Energy Efficiency of Gearboxes Application in Power Units of Electric Vehicles

Abstract

With all advantages, electric vehicles have a significant disadvantage — a relatively small driving range on a single charge of the traction battery compared to cars using hydrocarbon fuel. The solution to the issue is to choose a rational structural scheme of an electromechanical power unit to obtain its high energy efficiency regardless of the operating conditions. A significant number of electric vehicles produced today either do not contain gearboxes or contain single-speed reducers. The use of a multi-speed gearbox solves the problem of adapting the working processes of a traction electric motor to the loading conditions, bringing its efficiency as close as possible to the range of highly efficient values. Calculated estimation of energy consumption of the MAZ-4381EE electric delivery truck is carried out in the paper for various versions of the mechanical part of power unit: without a reducer, with the use of a reducer and two types of two-speed gearboxes (shaft and shaft-planetary). The evaluation is made based on consideration of the European test driving cycle NEDC, taking into account the use of efficiency maps of the traction induction electric motor. The calculation results showed that the use of two-speed gearboxes can reduce the total energy consumption by more than 1.8 times compared to a power unit with a high-torque motor and without a gearbox.