Current Sense Circuit for a DC Powered Three Phase Servo Motor Controller

This paper presents a new, high performance, inexpensive, current sense circuit that outputs signal currents that continuously track motor currents in a three phase servo motor. Each tracked motor current uses two current sense resistors, one connected to +bus and the other to ground, which are embedded in opposed op amp-mosFET current sources that provide level shifting and summation. The offset and gain of the circuit are very stable. This circuit has no isolation as it is designed to be used with a DC powered motor controller that shares a common ground with the controlling electronics