Impact of PWM schemes on induction motor losses

This paper presents the results of an investigation into the impact of pulse width modulation (PWM) switching schemes on power losses in induction motors and their inverter drives. The PWM schemes considered include sinusoidal PWM, spacevector PWM and discontinuous PWM. Both experimental results and simulated predictions are presented for fractional horsepower and small integral horsepower motors. Direct loss measurements have been carried out using a calorimetric test rig; detailed simulations of the skewed motors have been carried out using multi-slice time-stepped 2D FEA. The simulated and measured losses under the different modulation schemes are compared and discussed. © 2006 IEEE.

A comparison of power losses for small (< 1 kW) induction motor drives adopting squarewave and sinusoidal PWM excitation

In this paper the influence of the form of motor excitation on the performance of a small (< 1 kW) induction motor drive is studied. Two forms of excitation, namely sine waves generated by pulse width modulation and simple square wave are explored. Sine wave excitation gives lower motor losses but increases inverter losses. Conversely, square wave excitation increases motor losses but decreases inverter losses. Losses have been measured directly by calorimetric means or, in the case of the inverter, predicted by a Pspice model that has been verified by calorimetric methods. The work shows that overall, the use of square wave excitation leads to a more efficient drive. © 2004 The Institution of Electrical Engineers.

Power losses in small inverter-fed induction motors

This paper presents the results of experimental and simulation investigations of the breakdown of losses in a small inverter fed induction motor. Factors that are considered include the impact of skew, excitation voltage waveform shape and PWM switching frequency. Detailed finite element simulations of the motor performance are carried out for the various conditions, with simulation results compared to calorimetric test results. © 2005 IEEE.

Advanced DC link capacitor technology application for a stiff voltage-source inverter

Problem of DC link size in a stiff voltage-source inverter for electric drive is described in the paper. Advantages of advanced film capacitor technology over conventional one for DC link application are reviewed. Conventional DC link capacitor selection methods are questioned in view of advanced capacitor technology utilization in stiff voltage-source inverter. For capacitor selection maximum ripple rms current point is shown. DC link ripple current spectrum analysis under modern PWM techniques is presented. Some capacitor selection recommendations are given. The analysis has been aided greatly by computer modeling in PSpice. ©2005 IEEE.

Investigation and comparison of inverter-fed induction machine loss

This paper presents an investigation into the losses in a three-phase induction motor under different pulse width modulation (PWM) excitation conditions. The impacts of Sinusoidal PWM, Space Vector PWM and Discontinuous PWM on machine loss are compared and studied. Finite element analysis simulations are employed to predict the machine losses with the loss breakdown analysis under different PWM schemes. Direct Calorimetric measurements are utilized to verify the finite element modeling and provide direct quantifications of machine loss under modern PWM techniques. © 2008 IEEE.

High temperature direct double side cooled inverter module for hybrid electric vehicle application

In this paper a novel approach to the design and fabrication of a high temperature inverter module for hybrid electrical vehicles is presented. Firstly, SiC power electronic devices are considered in place of the conventional Si devices. Use of SiC raises the maximum practical operating junction temperature to well over 200°C, giving much greater thermal headroom between the chips and the coolant. In the first fabrication, a SiC Schottky barrier diode (SBD) replaces the Si pin diode and is paired with a Si-IGBT. Secondly, double-sided cooling is employed, in which the semiconductor chips are sandwiched between two substrate tiles. The tiles provide electrical connections to the top and the bottom of the chips, thus replacing the conventional wire bonded interconnect. Each tile assembly supports two IGBTs and two SBDs in a half-bridge configuration. Both sides of the assembly are cooled directly using a high-performance liquid impingement system. Specific features of the design ensure that thermo-mechanical stresses are controlled so as to achieve long thermal cycling life. A prototype 10 kW inverter module is described incorporating three half-bridge sandwich assemblies, gate drives, dc-link capacitance and two heat-exchangers. This achieves a volumetric power density of 30W/cm3.