Switch arrangement
Control apparatus includes an inverter having a plurality of switches arranged to generate a plurality of different voltage phases, and a switch arrangement having a rectifier arranged to be coupled to the respective plurality of coil windings. The rectifier is arranged to rectify an alternating current flowing in respective coil windings and provide the rectified AC current to a DC output, and a switch is coupled across the DC output. The switch is operable to electrically isolate the plurality of coil windings from each other. A controller is arranged to operate the switch to electrically isolate the plurality of coil windings upon a failure of an inverter switch or upon detection of a current flow in the inverter or the switch that is greater than a predetermined threshold.
1. A control apparatus for controlling an electric motor or generator having a plurality of coil windings that during operation of the electric motor or generator are electrically coupled to form a star point connection and that are arranged to have different voltage phases applied across the respective coil windings, the control apparatus comprising an inverter having a plurality of switches arranged to generate the plurality of different voltage phases, a switch arrangement comprising a rectifier arranged to be coupled to the respective plurality of coil windings, wherein the rectifier is arranged to rectify an alternating current flowing in the respective coil windings and provide the rectified AC current to a DC output; and a switch coupled across the DC output, wherein the switch is operable to electrically isolate the plurality of coil windings from each other, and a controller arranged to operate the switch to electrically isolate the plurality of coil windings upon a failure of an inverter switch or upon detection of a current flow in the inverter or the switch that is greater than a predetermined threshold.
2. A control apparatus according to claim 1 , wherein the switch arrangement further comprises a voltage clamping device coupled across the DC output in parallel with the switch.
3. A control apparatus according to claim 2 , wherein the voltage clamping device is a varistor, a zener diode, a capacitor, a snubber circuit or an actively controlled device.
4. A control apparatus according to claim 2 , wherein the voltage clamping device has a clamping voltage greater than a DC bus voltage coupled to the inverter.
5. A control apparatus according to claim 1 further comprising means to determine current flow in the plurality of coil windings and/or a temperature within the electric motor or generator and/or torque generated by the electric motor or generator, and a failure of an inverter switch is identified based on predetermined current and/or temperature and/or torque value.
6. A control apparatus according to claim 1 , wherein the controller is arranged to operate the switch to electrically isolate the plurality of coil windings if no AC voltage is generated by the inverter.
7. A control apparatus according to claim 1 , wherein the inverter and switch arrangement are formed on the same power module for operating an electric motor or generator.
8. An electric motor or generator comprising a control apparatus according to claim 1 .
9. An electric motor or generator according to claim 8 , having a plurality of sub motors, wherein each sub motor has a plurality of coil windings that during operation of the electric motor or generator are electrically coupled to form a star point connection and that are arranged to have different voltage phases applied across the respective coil windings, wherein each sub motor has a control apparatus according to claim 4 coupled to the respective sub motor to control operation of the respective sub motor.