Nonintrusive Current Sensor for the Two-Wire Power Cords

This paper presents a nonintrusive current sensor for the two-wire power cords connected to household and commercial appliances. The sensor uses a gapped magnetic core surrounding the power cord to constrain the distribution of the magnetic field induced by the current. The magnetic fields in four air gaps of the magnetic core are respectively measured by four magnetoresistive (MR) sensors. The current in the power cord and the rotation angle of the power cord around its central axis are calculated together by the output voltages of the four MR sensors. The current sensor encircles the power cord without any alignment process and can detect the current nonintrusively in the two-wire power cords of any type, such as zip-cord or nonmetallic sheathed cable. The experimental results show that the nonlinearity of the sensor is ±1.5% for the current range from 0 to 20 A with the maximum error limited to ±1.8%, this sensor is ideally suited for measuring the end use of electric power in residential and commercial areas.