Abstract
This article presents a short-circuit and over current protection method using a new current sensor-tunnel magnetoresistance (TMR). The resistance of TMR changes with the magnetic flux density and a Wheatstone bridge circuit-based TMR can be used for current measurement. A toroid TMR current sensor is first proposed to measure the IGBT current, and the measured current is compared to references for protection. A prototype based on a 1200-V/200-A IGBT module is constructed to test the TMR sensor. A 120 A over-current can be detected in 604 ns. The measured current is also utilized to estimate the dc bus capacitance, experimental results show the maximum estimation error is 0.26%. Next, the TMR sensors are integrated into an IGBT module to expand the application scenario. The Calculation method and finite element method (FEM) are proposed to find optimal install locations of the TMR inside a 62-mm IGBT module. A differential TMR sensor circuit is employed to suppress the interference of the adjacent magnetic field. Experimental results based on a commercial IGBT with an integrated TMR sensor have been provided. The reaction time of the integrated TMR sensor is 530 ns and the maximum measurement error for the dc current is 0.85%. The detection and protection time for a 280-A short-circuit fault is 677 ns and 1.23 μs, respectively.
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