The subject matter of this invention relates generally to circuit breakers and to circuit breakers with an anti-pumping feature specifically.
The utilization of anti-pumping apparatus in circuit breakers is well known. Such apparatus is taught in U.S. Pat. No. 3,644,790 issued Feb. 22, 1972 to J. M. Kozlovic et al. and assigned to the assignee of the present invention. Generally, a source of power is interconnected by way of a power switch with three parallel connected circuit each of which provide a different function. A first of the parallel connected circuits includes a spring charging motor connected in series circuit relationship with contacts which open when the spring is fully charged and which closes when the spring is not fully charged. The spring is utilized to close the separable main contacts of the circuit breaker. The second of the parallel circuits includes the trip coil for the circuit breaker. When energized, the trip coil allows mechanical energy to be applied to the separable main contacts of the circuit breaker to open those contacts. The circuit breaker usually includes main contacts and auxiliary contacts which duplicate the status of the main contacts. Said in another way, the auxiliary contacts are closed when the main contacts are closed and are open when the main contacts are open. These auxiliary contacts are generally designated as "a" contacts. The trip coil, the trip switch, and the lattermentioned auxiliary contacts are connected together in series circuit relationship such that if the trip switch is closed while the separable main contacts are closed, the trip coil will be energized to cause the separable main contacts to open. The last of the parallel circuits in the prior art includes a closing switch connected in series circuit relationship with two parallel circuits. The first parallel branch or combination includes an auxiliary coil sometimes known as a "Y" coil. The auxiliary coil is connected in parallel circuit relationship with the series combination of a set of complementary contacts for the separable main contacts and with the normally closed contact of the Y coil. The complementary contacts for the separable main contacts are always in a disposition which is opposite to the disposition of the separable main contacts. Said in another way, this means that when the separable main contacts are closed, the complementary contacts are opened and vice versa. The latter-mentioned parallel subcombination of the Y coil, the Y contacts and the complementary auxiliary contacts are connected in series circuit relationship with the second parallel subcombination which includes: a resistive element connected in parallel with the series combination of a spring release coil and a complementary spring status contact. The complementary spring status contact is always closed when the spring is fully charged and open when the spring is not fully charged. This arrangement is shown in FIG. 2 of the previously-mentioned prior art patent to Kozlovic. In general, if the circuit breaker is open and the spring is charged, actuation of the closing switch will cause energization of the spring release coil thus releasing the spring to close the separable main contacts. At this point, the spring will immediately begin to charge again by actuation of the spring charging motor. Once the spring has again become fully charged, it will remain that way until the circuit breaker contacts open in which case the spring can be utilized to quickly reclose the circuit breaker main contacts once again. However, in the event that the circuit breaker is closed on a fault such that it opens again immediately, it is not desired to perform the wasted and even dangerous function of continuously closing the circuit breaker on the same fault. Consequently, most circuit breaker apparatus have an anti-pumping feature whereby reclosure of the circuit breaker will not occur until the closing switch has been deenergized and subsequently reenergized. This prior art anti-pump feature is desired in all circuit breaker control systems and is implemented in most. One of the disadvantages of the prior art control system, however, is the requirement that the complementary auxiliary contacts for the separable main contacts be operable. The complementary contacts in question are generally designated as the b contacts. These contacts have the characteristic of being open when the separable main contacts are closed and vice versa as was described previously. If for some reason, these contacts do not open when the separable main contacts close, the anti-pumping feature of the prior art circuit breaker will be defeated and catastrophic results may follow. Generally, in order for the closing of the separable main contacts to occur, it is necessary for the circuit breaker closing spring to discharge thus actuating a mechanism which eventually closes the separable main contacts and opens the auxiliary contacts. If the spring discharges in an appropriate manner, but something happens with the remaining portion of the linkage to prevent the auxiliary contacts from opening, the anti-pump feature will be defeated and circuit breaker pumping may occur. Another disadvantage with the prior art circuit breaker system lies in the fact that it is essentially a voltage divider type control system. It has generally been found that voltage divider type control systems require rather precise adjustment and balancing among the appropriate portions thereof. As an example, in the prior art system, resistance coordination is required between the intrinsic resistance of the Y coil, the spring release coil, and the main resistor R. It would be advantageous, therefore, if an anti-pumping circuit breaker could be found which eliminates the need for critical resistance coordination between components thereof and which performed the anti-pumping function effectively. An electronic circuit for utilization in controlling an alternating current line generator is disclosed in U.S. Pat. No. 2,735,039, issued Feb. 14, 1956 by N. F. Schuh, Jr. and entitled "Overvoltage Protection for Alternating Current Generators". This circuit is essentially a latching circuit rather than an anti-pumping circuit. It is significantly distinguished from the present invention by the fact that the utilization or need for an anti-pumping operation is manifestly not envisioned. This is clear from the fact that the switch arrangement which includes the wiper or blade 22 and the contacts 23 and 24 render a pumping action impossible by its mere construction. It is easy to envision that it is not possible to attempt to reset and trip the circuit at the same time because of the interarrangement of the elements.