A method for protecting an electric machine of a motor vehicle, In the method, a switch-on frequency for the electric machine is ascertained as a function of operating parameters of the motor vehicle stored in a control unit. The switch-on frequency is compared to a predefinable first threshold value. At least one further threshold value is preset. The electric machine is switched on in the event a control variance exceeds the at least one further threshold value. In the event the switch-on frequency exceeds the first predefinable threshold value, the at least one further threshold value is adapted in such a way that the switch-on frequency of the electric machine is limited.

A method for protecting an electric machine of a motor vehicle, In the method, a switch-on frequency for the electric machine is ascertained as a function of operating parameters of the motor vehicle stored in a control unit. The switch-on frequency is compared to a predefinable first threshold value. At least one further threshold value is preset. The electric machine is switched on in the event a control variance exceeds the at least one further threshold value. In the event the switch-on frequency exceeds the first predefinable threshold value, the at least one further threshold value is adapted in such a way that the switch-on frequency of the electric machine is limited.

A cart may include: a driving wheel; a motor configured to rotate the driving wheel; a motor drive circuit configured to drive the motor; a motor brake circuit configured to electrically brake the motor; a rotation speed sensor configured to detect a rotation speed of the motor; and a control device configured to control the motor via the motor drive circuit and the motor brake circuit based on a target rotation speed of the motor and the rotation speed detected by the rotation speed sensor. The motor brake circuit may include an electronically variable resistance element configured to operate in a linear mode and a switching mode in response to a control input signal. The motor brake circuit may be configured to operate. the electronically variable resistance element in the linear mode when braking the motor.

A protection apparatus and a brushless motor system reduce costs of the brushless motor system and ensure normal operation of a brushless motor. The protection apparatus includes a demagnetization apparatus and a control apparatus. The demagnetization apparatus is configured to be bridged between a rectifier circuit and an excitation winding, and is configured to consume, when the brushless motor system is faulty, excess electric energy generated on the excitation winding. The control apparatus is configured to separately connect to an excitation power supply circuit and a controller; and is configured to detect electrical parameters of an input terminal and an output terminal of the excitation power supply circuit, and when determining that the electrical parameters exceed a preset threshold, generate an alarm to the controller and adjust the output electrical parameter of the excitation power supply circuit.

A protection apparatus and a brushless motor system reduce costs of the brushless motor system and ensure normal operation of a brushless motor. The protection apparatus includes a demagnetization apparatus and a control apparatus. The demagnetization apparatus is configured to be bridged between a rectifier circuit and an excitation winding, and is configured to consume, when the brushless motor system is faulty, excess electric energy generated on the excitation winding. The control apparatus is configured to separately connect to an excitation power supply circuit and a controller; and is configured to detect electrical parameters of an input terminal and an output terminal of the excitation power supply circuit, and when determining that the electrical parameters exceed a preset threshold, generate an alarm to the controller and adjust the output electrical parameter of the excitation power supply circuit.

A motor iron-loss calculation device calculates an iron-loss value of a motor on the basis of a primary frequency and a q-axis current component in a dq-axis rotating coordinate system having a d axis in a rotor magnetic flux direction of the motor.

A motor iron-loss calculation device calculates an iron-loss value of a motor on the basis of a primary frequency and a q-axis current component in a dq-axis rotating coordinate system having a d axis in a rotor magnetic flux direction of the motor.

A method for dissipating power of an automotive electric drive system that includes a traction battery, and an inverter, wherein the inverter includes a DC bus between, and a dissipation circuit between the traction battery and DC bus, wherein the dissipation circuit includes a plurality of resistors connected in series between positive and negative terminals of the DC bus and a dissipation resistor and switch connected in series between the positive and negative terminals, the method includes responsive to a voltage across one of the plurality of resistors being less than a threshold value, deactivating the switch to prevent current flow from the positive terminal to the negative terminal through the dissipation resistor, and responsive to the voltage exceeding the threshold value, activating the switch to permit current flow from the positive terminal to the negative terminal through the dissipation resistor.

A method for dissipating power of an automotive electric drive system that includes a traction battery, and an inverter, wherein the inverter includes a DC bus between, and a dissipation circuit between the traction battery and DC bus, wherein the dissipation circuit includes a plurality of resistors connected in series between positive and negative terminals of the DC bus and a dissipation resistor and switch connected in series between the positive and negative terminals, the method includes responsive to a voltage across one of the plurality of resistors being less than a threshold value, deactivating the switch to prevent current flow from the positive terminal to the negative terminal through the dissipation resistor, and responsive to the voltage exceeding the threshold value, activating the switch to permit current flow from the positive terminal to the negative terminal through the dissipation resistor.

In a method for monitoring the operation of an electric motor and a lifting mechanism, the motor current is acquired, and the electric motor has, for example, an electromagnetically actuable brake, e.g., a holding brake. In the method, a pre-magnetization is performed when the electric motor is switched on, the characteristic of the acquired values of the motor current is monitored for an exceeding of a permissible measure of deviation from a setpoint characteristic, and a brake of the electric motor is activated, e.g., remains applied.