High voltage control of an electrostatic precipitator system

In an electrostatic precipitator system including a voltage controller for producing from a primary alternating power source a variable output which varies in response to a control signal, a high voltage means comprising:

• a high voltage converter means driven by said voltage controller for producing therefrom a variable high voltage;
• and
• command means for producing and varying said control signal, said command means being operative to repress the drive to said converter means in response to its loading exceeding a predetermined limit during a corresponding limit interval, said command means being operative after said limit interval to restore productive drive to said converter means by the next half cycle of said power source that has a polarity opposite to that existing at the beginning of said limit interval so that the system is restabilized quickly, said command means including:
• polarity means for producing a polarity signal signifying the polarity of current last conducted by said controller;
• and
• disable means for preventing said controller from initiating conduction until said alternating current reverses polarity with respect to said polarity signal, whereby power interruption caused by said control signal is followed by power restoration at a polarity opposite to that existing prior to said power interruption, said polarity means comprising:
• pilot means having first and second states, said pilot means being operative to transfer to said first and second states during said positive and negative half cycles, respectively, in response to conduction by said controller, said disable means including:
• phase means for preventing initiation of conduction by said controller upon said first and second states coinciding with said positive and negative half cycles, respectively, of said alternating current, said phase means comprising:
• first gate means for producing a first signal in response to the occurrence of said second state during said positive half cycle of said alternating current;
• second gate means for producing a second signal in response to the occurrence of said first state during said negative half cycle of said alternating current;
• and
• combining means for preventing initiation of conduction by said controller in response to said first signal and in response to said second signal.

A method for varying the high output voltage produced by a high voltage converter means associated with an electrostatic precipitator, said converter means being driven by a voltage controller, said controller producing an output that varies in response to a control signal, said converter means having coupled thereto a conductive element for conducting by an amount corresponding to the extent to which said converter means is being driven to produce a high voltage, comprising the steps of:

• initially measuring the voltage across said conductive element;
• advancing said control signal in a direction to increase the extent to which said high voltage converter means is driven;
• remeasuring the voltage across said conductive element at a predetermined interval after the initial measurement thereof;
• varying said control signal in a first direction to decrease the output of said controller in response to a predetermined variation in the magnitude of the voltage across said conductive element over said predetermined interval;
• measuring the magnitude of voltage produced by said high voltage converter means;
• and
• varying said control signal in a direction opposite to said first direction upon the magnitude of voltage produced by said converter means falling below a predetermined quench value.

In an electrostatic precipitator system including a voltage controller for producing from a primary power source a variable output which varies in response to a control signal, a high voltage means comprising:

• a high voltage converter means driven by said voltage controller for producing therefrom a variable high voltage;
• a conductive element coupled to said high voltage converter means and operative to conduct in response to variations in the extent to which said high voltage converter means is being driven to produce a high voltage;
• and
• command means responsive to the voltage across said conductive element for producing said control signal, said command means including
• storage means for producing a base signal responsive to at least one prior value of the voltage across said conductive element, said command means producing said control signal at a magnitude bearing a predetermined relationship to said base signal and the present value of the voltage across said conductive element, whereby said precipitator system responds to parameters indiciating the imminence of high voltabe sparking;
• and
• high voltage sensing means for transmitting to said command means a signal signifying the magnitude of voltage produced by said converter means, said command means being responsive to said high voltage sensing means and its signal.