This document proposes a brushless DC motor drive system with a bridgeless isolated Cuk converter to provide power factor correction at the AC mains. The system includes a single-phase AC supply filtered and fed to the Cuk converter to maintain the DC link voltage for a three-phase voltage source inverter that drives the BLDC motor. This improves efficiency over existing boost converter topologies and draws less harmonic current from the mains for better power factor. The document outlines the components, operation, and advantages of the proposed system for applications requiring precise motor control.

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A Unity Power Factor Bridgeless Isolated
Cuk Converter-Fed Brushless DC Motor
Drive
Abstract
Introduction:
A BLDC motor consists of three-phase concentrated
windings on the stator and permanent magnets on the rotor. A
three-phase voltage-source inverter (VSI) is used for achieving
an electronic commutation of the BLDC motor based on the
rotor position as sensed by Hall-effect position sensors. A VSI-
fed BLDC motor drive is generally supplied by a combination of
a diode bridge rectifier (DBR) with a high value of smoothening
dc link capacitor. This combination of DBR and dc link
capacitor draws current only for a small duration when the
instantaneous value of supply voltage is higher than the dc link
voltage. Therefore, a peaky current is drawn from the ac mains,
which has very high value of harmonic contents. The total
harmonic distortion (THD) of such current is of the order of
60%–80% which leads to a very poor power factor (PF) of the
order of 0.6–0.7 at ac mains.

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Copyright © 2015 LeMeniz Infotech. All rights reserved
LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Existing system:
The boost converter charges a bulk energy storage
capacitor to a voltage higher than the peak line voltage. Finally a
voltage-fed, step-down inverter is used to drive the brushless DC
motor. These capacitors are typically electrolytic and are
physically large, expensive and failure prone, limiting the
lifetime of the drive. Under certain conditions efficiency may be
improved by the elimination of the boost stage.
Proposed system:
A single-phase supply followed by an LC filter is used to
feed a bridgeless isolated Cuk converter. This maintains the
required dc link voltage of the VSI and provides PFC at ac
mains. The proposed PFC converter is designed to operate in
DICM to act as an inherent power factor corrector. The dc link
voltage of the VSI is controlled for adjusting the speed of the
BLDC motor. The VSI feeding the BLDC motor is operated in a
low frequency switching to achieve an electronic commutation
of the BLDC motor for reduced switching losses. The proposed
configuration uses a single voltage sensor to control the dc link
voltage for the speed control of the BLDC motor.

3. Do Your Projects With Domain Experts…
Copyright © 2015 LeMeniz Infotech. All rights reserved
LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Block diagram:
Single
phase AC
supply
Filter
Bridgeless
isolated Cuk
converter
3 phase
voltage
source
inverter
BLDC
motor
BUFFER circuit
5VDC
PIC controller
circuit
OPTO coupler
circuit
3 phase gate
driver circuit
12 V
DC
12 V
DC

4. Do Your Projects With Domain Experts…
Copyright © 2015 LeMeniz Infotech. All rights reserved
LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Advantages:
 Reduced the switching losses.
 Reducing the conduction losses in the front-end converter.
Applications:
 Household appliances.
 Industrial tools.
 Medical equipment.
 Precise motion control.
 Automation and transportation.
Tools and software used:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation.