Efficiency-based methodology for the selection of electric motors for mini-tractor propulsion

Abstract

This article deals with the research and analysis of electric motors and their matched transmission systems within the context of a versatile electric mini-tractor designed for tasks such as street cleaning, urban park maintenance, and transportation of small loads. The primary objective of the research is to assess the strengths and weaknesses of several electric motor and transmission combinations designed to meet the specific operational demands of the tractor. As the driveline has to provide substantial torque while maintaining optimal operating conditions and avoiding overheating, a series of experiments were conducted, covering various electric motor configurations operating within the 60V range, with power outputs ranging from 1000 to 1500 watts and including multiple gearbox variations. A comparative analysis was performed to assess the advantages and disadvantages of direct chain drive transmission solutions without a differential on a rigid axle, in contrast to a sealed motor-gearbox unit featuring differential and semi-axles. The results of this research were used for mathematical comparison of the driveline solutions, enabling the detection of optimally matched transmission and motor solutions. The experiments also covered the identification of energy-efficient solutions and optimal design parameters for an electric tractor explicitly designed for continuous operation exceeding 10 hours, with cargo capacity exceeding 500 kg, high off-road maneuverability, and a service life exceeding 5000 hours. The dynamic tests carried out during the research have provided valuable insight into the relation of the overall power efficiency of the vehicle to the weight and transmission ratio variations.