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In electric motors the working torque results from the magnetic forces (due to the magnetic field). The magnetic forces are also a direct source of structural excitation; further, the magnetic field is an indirect source of structural excitation in the form of magnetostriction. In the last decade other sources of structural excitation (e.g. mechanical imbalance, natural dynamics of the electric motor) have been widely researched and are well understood. On the other hand, the excitation due to the magnetic forces and magnetostriction is gaining interest in the last period; especially in the field of auto-mobility. Due to the broadband properties of the magnetic field (e.g. Pulse-Width-Modulation(PWM), multi-harmonic excitation), the direct structural excitation in the form of magnetic forces is also broadband.

In the past decade the applicability of belt-drives has been extended significantly due to their increased reliability. With automotive engines it is now common to join a large number of belt-drives into a single, long belt-drive with several tensioner pulleys. However, these belt-drives can exhibit complex dynamic behaviors, which can lead to undesirable noise and vibrations. The aim of this paper is to present an effective and realistic numerical model to predict the dynamic response of such belt-drives. Based on the simulated responses the belt-drive construction can then be optimized in order to increase efficiency, reduce noise and vibrations, etc. The belt-drive model is based on flexible multibody system dynamics, where the belt is modeled using beam elements. With the developed contact model between the belt and the pulley, we can accurately predict the contact forces and stick-slip zones between the belt and pulley.