Capacitor Commutation by Ashakoor
21
C o m s a t s I n s t i t u t e o f I n f o r m a t i o n S c i e n c e T e c h n o l o g y A b b o t t a b a d 1
Transcript of Capacitor Commutation by Ashakoor
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
1
CAPACITOR COMMUTATION
PRESENTATION TOPIC:
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
2
GROUP MEMBERS
M. SHOAIB SP09-BEE-066RAMIZ-UD-DIN SP09-BEE-094WAQAR ALI SP09-BEE-097
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
3
WHAT IS COMMUTATION?
The process of turning off an SCR is called commutation.
It is achieved by1. Reducing anode current below holding
current2. Make anode negative with respect to cathode
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
4
SCR TURNOFF METHODS
1. Diverting the anode current to an alternate path
2. Shorting the SCR from anode to cathode
3. Applying a reverse voltage (by making the cathode positive with respect to the anode) across the SCR
4. Forcing the anode current to zero for a brief period
5. Opening the external path from its anode supply voltage
6. Momentarily reducing supply voltage to zero5
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
(1) CAPACITOR COMMUTATION
• SCR turnoff circuit using a transistor switch
6
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
DRAW BACK
Commutation through transistor is slow because in this method we decrease the anode current
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
7
DRAW BACK SOLUTION
We can overcome this draw back by using commutation method of reverse biasing the SCR as shown in next slide by fig……
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
8
• SCR turnoff circuit using commutation capacitor
9
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
10
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
11
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
12
HOW TO CHOOSE A COMMUTATING CAPACITOR
From circuit analysis or measurement, determine
application values for these six parameters:
Nominal capacitance in μF
Current pulse width in μs
Current pulse period in μs
Maximum peak voltage
Continuous AC voltage in Vrms
Maximum volt-amps (VA)
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
13
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
14
0
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
15
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
16
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
17
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
18
0
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
19
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
20
REFRENCES
Power electronocs for technology
By Ashfaq Ahmad
http://www.slideshare.net/prathikm/thyristor-commutation-techniques
Co
msa
ts Institu
te o
f Info
rma
tion
Scie
nce
T
ech
no
log
y Ab
bo
ttab
ad
21
