ZA Series
1.
Power Dissipation Ratings
Should transients occur in rapid succession, the average
power dissipation required is simply the energy (watt-
100
90
80
70
60
50
40
30
20
seconds) per pulse times the number of pulses per second.
The power so developed must be within the specifications
shown on the Device Ratings and Specifications table for the
specific device. Furthermore, the operating values need to
be derated at high temperatures as shown in Figure 1.
Because varistors can only dissipate a relatively small
amount of average power they are, therefore, not suitable for
repetitive applications that involve substantial amounts of
average power dissipation.
10
0
-55 50
60
70
80
90 100 110 120 130 140 150
o
AMBIENT TEMPERATURE ( C)
FIGURE 1. CURRENT, ENERGY AND POWER DERATING
CURVE
100
90
O
= Virtual Origin of Wave
1
T = Time From 10% to 90% of Peak
T
T
= Virtual Front time = 1.25 • t
= Virtual Time to Half Value (Impulse Duration)
1
2
50
Example: For an 8/20µs Current Waveform:
8µs = T = Virtual Front Time
1
20µs = T = Virtual Time to Half Value
2
10
O
T
TIME
1
T
1
T
2
FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM
Transient V-I Characteristics Curves
2000
1000
500
600
500
400
300
MAX CLAMPING VOLTAGE
MAX CLAMPING VOLTAGE
MODEL SIZE 5mm
MODEL SIZE 5mm
V330ZA05
V270ZA05
V240ZA05
V220ZA05
V205ZA05
V180ZA05
V150ZA05
V120ZA05
82 TO 330V
RATING
8 TO 68V
RATING
N(DC)
N(DC)
o
o
o
o
T
= -55 C TO 85 C
T
= -55 C TO 85 C
A
A
200
100
90
80
70
60
V68ZA05
V56ZA05
V47ZA05
50 V39ZA05
V33ZA05
40
V27ZA05
V22ZA05
30
200
100
V18ZA05
V12ZA05
20
10
V8ZA05
0.0001
0.001
0.01
0.1
1
10
100
1000
-3
10
-2
10
-1
10
0
1
2
3
10
10
10
10
PEAK AMPERES (A)
PEAK AMPERES (A)
FIGURE 3. CLAMPING VOLTAGE FOR V8ZA05 - V68ZA05
FIGURE 4. CLAMPING VOLTAGE FOR V82ZA05 - V330ZA05
4-38
HARRIS [ HARRIS CORPORATION ]
