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1)The objectives:The purpose of this experiment is to construct
asingle-phasecontrolled
rectifier(thyristor)and do the transient analysis using Pspice
software.
2)Theoretical background:Thethyristor will conduct ,on state,
when VTis positive and a
firing(trigger)current pulseIGis applied to the gate terminalor
by
applying a forward anode-to-cathode voltage greater than the
forward
blocking voltage VT. The controlled of the load voltage is
performed by
delaying the firing pulse by an angle . The load voltage is
given by(if
we suppose Vs=Vpeaksin t):
Vd av= = (1+cos )
Vdrms
the load current will be:Id av= ; Id rms=
FIG-1As the firing current pulse is increased, the forward
blocking voltage VT is
decreased(look FIG-2):
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3)Experimental setup:
We construct the circuitin fig-3usingPspice software :
V1=sin 0 310 50[310sin 2 50
; R3=1k
; R6=10MEG
;R4=1k R1=1k ; R2=1k ; R5=4k ;
D2:DN4007 diode ; X1:SN1596 silicon controlled rectifier
X2:center-tap transformer XFMR-TAP{ ratio=0.1} ;
4.A)Experimental data:Wesimulate our circuit using intransient
analysis bywriting in the Edit
controlscommand: .TRAN 1U 20M,then wedisplay theload current
(IA)and
the loadvoltage(across R3)versus time using the scope.we first
observe theload current IA(look FIG-4),we notice that the minimum
anode current (of
SN1596) that will cause the rectifier to remain in
forward-conduction is
IL=7.28mA at tL=822u sec(the latching current).And the minimum
value of
anode current necessary to keep the rectifier in
forward-conduction after it has
been operating at a high anode current is IH=4.75mA at tH=9.44m
sec(the
holding current).We measure the RMS and average values of the
load current
and load voltage: Vrms=15 volt ; Vav=9.36volt
IA rms=14mA ; IA av =9.36mA
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We can measure the firing angle 14.80.We noticethat the holding
current
is lower than the latching current( IH
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We can display the blocking voltage Vak using the
scope(FIG-6):
Now ,we vary the value of IGby varying the value of R1 in the
previous
circuit {500; 3Kand 4K which produce a different values of
(look
FIG-7),we notice that as R1 increases ,IGdecreases which
cause
a larger firing angle .
R1=500 10.80
R1=3k 32.400
R1=4k 51.660
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4.B)Theoretical data:we calculate the values of the RMS and
average value of the load current and
voltage , and we get: (we take 14.80=0.26 rad ; 31 )
Vrms
Vrms= 14.86 volt IA rms= 14.86mA
Vav= = (1+cos )
Vav=9.7 volt IA av= =9.7Ma
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5)Discussion:
The theoretical calculations are close to the experimental ones
with small
error because we have assumed theoretically an ideal diode
whereas in the
experiment using Pspice software we dealt with the real case of
the
diode(or more close to the reality).
6)conclusion:
Thyristors are typically used at the highest energy levels in
power conditioning
circuits because they are designed to handle the largest
currents and voltages
of any device technology ,and as we have seen in this report
,thyristor can beused to perform asingle-phase controlled rectifier
that allow to us controlling
the voltage and current wave.
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