Patent ID: 8106670

Claim:
An apparatus for monitoring line voltage in a circuit breaker, comprising: a controller; a neutral input for receiving a neutral voltage; a first input for receiving a first alternating current (AC) line voltage that periodically changes polarity with respect to the neutral voltage; a second input for receiving a second AC line voltage that periodically changes polarity with respect to the neutral voltage and is 180 degrees out of phase from the first AC line voltage; a first circuit coupled to the first input, the second input, and the controller configured to output to the controller a first signal representing the voltage difference between the first AC line voltage and the second AC line voltage; a second circuit coupled to the neutral input and the controller configured to output to the controller a second signal representing the difference between the neutral input voltage and the AC line voltage of negative polarity; a third circuit coupled to the controller configured to output a polarity signal representing an identification of the AC line voltage, of the first AC line voltage and second AC line voltage, of negative polarity; and wherein the controller is configured to: calculate a voltage difference value representing the difference between the neutral voltage and the AC line voltage, of the first AC line voltage and second AC line voltage, of positive polarity based on the first signal and the second signal; and assign, using the polarity signal, the voltage difference value to the AC line voltage of positive polarity and the second signal to the AC line voltage of negative polarity.