This paper deals with computer simulation methods when constructing the equipment in iron rolling mill plants for dimensioning machines, which have become more important in the recent years. And it determines the ideal prerequisites to simulate driving system for electrical and mechanical subsystems. The drive systems is built around several components which have their own technology and multiple time-scales: electrical machines, power semiconductor, control circuits from the firing sequences to the different regulators. This requires the simulation of both the electrical and mechanical components in one model. The use of a uniform simulation program offers the possibility to combine in mechanical modeling with the electrical necessities. This research will be in the description of the simulation-aided design and its relationship with vibration caused by the twisting torque using the drive systems.