4-62

LA Series

Power Dissipation Ratings

Continuous power dissipation capability is not an applicable

design requirement for a suppressor, unless transients occur

in rapid succession. Under this condition, 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 der-

ated 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.

FIGURE 1. CURRENT, ENERGY AND POWER DERATING

CURVE

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 (oC)

FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM

100

90

50

10

O1

T

T1

T2

TIME

O1 = Virtual Origin of Wave

T = Time From 10% to 90% of Peak

T1 = Virtual Front Time = 1.25 • t

T2 = Virtual Time to Half Value (Impulse Duration)

Example: For an 8/20

µs Current Waveform:

8

µs = T

1 = Virtual Front Time

20

µs = T

2 = Virtual Time to Half Value

Transient V-I Characteristics Curves

FIGURE 3. CLAMPING VOLTAGE FOR V130LA1 - V300LA2

FIGURE 4. CLAMPING VOLTAGE FOR V130LA2 - V300LA4

200

6,000

5,000

4,000

3,000

1,000

900

800

700

600

500

400

300

10-3

10-2

10-1

100

101

102

104

PEAK AMPERES (A)

2,000

103

V150LA1

V130LA1

V300LA2

V275LA2

V250LA2

MAXIMUM CLAMPING VOLTAGE

MODEL SIZE 7mm

130 TO 300VM(AC) RATING

TA = -55

oC TO +85oC

10-3

10-2

10-1

100

101

102

104

PEAK AMPERES (A)

103

4,000

3,000

2,000

1,000

900

800

700

600

500

400

300

200

100

MAXIMUM CLAMPING VOLTAGE

MODEL SIZE 7mm

130 TO 300VM(AC) RATING

TA = -55

oC TO +85oC

V300LA4

V275LA4

V250LA4

V230LA4

V130LA2

V140LA2

V150LA2

V175LA2