Simulation of an industrial tractor with an electric transmission in a bulldozing technological cycle

Abstract

The emergence of affordable, relatively compact permanent magnet electric machines for heavy construction equipment opens up new prospects for the implementation of electric drives in industrial tractor transmissions. These are also continuously variable, externally adjustable transmissions, like hydrostatic ones. They are easily automated and allow the design of unmanned vehicles and technological equipment. The obvious advantage of electric transmissions over hydrostatic ones is their efficiency. Literary sources claim that the efficiency of permanent magnet electric machines is almost 100%. In contrast, hydrostatic machines have an average efficiency of approximately 80 %. Permanent magnet electric machines do not have the ability to recuperate power. There is no additional device in the form of an energy storage unit (ESU). For electrical energy, such capabilities are well known and widely used. An ESU, unlike the generally accepted understanding of a ESU, combines the properties of a capacitor, capable of rapid charging and discharging, and a battery, capable of storing energy for an extended period. The purpose of this study is to mathematically describe the combined operation of an internal combustion engine, generator, traction electric motors, and battery (as we will traditionally refer to the energy storage device) during bulldozer operations. The bulldozer loads the motor-transmission unit of an industrial tractor with rapidly changing (up to 10-fold) loads over a short period (100 seconds). Of interest is the magnitude of currents and voltages in the EMT during operation of a 21-ton D12E industrial tractor manufactured by the DST-Ural plant. Currents are approximately 200 A, and voltages are 500 V. The modeling results are also important for the newly designed DST-Ural D30 and D40 super-heavy bulldozers.