Advantages of Rogowski Coil over Desaturation Method for Leg Short Circuit Detection in Inverters

Leg short circuit detection is inconvenient to implement in IGBT modules due to its physical structure. There are several different solutions to detect overcurrent for inverters but this paper analyzes and discusses the most common ones. Inadvertent tripping can occur in a short circuit detection method using desaturation for premium motor drives with the excessive dynamic operation. Current flowing through the IGBTs can be measured using a Rogowski Coil where the flow of time-varying current in the center of the coil results in an induced voltage in which integration gives current waveform. The Rogowski Coil method can be easily implemented into the current path and its output has a high response time due to the absence of a magnetic core. This paper discusses the advantages of using the Rogowski Coil over desaturation method in leg short circuit current detection. Experimental results show that the Rogowski Coil method can detect leg short circuit with a small time delay which is mainly caused by response times of operational amplifier and comparator. Implementing Rogowski Coil structure on printed-circuit board occupies less space and results in low cost compact solution.