ZA Series
Power Dissipation Ratings
Should transients occur in rapid succession, the average
power dissipation required is simply the energy (watt-
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.
1.
100
90
PERCENT OF RATED VALUE
80
70
60
50
40
30
20
10
0
-55
50
60
70
80
90
100
110
120
130
140
150
AMBIENT TEMPERATURE (
o
C)
FIGURE 1. CURRENT, ENERGY AND POWER DERATING
CURVE
PERCENT OF PEAK VALUE
100
90
50
O
1
= Virtual Origin of Wave
T = Time From 10% to 90% of Peak
T
1
= Virtual Front time = 1.25
•
t
T
2
= Virtual Time to Half Value (Impulse Duration)
Example: For an 8/20µs Current Waveform:
8µs = T
1
= Virtual Front Time
20µs = T
2
= Virtual Time to Half Value
10
O
1
T
T
1
T
2
TIME
FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM
Transient V-I Characteristics Curves
600
500
400
300
MAXIMUM PEAK VOLTS (V)
200
MAX CLAMPING VOLTAGE
MODEL SIZE 5mm
8 TO 68V
N(DC)
RATING
T
A
= -55
o
C TO 85
o
C
MAXIMUM PEAK VOLTS (V)
2000
V330ZA05
V270ZA05
V240ZA05
V220ZA05
V205ZA05
V180ZA05
V150ZA05
V120ZA05
MAX CLAMPING VOLTAGE
MODEL SIZE 5mm
82 TO 330V
N(DC)
RATING
T
A
= -55
o
C TO 85
o
C
1000
100
90
80
70
60
50
40
500
V68ZA05
V56ZA05
V47ZA05
V39ZA05
V33ZA05
V27ZA05
30 V22ZA05
V18ZA05
20 V12ZA05
V8ZA05
200
5
A0
0Z
0
V1
05
ZA
2
V8
10
10
-3
10
-2
10
-1
10
0
10
1
10
2
10
3
100
0.0001
0.001
0.01
0.1
1
10
100
1000
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 ]
