Auto recovering protection of electromechanical components in a high magnetic field

1. An apparatus for protecting electromechanical components from excessive current draw due to saturation by a magnetic field, the apparatus comprising:

a current sensor which senses current draw in excess of safe operating conditions by a protected device; and

a current switch connected to the current sensor and interposed between a power supply and the protected device which interrupts the current flow to the protected device based on the current draw sensed by the current sensor;

wherein the apparatus is a separate component which the protected device plugs into and in turn plugs into a power outlet.

2. The apparatus according to claim 1 , wherein the current switch restarts the current flow when saturation conditions are reduced such that current in excess of the safe operating conditions is no longer drawn.

3. The apparatus according to claim 1 , wherein the safe operating conditions are determined by a hysteresis curve of a ferrous electromechanical component of the protected device.

4. The apparatus according to claim 1 , further including:

a warning device which warns a clinician that current is interrupted and the device has stopped functioning, the warning device includes at least one of:

a visual indicator;

an audible indicator;

a signal to the protected device; and

a signal to a host system.

5. The apparatus according to claim 1 , further including:

a time delay circuit which delays interruption of the current flow by the current switch by a pre-determined time period.

6. The apparatus according to claim 1 , further including:

a circuit which controls the current switch based on the sensed current draw by the current sensor, the circuit holding the current switch open for a pre-selected duration.

7. The apparatus according to claim 6 wherein after the preselected duration, the current switch closes supplying current to the device until and unless the current sensor senses that the current draw exceeds the safe operating conditions.

8. The apparatus according to claim 1 , wherein the protected device includes a patient monitoring device.

9. The apparatus according to claim 1 , wherein the protected device includes at least one of:

a pump;

a motor; and

a solenoid.

10. The apparatus according to claim 1 , wherein the protected device includes at least one of:

a NIBP monitor;

a CO2 monitor;

a printer;

a ventilator;

an anesthesia workstation;

an injector;

an infusion pump;

an entertainment device; and

an anesthesia gas monitor.

11. A MRI scanner room power supply comprising:

an MRI scanner which generates a magnetic field of at least 10,000 gauss; and

the apparatus according to claim 1 , for protecting a medical device for use in conjunction with a patient to be scanned by the MRI scanner by interrupting the current flow to the medical device in response to being moved into sufficient proximity to the MRI scanner that ferrous components in the medical device saturate.

12. An apparatus for protecting an electromechanical component from excessive current draw due to saturation by a magnetic field, the apparatus comprising:

a current sensor connected to sense current draw by a protected device;

a current switch interposed between a power supply and the protected device and configured to interrupt the current flow to the protected device in response to the current sensor sensing the current draw by the protected device exceeds a threshold; and

a time delay circuit which delays interruption of the current flow by the current switch by a pre-determined time period.

13. The apparatus according to claim 12 , wherein:

the current switch comprises an integrated circuit connected to the current sensor to compare the sensed current with the threshold and control an FET to open in accord with the comparison; and

the time delay circuit comprises a resistor and a capacitor connected with the integrated circuit to delay opening of the FET by the pre-determined time period.

14. The apparatus of claim 13 wherein the integrated circuit operates to close the FET after a selected duration and to subsequently reopen the FET if the current draw by the protected device is still in excess of the threshold.

15. The apparatus of claim 12 wherein the current switch is configured to periodically close to re-check the current draw and to re-open if the current draw by the protected device is still in excess of the threshold.

16. The apparatus of claim 12 wherein the current switch activates a light or tone generator to indicate the interruption of current flow to the protected device.

17. The apparatus of claim 12 wherein the apparatus is a separate component from the protected device.