Container power sensing system and method

1. A monitoring system for a refrigeration unit in a shipping container, said shipping container having a power line connected to the refrigeration unit, wherein the power line is connectable to one of a utility power source or a shipboard power source subject to limited transients in response to refrigeration unit load changes on the one hand and an engine driven genset subject to higher transients in response to refrigeration load changes on the other, said monitoring system, comprising:

an electrical transient sensor connected to a power line the container, and

a two-condition threshold indicator switch responsive to the output of the transient sensor;

said threshold indicator switch exhibiting one of two conditions;

one of said conditions indicating a transient beyond a threshold as a demonstration that the power line is connected to the genset; and

a threshold-exceeding transient condition transmitter.

2. A method for monitoring a refrigeration unit in a shipping container having a power line connected to the refrigeration unit from one of a utility power source or a shipboard power source subject to limited transients in response to refrigeration unit load changes on the one hand, and an engine driven genset subject to higher transients in response to refrigeration load changes on the other, comprising:

monitoring electrical conditions of the power line;

delivering an indication that the power line is connected to a genset or not, said step of delivering, including

sensing transients in the monitored electrical conditions;

comparing the value of the transients to a threshold; and

transmitting a signal indicative of whether or not a transient exceeds the threshold to a user as an indication of the power line being connected to a genset or not.

3. A method as in claim 2 , wherein said sensing step includes sensing transient variations in frequency in the monitored electrical conditions.

4. A method as in claim 2 , wherein said monitoring step includes digitally formatting the frequency signal in a microprocessor.

5. A method as in claim 2 , wherein said monitoring step includes detecting an onset of power from the power line and starting the sensing step while delaying the application of power to the refrigeration unit so as to allow incoming power on the line to operate at a no-load condition during the delay and to load the power source after the delay and produce a transient in response to the change from no-load to load.

6. A method as in claim 2 , wherein said monitoring step includes

detecting an onset of power from the power line and starting the sensing step while delaying the application of power to the refrigeration unit so as to allow incoming power on the line to operate at a no-load condition during the delay and to load the power source after the delay and produce a transient in response to the change from no-load to load, and

wherein said sensing step includes sensing the transient in one of frequency and voltage arising from a genset generator slowing down in response to the change from no-load to load.

7. A method as in claim 2 , wherein said monitoring step includes:

detecting the electrical frequency or voltage at the power line to produce a detector signal representing the frequency;

wherein said step of sensing transients includes:

averaging the detector signal to produce an averaged signal; and

subtracting the averaged signal from the detector signal at the power line to produce a transient signal; and

wherein the step of comparing includes:

comparing the transient signal with the threshold to produce a comparison signal indicative of whether or not the power line is connected to a genset; and

wherein the step of transmitting the signal indicative of a transient exceeding the threshold to a user includes:

transmitting an alarm to advise personnel of the condition.

8. A method as in claim 2 , wherein said monitoring step includes:

detecting the electrical frequency or voltage at the power line to produce a detector signal representing the frequency or voltage;

wherein said step of sensing transients includes:

averaging the detector signal to produce an averaged signal; and

subtracting the averaged signal from the detector signal to produce a transient signal; and

wherein the step of comparing includes:

comparing the transient signal with the threshold to produce a comparison signal indicative of whether or not the power line is connected to a genset; and

latching the comparison signal when the comparison signal exceeds the threshold; and

wherein the step of transmitting the latched signal indicative of whether the transient exceeds the threshold to a user includes:

transmitting an alarm to advise personnel of whether the transient exceeds the threshold.

9. A method as in claim 2 , wherein said monitoring step includes:

detecting the frequency at the power line to produce a detector signal representing the frequency;

wherein said step of sensing transients includes:

subtracting the detector signal representing the frequency at the power line to from the standard fifty or sixty Hertz frequency to produce a transient signal; and

wherein the step of comparing includes:

comparing the transient signal with the threshold to produce a comparison signal indicative of whether or not the power line is connected to a genset.

10. A method as in claim 2 , wherein at least portions said delivering step is carried out in the shipping container or off the shipping container at a network operations center.

11. A method as in claim 2 , wherein said sensing step includes sensing one of voltage, current, phase, frequency, rms value, and signal linearity of said power line.

12. A method as in claim 2 wherein said monitoring step includes remotely forcing the refrigeration unit into another mode of operation in order to stress the power source.

13. A system as in claim 1 , wherein said sensor includes:

An electrical condition detector connected to the output line, said electrical condition detector including one of voltage, current, phase, frequency, rms value, and signal linearity.

14. A system as in claim 1 , wherein said sensor includes a digitally formatting microprocessor connected to one of said transient detector, said switch, and said transmitter.

15. A system as in claim 1 , wherein said transient sensor includes:

a electrical onset or electrical change detector; and

a refrigeration unit power delay between said refrigeration unit and said detector;

said detector being coupled directly to said threshold indicator.

16. A system as in claim 1 , wherein said electrical transient sensor includes:

an electrical frequency detector or voltage detector at the power line;

an averaging arrangement responsive to said detector;

a subtracting arrangement responsive to the averaging arrangement and said detector;

a comparator responsive to said subtracting arrangement and to a threshold; and

wherein said transmitter includes an alarm signal.

17. A system as in claim 1 , wherein said electrical transient sensor includes:

an electrical frequency detector or voltage detector at the power line;

an averaging arrangement responsive to said detector;

a subtracting arrangement responsive to the averaging arrangement and said detector;

a threshold-exceeding-indicating comparator responsive to said subtracting arrangement and to a threshold; and

a latch responsive to said comparator; and

wherein said transmitter includes an alarm signal.

18. A system as in claim 1 , wherein said electrical transient sensor includes:

an electrical frequency detector or voltage detector at the power line;

a fifty Hertz or sixty Hertz frequency input;

a subtracting arrangement responsive to the fifty Hertz or sixty Hertz frequency input and said detector;

a comparator responsive to said subtracting arrangement and to a threshold; and

wherein said transmitter includes an alarm signal.

19. A system as in claim 1 wherein said transient sensor includes:

a power-source-stressing refrigeration-unit interrupter coupled to said refrigeration unit.