Fault monitor for fault tolerant implantable pump
A implantable pump system comprises an implantable pump motor and an external unit. An inverter comprises respective phases with redundant legs connected in parallel, and respective current sensors in series with each leg generating a respective measured current. A cable redundantly couples the inverter to the motor. The cable includes a respective conductor coupling each redundant leg to a respective phase of the motor. The controller receives the measured currents, monitors for a fault in the conductors by comparing the measured currents in the respective redundant legs. A fault in a pair of redundant conductors is detected if a ratio of the respective measured currents is not within a predetermined range.
1. A pump system comprising:
an implantable pump unit having a multiphase brushless motor;
an external unit including a controller and an H-bridge inverter, wherein the H-bridge inverter comprises:
a first phase with first and second redundant legs connected in parallel;
a first current sensor in series with the first leg generating a first measured current;
a second current sensor in series with the second leg generating a second measured current;
a second phase with third and fourth redundant legs connected in parallel;
a third current sensor in series with the third leg generating a third measured current; and
a fourth current sensor in series with the fourth leg generating
a fourth measured current; and
a cable redundantly coupling the H-bridge inverter to the motor, wherein the cable includes a first conductor coupling the first leg to a first respective phase of the motor, a second conductor coupling the second leg to the first respective phase of the motor, a third conductor coupling the third leg to a second respective phase of the motor, and a fourth conductor coupling the fourth leg to the second respective phase of the motor;
wherein the controller receives the measured currents, monitors for a fault in the first or second conductors by comparing the first and second measured currents, and monitors for a fault in the third or fourth conductors by comparing the third and fourth measured currents.
2. The system of claim 1 wherein the controller sums the first and second measured currents to provide a first phase current, sums the third and fourth measured currents to provide a second phase current, and controls operation of the H-bridge inverter in response to the phase currents.
3. The system of claim 1 wherein the first and second measured currents are compared by forming a first ratio of the first and second measured currents, the fault in the first or second conductors being detected if the first ratio is not within a predetermined range.
4. The system of claim 3 wherein the third and fourth measured currents are compared by forming a second ratio of the third and fourth measured currents, the fault in the third or fourth conductors being detected if the second ratio is not within the predetermined range.
5. The system of claim 1 wherein the H-bridge inverter further comprises a third phase with fifth and sixth redundant legs, a fifth current sensor in series with the fifth leg generating a fifth measured current, and a sixth current sensor in series with the sixth leg generating a sixth measured current;
wherein the cable further includes a fifth conductor coupling the fifth leg to a third respective phase of the motor, and a sixth conductor coupling the sixth leg to the third respective phase of the motor; and
wherein the controller monitors for a fault in the fifth or sixth conductors by comparing the fifth and sixth measured currents.
6. The system of claim 5 wherein the measured currents of each respective phase are compared by forming a respective ratio of the respective measured currents, the fault in the respective conductors for a respective phase being detected if the respective ratio is not within a predetermined range.