Power distribution system using solid state power controllers

1. A solid state power controller possessing a power connector, a load connector and at least one communication connector, comprising:

a solid state switch electrically connectable between the power connector and the load connector, where the switch includes an input;

circuitry for measuring a voltage at the power connector, the measuring circuitry configured to minimize a current drawn from the power connector by the measuring circuitry;

a microcontroller coupled to the input of the solid state switch; and

isolation circuitry connected to create a galvanic barrier between the microcontroller and the at least one communication connector;

wherein the microcontroller is configured to detect an overcurrent condition by comparing a trip constant to a time variable calculated value which is a function of a measured load current, a rated current and a threshold current.

2. The solid state power controller of claim 1 , wherein the isolation circuitry comprises one or more magnetoresistive signal isolators.

3. The solid state power controller of claim 1 , wherein the solid state switch comprises a MOSFET.

4. The solid state power controller of claim 1 , further comprising current sensing circuitry connected to the microcontroller and configured to sense the current flowing through the solid state switch.

5. The solid state power controller of claim 1 , wherein the measuring circuitry is configured to eliminate the current drawn from the power connector by the measuring circuitry.

6. The solid state power controller of claim 1 , wherein the internal microcontroller is configured to calculate the time variable value of the time variable integral expression:

∫

t

0

t

1

⁢

[

(

i

2

-

I

Threshold

2

)

/

I

Rated

2

]

⁢

⁢

ⅆ

t

where i is the measured load current, I Threshold is the threshold current and I rated is the rated current.

7. The solid state power controller of claim 1 , wherein the internal microcontroller is configured to calculate the time variable value of the discrete time variable sum expression:

∑

Δ

⁢

⁢

t

⁢

⁢

[

(

i

2

-

I

Threshold

2

)

/

I

Rated

2

]

⁢

⁢

Δ

⁢

⁢

t

where i is the measured load current, I Threshold is the threshold current and I rated is the rated current.

8. The solid state power controller of claim 1 , wherein the time variable value accounts for thermal memory.

9. The solid state power controller of claim 1 , further comprising:

an arc fault microcontroller coupled to the microcontroller and configured to detect an arc fault in circuitry connected to the power connector or the load connector of the SSPC;

wherein the arc fault microcontroller is configured to respond to the sensing of an arc fault by generating a signal to open the solid state switch.

10. The solid state power controller of claim 9 , wherein the arc fault microcontroller detects arc faults with different levels of sensitivity.

11. The solid state power controller of claim 1 , wherein an external device is connected to at least one of the communications connectors.

12. The solid state power controller of claim 11 , wherein the external device is a microcontroller.

13. The solid state power controller of claim 1 , further comprising:

a time delay circuit coupled between the input of the solid state switch and the power connector;

wherein the time delay circuit is configured to change switching characteristics of the solid state switch.

14. The solid state power controller of claim 13 , wherein the time delay circuit includes a resistor coupled in series with a capacitor.

15. The solid state power controller of claim 1 , wherein the internal microcontroller is configured to provide a programmable emergency trip.

16. The solid state power controller of claim 15 , wherein the programmable emergency trip comprises a load current threshold.

17. The solid state power controller of claim 1 , wherein the microcontroller is configured to generate an input to the solid state switch in accordance with at least one predetermined operational characteristic.

18. The solid state power controller of claim 17 , wherein one of the predetermined operational characteristics is a rated current.

19. The solid state power controller of claim 17 , wherein one of the predetermined operational characteristics is a trip current threshold.

20. The solid state power controller of claim 17 , wherein the microcontroller is programmed with instructions received from an external device after an initialization of the solid state power controller.

21. The solid state power controller of claim 20 , wherein the microcontroller is further programmed with instructions stored in a memory inside the microcontroller prior to the initialization of the solid state power controller.

22. A power distribution assembly, comprising:

a plurality of solid state power controllers, each having a power connector, a load connector and at least one communication connector; and

an external microcontroller connected to each solid state power controller via the at least one communication connector;

wherein each solid state power controller includes an internal microcontroller that is connected to the at least one communication connector via isolation circuitry, where the isolation circuitry creates a galvanic barrier between the internal microcontroller and the external microcontroller;

wherein each solid state power controller is galvanically isolated from the next solid state power controller by the isolation circuitry; and

wherein the internal microcontroller is configured to detect an overcurrent condition by comparing a trip constant to a time variable calculated value which is a function of a measured load current, a rated current and a threshold current.

23. The power distribution assembly of claim 22 , wherein the isolation circuitry includes a magnetoresistive signal isolator.

24. The power distribution assembly of claim 22 , further comprising:

a computer connected to the external microcontroller;

wherein the computer generates a graphical user interface that conveys information concerning the operational characteristics of the solid state power controller to the user and enables the modification of the operational characteristics of a solid state power controller in response to instructions from the user.

25. The solid state power controller of claim 22 , wherein the internal microcontroller is configured to calculate the time variable value of the time variable integral expression:

∫

t

0

t

1

⁢

[

(

i

2

-

I

Threshold

2

)

/

I

Rated

2

]

⁢

⁢

ⅆ

t

where i is the measured load current, I Threshold is the threshold current and I rated is the rated current.

26. The solid state power controller of claim 22 , wherein the internal microcontroller is configured to calculate the time variable value of the discrete time variable sum expression:

∑

Δ

⁢

⁢

t

⁢

⁢

[

(

i

2

-

I

Threshold

2

)

/

I

Rated

2

]

⁢

⁢

Δ

⁢

⁢

t

where i is the measured load current, I Threshold is the threshold current and I rated is the rated current.

27. The solid state power controller of claim 22 , wherein the time variable value accounts for thermal memory.

28. The power distribution assembly of claim 22 , wherein:

each solid state power controller includes a solid state switch;

wherein the internal microcontroller in each solid state power controller is configured to control the operation of the solid state switch.

29. The power distribution assembly of claim 28 , wherein:

the external microcontroller is configured to send messages to the microcontrollers in the solid state power controllers; and

the internal microcontrollers of the solid state power controllers are configured to respond to the messages sent by the external microcontrollers.

30. The power distribution assembly of claim 29 , wherein at least one of the internal microcontrollers is configured to modify the manner in which the operation of the solid state switch is controlled in response to receipt of a predetermined message from the external microcontroller.

31. The power distribution assembly of claim 22 , further comprising:

a keypad connected to the external microcontroller; and

at least one LED connected to each of the solid state power controllers.

32. The power distribution assembly of claim 31 , wherein the keypad includes four buttons.

33. The power distribution assembly of claim 32 , wherein each of the solid state power controllers is connected to three LEDs.

34. The power distribution assembly of claim 31 , wherein the external microcontroller is configured to send messages to solid state power controllers in response to input received via the keypad.

35. The power distribution assembly of claim 31 , wherein the internal microcontrollers of the solid state power controllers are configured to generate signals that illuminate the LEDs and convey information to a user.