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Varistor Products
High Energy Industrial Square Disc
NA V aristor Series
The NA Series of transient surge suppressors are varistors (MOVs) in
square disc form, intended for special industrial high-energy applications
requiring unique electrical contact or packaging methods provided by the
customer. The electrode finish of these devices is solderable and can
also be used with pressure contacts. Discs may also be stacked.
The NA Series varistor is a square 34mm device, with thicknesses
ranging from 1.7mm minimum for the 250V device to 7.5mm maximum
for the 750V device. For information on mounting considerations refer to
Application Note AN8820.
This disc is also available with encapsulation and PCB leads. See
Littelfuse HB34 Sales.
Features
• Provided in Disc For m for Unique Packaging by Customer
• Solderable Electrode Finish.
• Pressure Contacts and/or Disc Stacking may be Utilized
• Wide Operating Voltage Range
VM(AC)RMS ...................................250V to 750V
• Peak Pulse Current Capability (ITM)....................40,000A
• High Energy Capability (WTM)....................370J to 1050J
• No Derating Up to 8oC Ambient
ALSO SEE HB34 SERIES
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VARISTOR
PRODUCTS
High Energy Industrial Square Disc
NA V aristor Series
Absolute Maximum Ratings For ratings of individual members of a series, see Device Ratings and Specifications chart
Continuous:
Steady State Applied Voltage:
AC Voltage Range (VM(AC)RMS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 to 750 V
DC Voltage Range (VM(DC)). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 to 970 V
Transient:
Peak Pulse Current (ITM)
For 8/20µs Current Wave (See Figure 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40,000 A
Single Pulse Energy Range
For 2ms Current Square Wave (WTM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 to1050 J
Operating Ambient Temperature Range (TA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to 85 OC
Storage Temperature Range (TSTG). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to 125 OC
Temperature Coefficient (αV) of Clamping Voltage (VC) at Specified Test Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <0.01 %/OC
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device.This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
Device Ratings and Specifications
NA SERIES UNITS
MODEL
NUMBER
SIZE
MAXIMUM RATINGS (85oC) SPECIFICATIONS (25 oC)
CONTINUOUS TRANSIENT
VARISTOR VOLTAGE
AT 1mA DC TEST
CURRENT
MAXIMUM
CLAMPING
VOLTAGE
(VC) AT 200A
(8/20µs)
TYPICAL
CAPACI-
TANCEVRMS VDC
ENERGY
(2ms)
PEAK
CURRENT
(8/20µs)
VM(AC) VM(DC) WTM ITM MIN VN(DC) MAX VCf = 1MHz
(mm) (V) (V) (J) (A) (V) (V) (V) (V) (pF)
V131NA34
V141NA34
34
34
130
140
175
188
270
291
40,000 184
198 220
200 228
248
345
375
10,000
V151NA34 34 150 200 300 40,000 212 240 268 405 8,000
9,000
V251NA34 34 250 330 370 40,000 354 390 429 650 5,000
V271NA34 34 275 369 400 40,000 389 430 473 730 4,500
V321NA34 34 320 420 460 40,000 462 510 561 830 3,800
V421NA34 34 420 560 600 40,000 610 680 748 1,130 3,000
V481NA34 34 480 640 650 40,000 670 750 825 1,240 2,700
V511NA34 34 510 675 700 40,000 735 820 910 1,350 2,500
V571NA34 34 575 730 770 40,000 805 910 1000 1,480 2,200
V661NA34 34 660 850 900 40,000 940 1050 1160 1,720 2,000
V751NA34 34 750 970 1050 40,000 1080 1200 1320 2,000 1,800
NOTE: Average power dissipation of transients not to exceed 2.0W.
1
40,0003
2
1. Peak current applies to applications rated up to 115V . Peak current is 30kA for applications greater than 115V .
2. Peak current applies to applications rated up to 132V . Peak current is 30kA for applications greater than 132V .
3. Peak current applies to applications rated up to 123V . Peak current is 30kA for applications greater than 123V .
RMS
RMS
RMS
RMS
RMS
RMS
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Varistor Products
NA V aristor Series
High Energy Industrial Square Disc
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.The operating values must be derated as
shown in Figure 1.
Transient V-I Characteristics Curves
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
PERCENT OF RATED VALUE
AMBIENT TEMPERATURE (oC)
FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM
100
90
50
10
O1T
T1T2
TIME
PERCENT OF PEAK VALUE
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 8/20µs Current Waveform:
8µs = T1 = Virtual Front Time
20µs = T2 = Virtual Time to Half Value
FIGURE 3. CLAMPING VOLTAGE FOR V131NA34 - V751NA34
VOLTAGE (V)
10000
1000
100
CURRENT (A)
V751NA34
V131NA34
V321NA34
V511NA34
V481NA34 V571NA34
V661NA34
TA = -55oC TO 85oC
MAXIMUM CLAMPING VOLTAGE
VARISTOR SIZE 34mm
130 TO 750 VM(AC) RATING
V271NA34
V251NA34
V151NA34
V421NA34
-5 -4 1E-3 0.01 0.1 1 10 100 1,000 10,000 100,000
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Varistor Products
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VARISTOR
PRODUCTS
High Energy Industrial Square Disc
NA V aristor Series
FIGURE 4. SURGE CURRENT RATING CURVES FOR
V131NA34 - V751NA34
DISC SIZE 34mm
V131NA34 - V751NA34
50,000
20,000
10,000
5,000
2,000
1,000
500
200
100
50
20
1020 100 1,000 10,000
SURGE CURRENT (A)
IMPULSE DURATION (µs)
10
1
INDEFINITE
105
102
2
103
104
106
Pulse Rating Curves
NOTE:If pulse ratings are exceeded, a shift of VN(DC) (at specified current) of more than ±10% could result.This type of shift, which nor mally results in a decrease of V N(DC),
may result in the device not meeting the original published specifications, but it does not prevent the device from continuing to function, and to provide ample protection.
Mechanical Dimensions
(MILLIMETERS)
MODEL
NUMBER
NA SERIES
VARISTOR THICKNESS
MILLIMETERS INCHES
MIN MAX MIN MAX
V131NA34
V141NA34
1.40 2.30 0.055 0.090
V151NA34 1.50
1.45
2.80
2.55
0.059
0.057
0.011
0.100
V251NA34 1.70 2.30 0.066 0.090
V271NA34 1.80 2.70 0.070 0.106
V321NA34 2.10 3.00 0.082 0.118
V421NA34 3.00 4.00 0.118 0.157
V481NA34 3.20 4.40 0.125 0.173
V511NA34 3.60 4.90 0.141 0.192
V571NA34 4.00 5.60 0.118 0.220
V661NA34 4.50 6.80 0.176 0.267
V751NA34 5.20 7.50 0.204 0.294
NOTE: Parts available encapsulated with soldered
tabs, to standard design or customer specific
requirements. Also see HB34 Series.
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Varistor Products
NA V aristor Series
Passivation Layer
The standard NA Series is supplied with passivation layer around the
outside perimeter of the disc forming an electrical insulator as detailed in
the dimensional drawing.
Encapsulated Recommendations
After lead attachment, the disc/lead assembly may be coated or
encapsulated in a package to provide electrical insulation and isolation
from environmental contamination as required by the application.
Coating/Filler materials for containers may include silicones,
polyurethanes, and some epoxy resins.Two examples of acceptable
polyurethanes are Dexter Hysol (US7013, parts A and B) and Rhenatech
(resin 4714, hardener 4900), or their equivalents. Mater ials containing
halogens, sulfides, or alkalines are not recommended.
Electrode Metallization
The NA Series is supplied with a sintered silver metallization for the
electrode finish.The silver metallization is typically used for solder reflow
lead attach operations (I-R, Vapour-Phase).
The recommended temperature profile of a belt-fed convection oven is
shown in Figure 6.
Stacking and Contact Pressure
Recommendations
When applications require the stacking of Littelfuse NA discs or when
electrical connection is made by pressure contacts, the minimum pres-
sure applied to the disc electrode surface should be 2.2kGs (5 pounds).
The maximum recommended pressure applied to the disc electrode is
16N/CM2(23LBs/IN2).
Packaging and Shipping
The NA Series is supplied in bulk for shipment. Discs are packaged in
compar tmentalized car tons to protect from scratching or edge-chipping
during shipment.
TEMPERATURE (oC)
250
200
150
100
50
00 100 200 300 400 500 600 700 800 900
TIME (SEC)
FIGURE 6. TYPICAL BELT OVEN TEMPERATURE PROFILE
Ordering Information
VARISTOR DESIGNATOR
MAX A CRMS WORKING VOLTAGE
(FIRST SIGNIFICANT DIGITS) VM(AC)
DISC SIZE (mm)
SERIES DESIGNATOR
VM(AC) V OLTAGE DECADE MULTIPLIER
V 25 1 NA 34
High Energy Industrial Square Disc
