Reducing Common-Mode Voltage in Three-Phase Sine-Triangle PWM with Interleaved Carriers


Interleaving pulse width modulation (PWM) waveforms is a proven method to reduce ripple in dc-dc converters. The present study explores interleaving for three-phase motor drives. Fourier analysis shows that interleaving the carriers in conventional uniform PWM significantly reduces the common-mode voltage. New digital signal processor (DSP) hardware supports interleaving directly with changes to just two registers at setup time, so no additional computation time is needed during operation. The common-mode voltage reduction ranges from 36 at full modulation to 67 when idling with zero modulation. Third-harmonic injection slightly reduces the advantage (to 25 at full modulation). However, the maximum RMS common-mode voltage is still less than 20 of the bus voltage under all conditions. The disadvantage of the proposed approach is an increase in current ripple at the switching frequency. Simulations verify the findings. Experiments on a motor drive that uses a commercially available motor-control DSP, connected to a 5 hp motor, agree well with calculations and simulations.


Electrical and Computer Engineering


ITW Military GSE
National Science Foundation (U.S.). Industry/University Cooperative Research Centers Program


This work was supported in part by the ITW Military GSE and in part by the National Science Foundation I/UCRC on Intelligent Maintenance Systems.

Keywords and Phrases

Additional Computation Time; Bus Voltage; Common Mode Voltage; Current Ripples; Fourier; Hardware Supports; Motor Control; Motor Drive; Photovoltaic Systems; Pulse Width; Set-Up Time; Third Harmonic; Three Phase Motor; Uniform PWM; Variable Speed; Wave Forms; Zero Modulation; DC-DC Converters; Digital Signal Processors; Electric Drives; Fourier Analysis; Fourier Series; Modulation; Photovoltaic Effects; Speed Control; Variable Speed Drives; Pulse Width Modulation; Inverters

International Standard Serial Number (ISSN)

0885-8993; 1941-0107

Document Type

Article - Journal

Document Version


File Type





© 2011 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Aug 2011