Three-phase detection module

1. A monitoring apparatus connected, in parallel with a motor, to a plurality of power supply lines, each of the plurality of power supply lines having a different phase, the monitoring apparatus comprising:

a first isolator configured to, in response to a first control signal, selectively allow a first current to flow from a first power supply line of the plurality of power supply lines to a second power supply line of the plurality of power supply lines through a third isolator, wherein the first current is electrically isolated from the first control signal;

a second isolator configured to, in response to a second control signal, selectively allow a second current to flow from the second power supply line of the plurality of power supply lines to a third power supply line of the plurality of power supply lines through the third isolator, wherein the second current is electrically isolated from the second control signal; and

a control module configured to:

generate the first control signal to control the first isolator,

generate the second control signal to control the second isolator,

receive a first signal corresponding to a total current flowing through the third isolator, wherein the total current includes both the first current and the second current, and

selectively generate a phase failure signal in response to the first signal indicating that a failure of at least one of the plurality of power supply lines has occurred.

2. The monitoring apparatus of claim 1 further comprising a fourth isolator configured to, in response to a third control signal from the control module, selectively allow a third current to flow from the third power supply line of the plurality of power supply lines to the first power supply line of the plurality of power supply lines through the third isolator, wherein the total current also includes the third current, and wherein the third current is electrically isolated from the third control signal.

3. The monitoring apparatus of claim 2 wherein the control module is configured to:

sequentially activate the first isolator, the second isolator, and the fourth isolator; and

repeat the sequential activation.

4. The monitoring apparatus of claim 2 wherein the plurality of power supply lines consists of only the first power supply line, the second power supply line, and the third power supply line.

5. The monitoring apparatus of claim 4 wherein the monitoring apparatus is further connected to a neutral line associated with the plurality of power supply lines.

6. The monitoring apparatus of claim 2 wherein the first isolator comprises a first optocoupler, the second isolator comprises a second optocoupler, and the fourth isolator comprises a third optocoupler.

7. The monitoring apparatus of claim 1 wherein the first isolator comprises a first optocoupler and the second isolator comprises a second optocoupler.

8. The monitoring apparatus of claim 1 further comprising the third isolator, wherein the third isolator is configured to output the first signal to the control module in response to the total current, wherein the first signal is electrically isolated from the total current.

9. The monitoring apparatus of claim 8 wherein the third isolator comprises an optocoupler.

10. The monitoring apparatus of claim 1 wherein the control module is configured to:

while the first isolator is activated, deactivate the second isolator; and

while the second isolator is activated, deactivate the first isolator.

11. The monitoring apparatus of claim 1 wherein the control module is configured to halt operation of the motor in response to generation of the phase failure signal.

12. The monitoring apparatus of claim 1 wherein:

the control module is configured to activate the first isolator for a predetermined duration;

the plurality of power supply lines carry periodic power signals characterized by a first period; and

the predetermined duration is based on a length of the first period.

13. The monitoring apparatus of claim 12 wherein the predetermined duration is equal to the length of the first period plus a predetermined offset.

14. The monitoring apparatus of claim 1 wherein the first signal is directly proportional to the total current.

15. The monitoring apparatus of claim 1 further comprising generating the phase failure signal in response to a peak value of the first signal over a predetermined period of time being less than a predetermined threshold.

16. A motor system comprising:

the monitoring apparatus of claim 1 ; and

the motor.

17. A method of operating a monitoring apparatus connected, in parallel with a motor, to a plurality of power supply lines, each of the plurality of power supply lines having a different phase, the method comprising:

generating a first control signal that selectively activates a first isolator to allow a first current to flow from a first power supply line of the plurality of power supply lines to a second power supply line of the plurality of power supply lines through a third isolator, wherein the first control signal is electrically isolated from the first current;

generating a second control signal that selectively activates a second isolator to allow a second current to flow from the second power supply line of the plurality of power supply lines to a third power supply line of the plurality of power supply lines through the third isolator, wherein the second control signal is electrically isolated from the second current;

receiving a first signal corresponding to a total current, wherein the total current includes both the first current and the second current flowing through the third isolator; and

selectively generating a phase failure signal in response to the first signal indicating that a failure of at least one of the plurality of power supply lines has occurred.

18. The method of claim 17 further comprising generating a third control signal that selectively activates a fourth isolator to allow a third current to flow from the third power supply line of the plurality of power supply lines to the first power supply line of the plurality of power supply lines through the third isolator, wherein the total current also includes the third current and wherein the third control signal is electrically isolated from the third current.

19. The method of claim 18 further comprising:

sequentially activating the first isolator, the second isolator, and the fourth isolator; and

repeating the sequential activation.

20. The method of claim 18 wherein the plurality of power supply lines consists of only the first power supply line, the second power supply line, and the third power supply line.

21. The method of claim 20 wherein the monitoring apparatus is further connected to a neutral line associated with the plurality of power supply lines.

22. The method of claim 17 further comprising:

while the first isolator is activated, deactivating the second isolator; and

while the second isolator is activated, deactivating the first isolator.

23. The method of claim 17 further comprising halting operation of the motor in response to generation of the phase failure signal.

24. The method of claim 17 further comprising activating the first isolator for a predetermined duration, wherein the plurality of power supply lines carry periodic power signals characterized by a first period, and wherein the predetermined duration is based on a length of the first period.

25. The method of claim 24 wherein the predetermined duration is equal to the length of the first period plus a predetermined offset.

26. The method of claim 17 wherein the first signal is directly proportional to the total current.

27. The method of claim 17 further comprising generating the phase failure signal in response to a peak value of the first signal over a predetermined period of time being less than a predetermined threshold.