Abstract: Method for controlling an electrical machine (14), in particular for an electric or hybrid drive train (12) of a motor vehicle (10), wherein the electrical machine (14) can provide a torque (T) both at positive and at negative speeds (n), having the steps of:—using a characteristic curve (M; G) to check whether a torque desired value (72; 74) can or may be provided by the electrical machine (14), wherein the characteristic curve (M; G) represents a limit torque with respect to the speed (n) and has a first section (A1; A4) for positive speeds and a second section (A2; A3) for negative speeds. In this case, the first section (A1; A4) and the second section (A2; A3) are arranged in the same quadrant (I; IV) of the characteristic curve (70).

Abstract: A method and a device for operating an electrical machine having separate excitation, especially a synchronous machine. With the aid of a sensor system, a variable characterizing a rotor temperature and/or a stator temperature are/is determined, and an excitation current and stator currents for the electrical machine are specified by a control unit as a function of the variable characterizing the rotor temperature and/or the stator temperature, at least in specifiable operating ranges.

Abstract: A device and a method for detecting a polarity reversal on a low voltage side of a DC voltage transformer in a dual-voltage vehicle electrical system, particularly in a motor vehicle. A current flow is enabled, in this instance, in a connecting line on the low voltage side of the DC voltage transformer by a controllable switching element, a current is detected in a connecting line on the low voltage side of the DC voltage transformer, with the aid of a current sensor system, the direction of the detected current is evaluated by an evaluation unit and a polarity reversal is detected if the direction of the detected current differs from an expected current direction.

Abstract: Method for controlling an electrical machine (14), in particular for an electric or hybrid drive train (12) of a motor vehicle (10), wherein the electrical machine (14) can provide a torque (T) both at positive and at negative speeds (n), having the steps of: using a characteristic curve (M; G) to check whether a torque desired value (72; 74) can or may be provided by the electrical machine (14), wherein the characteristic curve (M; G) represents a limit torque with respect to the speed (n) and has a first section (A1; A4) for positive speeds and a second section (A2; A3) for negative speeds. In this case, the first section (A1; A4) and the second section (A2; A3) are arranged in the same quadrant (I; IV) of the characteristic curve (70).

Abstract: In a method for determining a power limiting value for an electric machine in a vehicle, the electric machine being assigned an energy storage device, an intermediate power value is calculated from a maximally allowable current of the energy storage device and an instantaneous voltage. A corrected intermediate power value is determined by adding at least one power loss to the intermediate power value. A first correction value is determined for reducing the absolute value of the corrected intermediate power value if an instantaneous power of the energy storage device is greater than the absolute value of the calculated intermediate power value. The power limiting value is determined by superimposing the first correction value on the corrected intermediate power value.

Abstract: A method and a device for operating an electrical machine having separate excitation, especially a synchronous machine. With the aid of a sensor system, a variable characterizing a rotor temperature and/or a stator temperature are/is determined, and an excitation current and stator currents for the electrical machine are specified by a control unit as a function of the variable characterizing the rotor temperature and/or the stator temperature, at least in specifiable operating ranges.

Abstract: In a method for determining a power limiting value for an electric machine in a vehicle, the electric machine being assigned an energy storage device, an intermediate power value is calculated from a maximally allowable current of the energy storage device and an instantaneous voltage. A corrected intermediate power value is determined by adding at least one power loss to the intermediate power value. A first correction value is determined for reducing the absolute value of the corrected intermediate power value if an instantaneous power of the energy storage device is greater than the absolute value of the calculated intermediate power value. The power limiting value is determined by superimposing the first correction value on the corrected intermediate power value.

Abstract: A device and a method for detecting a polarity reversal on a low voltage side of a DC voltage transformer in a dual-voltage vehicle electrical system, particularly in a motor vehicle. A current flow is enabled, in this instance, in a connecting line on the low voltage side of the DC voltage transformer by a controllable switching element, a current is detected in a connecting line on the low voltage side of the DC voltage transformer, with the aid of a current sensor system, the direction of the detected current is evaluated by an evaluation unit and a polarity reversal is detected if the direction of the detected current differs from an expected current direction.