International Conference on Emerging Trends in Computer and Image Processing (ICETCIP'2011) Bangkok Dec., 2011
Series and Parallel Resonant Inverter Fed
Ferromagnetic Load-A Comparative Analysis
A. Suresh and S. Rama Reddy
employs an unequal duty cycle operation of the switches in
the convertor [7]. The asymmetrical voltage cancellation
(AVC) is proposed in [8] where the author’s describes voltage
cancellation for conventional fixed-frequency control
strategies. In induction heating application the output power
control using the mentioned techniques in fixed frequency and
optimum duty cycle for ZVS operation are rather difficult due
to variation of parameters in resonance load. In [9] AVC is
implemented in full bridge series resonant inverter. The SRI
needs an output power for matching the output power to the
load and also it imposes restriction on bandwidth. The
foresaid drawbacks in SRI can be overcome in PRI which is
been justified by simulation results presented in the current
paper.
Abstract—Resonant converters find a very wide application in
Induction heating, which requires high frequency currents. Series and
Parallel resonant inverters are employed for this purpose. This paper
gives a comparative analysis of series and parallel resonant inverter
fed ferromagnetic load based on experiments carried out and finally
concluded which is the suitable inverter for Induction heating
application, whether it is Series Resonant Inverter (SRI) or Parallel
Resonant Inverter (PRI) based on the experimental results. The
results of SRI are compared with that of PRI and presented in this
paper.
Keywords—Series Resonant Inverter, Parallel Resonant Inverter,
Induction Heating.
I. INTRODUCTION
I
NDUCTION heating is a well known technique to produce
very high temperature for applications such as steel melting,
brazing and surface hardening. In each application appropriate
frequency must be used depending on the work piece
geometry and skin depth requirement [1, 2]. This technique
requires high frequency current supply that is capable of
inducing high frequency eddy currents in the work piece and
thus results in the heating effect [1]. A large number of
topologies have been developed in this area among them
current-fed and voltage-fed inverters are most commonly used
[3]. One of the most important advantages of current-fed
inverter is the short circuit protection capability. However the
current source inverter can only be controlled by using phasecontrolled rectifier for adjusting the DC link. This differs from
voltage source inverter which has various controls.
Recent developments in switching schemes and control
methods have made the voltage source resonant inverters
widely used in several applications require output power
control. In pulse frequency modulation (PFM) the output
power can be controlled by varying the switching frequency
and it is operated at under zero voltage switching scheme [4].
The pulse density modulation (PDM) scheme regulates the
output power by varying the period in which the inverter
supplies high frequency current to the induction coil [5]. The
phase shift (PS) control technique in [6] varies output power
by shifting the phase of the switch conduction sequences
while the asymmetrical duty cycle (ADC) control technique
II. PARALLEL RESONANT INVERTER
The PRI is shown in Fig1a.The inverter consists of two
switches S 1 and S 2 with blocking diodes D 1 and D 2 , a
resonating capacitor C, a DC inductor L 1 and an induction
coil that comprises of a series combination of resistance R and
coil inductance L. The full bridge inverter is based on the use
of quasi square wave control technique. This control method
uses the phase lock loop to automatically adjust the inverter’s
operating frequency to a small constant leading phase angle
when load parameters change.
Fig 1a A parallel class D current source inverter
Fig 1b Changing series circuit to parallel circuit
To simplify the calculation of necessary circuit parameters,
series combination of L coil and R eq is transferred to its
equivalent parallel configuration of L coil and R p as shown in
Fig1b.The R p is given as
A. Suresh is Research Scholar Sathyabama University, Chennai, India
S. Rama Reddy is Professor, Jerusalem College of Engineering, Chennai,
India.
1
International Conference on Emerging Trends in Computer and Image Processing (ICETCIP'2011) Bangkok Dec., 2011
(1)
where ω is the system switching frequency. The total
impedance Z Total of the resonant circuit in Fig1a can be
expressed as,
T(s)
Fig.2.c. V gs and V ds across switch1
(2)
Voltage(V)
and the resonant frequency is given as ,
(3)
Note that the inverter is designed to operate such that the
switching frequency is slightly higher than the resonant
frequency for maximum output power. The parallel
impedance at resonant frequency ω o is
Voltage(V)
Fig.2.d. V gs and V ds across switch2
T(s)
(4)
And the average output power P is provided as
(or)
(5)
Fig.2.e Output voltage
T(s)
Voltage(V)
III. SIMULATION RESULTS PRI FED FERROMAGNETIC LOAD
Fig.2.a shows the simulink circuit of current source inverter
for ferromagnetic load. For induction heating class D inverter
is used. This inverter converts DC input power into AC output
power. This conversion is achieved by turning on and off
alternately switches 1 and 2.
Fig.3.a Circuit Diagram of open loop system
The open loop operating system makes use of PRI. The
output voltage of the inverter is sinusoidal, in the case of low
damping factor and the operating frequency near resonant
frequency to achieve maximum power across output and for
soft- switching operation as shown in Fig2. But the harmonic
effect of the voltage and current are not considered while the
output contains harmonics in this technique. The AC output of
the inverter and the RMS value are shown Fig.3.b and Fig.3.c
respectively.
Fig.2.a Circuit Diagram
Fig.2.b shows the AC input voltage. Driving pulses and
output of MOSFET1 are shown in Fig 2c. Driving pulses and
output MOSFET2 are shown in Fig 2d. Output voltage of the
inverter is shown in Fig 2e.Output voltage is sinusoidal due to
resonance action.
Fig.3.b AC input voltage with disturbance
T(s)
T(s)
Voltage(V)
Fig.2.b AC input voltage
Fig.3.c Inverter Output voltage
2
T(s)
International Conference on Emerging Trends in Computer and Image Processing (ICETCIP'2011) Bangkok Dec., 2011
Voltage(V)
The output voltage of the inverter is measured with the help of
voltmeter and it is observed using a scope. Similarly the
current through the load is measured with the help of ammeter
and it is observed using a scope. Input voltage and output
voltage with a disturbance are shown from Fig.6.b to 6.f
Fig.3.d Rectifier Output voltage
T(s)
IV. CLASS D SRI
A class D inverter is generally used to energize the
induction coil to generate high frequency magnetic induction.
Fig.4 shows the class D inverter system for induction heating.
The class D inverter consists of two switches S1 and S2, a
resonant capacitor C1, inductor L1 and an induction coil.
Induction coil is represented as parallel combination of
inductor L2 and resistor R. Fig.5 represents the equivalent
circuit model of the class D inverter.
The currents in positive and negative half cycles are as
follows:
(6)
Fig. 6.a: Circuit diagram
(7)
Fig.6.b: Output voltage and current
T(s)
Fig.4: Class D inverter system for IH
Fig. 6.c: Circuit diagram of open loop system
Voltage(V)
Fig.5. Equivalent circuit
V. SIMULATION RESULTS OF SRI FED
FERROMAGNETIC LOAD
Class D inverter simulink circuit is shown in Fig.3a. For
induction heating class D inverter is used. This inverter
converts DC input power into AC output power. This
conversion is achieved by turning on and off alternately.
Switches 1 and 2 .The voltage across the load is measured
with the help of voltage measurement block and the output
current is measured with the help of current measurement
block and they are observed using a scope. Driving pulses
given to the MOSFET are shown in Fig. 3b. Output voltage
and current are shown in Fig. 3c. Both are sinusoidal due to
the presence of L and C. The variation of output with the
variation in the input is shown in Fig. 3d. The output voltage
increases with the increase in the input voltage.
The circuit of open loop system is shown in Fig.6.The
rectifier output voltage increases due to the step rise in input.
T(s)
Voltage(V)
Fig.6.d: Input voltage with disturbance
T(s)
Fig. 6.e: Output voltage with disturbance RMS Value)
3
Voltage(V)
International Conference on Emerging Trends in Computer and Image Processing (ICETCIP'2011) Bangkok Dec., 2011
Fig.6.f: Rectifier output voltage
T(s)
Fig.8 Input Voltage v/s Output Power
VI. EXPERIMENTAL RESULTS
The Experimental set up is as shown in Fig.7. Parameters
are listed in Table.1 are presented from Fig.8 to Fig.10. The
variation of output power with input is shown in Fig8. The
variation of output voltage with input voltage is shown in
Fig9. Variation of output power with resistance is shown in
Fig10.
Fig.9 Input Voltage v/s Output Voltage
Fig.7 Experimental Set Up
Fig.10 Output Resistance v/s Output Power
VII. CONCLUSION
From Fig.8 and Fig.9, it is observed that output power and
output voltage of Parallel resonant inverter are higher than
that of series resonant inverter. Therefore Parallel Resonant
Inverter is a better choice for Induction Heating application.
TABLE I
SYSTEM PARAMETERS
Parameter
Switching
Frequency
Resonant Capacitor
Induction
Inductor
DC Inductor
Coil
Sym
bol
f
Value
REFERENCES
35 KHz
[1]
C
L
100
KpF
12 µH
L1
6 µH
[2]
[3]
4
Chudjuarjeen.S,et.al, “ Full bridge current fed inverter with automatic
frequency control for forging applications”,IEEE tecon 2004,Vol
4,pp.128-131,Nov 2004.
C.Chunwattanapraniti,et.al “Half bridge current fed inverter power
supply for Forging Applications,”25th electrical Engineering
Conference,Thailand,pp.97-101,2002.
E.J.Davies,J.
and
Simpson,P.,1979,Induction
Heating
Handbook,McGraw-Hill,UK.
International Conference on Emerging Trends in Computer and Image Processing (ICETCIP'2011) Bangkok Dec., 2011
[4]
M.K.Kazimierczuk and D.Czarkowski, Resonant
Power
Converter.New York:Wiley,1995.
[5] Viriya,et.al, “Analysis of High frequency Induction cooker with variable
frequency power control,” Power Conversion Conference,2002.PCC
Osaka2002.Procedings of the Vol.3,5-2 April 2002 Page(s)1507-1512
Vol.3
[6] Nam-Ju Park,et.al “A power control
scheme with constant switching
frequency in class- D inverter for induction heating jar
application,”IEEE Tran.Ind Electronics,vol54,no 3 pp1252-1260,
June,2007.
[7] L.Grajales and F.C.Lee, “Control system design and small-signal
analysis of a phase shift controlled series resonant inverter for induction
heating,”in Proc.IEEE Power Electron.Spec.Conf, 1995, pp.450-456.
[8] J.T.Matysik “A new method of integration control with instantaneous
current monitoring for class D series resonant converter,” IEEE Tran.Ind
Appl, vol53, no 5 pp1564-1576, Oct, 2006.
[9] H.Sugimura,
H.Muraoka,T.Ahmed,S.Chandhaket
,E.Horaki,
M.Nakanoda and H.W.Lee, “ Dual mode phase shifted ZVS-PWM series
load resonant high frequency inverter for induction heating super heated
steamer,”J.Power Electron,vol 4, no 3, pp 138-151,Jul 2004.
[10] A.Suresh and S.Rama Reddy , “Parallel resonance based current source
inverter for induction heating,” European journal of scientific research
Vol 58 No 2 ,pp 148-155,Aug 2011.
[11] A.Suresh and S.Rama Reddy , “Comparison of simulation and
experimental results of class D inverter fed induction heater,” Research
journal of applied sciences,Engineering and Technology 2(7) ,pp 635641 ,Oct 2010.
A. Suresh is a research scholar at Sathyabama
University, Chennai. His area of interest is Induction
Heating. He has a decade of teaching experience in
engineering college and a life member in ISTE.
Dr. S. Rama Reddy obtained his ME degree from
Anna University, Tamil Nadu, India, in 1989. He has
pursued research in the area of resonant converters in
1995. He has 2 years of industrial experience and 18
years of teaching experience. He is a life member of IE,
IETE, ISTE, SSI, and SPE. He has published 20 papers
in the area of Power Electronics and FACTs.
5