Shielding Technique for Noise Reduction in Hall-Effect Current Sensor of Voltage Source Inverter

Due to the high dv/dt of the voltage source inverter (VSI), the signal quality of the Hall-effect sensors for current feedback would deteriorate. Especially in signal injection sensorless drives, which utilize the differentiation of output current, the current sensing noise induced by high dv/dt of VSI would not be negligible. This paper proposes a shielding strategy for the dv/dt noise reduction in the current sensor of VSI. Firstly, it is shown that the conventional shielding cable connected to the frame ground can mitigate the interference of dv/dt noise in output current measurements. However, the distributed impedance of the ground plane may reduce the effectiveness of the shielding cable. For better noise rejection in current measurement, this paper proposes a shielding technique directly connected to the dc-link of the inverter. Connecting the shield to the dc-link terminal firmly defines the potential of the shield, which prevents the dv/dt of the output cable from contaminating the current measurement system. The proposed shielding of the output cable only ranges from the inverter switch to the current sensor. Therefore, conventional ground shielding, which reduces the EMI of the system, also can be employed at the load-side. The experiments evaluate the effectiveness of the proposed shielding technique.