THEORETICAL SUBSTANTIATION OF IMPROVING THE TRACTION EFFICIENCY OF ELECTRIC TRACTORS THROUGH A PTO-BASED POWER ASSIST SYSTEM

This article develops the theoretical basis of a power assist system connected to the power take-off (PTO) shaft to increase the traction capability of electric tractors under high-load operating conditions. The study theoretically compares three powertrain layouts: a baseline dual-motor coupled powertrain (DMCP), a speed-coupling configuration with a power assist system, and a mixed-coupling configuration with a power assist system. The longitudinal motion of the tractor, wheel traction force, kinematic relationships of the planetary gear set, motor power demand, and energy consumption are described using mathematical equations. For 46 kW and 55 kW ploughing workload conditions, the power envelope, maximum traction force, and relative energy consumption were evaluated. The calculation results show that the integration of a PTO-based assist motor increases the traction force by 24.92-30.83% compared with the baseline DMCP. The speed-coupling configuration provides the highest traction force, whereas the mixed-coupling configuration is distinguished as a structurally simpler solution because it delivers torque directly to the output shaft. The proposed article can serve as a theoretical basis for selecting the power transmission architecture of electric tractors intended for agricultural working units.