PERFORMANCE IMPROVEMENT OF CEILING FAN MOTOR USING VARIABLE FREQUENCY DRIVE WITH SEPIC CONVERTER

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1 Volume 118 No , ISSN: (printed version); ISSN: (on-line version) url: doi: /ijpam.v118i11.97 ijpam.eu PERFORMANCE IMPROVEMENT OF CEILING FAN MOTOR USING VARIABLE FREQUENCY DRIVE WITH SEPIC CONVERTER 1 V.Jethose, 2 S.Manoharan 1 Associate Professor, Department of EEE, JCT College of Engineering and Technology, 1 jethose.v@jct.ac.in 2 Professor & Head, Department of EIE, Karpagam College of Engineering, 2 manoish07@yahoo.co.in Abstract: Single phase induction motors(spim) are the commonly used motor in household appliances because of its rugged construction and low cost. The major problem associated with SPIM is the low power factor and the high harmonic distortion. The power factor was found very poor and a huge amount of power is being wasted up and this affects the quality of power. The main objective of this paper is to improve power factor and to reduce ripples in the input current and also to provide an efficient speed control method. The proposed system is used for the single phase induction motor in ceiling fan or refrigerator. Conventional speed control techniques using TRIAC consumes huge amount of energy for the speed control of induction machine. The above mentioned problem is overcome by means of a Power Factor Correction Circuit with single-ended primary-inductor converter (SEPIC)converter which is operating in Discontinuous Conduction Mode (DCM) with Pulse Width Modulation(PWM) control technique for the smooth speed control.. As a result a smooth speed control is achieved with improved power factor and reduced Total Harmonic Distortion (THD). To validate the above, the simulink model of SEPIC PFC converter fed induction motor drive in MATLAB/Simulink platform is developed and the results achieved were compared with and without the PFC converter. Keywords: SEPIC, Pulse with modulation, DCM, motor speed, PWM inverter 1. Introduction Development in the field of power electronics is quick and appreciable. These developments have increased the non-linearity of the electrical system. With increasing Quantities of non-linear loads being added to the electrical systems, it has become necessary to maintain the power quality. The problems related power quality becomes an issue of concern. If electrical equipment operates correctly and reliably without being damaged or stressed[1], then the electrical power is of good quality. Power quality determines how efficiently the power is utilized by the consumer devices. Poor power quality can be described as any event related to the electrical network that ultimately results in a financial loss and reduce the life of the appliance connected to the supply of poor quality[3]. The induction motors are the commonly used motor in household appliances because of its rugged construction and low cost. The major problem associated with the induction motors are the low power factor and the high harmonic distortion. The power factor was found to be 0.6 to 0.7 and a huge amount of power is being wasted up and this affects the quality of power[4]. The main objective of the work is to improve power factor and to reduce ripples in the input current and also to provide an efficient speed control method [9]. The proposed system is used for the single phase induction motor in ceiling fan or refrigerator. Normally the speed control of the single phase induction motor is done using triac[3]. This is not an energy efficient technique as huge amount of energy is wasted in the speed control of induction machine. The above mentioned problem is overcome by means of a PFC SEPIC converter which Operating in DCM and a PWM control technique is used for the smooth speed control of the induction machine. As a result the problem related to power factor and harmonic distortions were solved [2] Induction motor 753

2 Single phase power system is widely used as compared to three phase system for domestic and commercial purpose. In most of the household appliances single phase induction motors are used. Single phase induction motors have several advantages i.e.; they are simple in construction [11, 5], cheap in cost, reliable and easy to repair and maintain. Due to all these advantages the single phase induction motor finds its application in vacuum cleaner, ceiling fans, washing machine, and refrigerator, centrifugal pump, blowers, washing machine, small toys etc [6,7]. 1.2 Speed Control Techniques Due- to the advancement in power electronics the induction motors are used for variable speed services by making use of variable speed drives[2,5]. A variable-frequency drive (VFD) is a system for controlling the speed of a rotational or linear alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor[7,2]. A variable frequency drive is a specific type of adjustable-speed drive. Variable frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, micro drives or inverter drives. In the previous days, the variable speed drives had various limitations such as larger space, low efficiency, lower speed and etc. 2. Existing System In the existing system, bridgeless converter with TRIAC is used as a power factor correction device. Here converter is operated in continuous conduction mode 2.1 Existing System VFD Drives Figure 1. Block diagram of existing system The VFD is a system made up of active/passive power electronics devices; Fig 2 shows electronic speed control of the motor supply frequency. The basic concept of these drives, is that a rectifier converts the fixed frequency supply to DC (which converts commercial power into a direct current). A DC power of the AC supply delivered to the motor is controlled by inverter. link stage smoothes the rectified [11] Figure 2. Modified SEPIC converter fed induction motor drive The existing V/F technique provides efficient speed control and better efficiency, but power factor is very low and a huge amount of energy is wasted out in order to rectify this problem a new topology is proposed 754

3 is a PFC Converter after the bridge rectifier 3. Proposed System The Proposed system consists of a PFC converter circuit and an inverter circuit.sepic converter is used to improve the power quality at AC mains.the AC supply of about 230V is given to the Modified SEPIC PFC converter using an autotransformer. This 230V is stepped up to a value of 400V DC by the SEPIC PFC Converter. Controller Circuit consists of voltage regulator(lm7805) which helps for obtaining controlled constant output dc 400V.For working of controller circuit a 12 V supply is given to the controller circuit. Output of the AC-DC converter is given to the inverter circuit. Inverter circuit hence converts the DC into AC. Voltage regulator LM7805 in inverter circuit is used to get a regulated voltage. DSPIC30F2010 microcontroller is used to provide gate switching signals for the inverter switches. Figure 3. Block Diagram of the proposed topology Figure 4. Modified SEPIC converter 4. Power Factor Correction Power supplies connected to ac mains introduce harmonic currents in the utility. It is very well known that these harmonic currents cause several problems such as voltage distortion, heating, noise and reduce the capability of the line to provide energy [6]. To reduce these harmonic currents so many researches on power factor correction circuits have done. 755

4 Figure 5. Power Factor Correction Circuit Fig 1 is a two stage power factor correction circuit which comprises of a diode bridge, power factor preregulator and a DC-DC converter and the control circuit associated with the two converters [8,9]. The diode bridge and the first converter together are known as the power factor pre-regulator. Power factor pre-regulator is a converter; here the power factor is improved. The second converter is used to get a regulated output. Several researches on the two stage power factor correction circuits were done. The major drawback of the two stage power factor circuit is that the cost is very high. 5. DC-DC Conevrter Some converters are designed to work in discontinuous conduction mode are natural voltage followers and the inner current loop can be removed. Thus we can simplify the circuit. Sinusoidal line current is our aim and it is maintained in converters such as buck-boost and flyback, [8,10] SEPIC, Cuk and Zeta. Boost converter may be designed for sinusoidal line current but forcing a high output voltage. This is the best option for medium and low power application Modified version of SEPIC converter which is operating in DCM is used as a power factor pre-regulator. The switch voltage is lower than the output voltage. The converter operates as a voltage follower when designed in DCM with a low value for the inductor L 2 and using a high value for the inductor L 1. The input current presents low current ripple such as a classical SEPIC converter, designing the converter in DCM and using a low value for the inductor L 2 and a high value for the inductor L 1 [7]. 5.1 Modes of Operation of SEPIC PFC converter Figure 6. Modified SEPIC converter The modified SEPIC dc dc converter operating in DCM presents three operation stages. The steady state operation is considered and all the components are assumed to be ideal. The voltages across all capacitors are considered constant during a switching period, as an ideal voltage source. In DCM operation when the power switch is turned off the currents in all diodes of the circuit are zero. Therefore [5,9], the DCM operation occurs when D O and D M diodes are blocked before the switch turn-on. Considering the operation at steady state, the average voltage across the inductors L 1 and L 2 are zero and the sum of the input voltage V in and capacitor C S voltage is equal to the capacitor C M voltage [10]. The three operation stages of Modified SEPIC in DCM are presented as follows: Mode 1: When the switch is turned ON the full voltage comes across the input inductor. The voltage across the inductor L2 is equal to the voltage of the C M Capacitor minus the C S Capacitor. Both the inductor stores energy and have the same voltage across them. The two diodes are blocked during this stage [11]. Mode 2: The power switch is turned off at the instant t = t 1. The energy stored in the inductor L 1 is transferred to the output through the capacitor C S and the diode Do. There is also energy transfer to the capacitor C M and diode D M. The switch voltage is reduced to the capacitor voltage. The stored energy in the inductor L 2 is transferred to the output and the capacitor C M through the diodes D O and D M. The period (t 2 t 1 ) 756

5 is defined as td and it is the transference period of the energy stored in than the output voltage. The L 1 inductor average current is equal to the input current and the L 2 inductor average current is equal to the output current. The average current in the capacitors C S and C M are null at steady state; thus, the average current of diodes D M and D o are equal to the output current [7,4]. Figure 7. Switching current and voltage waveform 6. Third-Harmonic Reduction Technique (THD ) The classical boost rectifier operating in DCM and the modified SEPIC rectifier present a third-harmonic distortion in the input current. This current distortion is a function of the voltage difference between the input and output Voltage e. [4]Normally, the output voltage is increased in order to reduce the third-harmonic distortion and to maintain HPF, but the semiconductors losses are increased. Only the information of the input and output voltage are necessary to define a duty-cycle variation in a line voltage half period, reducing the third-harmonic distortion even for a relatively low output voltage. The same open-loop technique is developed in this paper for the modified SEPIC converter using a digital implementation, obtaining HPF. Considering by simplification that the converter operates without losses, the input power is equal to the output power [3]. 7. Results & Discussions 757

6 Figure 7. Simulation of induction motor drive The simulation of a Modified SEPIC PFC converter fed induction motor drive is done using MATLAB. Input voltage of 230V is given to the Modified SEPIC PFC Converter so that an output voltage of 400V DC is obtained. The input current waveform is of pure sinusoidal. Figure 8. Input Current Waveform The input current waveform is of pure sinosidal the above graph is plotted against current and time. X aaxis shows the input current whereas Y axis shows time 758

7 Figure 9. Output voltage waveform The above graph is plotted against voltage and time.x axis show the output voltage whereas Y asix shown in Time Input voltage of 230V is given to the modified SEPIC PFC converter so than an output of 400v DC is obtained.the power factor was improved to 0.99 and the harmonic distortion was reduced from 88% to 5%. Using variable frequency drive the efficient speed control is made possible. Thus the power loss in the speed control of induction motor was reduced by means of the VFD. The input current waveform attains pure sinusoidal shape. This improved the power factor and has reduced the harmonic distortion. 6. Conclusion The single-phase induction motor can successfully be driven from a variable frequency power supply. Hence, the motor speed can be easily adjusted. The torque performance of the capacitor- connected motors can be enhanced at low frequency range by altering the V/f control law such that the internal power dissipation in the motor is held constant. VFD control provides efficient speed control the speed is controlled by varying the frequency not the stator voltage. The power factor is improved and the harmonic distortions were less. References [1] A. S. Ba-thunya, R. Khopkar, Kexin Wei, H.A.Toliyat (2001), "Single phase induction motor drives-a literature survey," proc. of IEEE International Electric Machines and Drives Conference 1) [2] Carlos Gabriel Bianchin, Roger Gules(2005), Member, IEEE, Alceu Andr e Badin, Member, IEEE, and Eduardo F elix Ribeiro Romaneli High-Power-Factor Rectifier Using the Modified SEPIC Converter Operating in Discontinuous Conduction mode [3] D. Jang and G. Choe(1995), "Improvement of Input Power Factor in ac Choppers using Asymmetrical PWM Technique," IEEE Transactions on Industrial Electronics, Vol [4] 4. D S Henderson,(2004) Variable Speed Electric Drives - Characteristics and applications Adjustable Frequency Control (Inverters) fundamentals application Consideration, Bulletin C870A. [5] D. S. L. Simonetti, J. Sebastiain, and J. Uceda(2003), A small signal model for SEPIC, CUK and flyback converters as power factor preregulators in discontinuous conduction mode, [6] 6.E. H. Ismail(2009), Bridgeless SEPIC rectifier with unity power factor and reduced conduction losses,ieee Trans. Ind. Electron., vol. 56, no. 4, pp [7] 7.Liu,T.H., Wu, H.Ch. and Lin, M.T,( 1997) A Single phase induction motor drive with efficiency and torque improvement, proc. of IEEE International Symposium on Industrial Electronics,, Vol.2, pp [8] 8.M. Mahdavi and H. Farzanehfard(2011), Bridgeless SEPIC PFC rectifier with reduced components and conduction losses,ǁ IEEE Trans. Ind. Electron., vol. 58, no. 9, pp [9] 9.O. Garc ıa, J. A. Cobos, R. Prieto, P. Alou, and J. Uceda,( 2003.) Single phase powerfactor correction: A survey,ǁieee Trans. PowerElectron., vol. 18, no. 3, pp , [10] 10. P. F. de Melo, R. Gules, E. F. R. Romaneli, and R. C. Annunziato,(2001) A modified SEPIC converter for high-power-factor rectifier and universal input voltage applications,ǁ IEEE Trans. Power Electron.,vol.25,no.2,pp [11] 11.I.Ibrahim,.M.T.Raja,Ismail,M.R.Ghazali,(2002) with Development of Variable Speed Drive for Single Phase Induction Motor Based on Frequency Control. vol.25,no.2,pp

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