Thermal modeling of overcurrent trip during power loss
First Claim
1. A circuit interrupting device comprising:
- sensing means for sensing electric current to an electrical load served by said interrupting device, said electrical load including electrical conductors;
interrupting means interrupting current to said load in response to a trip signal; and
processing means comprising digital processing means responsive to said sensing means and operative when energized to generate a digital current/time value and generating said trip signal when said current/time value reaches a trip value, said digital processing means being de-energized and losing said digital current/time value when current is interrupted by said interrupting means, analog processing means maintaining an analog current/time value, means forcing said analog current/time value to track both increases and decreases in said digital current/time value when said digital processing means is energized, said analog processing means including means causing said analog current/time value to decay at a rate mimicking cooling of said load when said digital processing means is de-energized, and means initializing said digital current/time value to said analog current/time value when current to said load is reestablished and said digital processing means is again energized.
0 Assignments
0 Petitions
Accused Products
Abstract
An electrical overcurrent circuit provides both digital based modeling and analog based modeling of the temperature of an electrical conductor to simulate the conductor temperature during all expected operating conditions including a condition when electrical power is unavailable to the electrical overcurrent circuitry. When electrical power is available to the circuitry, the conductor temperature is calculated from the sensed load currents to form the digital based model. During such a condition, the analog based model is forced to track the digital based model. Once the temperature of the electrical conductor exceeds its maximum safe operating temperature, the electrical overcurrent circuitry initiates a trip of the circuit breaker. Since the overcurrent circuitry is powered either by the sensed load currents or derived from the circuit breaker output, the circuit breaker trip will result in a loss of electrical power to the electrical overcurrent circuitry. This causes the digital based model to be reset to a cold conductor temperature value. However, the analog based model continues to operate to simulate the conductor temperature during this condition. When electrical power is restored to the circuit, for example, when the circuit breaker is closed, the digital model is initialized with the value from the analog model.
-
Citations
9 Claims
-
1. A circuit interrupting device comprising:
-
sensing means for sensing electric current to an electrical load served by said interrupting device, said electrical load including electrical conductors; interrupting means interrupting current to said load in response to a trip signal; and processing means comprising digital processing means responsive to said sensing means and operative when energized to generate a digital current/time value and generating said trip signal when said current/time value reaches a trip value, said digital processing means being de-energized and losing said digital current/time value when current is interrupted by said interrupting means, analog processing means maintaining an analog current/time value, means forcing said analog current/time value to track both increases and decreases in said digital current/time value when said digital processing means is energized, said analog processing means including means causing said analog current/time value to decay at a rate mimicking cooling of said load when said digital processing means is de-energized, and means initializing said digital current/time value to said analog current/time value when current to said load is reestablished and said digital processing means is again energized. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A circuit interrupting device comprising:
-
sensing means sensing electric current to an electrical load, said electrical load including electrical conductors; interrupting means interrupting current to said electrical load in response to a trip signal; and processing means including means responsive to said sensing means generating an overcurrent/time value when said current is above a pick-up value, means generating said trip signal when said overcurrent/time value reaches a trip value, and means initializing said overcurrent/time value to a predetermined proportion of said trip value in response to a predetermined time function of current below said pick-up value. - View Dependent Claims (8, 9)
-
Specification