of the electric motor 101 for pulse width modulation instead of overmodulation.

[0045] At least one flux harmonic of the clock signals 4 may have a d component in a d/q reference frame rotating with the rotor 1010.

[0046] The power electronics 100 may use the clock signals 4 to heat the rotor 1010 and/or the stator 1011 of the electric motor 101.

[0047] In particular, the rotor 1010 and/or the stator 1011 may heat an oil 2 disposed in the electric motor 101 and flowing around the rotor 1010 and/or the stator 1011 to heat the traction battery 102 of the vehicle 1.

[0048] Depending on the embodiment of the vehicle 1, a permanently excited synchronous motor, a synchronous reluctance motor, or an externally excited synchronous motor may be operated as the electric motor 101.

[0049] FIG. 3 shows a spectral diagram 5 of clock signals 4 provided by the power electronics 100 shown in FIG. 1. By way of example, the clock signals 4 are shown in the form of a square-wave voltage U.sub.UV having an amplitude U.sub.d.

[0050] The spectral diagram 5 comprises an abscissa 50, on which integer multiples 500, which is to say harmonics of order v, of a rotational frequency 501 of the rotor 1010, which is to say a fundamental oscillation, are plotted, and an ordinate 51, on which amplitudes 510, 511 respectively assigned to the orders v are plotted, and shows a bar-shaped spectrum of the clock signals 4 shown.

[0051] The rotational frequency 501 is assigned an amplitude 510 of magnitude 100%. The integer multiples 500 are each assigned amplitudes 500 of smaller magnitudes than 100%, which decrease inversely proportional to the order v. For example, it can be read that the two lowest harmonics of orders 5 and 7 are assigned amplitudes of respectively 20% and 14%. The lowest harmonics of the clock signals 4 provide the main contribution to the heating of the rotor 1010 of the electric motor 101.

[0052] German patent application no. 10 2021 130907.7, filed Nov. 25, 2021, to which this application claims priority, is hereby incorporated herein by reference, in its entirety.

[0053] Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.