Medium voltage IGBT-based converters in mine hoist systems

In underground mining industry, mineral transportation from lower levels to the surface is critical, thus demanding thorough equipment selection. The dc motor driven hoist dominated these applications, providing superior controllability. However, due to its increasing popularity, ac drive systems replaced dc application, including in mine hoisting. The high power ratings typical of these systems imply the use of medium voltage adjustable speed drive (MV-ASD), offering high power density, excellent efficiency and high reliability. This paper discusses two commonly used medium voltage topologies, namely the Three-Level Neutral-Point-Clamped and Active Neutral- Point-Clamped Voltage-Source Converter (3L-NPC and 3LANPC VSC). These topologies are compared to a recently proposed Fault-Tolerant realization of 3L-ANPC (FT-ANPC VSC). The hoist load cycle, which is severe in terms of thermal cycling profile, is used to evaluate the lifetime in power modules for all three topologies.