Patent ID: 8217642

Claim:
A current sensor for measurement of a primary current in a primary conductor, comprising: a secondary conductor; a ferromagnetic core magnetically coupled to the secondary conductor, and adapted for magnetic coupling of the primary conductor to the secondary conductor; a drive device, which is electrically connected to the secondary conductor, comprising: a controlled bipolar voltage source which is electrically connected to the secondary conductor and adapted to provide a bipolar voltage of a specific amplitude, such that a resultant secondary current flowing in the secondary conductor causes remagnetization of the ferromagnetic core; and a control device coupled with the controlled bipolar voltage source, so that the control device reverses the polarity of the controlled bipolar voltage source at least once at a time during remagnetization of the ferromagnetic core which occurs before that time at which the ferromagnetic core reaches its saturation magnetization; and a measurement device configured to determine the primary current as a function of the secondary current measured before and after the control device reverses polarity of the controlled bipolar voltage, and further configured to average the secondary current measurement so that hysteresis error caused by the secondary current is eliminated.