Littelfuse MA Varistor Series - Manual (Page 3)

© 2013 Littelfuse, Inc. 189
Revised: October 9, 2013
Varistor Products
MA Varistor Series
Axial Lead / Application Specifi c Varistors > MA Series
Specifi cations are subject to change without notice.
Please refer to www.littelfuse.com/series/ma.html for current information.
MA Series
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 specifi cations shown on the
Device Ratings and Specifi cations table for the specifi c device.
Furthermore, the operating values need to be derated at high
temperatures as shown above. 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.
Power Dissipation Ratings
100
90
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)
PERCENT OF R
ATED
VALUE
100
90
50
10
O
1 T
T
1
T 2
TIME
PERCENT OF PEAK V
ALUE
Peak Pulse Current Test Waveform
0
1
= Virtual Origin of Wave
T = Time from 10% to 90% of Peak
T
1
= Rise Time = 1.25 x T
T
2
= Decay Time
Example - For an 8/20 μs Current Waveform:
8μs = T
1
= Rise Time
20μs = T
2
= Decay Time
Repetitive Surge Capability
100
50
20
10
5
2
1
0.5
0.2
0.1
SURGE CURRENT (A)
20 100 1,000 10,000
IMPULSE DURATION (μs)
2
10
10 2
10 3
1
10 4
10 5
10 6
INDEFINITE
DISC SIZE 3mm
V120MA1A - V430MA7B
V120MA1A/S - V430MA3A
50
20
10
5
2
1
0.5
0.2
0.1
2
10
10 2
10 3
DISC SIZE 3mm
V18MA1A - V100MA4B
1
10 4
10 5
INDEFINITE
10 6
20 100 1,000 10,000
IMPULSE DURATION (μs)
SURGE CURRENT (A)
V18MA - V100MA
NOTE: If pulse ratings are exceeded, a shift of V
N(DC)
(at specifi ed current) of more than
+/-10% could result. This type of shift, which normally results in a decrease of V
N(DC)
, may
result in the device not meeting the original published specifi cations, but it does not
prevent the device from continuing to function, and to provide ample protection.
Figure 1 Figure 2
Figure 3 Figure 4