Circuit breaker including improved overcurrent protective device

Claim 2

A circuit breaker comprising relatively movable contacts, operating means for opening and closing said contacts, and an overcurrent-protective device disposed to be responsive to the current in said movable contacts and operatively connected to said operating means for producing an output to actuate said operating means to open said contacts, said protective device including first means responsive to said current in said movable contacts for actuating said protective device to produce said output when said current exceeds substantially a first predetermined value after substantially a predetermined time delay whose duration remains the same independently of the magnitude of said current in excess of said first predetermined value and second means responsive to said current for actuating said protective device to produce said output substantially instantaneously when said current exceeds substantially a second predetermined value which is relatively greater than said first predetermined value and which is substantially equal to the maximum momentary current that said movable contacts of said circuit breaker can safely carry for the duration of said predetermined time delay associated with said first means.

Claim 3

The combination as claimed in claim 1 wherein said protective device includes a third means responsive to said current in said movable contacts for actuating said protective device to produce said output when said current exceeds substantially a third predetermined value which is relatively less than both said first and said second predetermined values after a time delay which varies inversely with substantially the square of said current.

Claim 4

The combination as claimed in claim 1 wherein the second means comprises a level-detecting circuit responsive to the current in said movable contacts for producing an additional output to actuate said protective device to produce said first-mentioned output substantially instantaneously when said current exceeds substantially said second predetermined value.

Claim 5

A three-phase alternating-current circuit breaker comprising three sets of separable contacts, a common operating means for opening and closing said sets of contacts, an overcurrent-protective device disposed to be responsive to the currents in said sets of contacts and operatively connected to said operating means for producing an output to actuate said operating means to open said sets of contacts, said protective means including first means operatively connected to said sets of contacts for deriving therefrom a unidirectional output signal which is substantially proportional only to the highest of the currents in said sets of contacts, second means responsive to said output signal for actuating said protective device to produce said output when said highest current exceeds substantially a first predetermined value after substantially a predetermined time delay whose duration remains the same independently of the magnitude of said highest current in excess of said first predetermined value and third means responsive to said output signal for actuating said protective device to produce said output substantially instantaneously when said highest current exceeds substantially a second predetermined value which is relatively greater than said first predetermined value and which is substantially equal to the maximum momentary current that said circuit breaker can safely carry in said sets of contacts for the duration of said predetermined time delay associated with said second means.

Claim 6

A three-phase alternating-current circuit breaker comprising three sets of separable contacts, a common operating means for opening and closing said sets of contacts, an overcurrent-protective device disposed to be responsive to the currents in said sets of contacts and operatively connected to said operating means for producing an output to actuate said operating means to open said sets of contacts, said protective means including first means operatively connected to said sets of contacts for deriving therefrom a unidirectional output signal which is substantially proportional only to the highest of the currents in said sets of contacts, second means responsive to said output signal for actuating said protective device to produce said output when said highest current exceeds substantially a first predetermined value after substantially a predetermined time delay whose duration remains the same independently of the magnitude of said highest current in excess of said first predetermined value and third means responsive to said output signal for actuating said protective device to produce said output substantially instantaneously when said highest current exceeds substantially a second predetermined value which is relatively greater than said first predetermined value and which is substantially equal to the maximum momentary current that said circuit breaker can safely carry in said sets of contacts for the duration of said predetermined time delay associated with said second means.

Claim 7

The combination as claimed in claim 4 wherein said protective device includes a fourth means responsive to said output signal for actuating said protective device to produce said output when said highest current exceeds substantially a third predetermined value which is relatively less than both said first and said second predetermined values after a predetermined time delay which varies inversely with substantially the square of said highest current. 6. The combination as claimed in claim 4 wherein said third means comprises a level-detecting circuit responsive to said output signal for producing an additional output to actuate said protective device to produce said first-mentioned output substantially instantaneously when said highest current exceeds substantially said second predetermined value.

Claim 8

An overcurrent-protective device for actuating the operating means of a circuit breaker having separable contacts comprising first means responsive to the current in the contacts of the associated circuit breaker for actuating said protective device to produce an output to actuate the operating means of the associated circuit breaker to open said contacts when the current in said contacts exceeds a first predetermined value after substantially a predetermined time delay whose duration remains the same independently of the magnitude of said current in excess of said first predetermined value, and second means responsive to the current in the contacts of the associated circuit breaker for actuating said protective device to produce said output substantially instantaneously when the current in said contacts exceeds a second predetermined value which is relatively greater than said first predetermined value and which is substantially equal to the maximum momentary current that the contacts of the associated circuit breaker can safely carry for the duration of said predetermined time delay.

Claim 9

An overcurrent-protective device for actuating the operating means of a circuit breaker having separable contacts comprising first means responsive to the current in the contacts of the associated circuit breaker for actuating said protective device to produce an output to actuate the operating means of the associated circuit breaker to open said contacts when the current in said contacts exceeds a first predetermined value after substantially a predetermined time delay whose duration remains the same independently of the magnitude of said current in excess of said first predetermined value, and second means responsive to the current in the contacts of the associated circuit breaker for actuating said protective device to produce said output substantially instantaneously when the current in said contacts exceeds a second predetermined value which is relatively greater than said first predetermined value and which is substantially equal to the maximum momentary current that the contacts of the associated circuit breaker can safely carry for the duration of said predetermined time delay.

Claim 10

The combination as claimed in claim 7 wherein said protective device includes a third means responsive to the current in the contacts of the associated circuit breaker for actuating said protective device to produce said output when said current exceeds a third predetermined value which is relatively less than both said first and second predetermined values after a time delay which varies inversely with substantially the square of said current.

Claim 11

The combination as claimed in claim 7 wherein said second means comprises a level-detecting circuit responsive to the current in the contacts of the associated circuit breaker for producing an additional output to actuate said protective device to produce said first-mentioned output substantially instantaneously when said current exceeds substantially said second predetermined value.