Drive system and method for operating such a drive system
A drive system for an electric motor includes a connection for a battery, and an inverter having an input side connected to an intermediate circuit and an output side having a connection for an electric motor. The intermediate circuit includes a first thyristor connected in parallel with an intermediate circuit capacitance. The drive system may also include a rectifier having an input side connected at the output side of the inverter in parallel with the electric motor, and a second thyristor connected an output side of the rectifier. The first/second thyristor are configured to be activated by a monitor incorporated in or assigned to the drive system. In the event of a malfunction, the input and/or output side of the inverter can be electrically isolated to allow a multiply redundant armature short circuit.
1. A drive system for an electric motor, comprising:
a connection for a battery,
an inverter having an input side connected to an intermediate circuit having a DC intermediate circuit voltage and an output side having a connection for the electric motor, said intermediate circuit comprising an intermediate circuit capacitance and a first thyristor connected directly in parallel with the intermediate circuit capacitance and configured to be activated by a monitor incorporated in or assigned to the drive system when a measure of the intermediate circuit voltage exceeds a predetermined threshold value so as to cause an armature short circuit of the electric motor,
a rectifier having an input side connected at the output side of the inverter in parallel with the electric motor and the rectifier further having an output side providing a rectified DC output voltage which is a measure of the AC output voltage of the inverter, and
a second thyristor connected to the output side of the rectifier and configured to be activated by a monitor incorporated in or assigned to the drive system when the rectified DC output voltage exceeds a predetermined threshold value.
2. The drive system of claim 1 , further comprising a fuse disposed between the battery and the intermediate circuit, wherein the fuse and the first thyristor are connected in series to the battery operating as power source upon activation of the first thyristor.
3. The drive system of claim 1 , wherein the second thyristor is activated by the monitor when a measure of the AC output voltage of the inverter exceeds a predetermined threshold value.
4. The drive system of claim 1 , wherein the inverter comprises three upper transistors and three lower transistors, and wherein the monitor activates either the three lower transistors or the three upper transistors, or jointly the three lower and the three upper transistors, in addition to activating the first thyristor.
5. The drive system of claim 1 , wherein the inverter comprises three upper transistors and three lower transistors, and wherein the monitor activates either the three lower transistors or the three upper transistors, or jointly the three lower and the three upper transistors, in addition to activating the second thyristor.
6. The drive system of claim 4 , wherein the monitor terminates activation of the three upper and/or the three lower transistors when a measure of a speed of the electric motor drops below a predetermined threshold value.
7. The drive system of claim 5 , wherein the monitor terminates activation of the three upper and/or the three lower transistors when a measure of a speed of the electric motor drops below a predetermined threshold value.
8. The drive system of claim 4 , further comprising at least one electrical or electronic switch disposed between the battery and the intermediate circuit, wherein at least one electrical or electronic switch is opened before termination of the activation of the three upper and/or the three lower transistors by the monitor.
9. The drive system of claim 5 , further comprising at least one electrical or electronic switch disposed between the battery and the intermediate circuit, wherein at least one electrical or electronic switch is opened before termination of the activation of the three upper and/or the three lower transistors by the monitor.
10. The drive system of claim 1 , wherein the monitor activates the second thyristor and activates the inverter to cause the inverter to output successive short voltage pulses, and monitors, during or after each voltage pulse, whether the respective voltage pulse produces a current flow.