Direct torque control of four-switch brushless DC motor with non-sinusoidal back-EMF

Salih Baris Ozturk, William C. Alexander, Hamid A. Toliyat

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

15 Citations (Scopus)


This paper presents a direct torque control (DTC) technique for brushless dc (BLDC) motors with non-sinusoidal back-EMF using four-switch inverter in the constant torque region. This approach introduces a two-phase conduction mode as opposed to the conventional three-phase DTC drives. Unlike conventional six-step PWM current and voltage control schemes, by properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table at a predefined sampling time, the desired quasi-square wave current is obtained. Therefore, a much faster torque response is achieved compared to conventional PWM current and especially voltage control schemes. In addition, for effective torque control in two phase conduction mode, a novel switching pattern incorporating with the voltage vector look-up table is designed and implemented for four-switch inverter to produce the desired torque characteristics. Furthermore, to eliminate the low-frequency torque oscillations caused by the non-ideal trapezoidal shape of the actual back-EMF waveform of the BLDC motor, pre-stored back-EMF constant versus position lookup tables are designed and used in the torque estimation. As a result, it is possible to achieve two-phase conduction DTC of a BLDC motor drive using four-switch inverter with faster torque response due to the fact that the voltage space vectors are directly controlled. Therefore, the direct torque controlled four-switch three-phase BLDC motor drive could be a good alternative to the conventional six-switch counterpart with respect to low cost and high performance. A theoretical concept is developed and the validity and effectiveness of the proposed two phase conduction four-switch DTC scheme are verified through the simulations and experimental results.

Original languageEnglish
Title of host publicationPESC '08 - 39th IEEE Annual Power Electronics Specialists Conference - Proceedings
Number of pages7
Publication statusPublished - 2008
Externally publishedYes
EventPESC '08 - 39th IEEE Annual Power Electronics Specialists Conference - Rhodes, Greece
Duration: 15 Jun 200819 Jun 2008

Publication series

NamePESC Record - IEEE Annual Power Electronics Specialists Conference
ISSN (Print)0275-9306


ConferencePESC '08 - 39th IEEE Annual Power Electronics Specialists Conference


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