Adaptive sequential controller

An adaptive sequential controller for controlling a switching device that is disposed on an AC power line so as to ensure that an inherent time delay of the switching device in responding to a switching signal is adaptively compensated for changes in the inherent time delay, comprising:

• (a) a potential transformer couplable to the power line, said potential transformer producing potential signal indicative of zero crossings of a periodic electrical voltage on the power line;
• (b) transient detector means, coupled to the potential transformer to receive the potential signal, for detecting transients on the power line that occur when the flow of the electrical current in the power line is enabled by closure of the switching device and interrupted by opening the switching device, said transient detector means producing a transient signal indicative of the time that any such transient occurs;
• (c) phase angle determinative means for producing a phase angle signal indicative of a phase angle between a periodic electrical current flowing through the power line and the voltage on the power line;
• (d) timing means for producing:
• (i) a first timing signal;
• and
• (ii) a second timing signal having a frequency that is an integer multiple of the first timing signal and synchronized to it;
• (e) comparator means, coupled to the transient detector means to receive the transient signal and coupled to the timing means to receive the first timing signal, for comparing the transient signal to the first timing signal to produce a delay error signal as a function of a difference between the time that a transient was produced due to operation of the switching device and a zero crossing of the voltage on the power line occurred;
• (f) adaptive adjustment means, coupled to the timing means to receive the second timing signal and coupled to the comparator means to receive the delay error signal, for producing an adjusted delay signal For use during a subsequent operation of the switching device as a function of:
• (i) an actuation time interval used to compensate the inherent time delay of the switching device during a previous switching operation;
• (ii) the delay error signal produced as a result of that previous operation;
• and
• (iii) the second timing signal;
• and
• (g) control means, coupled to the adaptive adjustment means to receive the adjusted delay signal and to the phase angle determinative means for receiving the phase angle signal, For initiating operation of the switching device in response to an externally produced switching command, at a time determined as a function of the adjusted delay signal in response to the phase angle signal, by producing a control signal that enables opening of the switching device, said control means determining the time to initiate the operation of the switching device so that the electrical current flowing through the power line is interrupted at a zero crossing of said current, thereby substantially eliminating transients on the power line.

A method for controlling a switching device disposed on a power line to suppress arcing and minimize transients on the power line that can otherwise occur when the switching device switches electrical current flow through the power line, comprising the steps of:

• (a) producing a timing signal synchronized to zero crossings of at least one of a periodic electrical current flowing in the power line and a periodic voltage on the power line;
• (b) detecting any transients on the power line that occur when the switching device opens and closes and producing a transient signal indicative of a time when said transients occur;
• (c) producing a phase angle signal indicating a phase angle between the current flowing in the power line and its voltage;
• (d) producing an error signal indicating a time interval between the transient signal and the timing signal;
• (e) producing an adjusted delay signal as a function of both a previous delay used in operating the switching device and the error signal;
• and
• (f) initiating operation of the switching device in response to an externally produced switching command, at a time adaptively determined as a function of the adjusted delay signal and the phase angle signal, said time being determined so as to ensure that the switching device enables the flow of electrical current through the power line when the voltage on the power line is at a zero crossing and interrupts the flow of electrical current through the power line when the electrical current is at a zero crossing in order to substantially eliminate transients caused by operation of the switching device, any changes in a response time of the switching device being compensated by varying said time at which operation of the switching device is initiated after receipt of the externally produced switching command.