Methods and systems involving electric machine controllers

1. A method for operating a controller, the method comprising:

receiving a first accumulated thermal value of an electrical machine and an associated first time stamp from a memory;

initializing a processor of the controller with the first accumulated thermal value and the associated first time stamp;

determining whether a second time stamp has been received;

calculating a difference between the second time stamp and the first time stamp responsive to determining that the second time stamp has been received;

calculating a second accumulated thermal value as a function of the first accumulated thermal value, the first time stamp, and the second time stamp; and

updating the first accumulated thermal value with the second accumulated thermal value.

2. The method of claim 1 , wherein the method further comprises:

receiving an indication that the controller has stopped receiving power prior to receiving the first accumulated thermal value of the electrical machine and the associated first time stamp from the memory; and

storing the first accumulated thermal value of the electrical machine and the associated first time stamp in the memory responsive to receiving the indication that the motor controller has stopped receiving power.

3. The method of claim 1 , wherein the first time stamp is defined by a first clock associated with the processor.

4. The method of claim 1 , wherein the second time stamp is received from a second clock.

5. The method of claim 4 , wherein the second clock is associated with a second processor.

6. The method of claim 1 , wherein the method further comprises starting a time stamp clock following the initialization of the processor.

7. The method of claim 1 , wherein the method further comprises entering an operational mode using the first accumulated thermal value and the first time stamp responsive to determining that the second time stamp has not been received.

8. The method of claim 1 , wherein the first accumulated thermal value is defined as a function of measured current in the electrical machine and time.

9. A controller apparatus comprising:

a memory; and

a processor communicatively connected to the memory, the processor operative to receive a first accumulated thermal value of an electrical machine and an associated first time stamp from the memory, initialize a processor of the controller with the first accumulated thermal value and the associated first time stamp, determine whether a second time stamp has been received, calculate a difference between the second time stamp and the first time stamp responsive to determining that the second time stamp has been received, calculate a second accumulated thermal value as a function of the first accumulated thermal value, the first time stamp, and the second time stamp, and update the first accumulated thermal value with the second accumulated thermal value.

10. The apparatus of claim 9 , wherein the processor is further operative to, receive an indication that the controller has stopped receiving power prior to receiving the first accumulated thermal value of the electrical machine and the associated first time stamp from the memory, and store the first accumulated thermal value of the electrical machine and the associated first time stamp in the memory responsive to receiving the indication that the motor controller has stopped receiving power.

11. The apparatus of claim 9 , wherein the first time stamp is defined by a first clock associated with the processor.

12. The apparatus of claim 9 , wherein the second time stamp is received from a second clock.

13. The apparatus of claim 12 , wherein the second clock is associated with a second processor.

14. The apparatus of claim 9 , wherein the processor is further operative to start a time stamp clock following the initialization of the processor.

15. The apparatus of claim 9 , wherein the processor is further operative to enter an operational mode using the first accumulated thermal value and the first time stamp responsive to determining that the second time stamp has not been received.

16. The apparatus of claim 9 , wherein the first accumulated thermal value is defined as a function of measured current in the electrical machine and time.

17. A system comprising:

an electrical machine;

a sensing device; and

a controller apparatus comprising:

a memory; and

a processor communicatively connected to the memory and the sensing device, the processor operative to receive an indication of a current in the electrical machine from the sensing device, receive a first accumulated thermal value of an electrical machine and an associated first time stamp from the memory, initialize a processor of the controller with the first accumulated thermal value and the associated first time stamp, determine whether a second time stamp has been received, calculate a difference between the second time stamp and the first time stamp responsive to determining that the second time stamp has been received, calculate a second accumulated thermal value as a function of the first accumulated thermal value, the first time stamp, and the second time stamp, and update the first accumulated thermal value with the second accumulated thermal value.

18. The system of claim 17 , wherein the processor is further operative to, receive an indication that the controller has stopped receiving power prior to receiving the first accumulated thermal value of the electrical machine and the associated first time stamp from the memory, and store the first accumulated thermal value of the electrical machine and the associated first time stamp in the memory responsive to receiving the indication that the motor controller has stopped receiving power.

19. The apparatus of claim 17 , wherein the first time stamp is defined by a first clock associated with the processor.

20. The apparatus of claim 17 , wherein the second time stamp is received from a second clock.