TISP7072F3, TISP7082F3
TRIPLE BIDIRECTIONAL THYRISTOR OVERVOLTAGE PROTECTORS
MARCH 1994 - REVISED MARCH 2000
shunt resistor R , series resistor R and shunt capacitor C form the output shaping network.
1
2
2
series feed resistor R to connect to one line conductor for single surge
3
series feed resistor R to connect to the other line conductor for dual surging
4
VC
2.0 kV
R2
15 Ω
R3
25 Ω
50 A
5/310
SW
R
T
T
R
R
T
G
R1
50 Ω
C1
20 µF
C2
200 nF
50 A
5/310
G
G
T AND G
TEST
R AND G
TEST
R AND T
TEST
10/700 GENERATOR - SINGLE TERMINAL PAIR TEST
60 A
4/250
R4
25 Ω
VC
3.3 kV
60 A
4/250
R2
15 Ω
R3
25 Ω
SW
T
R
C1
20 µF
R1
50 Ω
C2
200 nF
120 A
4/250
G
DUAL
10/700 GENERATOR - DUAL TERMINAL PAIR TEST
T AND G,
R AND G
TEST
Figure 18.
In the normal single surge equipment test configuration, the unsurged line is grounded. This is shown by the
dotted lines in the top drawing of Figure 18. However, doing this at device test places one terminal pair in
parallel with another terminal pair. To check the individual terminal pairs of the TISP7xxxF3, without any
paralleled operation, the unsurged terminal is left unconnected.
With the generator output open circuit, when SW closes, C1 discharges through R . The decay time constant
1
will be C R , or 20 x 50 = 1000 µs. For the 50% voltage decay time the time constant needs to be multiplied
1
1
by 0.697, giving 0.697 x 1000 = 697 µs which is rounded to 700 µs.
The output rise time is controlled by the time constant of R and C . which is 15 x 200 = 3000 ns or 3 µs.
2
2
Virtual voltage rise times are given by straight line extrapolation through the 30% and 90% points of the
voltage waveform to zero and 100%. Mathematically this is equivalent to 3.24 times the time constant, which
gives 3.24 x 3 = 9.73 which is rounded to 10 µs. Thus the open circuit voltage rises in 10 µs and decays in
700 µs, giving the 10/700 generator its name.
When the overvoltage protector switches it effectively shorts the generator output via the series 25 Ω resistor.
Two short circuit conditions need to be considered: single output using R only (top circuit of Figure 18) and
3
dual output using R and R (bottom circuit of Figure 18).
3
4
For the single test, the series combination of R and R (15 + 25 = 40 Ω) is in shunt with R . This lowers the
2
3
1
discharge resistance from 50 Ω to 22.2 Ω, giving a discharge time constant of 444 µs and a 50% current
decay time of 309.7 µs, which is rounded to 310 µs.
For the rise time, R and R are in parallel, reducing the effective source resistance from 15 Ω to 9.38 Ω,
2
3
giving a time constant of 1.88 µs. Virtual current rise times are given by straight line extrapolation through the
10% and 90% points of the current waveform to zero and 100%. Mathematically this is equivalent to 2.75
P R O D U C T
I N F O R M A T I O N
12
POINN [ POWER INNOVATIONS LTD ]
