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International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963

Atul Gajare1 and Nitin Bhasme2

PG Student, 2Associate Professor
Department of Electrical Engineering,
Government College of Engineering, Aurangabad, India

The single phase induction motor is used in wide variety of industrial, commercial, workshop area and domestic
applications. In some applications like blower it is desired to control air flow rate in proportion to speed of
motor. This paper describes the control scheme of air flow rate of single phase induction motor (SPIM) with
blower application including variable voltage and variable frequency control, its implementation and test result.
For this purpose a SG3525 PWM control technique is used in which the air flow rate of blower can be changed
at various frequencies and voltages. The present paper analyses the torque, speed, slip, and current
characteristics of single phase induction motor. PWM technique has been employed in this drive to supply the
motor with an AC voltage for variable air flow rate under different frequencies and the practical results are
obtained and analyzed here. The systems as a whole consist of SG3525 PWM controller, power circuit and Hbridge inverter using IRF840 MOSFET. PWM method with adjustable voltage, variable frequency pot is used.
The system is implemented, tested and the experimental results are examined and discussed here.

KEYWORDS โ€“ PWM technique, Driver and Inverter circuit Single phase induction motor, Blower, V/f control



Single-phase induction motors (SPIM) are most widely used in the world due to their rugged
construction, low maintenance and high speed operation. The capacitor start motor in addition to the
main winding, a split phase arrangement auxiliary winding is provided through a centrifugal switch
for starting purpose. The single phase induction motors are working on the principle of double
revolving field theory. It is widely used in many maintenance workshop, residential, industrial,
commercial, and utility applications. Single-phase induction motors are widely used in home
appliances and industrial control especially in low duty application [6]. There are various controlling
technique such as voltage, scalar control, vector control and direct torque control methods. But, here
we are implementing scalar control is called v/f method. It is simple and popular open loop methods
of controlling and changing the speed of single phase induction motor simultaneously for air flow rate
of blower. There are various applications where continuous control of the single phase motors speed
would be advantageous. The multispeed operation and multipurpose operation are provided by
controlling the speed of these motors.
Single phase induction motor operate at fixed voltage, their speed varies with air flow rate on the fan
blades of blower. The air flow rate is directly proportional to speed of motor or fan blade of blower.
This method is used to control and change the air flow rate of a drive driving blower. Now a day the
home appliance manufacturers used the constant air flow rate criteria in selecting blower drive of air


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963
motion in appliances. Due to this development, the suggested technique can be used in domestic,
commercial and industrial applications such as heating and cooling system [2].
Traditionally, dc machines are extensively used as variable speed drive. But, the dc machine have
disadvantage of higher cost, maintenance problem with brushes and commutators. Also achieving
variable speed of d.c. motor suffers various limitations such as larger space, poor efficiency, limited
speed etc. But, the invention of semiconductor devices change the situation, so now variable speed
drives are constructed in smaller size, high efficiency and high reliability[4][7]. Therefore the system
has been built using variable-voltage/frequency with devices MOSFET and PWM technique have
been implemented. Drives are used in lots of applications in blowers, pumps, fans, hoists, conveyors,
and other machinery.
The variable frequency source is used with the types of single-phase induction motors which have a
permanent capacitor in the starting winding circuit. The performance characteristics of these blower
motors, such as torque, speed, slip, current etc. are analyzed when operated from suggested variable
voltage and frequency (v/f) method which has advantage of angular control over wide range of speed
In this work, a single phase variable frequency inverter has been implemented. The PWM technique
has been used to vary the voltage and frequency of output of power inverter where torque and speed
are utilized to achieve this control. In this paper, simple but effective method to control air flow rate of
blower is implemented.
In section II, speed control of motor is discussed. The system flow cum hardware system is described
in section III. Also development scheme and the performance curve justification are included in the
same section III. Finally, paper is concluded in section IV.



There are two speed terms -synchronous speed and rated speed, used in the electric machine.
Synchronous speed is the speed at which a motor's magnetic field rotates. The two factors affecting
synchronous speed are frequency of the electrical supply and the number of magnetic poles in the
stator [6]. The synchronous speed is given by
๐‘๐‘  =

Where, f is the supply frequency in Hz, P is the number of Poles. As the number of pole is not
variable, varying the supply frequency would result in variation in the speed of motor. Variation of
voltage should be in proportion to supply frequency so that torque developed is constant over the
speed range. The speed of induction motor is directly proportional to the frequency and inversely
proportional to the number of poles of the motor. Since the number of poles is fixed by design, the
best way to vary the speed of the induction motor is by varying the supply frequency.
The rotor speed of an Induction machine is different from the speed of rotating magnetic field. The
rotor speed of induction motor when driving load will always be less than the synchronous speed [8].
The percent difference in synchronous speed and rotor speed is called slip as shown in equation 2.
๐‘๐‘ โˆ’๐‘๐‘Ÿ

๐‘† = ๐‘๐‘ 
Where, Ns are the synchronous speed in rpm, Nr is the rotor speed in rpm.




Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963

Figure 1: Block diagram of system

This design for speed control system using voltage and frequency control have been divided into
SG3525 PWM control circuit, AND gate circuit, driver circuit and H-Bridge inverter. This drive by
using variable voltage variable frequency or v/f control method is commonly used to control and
change the speed of the single-phase induction motor for blower application. Due to compact
integrated circuit, low cost and high performance speed control can be obtained. Figure1 shows the
block diagram of system implemented for this work.


Development Scheme

The performance of the control scheme is performed on 0.18 hp, 230V, 2 pole, and single phase
induction motor. The constant/variable motor voltage; variable frequency and current vs. frequency,
motor speed vs. motor torque, and motor torque vs. slip etc. characteristics for air flow rate change
and control are discussed in this scheme. The unit for air flow rate is cubic meter per minute (CMM).
The air flow rate changes with blower shape, size and capacity. The following table 1 shows the motor
Table 1: 0.18 Hp permanent capacitor single phase induction motor model rating
220 volts
0.18 hp
0.4 Amp.
50 Hz
2800 rpm
No. of pole
Aux. Winding resistance - 71.1ฮฉ, Main Winding
resistance - 70.0ฮฉ ,Capacitor - 2ยตF

The variable frequency drive also called scalar control drive is a system made up of semiconductor
devices. Figure 1 shows electronic speed control of the motor supply frequency. The SG3525PWM
circuit that controls the frequency of the voltage applied to AND gate drives and as a result of this it
can be control the variable voltage; variable frequency of inverter. The pulse width modulation output
result is as shown in figure 2.


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963

Figure 2: PWM Output Waveform

The inverter circuit consists of four IRF840 MOSFET which converts of the dc voltage into adjustable
AC voltage. The control scheme used to control the output voltage and frequency by modulating the
on and off times of power switches. In this system rectifier converts the ac to d.c. This d.c. is then
inverted to provide a synthesized a.c. waveform at the motor terminals. The frequency and power of
the a.c. supply delivered to the motor is controlled by inverter. The experimental hardware
development and constructed of H bridge inverter using MOSFET as shown in figure3 and the output
result of this inverter at a running conduction of motor as shown in figure 4.

Figure 3: Hardware circuit of H bridge inverter

Figure 4: Practical result of H bridge inverter at load.

At low frequencies rated torque cannot be obtained. Analysis shows that the current is reduced at
increasing frequencies, hence reducing the torque from equation 3

๐‘‡๐‘œ๐‘Ÿ๐‘ž๐‘ข๐‘’ = ๐‘“๐‘Ÿ๐‘’๐‘ž๐‘ข๐‘’๐‘›๐‘๐‘ฆ


Another equation 4 is related to flux, voltage and frequency.
๐‘š๐‘Ž๐‘”๐‘›๐‘’๐‘ก๐‘–๐‘ ๐‘“๐‘™๐‘ข๐‘ฅ โˆ ๐‘“๐‘Ÿ๐‘’๐‘ž๐‘ข๐‘’๐‘›๐‘๐‘ฆ = ๐‘๐‘œ๐‘›๐‘ ๐‘ก๐‘Ž๐‘›๐‘ก


The motor is being utilized at various frequency ranges and the maximum torque obtained at each
value causes decrement in its value. By increasing the voltages and frequency the winding current
increases, and it simultaneously changes the speed of motor and air flow volume of blower and
increasing the slip. Modifications are made on the drive to allow for independent control of both the
voltage and frequency using PWM IC.
Experimentally the air flow rate for a single phase induction motor mounted with centrifugal type


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963
blower is tested and various parameters are obtained by practical tests. Schematic arrangement of the
experimental setup is shown in figure 1. The blower air can be used commonly used for various
domestic and industrial applications. The blower air flow rate is changed and measured under variable
voltage and variable frequency condition. The speeds versus torque, current versus frequency against
the air flow rate are measured experimentally.

B. Performance Curve
Calculated motor torque vs. motor speed curve for various frequencies under variable voltage as
shown in figure 5.It shows the linear relationship between the motor torque and motor speed under
these circumstances.So,air flow rate also changes with respective to frequency under variable
voltage.And approximatly linear relationship between the current and motor speed seen figure 5.

Figure 5: Torque/Current โ€“ motor speed characteristics at variable voltage and variable frequency.

Figure 6: Torque/current - speed characteristics at constant voltage and variable frequency.

Figure 6 shows the calculated motor torque vs. motor speed of blower for variable frequency under
contant voltages of 230V.The torque remains approximatively constant in the initial speed range of the
blower but as soon as the speed of blower increases torque falls down linerly.In Figure 6 the starting
current is remains constant some speed range and then after constant till at the end.The minimum air
flow rate is around 440 CMM for the motor and blower analyzed in this paper.

Figure 7: Comparison between motor speed vs. frequency characteristics under variable volatge and variable


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963
Above figure 7 shows the comparision between the practical value and theoretical value of motor
speed vs. frequency under the operation of variable voltage and variable frequency.In the experiment,
the lowest frequency is 25Hz at 1440 rpm while the highest frequency is 71 Hz at 3510 rpm.

Figure 8: Comparison between motor speed vs. frequency under constant volatge and variable frequency

Above figure 8 shows the comparision between the practical value and theoretical value of motor
speed vs. frequency under the constant voltage and variable frequency condition.

Figure 9: Air flow rate/speed vs. motor torque under variable voltage and variable frequency

From the above figure 9 air flow rate is linearly increases with the decrease in motor torque and
blower fan speed also changes. It is seen that the motor torque, speed and air flow rate of blower can
be smoothly changed or controlled under variable voltage variable frequency (v/f) method. Volume of
blower air flow can be described by the equation below
Where, Q is the air flow rate of blower in Cubic meter per minute (CMM), N is the speed of motor in
Figure 10 shows motor torque vs. slip characteristics for change frequencies when the terminal
voltage is constant.


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963

Figure 10: Motor torque vs. slip at constant voltage and variable frequency



Form the above implemented method, it can be concluded that the various parameters like torque,
speed, current and slip can be controlled through variable voltage and frequency. The above plotted
curves clearly shows that under the constant voltage of 230V when the frequency is varied from
approximately form 25Hz to 70Hz the speed of motor gradually increases up to 3510 rpm whereas
current gradually decreases from 0.6 amp. to 0.3 amp as shown in figure 6.So, under this condition a
high starting torque occurs at constant current up to 1780 rpm then current drops along with torque at
high speed of 3510 rpm, whereas in variable voltage variable frequency condition it is observed that
varying frequency with the prescribed range cause negligible change in starting current, thus V/f
method proving to be more efficient during starting period. Also, the linear increase in air flow rate is
observed with respect to the decrease in motor torque.



The present work analyzed with respect to variable voltage variable frequency (v/f) method. This
speed control method it can be implemented using closed loop system, DSP processor and
microcontroller kit. More work can be done to minimize the losses of motor and maximize the
efficiency. The same technique can be extended for three phase induction motors.

[1]. E.R.Collins, R.E. Ashley, โ€œOperating characteristics of single phase induction motor driven from
variable frequency supplies,โ€ 1991 IEEE, pp. 52 - 57.
[2]. Sheng - Ming Yang, โ€œA constant Air Flow rate control f blower for residential Application,โ€ Vol.34,
No.2, March/April 1998, pp. 263 - 267.
[3]. Hamad S. H, S. M. Bashi, I. Aris and N.F. Marlah, โ€Speed drive of Single phase induction motor,
โ€œNational Power and Energy Conference (PECon) 2004 Proceeding, Kula Lumpur, Malaysia, pp. 121125.
[4]. Ronilson Rocha, Luiz de Siqueira Martins Filho, Julio Cesar David de Melo, โ€œA Speed Control for
Variable speed Single-Phase Induction Motor Drives, โ€œFederal University of Ouro Preto ICEB/DECO,
Ouro Preto, Brazil IEEE ISIE 2005, June 20 - 23, 2005,Dubrovnik, Croatia, pp.43 - 48.
[5]. Auzani Jidin, Jurifa Mat Lazi, Abd Rahim Abdullah,Fazlli Patkar, Aida Fazliana Abd Kadir, Mohd
Ariff. Mat Hanafiah, โ€œSpeed Drive Based on Torque - Slip Characteristic of the Single Phase Induction
Motor,โ€IEEE PEDS 2005, pp. 771 - 775.
[6]. Mr. Aung Zaw Latt, Dr. Ni Ni Win,โ€ Variable Speed Drive of Single Phase Induction Motor Using
Frequency Control Methodโ€, International Conference on Education Technology and Computer, 2009,
pp. 30 - 34.
[7]. Khaled A. Madi Ali and Mohammad E. Salem Abozaed, โ€Microcontroller Based Variable frequency
Power Inverter,โ€ Proceedings of the International Multi International Multi Conference of Engineers
and Computer Scientists 2010 Vol II, IMECS 2010, March 17 - 19, 2010, Hong Kong.


Vol. 6, Issue 6, pp. 2548-2555

International Journal of Advances in Engineering & Technology, Jan. 2014.
ISSN: 22311963
[8]. W.I. Ibrahim, M. T. Raja, Ismail, M.R. Ghaz ali,โ€ Development of Variable Speed Drive for Single
Phase Induction Motor Based on Frequency Controlโ€, Proceeding of EnCon 2011 4th Engineering
Conference Kuching, Sarawak, Malaysia, pp. 1 - 6.
[9]. Deniz Yildirim, Murat Bilgic, โ€œ PWM AC chopper control of single phase induction motor for variable
speed fan application,โ€2008 IEEE, pp.1337 - 1342.
[10].M. Caruso,V. Cecconi,A.O. Di Tommaso, R. Rochat , โ€œSensorless Variable Speed Single - Phase
Induction Motor Drive System,โ€ 2012 IEEE, pp 731 โ€“ 736.

Atul Gajare received the Bachelor Degree in Electrical Engineering from North
Maharashtra University, Jalgaon, India in 2004. He is pursuing M.E. (Electrical Machine
and Drives) from Government College of Engineering, Aurangabad, Maharashtra

Nitin Bhasme is working as an Associate Professor in Electrical Engineering at
Government College of Engineering, Aurangabad-India since 1998. His research area is
related to Electrical Drives, Power Electronics and Renewable Energy Technologies. He
is associated with various activities in engineering field at national level.


Vol. 6, Issue 6, pp. 2548-2555

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