Download gate circuit

CHAPTER SEVEN
(New textbook)
CONTROLABLE SWITCHING DEVIES
DESIGNED
BY
DR. SAMEER KHADER
PPU
“E-learning Project”
CONTENT
Introduction, Classification &Applications,
Thryristor Circuits
Triac Circuits
Diac Circuits
Practical Firing ( Triggering) Circuits
Thyristor Commutation (turning-off)
Chapter 7-A
Thyristor Circuits
1- Construction : Four PNPN layers with special doping
in each layer, with purpose to obtain different electron and
holes in these layers. Each one has different potential voltage
A
P
N P
G
N
Th.
K
A
K
Principle of operation :
G
K
The thyristor construction A
Presents three diodes
D1
D3
D2
In series ( two forward
G
biased and the third reverse biased).
The thyristor will conduct only if D2 forward biased, therefore current will flow
from A to K. This case could be achieved by different ways as follow :
Methods for Switching- on the thyristor
The switching process of the thyristor is called “ Firing”, because after Switching
process is ceased, WHERE the firing signal may can removed with purpose to reduce
the gate loss .There're several methodS Applied to realize this purpose :
1-Gate-firing method :by supplying the gate terminal with positive voltage
( this is the most applied method - major method).
2-by suddenly increasing the Anode voltage
3-by increasing the thyristor temperature over predetermined limit.
4- Photo effect method, which used in photo devices ( Photo thyristor)
Gate-firing method: the firing circuit is shown below:
Thyristor
I-V
curve
Thyristor Main Parameters:
There’re several parameters related to static & dynamic performance of the thyristor,
these parameters are as follow :
1-VAK- thyristor voltage at steady state 2 V;
2-VBO- -break over voltage , voltage after which thyristor will turning on at constant
gate current ;
3-VBR- break down voltage in reverse biasing state;
4-IH- thyristor holding current :this a minimized load current keeping the thyristor in
conducting state ( if the current goes down the thyristor will switch-off);
5- IL- thyristor latching current :this a minimized load current keeping the thyristor in
conducting state after removing the gate signal ;
6-VGT- minimum gate voltage required to firing the thyristor at given loadind condition
, VGT  0.8…12V;
7-IGT- minimum gate current., IGmax- maximum gate current ;
8-di/dt- speed of (increasing/decreasing) of thyristor current ;
9-dv/dt - speed of (increasing/decreasing) of thyristor voltage .
Thyristor Dynamic Performances
R4
100
C
V2
220/-220V
R8
5k 90%
D
R3
10k D4
30%
BAR74
50 Hz
V5
85/-85V
SCR2
2N5064
V-source
A: s4_1
50.00 V
R10
2.5k
-250.0 V
35.00ms
100.0 V
50.00 V
0.000 V
-150.0 V
-50.00 V
50.00ms
65.00ms
-100.0 V
0.000ms
80.00ms
15.00ms
30.00ms
45.00ms
1.250 V
V-gate
0.750 V
V-gate
A: scr5_1
50.00 V
-0.250 V
-0.750 V
35.00ms
30.00 V
10.00 V
50.00ms
65.00ms
80.00ms
2.250 A
-10.00 V
0.000ms
P-load
1.750 A
0.750 A
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
150.0 W
100.0 W
0.250 A
50.00ms
65.00ms
50.00 W
80.00ms
250.0 V
V-thyris
150.0 V
50.00 V
-50.00 V
-150.0 V
-250.0 V
35.00ms
P-load
A: r10[p]
1.250 A
-0.250 A
35.00ms
90.00 V
70.00 V
0.250 V
A: scr2_1
+
V-source
-50.00 V
A: r4[i]
C3
1.0uF
250.0 V
150.0 V
A: d4_k
R9
50
SCR6
BRX44
50 Hz
A: v2_1
SCR5
MCR22-4
S3
50.00ms
65.00ms
80.00ms
0.000 W
0.000ms
Gate Firing Circuits:
2-Phase Control
1- S1RC relaxation oscillator
S1
S2
R1
R5
5k 60%
V3
120/-120V
50 Hz
C
A: r5_3
Th1
Th2
SCR3
BRX45
+
+ V4
80V
R-load
C2
1.0uF R2
R7
50
S2
A
AC circuit
DC circuit
SCR4
MCR22-3
V3
120/-120V
+ V4
80V
R6
0.5k
C
V-source
125.0 V
V-source
A: s1_1
R-load
Th1
Th2
SCR3
BRX45
50 Hz
R7
50
R5
5k 60%
R1
SCR4
MCR22-3
+
A
C2
1.0uF R2
R6
0.5k
87.00 V
75.00 V
25.00 V
85.00 V
-25.00 V
-75.00 V
-125.0 V
0.000ms
A: scr3_1
15.00ms
30.00ms
83.00 V
0.000ms
45.00ms
V-gate
2.000 V
V-gate
A: scr3_1
0.000 V
0.300ms
0.600ms
0.900ms
1.3940 V
-2.000 V
1.3938 V
-4.000 V
-6.000 V
0.000ms
A: scr4_1
15.00ms
30.00ms
1.3936 V
0.000ms
45.00ms
V-thyris
25.00 V
V-thyris
A: scr4_1
0.300ms
0.600ms
0.900ms
1.65525 V
1.65475 V
-25.00 V
1.65425 V
-75.00 V
1.65375 V
1.65325 V
-125.0 V
0.000ms
A: r7[p]
15.00ms
30.00ms
1.65275 V
0.000ms
45.00ms
P-load
300.0 W
P-load
A: r7[p]
0.300ms
0.600ms
0.900ms
138.936 W
138.934 W
200.0 W
138.932 W
100.0 W
0.000 W
0.000ms
138.930 W
15.00ms
30.00ms
45.00ms
138.928 W
0.000ms
0.300ms
0.600ms
0.900ms
Mathematical . Modeling
1- Gate firing circuit using RC relaxation oscillator;
2- Gate firing circuits using RC circuit and called Phase control ;
These circuits may can use to fire thyristor in AC or DC circuit: in both sources
the connected elements must be with the following relations with purpose to
realized successful operation: R2<<R1; and R-load << R1;
* DC source VBOTh2 < Vs ; and IH2 < Vs/R1;
thyristor
** AC source VBOTh2 < Vm; and IH2 < Vm/R1; Vs(t)=Vm.sin (t); The
Th2 will
t
Vc( t )
Vs 1
e
Vc( tp )

tp

conduct when
Vc=VBOTh2;
This could be
occurred at
t=tp ; this time
called (firing
instant)
VBOTh2
Vs
R1  C ln
Vs
R1  C
VBOTh2
The firing angle of previous firning circuits in AC circuit can
Determine as follow :
 min
sin
VTG
1
R1min
RGK
 max
sin
Vm
Vm
RGK
R1max
VGT
IGT
9<<90  ( without C)
Vm
RGK
IGmax
IGT
Vm
1
Vm

tp 
360
T
I-V curve
Conclusion
•In DC source, tp- presents delay time , so by increasing Ig the
thyristor allow more current to follow ; therefore increasing the load
power ;
• In AC source, tp- presents delay angle which corresponds to
=tp.360/T, so by increasing Ig,  decreases, thus load power
increases P()=Pmax . Cos(), where Pmax-maximum allowable
power.
•  may can change from 0 to 90 ( without C) or to 145  (with C) ;
• The thyristor gate voltage must be > + 0.85 V at least;
VBR > Vm ; ILmin > IL at firing( remains conduct); and ILmin <
IH ( swith off) .
• By increasing di/dt at given Ig the thyristor capable to carry
additional current ILoad .
• By increasing Ig, VBO ( ac circuits), which means that the thyristor
is fired at earliest time , therefore increasing the load voltage and
power .
•The gate pulse must removed after successfully firing the thyristor ,
with aim to reduce the gate losses .
Chapter 7-B
Triac Circuits
1- Triac ( Triode Alternating Current Switch ) – presents two parallel connected
thyristors with common gate, which energized with positive and negative voltage. The main
purpose of the Triac is to control the RMS load voltage, therefore there're several applications
such as : * Lighting control ( dimmer circuits); **- Temperature control ;
*** Torque –speed control of induction machines.
2- Symbol:
3- Circuit application:
3- I-V Curve:
Triac Firing Circuits
1- Phase angle control without diode
R2
100
B
V1
220/-220V
A
50 Hz
MAC210-6
C1
0.3uF
A: r2_2
Load
R1
10k 20%
100HF120PV
D1
+
50 Hz
R2
100
Triac
voltage
Triac
voltage
200.0 V
100.0 V
0.000 V
-100.0 V
-200.0 V
35.00ms
A: r2[i]
50.00ms
65.00ms
80.00ms
Load
current
Load
current
2.500 A
1.500 A
0.500 A
-0.500 A
-1.500 A
-2.500 A
35.00ms
A: d1_k
50.00ms
65.00ms
80.00ms
1.500 V
0.500 V
-0.500 V
-1.500 V
35.00ms
50.00ms
65.00ms
80.00ms
R1
10k 5%
100HF120PV
D1
+
B
V1
220/-220V
2- Phase angle control with diode
Gate
voltage
Gate
voltage
C1
1uF
300.0 V
200.0 V
100.0 V
0.000 V
-100.0 V
-200.0 V
-300.0 V
0.000ms
15.00ms
3.000 A
2.000 A
1.000 A
0.000 A
-1.000 A
-2.000 A
-3.000 A
0.000ms
15.00ms
1.500 V
1.000 V
2.500
0.500
V V
0.000 V
-0.500 V
-1.000 V
-1.500 V
0.000ms
15.00ms
30.00ms
30.00ms
30.00ms
A
MAC210-6
45.00ms
45.00ms
45.00ms
3-Triac firing circuits using UJT
A: v3_1
Source
voltage
AC source
120/-120V
C
125.0 V
75.00 V
25.00 V
-25.00 V
50 Hz
-75.00 V
-125.0 V
0.000ms
Rload
100
0/15V
A
Q2004L4
100 Hz
Pulse
generator
Tr
B
20V
LoadA: tr_2
voltage
2N2646
0.5uF
B2
D
30.00ms
10.00ms
20.00ms
30.00ms
10.00ms
20.00ms
30.00ms
10.00ms
20.00ms
30.00ms
125.0 V
75.00 V
25.00 V
-125.0 V
0.000ms
UJT
A: tr_3
needles
5.000 V
3.000 V
15.00 V
1.000 V
5.000 V
-1.000 V
-5.000 V
-3.000 V
-15.00 V
-5.000 V
0.000ms
15.00ms
20.00ms
-75.00 V
25.00 V
-25.00 V
5.000ms
10.00ms
15.00 V
5.000 V
-25.00 V
R3
47
Capacitor
voltage
A: c1_2
30.00ms
25.00 V
-15.00 V
-25.00 V
0.000ms
S1
B1
UJT
20.00ms
-5.000 V
R1
20
R4
150
R5
9k
PulseA: tr_3
generator
10.00ms
25.00ms
35.00ms
Load
A: tr_2
voltage
250.0 V
150.0 V
50.00 V
-50.00 V
-150.0 V
-250.0 V
0.000ms
Mathematical Modeling of Triac Circuits
Three main circuits are introduced with purpose to fire the Triac device( Phase
control with or without diode, with UJT and with Diac device). The presence of
diode in the gate circuit remove one half cycle , therefore convert the Triac into
Thyristor . In both circuits there are several relations characterized the application
of such a device . These relations are as follow :
1- when 0<</2
Prms (  )
T
Vdc
2
2
Vm  sin (  t ) d  t
T
Vrms
T
Pdc(  )
2
2
( Vmsin t ) d  t
R1 C ln
Pdcmax
Pdcmax cos
Vdc(  0 )
RLoad
0
UJT – circuit:
tp
2
RLoad
T
2
Vrms (  0 )
Pmax
0
Pmax cos
Vp ( t
tp )
Vc( tp )
VBB
tp
VBB Vp( tp )
Vp( tp ) ujt  Xr  VBB
*
0.6
Vc( tp )
Xr
VBB 1
RBB
RBB
R4
e

2
0<Vrms<Vs;
2- Vdc=0 for
symmetrical firing
3- Vdc0 for
asymmetrical firing
4- the existing of
inductance , reduced
The control rang of
Prms=F().
,VBB-base to base UJT’s voltage:
, ujt- UJT’s intrinsic factor <=1
,Vp- UJT’s peak voltage;
, tp-delay time ( firing instant) .
Chapter 7C
Diac Circuits
1- Diac ( Diode Alternating Current Switch ) – presents two anti-parallel connected
diodes with special construction , aiming to maintain relatively high threshold voltage across
its terminals . The main purpose of the Diac is to divide the source voltage between its
terminals and the load terminals , therefore there're several applications such as :
* Firing device in Triac –gate circuit ; **- Over voltage protective device ;
2- Symbol:
3- Circuit modification:
4- I-V Curve:
5- Time-varying performances:
Phase control circuit with Diac & Triac:
Vd
Vc( x)
Vc( C )  Vcm s in x
Vcm
Vs
2
1
The main equations are as follow , and can derives
when Vdiac =Vc at given angle.
c

tan
c
2
 RC
1
x
The firing
angle
(  RC )
Additional Firing circuits
1- Practical circuit using UJT:
A: d1_3
Source
voltage
S1
65.00 V
45.00 V
25.00 V
5.000 V
-15.00 V
-35.00 V
0.000ms
D1
18DB2
R6
50
R4
6k 10%
V2
60/-60V
50 Hz
D2
BZG03C30
C1
0.5uF
R7
250
R5
50
Zener
A: r4_3
voltage
SCR2
10RIA20
Q1
2N2646
Capacitor
A: r4_1
voltage
R8
50
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
65.00 V
45.00 V
25.00 V
5.000 V
-15.00 V
-35.00 V
0.000ms
40.00 V
30.00 V
20.00 V
10.00 V
Gate
A: needles
scr2_2
0.000 V
-10.00 V
0.000ms
1.250 V
0.750 V
Gate
A: scr2_2
needles
0.250 V
-0.250 V
-0.750 V
-1.250 V
0.000ms
30.00ms
45.00ms
-1.500 V
0.000ms
Thyristor
A: scr2_1
voltage
0.000 V
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
61.00 V
41.00 V
21.00 V
-20.00 V
1.000 V
-19.00 V
15.00ms
30.00ms
45.00ms
-39.00 V
0.000ms
Load
A: r5[p]
power
60.00 W
40.00 W
20.00 W
0.000 W
71.00 W
51.00 W
31.00 W
11.00 W
-20.00 W
-40.00 W
0.000ms
1.500 V
-0.500 V
20.00 V
Load
A: r5[p]
power
2.500 V
0.500 V
15.00ms
Thyristor
60.00 V
A: scr2_1
voltage 40.00 V
-40.00 V
0.000ms
3.500 V
15.00ms
2- High
=R4C1
30.00ms
45.00ms
1- Low
=R4C1
-9.000 W
-29.00 W
0.000ms
15.00ms
30.00ms
45.00ms
2- Practical circuits using UJT and
Isolation
Transformer:
S2
R9
50
R1
6k 30%
V1
60/-60V
R3
250
B1
D3
BZG03C30
C2
1.5uF
R10
50
SCR1
10RIA20
UJT
SignalA:atq2_2
B2
Q2 T1
2N26461TO1
B2 R2
7.500 V
-2.500 V
5.000ms
A: scr1_2
20.00ms
35.00ms
A:
scr1_2
Gate
30.00ms
45.00ms
30.00ms
45.00ms
Gate
needles
0.500 V
15.00ms
2.000 V
needles
1.000 V
0.000 V
0.000ms
50.00ms
1.000 V
15.00ms
26.50 V
-13.50 V
0.000ms
Capacitor
voltage
2.500 V
-33.50 V
0.000ms
6.500 V
150
A: c2_2
66.50 V
16.50 V
D4
18DB2
50 Hz
A: c2_2
Capacitor
voltage
Thyristor
A: scr1_1
voltage
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
20.00ms
35.00ms
50.00ms
50.00 V
0.000 V
0.000 V
5.000ms
A: scr1_1
20.00ms
35.00ms
50.00ms
50.50 V
Thyristor
voltage
0.500 V
-49.50 V
5.000ms
A: r10[p]
20.00ms
35.00ms
50.00ms
100.5 W
0.500 W
-99.50 W
5.000ms
Load
power
-50.00 V
0.000ms
Load
A: r10[p]
power
100.0 W
0.000 W
-100.0 W
5.000ms
20.00ms
35.00ms
50.00ms
3: ON-OFF firing circuit :This circuit
illustrates firing techniques used in AC Voltage
controller based on so called ON-OFF method,
where it’s necessary to fire the thyristor at the
beginning of both half-cycles .
S1
Load
A: r6_2
Source
voltage
250.1 V
150.1 V
50.10 V
-49.90 V
-149.9 V
-249.9 V
0.000ms
A: r8_2
Vg-th1
30.00ms
60.00ms
90.00ms
30.00ms
60.00ms
90.00ms
30.00ms
60.00ms
90.00ms
15.00ms
30.00ms
45.00ms
15.00ms
30.00ms
45.00ms
250.1 V
150.1 V
50.10 V
SCR1
50 Hz
SCR2
S2003LS1
S2003LS1
V3
120/-120V
R8
0.9k
R1
0.1k
R6
0.1k
R5
0.9k
C4
2uF
D1
1N5402
R4
0.1k
A: r5_1
Vg-th2
-149.9 V
-249.9 V
0.000ms
A: r6_1
V-triac
15.00 V
5.000 V
-5.000 V
100.0 W
-15.00 V
50.00 W
-25.00 V
0.000 W
-35.00 V
0.000ms
-50.00 W
A: c1[p]
150.1 V
-49.90 V
150.0 W
-100.0 W
0.000ms
250.1 V
50.10 V
R7
47
P-load
A: r6[p]
-149.9 V
-249.9 V
0.000ms
Q2
MAC15A6
C1
2uF
D3
1N5402
-49.90 V
15.00ms
30.00ms
45.00ms
Ic1
12.49 W
A: r6[i]
I-load
1.250 A
0.750 A
7.490 W
0.250 A
2.490 W
-0.250 A
-2.510 W
-0.750 A
-7.510 W
-1.250 A
0.000ms
-12.51 W
0.000ms
15.00ms
30.00ms
45.00ms
D1
1N5402
C1
2uF
V1
120/-120V
R1
5.1k
R4
0.1k
S
S1
SCR2
S2003LS1
SCR1
S2003LS1
S=Off
0.000 V
A: scr1_3
S1
SCR2
S2003LS1
SCR1
S2003LS1
250.0 V
50.00 V
-50.00 V
-150.0 V
-250.0 V
20.00ms
10.00 V
A: v1_2
50.00ms
80.00ms
110.0ms
50.00ms
80.00ms
110.0ms
300.0 V
100.0 V
Vg-th1
0.000 V
S
150.0 V
110.0ms
-100.0 V
-10.00 V
20.00ms
A: scr1_2
50.00ms
80.00ms
-300.0 V
20.00ms
110.0ms
5.000 V
A: scr1_2
250.0 V
150.0 V
50.00 V
Vth1
0.000 V
-50.00 V
-150.0 V
-5.000 V
20.00ms
A: r4[p]
50.00ms
80.00ms
-250.0 V
20.00ms
110.0ms
200.0 W
A: r4[p]
Load
power
0.000 W
-200.0 W
20.00ms
50.00ms
80.00ms
110.0ms
R3
0.9k
C2
2uF
S=ON
Vsource
80.00ms
R5
5.1k
R4
0.1k
50 Hz
A: v1_1
50.00ms
R1
5.1k
R3
0.9k
200.0 V
-200.0 V
20.00ms
D1
1N5402
C1
2uF
V1
120/-120V
C2
2uF
50 Hz
A: v1_1
R5
4.1k
Zero-Voltage switching
50.00ms
80.00ms
110.0ms
250.0 W
150.0 W
50.00 W
-50.00 W
-150.0 W
-250.0 W
20.00ms
50.00ms
80.00ms
110.0ms
Chapter 7D
Thyristor Commutation
1. Objectives:
1. to study the concept of thyristor commutation
2. to illustrate some of commutation techniques
3. to study how to express the required mathematical model
4. To determine the turning-off time, and how could be affected
5. Describing some examples
2. The Concept of Commutation Process:
- This is a process of removing the circuit current by forcing it to
flow in another loop with purpose to be ceased “eliminated”.
- Depending on the source voltage, there are two types of
commutation strategies:
- Natural commutation : applied in AC circuits
- Forced commutation : Applied in DC circuits.
2.1 Natural Commutation:
Because of the load current varies sinusoidally, the thyristor
should be turned –off when the load current falls below the
holding value: ILoad<IH . Furthermore, in the negative half
cycle, the applied source voltage being negative with respect to
anode-cathode terminals, causing reverse biasing of the device.
Principle electrical circuit is shown below:
2.1 Forced Commutation:
In this case, because of no alternating character of the current “ DC “,
therefore it must force decreases by applying the following
approaches:
- the load current must reduced below the holding value:
ILoad<IH
- by applying negative voltage across the thyristor, causing
forced removing of internal charge, therefore the load current falls
below the holding value IH .
Several techniques realized these approaches:
•
•
•
•
•
•
Self Commutation
Complementary Commutation
Resonant Commutation
Impulse Commutation
Load-side commutation
Line-side commutation
*- Self Commutation:
The thyristor is self turning-off due to resonant behavior of the
current flows in RLC circuit as well shown on the figure below,
where it is clearly shown that when the current becomes negative
the thyristor turned-off.
Mathematical modeling:
i( t )  Im . sin t
C
1
; 
L
L.C
Vc ( t )  Vs (1  cos t );
Im  Vs.
to   L.C
*- Complementary Commutation:
In this case, second thyristor which called " Auxiliary" operates in
complementary sequence ( turning-on first thyristor caused
turning-off second device) .
The figure shown below illustrates the principle circuit, where it is
clearly shown that each thyritor operates for predetermine time
with complementary sequence. The connected capacitor play the
role of applying negative voltage across T1 and T2.
Mathematical modeling:
T1=ON
Vs  R.i( t )  Vc ( t )
i1( t ) 
2. Vs
R
.  t /  ;   R.C
The turning  off time :
toff  R.C. ln 2
R  R1  R 2;
Vc (0)   Vs;
Let Vs=200V;
R=5Ω; =10µF
Therefore:
toff=34.4µS
Waveforms:
Hereinafter the circuit waveforms for both T1, T2, Vg1, Vg2, I1,I2,
and VR1.
*- Impulse Commutation:
In this case, second thyristor T2 which called " Auxiliary" used to
connect the capacitor across T1 with inverse voltage, therefore
reducing the thyristor current below IH.
The figure shown below illustrates the principle circuit, where the
circuit waveforms illustrates these behaviors.
Mathematical modeling:
T1=ON, after then T2=ON
Vs  R.i( t )  Vc ( t )
t
1
 R.i( t )   i( t )  Vc (0)
C0
 i( t ) 
Let Vs=200V; R=5Ω; =10µF
Therefore: toff=34.6µS
2.Vs
R
.  t /  ;   R.C
Vc ( t )  Vs.(1  2  t /  )
The turning  off time :
toff  R.C. ln 2
Vc (0)  Vs;
Waveforms:
Hereinafter the circuit waveforms for both T1, T2, Vg1, Vg2, I1, and
Vload.
*- Resonant Commutation:
In this case, second thyristor T2 used to connect the capacitor
across T1 with inverse voltage, therefore reducing the thyristor
current below IH, while third thyristor T3 is used to recharging
the capacitor with polarity appropriate to turning-off T1.
The figure shown below illustrates the principle circuit, where the
circuit waveforms illustrates these behaviors.
Waveforms:
Hereinafter the circuit waveforms for two cases: 1- C is recharged
through resistance R2; 2- C is recharged throug inductance L2
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