Active current surge limiters with disturbance sensor and multistage current limiting
First Claim
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1. A method for reducing inrush current to an electrical load in response to detection of a disturbance occurring in an input AC power supply coupled to the electrical load, comprising:
- applying an input voltage to the electrical load;
monitoring the current drawn by the load;
recording peak values of the current drawn by the load;
continuously monitoring the voltage of the input AC power supply to detect a voltage sag to a predetermined level below rated voltage for short periods of time of one half cycle or more indicating a disturbance in the input AC power supply that would cause an inrush current to the electrical load upon ending of the disturbance;
in response to detection of the voltage sag, recording a peak current limit reference (Imax) corresponding to a maximum peak current value thus far recorded;
detecting when the current level exceeds the peak current limit reference (Imax) as indicating the disturbance occurring in the input AC power supply; and
adding an impedance to the electrical load in response to detecting the disturbance, wherein an inrush current to the electrical load is limited as the input voltage returns to a normal operating level voltage.
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Abstract
Active current surge limiters and methods of use are disclosed. One exemplary system, among others, comprises a current limiter, including an interface configured to be connected between a power supply and a load; a disturbance sensor, configured to monitor the power supply for a disturbance during operation of the load; and an activator, configured to receive a control signal from the disturbance sensor and to activate the current limiter based on the control signal.
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Citations
57 Claims
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1. A method for reducing inrush current to an electrical load in response to detection of a disturbance occurring in an input AC power supply coupled to the electrical load, comprising:
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applying an input voltage to the electrical load; monitoring the current drawn by the load; recording peak values of the current drawn by the load; continuously monitoring the voltage of the input AC power supply to detect a voltage sag to a predetermined level below rated voltage for short periods of time of one half cycle or more indicating a disturbance in the input AC power supply that would cause an inrush current to the electrical load upon ending of the disturbance; in response to detection of the voltage sag, recording a peak current limit reference (Imax) corresponding to a maximum peak current value thus far recorded; detecting when the current level exceeds the peak current limit reference (Imax) as indicating the disturbance occurring in the input AC power supply; and adding an impedance to the electrical load in response to detecting the disturbance, wherein an inrush current to the electrical load is limited as the input voltage returns to a normal operating level voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A system for reducing inrush current to an electrical load in response to detection of a disturbance occurring on an input AC power supply coupled to the electrical load, comprising:
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a control circuit including a programmed microcontroller configured to detect a disturbance in the input AC power supply during steady-state operation of an electrical load by continuously monitoring the voltage of the input AC power supply and the current drawn by the load and provide a control signal; a current limiting device configured to be selectively connected between the input AC power supply and the electrical load; an activator configured to receive the control signal from the control circuit and to insert the current limiting device based on the control signal; wherein the microcontroller is programmed to record peak values of the current drawn by the load; wherein the microcontroller is programmed to detect a voltage sag in the input AC power supply to a predetermined level below rated voltage for short periods of time of one half cycle or more indicating a disturbance in the input AC power supply that would cause an inrush current to the electrical load upon ending of the disturbance; wherein the microcontroller is programmed, in response to detection of the voltage sag, to record a peak current limit reference (Imax) corresponding to a maximum peak current value thus far recorded; and wherein the microcontroller is programmed to detect when the current level exceeds the peak current limit reference (Imax) as indicating the disturbance occurring in the input AC power supply and to provide the control signal to the activator to insert the current limiting device. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A multi-step active current surge limiting apparatus for reduction of inrush current to an electrical load in response to detection of a disturbance in an input AC power supply coupled to the electrical load, comprising:
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a current-limiting circuit coupled between the input power supply and the electrical load, the current-limiting circuit comprising; (a) a current limiting impedance comprising (i) first resistor, (ii) a second resistor in series with the first resistor, and (iii) a switch in parallel with the second resistor that is actuated by a first control signal to bypass the second resistor, and (b) a relay in parallel with the current limiting impedance and having contacts that are in an open position to couple the input AC power supply to the electrical load through the current limiting impedance and close in response to a second control signal to couple the input AC power supply to the electrical load and bypass the current limiting impedance; and a control circuit that provides the first control signal and the second control signal to provide multiple levels of impedance to the inrush of current to the electrical load in response to predetermined conditions. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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Specification