Abstract: A thyristor power controller for rapidly varying the current delivered to a load and including: a clock circuit for developing a clock pulse for each zero crossing of an AC source, an analog phase circuit responsive to an adjustment current and operative to produce a firing signal for each clock pulse, a first thyristor acting on a positive half cycle of an AC source, a second thyristor acting on a negative half cycle of an AC source, a first thyristor control circuit enabling and disabling the first thyristor, a second thyristor control circuit enabling and disabling the second thyristor, and a thyristor selector operative to route the firing signal to the first or second control circuit.

Abstract: Electrically-activated shaking devices are arranged in modules to shake the electrodes of an electrostatic precipitator, each module corresponding to a different section of the precipitator. An operating system for the shaking devices includes a main distributor circuit that sends electrical signals to individual control circuits at each of the modules in sequence and at a relatively fast rate. Each control circuit has an adjustable timer that independently generates pulses at a relatively slow rate and a synchronizing circuit that generates an output signal only if it receives a signal from the timer followed by a signal from the main distributor. Each control circuit further includes a secondary distributor circuit that operates in response to the synchronizing circuit to activate the shaking devices in the associated module sequentially. An inhibit device operated by the synchronizing circuit prevents more than a single shaker from being activated at a time.