Load simulation of icebreaker propulsion motors at laboratory and virtual tests of electric propulsion systems

Abstract

Object and purpose of research. This paper discusses ice loads on shaft-lines of icebreakers and ice-going ships as their propellers interact with ice. These loads are needed as inputs for development and fine-tuning of electric propulsion control systems, including those involving load test rigs, with the final purpose of ensuring reliable and safe operation of electric propulsion plants in ice navigation conditions. Materials and methods. This study is based on the publications about ice loads on shafting of electric propulsion plants. It analyses the terminology used in the papers on this subject. It also analyses the data on ice-induced shafting torques, as obtained from full-scale trials of Akademik Tryoshnikov ice-class research vessel. Main results. The paper describes typical cases of extreme ice loads on the propulsion system, with the input data characterizing these loads and needed, in particular, for numerical simulation of ice loads on shafting in order to fine-tune electric propulsion control system by means of computer-based simulations or laboratory tests. The paper shows the importance of considering the inertial elements of the shaft line for correct determination of limit loads. It also formulates the challenges that have to be solved in order to obtain efficient control systems for electric propulsion plants of icebreakers and ice-going ships. It determines the requirements to special full-scale trials needed to validate calculation methods for shafting loads. Conclusion. Electric propulsion systems of ice-going ships must have highly efficient control tools for the propulsion motor that would ensure its reliable and safe operation as propeller interacts with ice. Such a tool is quite hard to obtain because shafting loads are quite various and difficult to predict. One of the ways to improve an electric propulsion system is to build up a test rig with the load part simulating various scenarios of shafting loads as per the mathematical model specially developed for this purpose and validated by the accumulated database of full-scale ice loads on shaft lines. The paper also demonstrates that propulsion motor control system must properly take into account not only external loads but also inertial torques of shaft line, motor rotor and propeller with added water mass.