Reliability analysis of a direct-liquid cooling system of direct drive permanent magnet synchronous generator

Wind turbines intended for electricity production are growing in power capacity with each new generation. At the same time, wind farm economics is demanding increased reliability to minimize costs and maximize productivity. These trends are driving a need for more powerful and more reliable energy conversion, and the DD-PMSG is quickly becoming the standard wind turbine generator. Larger DD-PMSGs must be liquid cooled to meet upcoming power capacity demands without exceeding practical limits for size, weight, and capital cost. However, liquid cooling is a new technology for wind turbines and its impact on reliability must be evaluated. This paper presents a reliability analysis for a liquid-cooled 8 MW DD-PMSG coupled with primary and secondary liquid coolant systems. Reliability has been calculated analytically and assessed based on the following reliability metrics: MTBF, MDT, MTTF, failure intensity, and availability.