Lassi Aarniovuori

Measurements and Simulations of DTC Voltage Source Converter and Induction Motor Losses

Energy efficient pulse-width modulation inverters are widely used to control electrical machines accurately for process needs. The pulse-width modulation, however, has also adverse effects and produces additional losses in the motor. These losses increase the motor temperature and result in derating of the machine power in converter use. A reliable and reasonably accurate loss model of an induction motor drive system is important for the performance prediction of a variable-speed drive. A two-level frequency converter main circuit model is coupled to a finite-element method motor model. The drive model is controlled by closed-loop direct torque control. The frequency converter losses are calculated analytically, and the finite-element method motor model provides an analysis of the motor losses. The simulation results are compared with measurement results.

Loss Definition of Electric Drives by a Calorimetric System With Data Processing

An accurate measurement of power or heat losses of high-efficiency electrical devices is difficult with input and output powers. In the calorimetric method, these losses are measured directly. In this paper, a functional heat loss measurement concept with adequate data processing methods is suggested for heat losses up to 2 kW. Such a heat loss range can be applied to present-day power electronic converters with the rated power of up to 110 kW and motors up to 37 kW. The measurement system does not require a complex mechanical structure or a large footprint area on the measurement site. The concept is scalable to different sizes. New features to the balance type calorimeter data processing are introduced. These include a mass flow correction, a technique to detect the thermal equilibrium, and a method to correct measured heat losses to improve the measurement repeatability and reduce the measurement uncertainty. The measurement uncertainty of the proposed calorimetric concept is 0.4%. Laboratory measurements are carried out both for a commercial frequency converter and an electric motor. These are measured at the same time with two calorimeters. The losses of these devices are measured both by the input-output and calorimetric methods.

Loss calculation of a frequency converter with a fixed-step circuit simulator

The total losses of a frequency converter are calculated by using a fast fixed-step circuit simulator. A simple model for calculating the frequency converter total losses at different operating points is presented. Direct torque control (DTC) is applied as the control method of the converter. The simulated converter losses are verified by measurements.

Analysis of 37-kW Converter-Fed Induction Motor Losses

This paper presents an energy efficiency analysis of a 37-kW standard squirrel-cage induction motor under sinusoidal and nonsinusoidal supply. The motor losses are analyzed using the conventional IEC loss segregation method and also numerically modeled using finite-element simulations. The measured and simulated loss components are compared with three different modulation methods. The overall simulated losses are in good agreement with the measured ones, but there exist differences in the loss components.

Application of Calorimetric Method for Loss Measurement of a SynRM Drive System

Synchronous reluctance motors (SynRMs) are gaining in popularity in industrial drives due to their permanent magnet-free, competitive performance, and robust features. This paper studies the power losses in a 90-kW converter-fed SynRM drive by a calorimetric method in comparison of the traditional input-output method. After the converter and the motor were measured simultaneously in separate chambers, the converter was installed inside the large-size chamber next to the motor and the total drive system losses were obtained using one chamber. The uncertainty of both measurement methods is analyzed and discussed.

Multidisciplinary Design of a Permanent-Magnet Traction Motor for a Hybrid Bus Taking the Load Cycle into Account

An electrical and mechanical design process for a traction motor in a hybrid bus application is studied. Usually, the design process of an electric machine calls for close cooperation between various engineering disciplines. Compromises may be required to satisfy the boundary conditions of electrical, thermal, and mechanical performances. From the mechanical point of view, the stress values and the safety factors should be at a reasonable level and the construction lifetime predicted by a fatigue analysis. In a vehicle application, the motor has to be capable of generating high torque when accelerating, and in normal operation, the losses of the machine should be low to be able to cool the machine. Minimization of the no-load iron losses becomes a very important electrical design requirement if the traction motor and the generator are mechanically connected with an internal combustion engine when it is operating as the only source of torque. The manufacturing costs of the motor are also taken into account in this paper.

On Low-Voltage DC Network Customer-End Inverter Energy Efficiency

In this paper, the results of the energy efficiency and power loss measurements of a 16 kVA customer-end inverter (CEI) unit are analyzed. The CEI is part of the low-voltage dc (LVDC) distribution network. The efficiency of the CEI power conversion significantly affects the energy efficiency of the LVDC distribution network and the electricity supply chain. The efficiency of the CEI and its components is measured by applying calorimetric and electrical input-output methods. The power loss measurement results are analyzed, and the power loss mechanisms are described. The efficiency optimization goals are discussed and set.

Parallel chamber calorimetric concept

A new type of a calorimetric measurement system concept for drives measurements based on open- and balance-type calorimeter is introduced and practically verified. The calorimetric concept with two parallel chambers is used to obtain the losses of the commercial frequency converter. The main advantage of this concept is the measurement rate of different operating points compared to the standard open- and balance-type calorimeter, because the main and balance test are carried out at the same time.

Uncertainty in motor efficiency measurements

Results of five induction motor efficiency measurements according IEC 60034-2-1 are presented. The uncertainty of the measurements is analyzed using scientific and numerical methods.

Direct Liquid Cooling in Low-Power Electrical Machines: Proof-of-Concept

This paper evaluates the feasibility of a direct liquid cooling approach in the thermal management of an axial flux permanent-magnet machine. To demonstrate the cooling method, a test motor was fitted with helical tooth coil windings formed from a hybrid conductor comprising a stainless steel coolant conduit tightly wrapped with a stranded Litz wire. The motor is a 100-kW permanent-magnet, axial-flux, double-stator, single-rotor machine. The proof of concept integrated the motor with a closed liquid coolant loop, appropriate instrumentation, and a data acquisition system. The general performance of the motor was examined at various power levels using polyalphaolefin oil as the cooling fluid. The results show the proposed cooling method to be feasible, and furthermore, to provide significant improvements to the machine thermal management.