The report describes the development and preliminary investigation of an experimental drive system, of which the central component is a permanent-magnet synchronous motor optimized for a hybrid electric vehicle. The maximum output power of the motor is 50 kW in continuous operation and 100 kW in intermittent operation.
The synthesis of the motor was based on numerical calculations of the motor properties and losses by means of a finite-element method. Simulations according to standardized driving-cycles were used to predict the energy consumption of the drive line. A thermal model was developed and implemented as a thermal network and the numerically calculated losses were applied for evaluation of the temperature distribution in the motor.
Experimental results have shown discrepancies less than 5 K between the measured and the calculated temperature rises in the stator windings. Control of the drive was done with a control computer based on a digital signal processor. A simple comparison of two different control strategies indicates that the motor efficiency is affected by the chosen strategy. A calorimetric method was implemented to improve the accuracy of the loss measurements, since the traditional input-output method is useless for high efficiency motors.
The maximum relative error in the measurement of the total motor losses was estimated to be ±2.3 % at the nominal operating point and less than ±3.5 % at any operating point in the investigated region. The measured maximum efficiency of the motor was 95.5 %, obtained at the nominal operating point. The motor concept chosen for the vehicle application can be designed for high efficiency in a wide range of speeds and loads.
Source: Chalmers University of Technology
Author: Joachim Lindstrom