Method and device for operating a brushless motor
View Patent ↗A method and device for operating a brushless electric motor, having windings controlled by an inverter using six switches. The inverter includes three outputs that are associated with the windings of the electric motor. A respective power semiconductor switch is arranged between the outputs of the inverter and the windings, and wherein a detection unit detects defective switches, a measuring unit measures the voltage at the outputs of the inverter, and a motor angle position sensor determines the motor angle position arc. The invention further relates to a device for operating a brushless electric motor. The inverter is switched off after a defective switch has been detected, such that no additional power is introduced in the windings of the electric motor. The motor angle position sensor consecutively opens the power semiconductor switches in a predetermined motor angle position.
1. A method for operating a brushless electric motor with an AC converter comprising three outputs that are allocated to the windings (U, V, W) of the electric motor, a respective power semiconductor switch arranged between each output of the AC converter and the windings (U, V, W) of the brushless electric motor, a plurality of supply voltage switches, a detection unit, a measuring unit, a motor position angle sensor, and a switch driver circuit connected to an output of the motor position angle sensor, the method comprising:
detecting, by the detection unit, a defective switch of the plurality of supply voltage switches,
measuring, by the measuring unit, the voltage at the outputs of the AC converter,
determining, by the motor position angle sensor, the motor position angle (φ), and
performing the following steps sequentially:
controlling all of the plurality of supply voltage switches to switch off following the detection of the defective switch so that power is no longer introduced into the windings (U, V, W) of the electric motor, and then
while all of the plurality of supply voltage switches are switched off, generating and directly applying, by the switch driver circuit in response to an output signal of the motor position angle sensor, control signals to control the power semiconductor switches to individually switch off in succession at previously defined motor position angles (φU, φV, φW) respectively, the previously defined motor position angles (φU, φV, φW) are defined to prevent electric current generated by rotation of the electric motor from flowing to the plurality of supply voltage switches.
2. The method as claimed in claim 1 , wherein the motor position angles (φU, φV, φW) are allocated in each case to a winding (U, V, W) and to the power semiconductor switch thereof and are selected so that the allocated power semiconductor switches are not damaged during the opening process.
3. The method as claimed in claim 1 , wherein the motor position angles (φU, φV, φW) are selected so that the drain current (ID) prevailing at the power semiconductor switches is zero or almost zero.
4. The method as claimed in claim 1 , wherein the motor position angles (φU, φV, φW) are selected so that the drain current (ID) prevailing at the power semiconductor switches is negative.
5. The method as claimed in claim 1 , wherein the motor position angles (φU, φV, φW) are not dependent upon the position of the defective switch and are defined solely in dependence upon the rotation direction of the electric motor.
6. A device for operating a brushless electric motor comprising:
an AC converter including three outputs that are allocated to the windings (U, V, W) of the electric motor;
a respective power semiconductor switch arranged between each output of the AC converter and the windings (U, V, W) of the brushless electric motor;
a plurality of supply voltage switches;
a detection unit for detecting a defective switch of the plurality of supply voltage switches;
a measuring unit for measuring the voltage at the outputs of the AC converter; and
a motor position angle sensor for determining the motor position angle (φ); and
a switch driver circuit connected to an output of the motor position angle sensor;
wherein the following steps are performed sequentially:
all of the plurality of supply voltage switches are switched off after the detection of the defective switch so that power is no longer introduced into the windings (U, V, W) of the electric motor, and then
while all of the plurality of supply voltage switches are switched off, the switch driver circuit, in response an output signal of the motor position angle sensor, generates and directly applies control signals to control the power semiconductor switches to individually switch off in succession at previously defined motor position angles (φU, φV, φW) respectively, the previously defined motor position angles (φU, φV, φW) are defined to prevent electric current generated by rotation of the electric motor from flowing to the plurality of supply voltage switches.
7. The device as claimed in claim 6 , wherein the motor position angle sensor is designed so as to allocate the motor position angles (φU, φV, φW) in each case to a winding (U, V, W) and the power semiconductor switch of said winding and to select said motor position angles so that the allocated power semiconductor switches are not damaged during the opening process.
8. The device as claimed in claim 6 , wherein the motor position angle sensor is designed so as to select the motor position angles (φU, φV, φW) so that the drain current (ID) that is prevailing at the power semiconductor switches is zero, almost zero or negative.
9. The device as claimed in claim 6 , wherein the power semiconductor switches are embodied as power MOSFET transistors.
10. The device as claimed in claim 6 , wherein the unit for detecting defective switches and the unit for measuring the voltage at the outputs of the AC converter are integrated into the microcontroller.