High-frequency modeling of current sensors [of IGBT VSI]

Reflected-wave transient voltages that result from fast insulated gate bipolar transistor voltage-source inverters have received considerable investigation. Modeling, simulation and attenuation of these transients require sophisticated motor and cable models. Most drive suppliers now provide combinations of passive and active solutions to mitigate the adverse effects of overvoltage stress, however, the costs of the passive solutions often exceed the cost of the drive. Another aspect of low-risetime devices, not examined to the extent of the overvoltage problem, is the resulting current from traveling waves. Current sensor fidelity limits the ability of modern drives to detect peak current and can result in current feedback distortion. This paper presents recent research into the response, modeling and construction of Hall-effect current sensors. Models for Hall-effect current sensors are introduced and compared. Experimental and simulation results demonstrate the complexity of the common current sensors employed in modern adjustable-speed drives. A comparison of the sensor response and the model's prediction demonstrates the difficulty associated with accurate current detection. Finally, the paper presents design guidelines to reduce the corrupting influence of high-frequency differential and common-mode currents.