Electric traction is omnipresent and will find its place in car drivetrain technology, regardless of some open challenges to be overcome. There are the topics of energy storage, the availability of raw materials and the need for significant cost reduction in all components. Hofer powertrain follow the debates since some years and try to give their own contributions to a holistic system package consisting of electric motor, power electronics, control algorithms, gear set and thermal management. It seems to be a generally accepted fact that in the end the system point of view is the key. The best electronic motor together with the best inverter and the best transmission does not necessarily yield the best system. This implies that since the very beginning of component dimensioning, the additionally involved components must be taken into consideration. Limits may vanish - even those between two supplier parts. For the system, it may not be the optimum to use supplier As electric motor with supplier Bs gear set. A common bearing concept seems more useful. A common oil circuit realizing both rotor cooling and lubrication brings the system even more towards optimum. Today, water cooling circuits of electric motor and inverter are normally connected in line. As stated, it makes sense to use the same principle for the rotor cooling and the gear set lubrication. The waste heat of the rotor is a good energy source for warming up the transmission in cold conditions, which is easy to prove by simple math. With this principle of rotor cooling it becomes attractive to substitute the permanent magnet machine with an induction machine. With axle drives, the advantages of the permanent magnet motor regarding power density and efficiency is to be equalised rather quickly, cost and other advantages of the induction machine may prevail. In total it becomes possible to achieve system torque densities of more than 21 Nm/kg and system power densities of above 1,1 kW/kg, both from DC side to wheel. For high volumes it might be attractive to integrate the power electronics as well; the piece cost may come down even more.
The integrated electric drivetrain. A holistic approach to future mobility concepts
2011
9 Seiten, 4 Bilder, 8 Quellen
Aufsatz (Konferenz)
Englisch
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