Trek 50 - Page 17

To calculate the maximum energy in joules
that the ZD1 and ZD2 can dissipate, use the
formula:
Maximum energy in joules = (V
m
)(I
s
)(T
s
),
Where V
m
is the voltage rating of ZD1 or
ZD2, I
s
is the maximum surge current that
ZD1 or ZD2 can absorb for a certain duration
(T
s
), and T
s
is the maximum duration of the
particular surge current from the load that
ZD1 and ZD2 can withstand. The calcula-
tions for the different voltage ranges of the
50/750 are shown in Table 1.
Now the energy that can be supplied by an
active load can be compared to the
maximum energy dissipation of the 50/750
for a certain output voltage range.
If the energy that can be supplied by the
active load device is greater than the
maximum energy dissipation of the 50/750
for a certain output voltage range, then
additional external protection is required.
Some examples of external protection are
adding series impedance to the output or
using a spark gap device.
TABLE 1
VOLTAGE
RANGE
DESIGNATION
VOLTAGE
RATING
NONRECURRENT
SURGE
CURRENT (MAX.)
CURRENT
DURATION
(MAX.)
MAXIMUM
ENERGY
(in Joules)
0 to ±750 V
ZD1
ZD2
+1000 V, ±5%
-1000 V, ±5%
0.005 amps
0.35 amps
0.85 amps
2 amps
continuous
100 ms
10 ms
1 ms
-
35
8.5
2
0 to +1500 V
0 to -1500 V
ZD1
ZD2
+2000 V, ±5%
-2000 V, ±5%
0.005 amps
0.35 amps
0.85 amps
2 amps
continuous
100 ms
10 ms
1 ms
-
70
17
4
0 to +1500 V
0 to -1500 V
ZD2
ZD1
-115 V, ±10%
+115 V, ±10%
0.01 amps
1.2 amps
2 amps
5 amps
continuous
100 ms
10 ms
1 ms
-
13.8
2.3
0.575
A2