Varistor Products High Energy, High Multiple Pulse Capability Radial Lead RoHS Pb C-III Varistor Series (R) (R) D V E The C-III Series of metal-oxide varistors are specifically designed for applications requiring high surge energy absorption ratings and superior multiple pulse absorbtion rating. This is achieved through a special dielectric material formulation which also results in higher repetitive surge ratings than other MOV types. The C-III series is primarily intended for use in AC line Transient Voltage Surge Suppressor (TVSS) product environment and other similar applications requiring high transient energy and peak current capability in a relatively small package size. The C-III series is supplied in 10mm, 14mm and 20mm disc versions with various lead options. These types are shipped in bulk or Tape and Reel packaging. Part number and brand information is provided in the Ratings table. Features * Lead-free and RoHS compliant option available. Please see the device and ratings specifications table for more information. * High Energy Absorption Capability WTM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40J to 530J (2ms) * High Pulse Life Rating * High Peak Pulse Current Capability ITM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3500A to 9000A (8/20s) * Wide Operating Voltage Range VM(AC)RMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130V to 660V NEW LEAD-FREE AND RoHS COMPLIANT PARTS AVAILABLE * Available in Tape and Reel for Automatic Insertion; Also Available with Crimped and/or Trimmed Lead Styles * No Derating Up to 85oC Ambient AGENCY APPROVALS: Recognized under the components program of Underwriters Laboratories. Certified by CSA, VDE and CECC. VDE certification of Lead-free and RoHS compliant parts pending. AGENCY FILE NUMBERS: UL E75961, CSA LR91788, VDE 116895E, CECC 42201-006. ALSO SEE LITTELFUSE ULTRAMOVTM VARISTOR SERIES 48 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Radial Lead Pb C-III Varistor Series Absolute Maximum Ratings For ratings of individual members of a series, see Device Ratings and Specifications chart C-III SERIES Continuous: Steady State AC Voltage Range (VM(AC)RMS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 to 660 Transients: Single-Pulse Peak Current (ITM) 8/20s Wave (See Figure 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3500 to 9000 Single-Pulse Energy Range (WTM) 2ms Rectangular Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 to 530 UNITS V A J Maximum Temporary Overvoltage of VM(AC): 5 Minutes Duration @ 25oC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5 Minutes Duration @ 125oC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 % % Operating Ambient Temperature Range (TA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to 85 Storage Temperature Range (TSTG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to125 Temperature Coefficient ( V) of Clamping Voltage (VC) at Specified Test Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <0.0 C C %/oC o o 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 thedevice at these or any other conditions above those indicated in the operational sections of this specification is not implied. C-III Series Ratings RoHS MAXIMUM RATINGS (85 oC) Pb LEAD-FREE AND RoHS COMPLIANT MODELS PART NUMBER BRANDING CONTINUOUS STANDARD MODELS PART NUMBER BRANDING MAXIMUM VRMS VM(AC) (V) TRANSIENT WITHSTANDING ENERGY (2ms) ) WTM ( (J) PEAK CURRENT (8/20 s) ITM1 1 PULSE (A) ITM2 2 PULSES (A) V130LA5CP V130LA10CP V130LA20CP V130LA20CX325P P130L5C P130L10C P130L20C P130CX325 V130LA5C V130LA10C V130LA20C V130LA20CX325 130L5C 130L10C 130L20C 130CX325 130 130 130 130 40 80 200 200 3500 6000 9000 9000 3000 5000 7000 7000 V140LA5CP V140LA10CP V140LA20CP V140LA20CX340P P140L5C P140L10C P140L20C P140CX340 V140LA5C V140LA10C V140LA20C V140LA20CX340 140L5C 140L10C 140L20C 140CX340 140 140 140 140 45 90 210 210 3500 6000 9000 9000 3000 5000 7000 7000 V150LA5CP V150LA10CP V150LA20CP V150LA20CX360P P150L5C P150L10C P150L20C P150CX360 V150LA5C V150LA10C V150LA20C V150LA20CX360 150L5C 150L10C 150L20C 150CX360 150 150 150 150 50 100 215 215 3500 6000 9000 9000 3000 5000 7000 7000 V175LA5CP V175LA10CP V175LA20CP V175LA20CX425P P175L5C P175L10C P175L20C P175CX425 V175LA5C V175LA10C V175LA20C V175LA20CX425 175L5C 175L10C 175L20C 175CX425 175 175 175 175 55 110 220 220 3500 6000 9000 9000 3000 5000 7000 7000 V230LA10CP V230LA20CP V230LA40CP V230LA40CX570P P230L10C P230L20C P230L40C P230X570 V230LA10C V230LA20C V230LA40C V230LA40CX570 230L10C 230L20C 230L40C 230X570 230 230 230 230 60 125 280 280 3500 6000 9000 9000 3000 5000 7000 7000 V250LA10CP V250LA20CP V250LA40CP V250LA40CX620P P250L10C P250L20C P250L40C P250CX620 V250LA10C V250LA20C V250LA40C V250LA40CX620 250L10C 250L20C 250L40C 250CX620 250 250 250 250 65 135 300 300 3500 6000 9000 9000 3000 5000 7000 7000 V275LA10CP V275LA20CP V275LA40CP V275LA40CX680P V300LA10CP V300LA20CP V300LA40CP V300LA40CX745P P275L10C P275L20C P275L40C P275CX680 P300L10C P300L20C P300L40C P300CX745 V275LA10C V275LA20C V275LA40C V275LA40CX680 275L10C 275L20C 275L40C 275CX680 275 275 275 275 V300LA10C V300LA20C V300LA40C V300LA40CX745 300L10C 300L20C 300L40C 300CX745 300 300 300 300 70 145 320 320 75 155 335 335 3500 6000 9000 9000 3500 6000 9000 9000 3000 5000 7000 7000 3000 5000 7000 7000 V320LA10CP V320LA20CP V320LA40CP V320LA40CX810P P320L10C P320L20C P320L40C P320CX810 V320LA10C V320LA20C V320LA40C V320LA40CX810 320L10C 320L20C 320L40C 320CX810 320 320 320 320 80 165 345 345 3500 6000 9000 9000 3000 5000 7000 7000 V385LA20CP V385LA40CP P385L20C P385L40C V385LA20C V385LA40C 385L20C 385L40C 385 385 175 370 6000 9000 5000 7000 V420LA20CP V420LA40CP P420L20C P420L40C V420LA20C V420LA40C 420L20C 420L40C 420 420 185 390 6000 9000 5000 7000 V460LA40CP P460L40C V460LA40C 460L40C 460 430 9000 7000 V480LA80CP V510LA80CP V550LA80CP V575LA80CP P480L80C P510L80C P550L80C P575L80C V480LA80C V510LA80C V550LA80C V575LA80C 480L80C 510L80C 550L80C 575L80C 480 510 550 575 420 440 450 460 9000 9000 9000 9000 7000 7000 7000 7000 V625LA80CP P625L80C V625LA80C 625L80C 625 490 9000 7000 V660LA80CP P660L80C V660LA80C 660L80C 660 510 9000 7000 w w w. l i t t e l f u s e . c o m 49 2 VARISTOR PRODUCTS RoHS Varistor Products High Energy Radial Lead RoHS Pb C-III Varistor Series C-III Series Specifications RoHS SPECIFICATIONS (25 oC) Pb LEAD-FREE AND RoHS COMPLIANT MODELS STANDARD MODELS PART NUMBER PART NUMBER VARISTOR VOLTAGE AT 1mA DC TEST CURRENT MODEL SIZE DISC DIAMETER (mm) MAXIMUM CLAMPING VOLTAGE (8/20s) DUTY CYCLE SURGE RATING VN MIN (V) VN MAX (V) VC (V) Ip (A) 3kA (8/20s) # PULSES 750A (8/20s) # PULSES V130LA5CP V130LA10CP V130LA20CP V130LA20CX325P V140LA5CP V140LA10CP V140LA20CP V140LA20CX340P V150LA5CP V150LA10CP V150LA20CP V150LA20CX360P V175LA5CP V175LA10CP V175LA20CP V175LA20CX425P V230LA10CP V230LA20CP V230LA40CP V230LA40CX570P V130LA5C V130LA10C V130LA20C V130LA20CX325 V140LA5C V140LA10C V140LA20C V140LA20CX340 V150LA5C V150LA10C V150LA20C V150LA20CX360 V175LA5C V175LA10C V175LA20C V175LA20CX425 V230LA10C V230LA20C V230LA40C V230LA40CX570 10 14 20 20 10 14 20 20 10 14 20 20 10 14 20 20 10 14 20 20 184 184 184 184 198 198 198 198 212 212 212 212 247 247 247 247 324 324 324 324 228 228 228 220 242 242 242 230 268 268 268 243 303 303 303 285 396 396 396 384 340 340 340 325 360 360 360 340 395 395 395 360 455 455 455 425 595 595 595 570 25 50 100 100 25 50 100 100 25 50 100 100 25 50 100 100 25 50 100 100 2 40 80 80 2 40 80 80 2 40 80 80 2 40 80 80 2 40 80 80 100 600 1600 1600 100 600 1600 1600 100 600 1600 1600 100 600 1600 1600 100 600 1600 1600 V250LA10CP V250LA20CP V250LA40CP V250LA40CX620P V275LA10CP V275LA20CP V275LA40CP V275LA40CX680P V250LA10C V250LA20C V250LA40C V250LA40CX620 V275LA10C V275LA20C V275LA40C V275LA40CX680 10 14 20 20 10 14 20 20 354 354 354 354 389 389 389 389 429 429 429 413 473 473 473 453 650 650 650 620 710 710 710 680 25 50 100 100 25 50 100 100 2 40 80 80 2 40 80 80 100 600 600 1600 100 600 1600 1600 V300LA10CP V300LA20CP V300LA40CP V300LA40CX745P V300LA10C V300LA20C V300LA40C V300LA40CX745 10 14 20 20 420 420 420 420 517 517 517 490 775 775 775 745 25 50 100 100 2 40 80 80 100 600 1600 1600 V320LA10CP V320LA20CP V320LA40CP V320LA40CX810P V320LA10C V320LA20C V320LA40C V320LA40CX810 10 14 20 20 462 462 462 462 565 565 565 540 850 850 850 810 25 50 100 100 2 40 80 80 100 600 1600 1600 V385LA20CP V385LA40CP V385LA20C V385LA40C 14 20 558 558 682 682 1025 1025 50 100 40 80 600 1600 V420LA20CP V420LA40CP V420LA20C V420LA40C 14 20 610 610 748 748 1120 1120 50 100 40 80 600 1600 V460LA40CP V480LA80CP V510LA80CP V460LA40C V480LA80C V510LA80C 20 20 20 640 670 735 790 825 910 1190 1240 1350 100 100 100 80 80 80 1600 1600 1600 V550LA80CP V550LA80C 20 780 970 1435 100 80 1600 V575LA80CP V625LA80CP V660LA80CP V575LA80C V625LA80C V660LA80C 20 20 20 805 900 940 1000 1100 1210 1500 1725 1820 100 100 100 80 80 80 1600 1600 1600 NOTE: * Average power dissipation of transients not to exceed 0.6W and 1W for model sizes 14mm and 20mm, respectively. * 7mm and 12mm parts also available-contact factory for further information * For additional or intermediary voltage ratings contact factory 50 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Radial Lead RoHS Pb C-III Varistor Series o 100 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 s Current Waveform: 8 s = T1 = Virtual Front Time 20 s = T2 = Virtual Time to Half Value 90 50 10 O1 T 2 TIME T1 T2 VARISTOR PRODUCTS PERCENT OF RATED VALUE Should transients occur 100 90 in rapid succession, the 80 average power 70 60 dissipation is the energy 50 (watt-seconds) per pulse 40 30 times the number of puls20 es per second. The 10 0 -55 50 60 70 80 90 100 110 120 130 140 150 power so developed AMBIENT TEMPERATURE ( C) must be within the speciFIGURE 1. CURRENT, ENERGY AND POWER DERATING fications shown on the CURVE Device Ratings and Specifications table for the specific device.The operating values of a MOV need to be deratedat high temperatures as shown in Figure 1. Because varistors only dissipate a relatively small amount of average power they are not suitable 0for repetitive applications that involve substantial amounts of average power dissipation. PERCENT OF PEAK VALUE Power Dissipation Ratings FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM Transient V-I Characteristics Curves 10,000 10,000 MODEL SIZE = 10mm MODEL SIZE = 14mm Maximum Voltage (V) Maximum Voltage (V) V420LA20C(P) V320LA10C(P) V300LA10C(P) V275LA10C(P) V250LA10C(P) 1,000 V230LA10C(P) V230LA20C(P) V385LA20C(P) V320LA20C(P) V300LA20C(P) 1,000 V275LA20C(P) V250LA20C(P) V175LA10C(P) V175LA5C(P) V150LA10C(P) V150LA5C(P) V140LA10C(P) V130LA10C(P) V140LA5C(P) V130LA5C(P) 100 100 0.001 0.01 0.1 1 1.0 100 1000 0.01 0.001 10000 1 0.1 100 1.0 10000 1000 Peak Amperes (A) Peak Amperes (A) Figure 4. Maximum Clamping Voltage for 14mm Parts (V130LA10C(P) -V420LA20C(P)) Figure 3. Maximum Clamping Voltage for 10mm Parts (V130LA5C(P) -V320LA10C(P)) 10,000 10,000 V660LA100C(P) V625LA80C(P) MODEL SIZE = 20mm V300LA40CX810(P) Maximum Voltage (V) V510LA80C(P) V420LA40C(P) V480LA80C(P) V385LA40C(P) 1,000 V320LA40C(P) V300LA40C(P) V275LA40C(P) V250LA40C(P) V230LA40C(P) V175LA20C(P) Maximum Voltage (V) V575LA80C(P) V300LA40CX745(P) V275LA40CX680(P) V250LA40CX620(P) 1,000 V230LA40CX570(P) V175LA20CX425(P) V150LA20C(P) V150LA20CX360(P) V140LA20CX340(P) V130LA20CX325(P) V140LA20C(P) V130LA20C(P) 100 100 0.001 0.01 0.1 1 1.0 100 1000 0.001 10000 0.01 0.1 1 1.0 100 1000 10000 Peak Amperes (A) Peak Amperes (A) Figure 5. Maximum Clamping Voltage for 20mm Parts (V130LA20C(P) -V660LA100C(P)) Figure 6. Maximum Clamping Voltage for Low Clamping Voltage Parts (V130LA20CX325(P) -V300LA40CX245(P)) w w w. l i t t e l f u s e . c o m 51 Varistor Products High Energy Radial Lead RoHS Pb C-III Varistor Series Pulse Rating Curves 10,000 1 1 2 10 10 MODEL SIZE = 10mm 102 10 3 104 100 10 1 1,000 3 10 10 3 10140 100 4 10 10 10,000 100 1,000 10,000 Figure 8. Repetitive Surge Capability for 14mm Parts (V130LA10C(P)-V420LA20C(P)) * Phenolic Coated CIII Series devices are available with improved maximum operating maximum temperature 125C. * These devices also have improved temperature cycling performance capability. * Ratings and Specifications are as per standard CIII Series except Hi-Pot encapsulation Isolation Voltage Capability = 500V. * To order: add X1347 to part number (e.g. V230LA40CX1347) * These devices are not UL, CSA, VDE or CECC certified. * Contact factory for further details. 3 10 103 104 8 10 100 10,000 1,000 Surge Impulse Duration (s) Figure 9. Repetitive Surge Capability for 20mm Parts (V130LA20C(P)-V660LA100C(P)) 52 10,000 CIII series varistors for Hi-Temperature operating conditions: MODEL SIZE = 20mm 10 1,000 Figure 7. Repetitive Surge Capability for 10mm Parts (V130LA5C(P)-V320LA10C(P)) 102 10 100 100 Surge Impulse Duration (s) 1 2 10 1,000 10 Surge Impulse Duration (s) 2 Peak Rated Surge Current (A) MODEL SIZE = 14mm 102 8 1,000 Peak Rated Surge Current (A) 2 10 8 Peak Rated Surge Current (A) 10,000 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Radial Lead RoHS Pb C-III Varistor Series Tape and Reel Specification(available for voltage ratings up to 320V only) P E DP MODEL SIZE DP DH DH SYMBOL C SEATING PLANE H1 W0 W2 W1 H0 b W DESCRIPTION 10mm 14mm P Pitch of Component 25.4 1.0 P0 Feed Hole Pitch 12.7 0.2 P1 Feed Hole Center to Pitch 8.85 0.8 P2 Hole Center to Component Center 12.7 0.7 F Lead to Lead Distance 7.50 0.8 h Component Alignment 2.00 Max W Tape Width W0 Hold Down Tape Width W1 Hole Position W2 Hold Down Tape Position 20mm 2 VARISTOR PRODUCTS P2 D0 P1 t F P1 Crimped Leads "LT" P2 P E DP DP DH DH H1 W0 W2 W1 H b 18.25 0.75 12.0 0.3 9.125 0.625 0.5 Max H Height From Tape Center To Component Base 19.0 1.0 H0 Seating Plane Height H1 Component Height D0 Feed Hole Diameter 4.0 0.2 t Total Tape Thickness 0.7 0.2 p Component Alignment 3o Max U Under-crimp Width 8.0 Max 16.0 0.5 36 Max 40 Max 46.5 Max W D0 P1 t F P0 Straight Leads "LS" P2 P E DP DP DH DH U H1 W0 W2 W1 Ho b W D0 P1 F t P0 Under-crimped Leads "LU" w w w. l i t t e l f u s e . c o m 53 Varistor Products High Energy Radial Lead RoHS C-III Varistor Series Pb Additional Lead Style Options Tape and Reel Data Radial lead types can be supplied with combination preformed crimp and trimmed leads. This option is suppliedto the dimensions shown below. *Seating plane interpretation per IEC-717 * Conforms to ANSI and EIA Specifications * Can be supplied to IEC publication 286-2 * Radial devices on tape and reel are supplied with either crimped leads, straight leads, or under-crimped leads VARISTOR MODEL SIZE * Available for voltage ratings up to 320V only 10mm Tape and Reel Ordering Information SYMBOL * Crimped leads are standard on LA types supplied in tape and reel and are denoted by the model letter "T". Also, in tape and reel, model letter "S" denotes straight leads and letter "U" denotes special under-crimped leads. 14mm 20mm MIN MAX MIN MAX MIN A - 19.5 (0.768) - 23.5 (0.925) - 30 (1.18) LTRIM 2.41 (0.095) 4.69 (0.185) 2.41 (0.095) 2.41 (0.095) 4.69 (0.185) Example: 4.69 (0.185) MAX NOTE: Dimensions are in millimeters (inches). STANDARD MODEL V130LA20C CRIMPED LEADS STRAIGHT LEADS UNDER CRIMP LEADS V130LT20C V130LS20C V130LU20C *SEATING Shipping Quantity PLANE A QUANTITY PER REEL DEVICE SIZE "T"REEL "S"REEL "U"REEL 10mm 14mm 500 500 500 500 500 500 20mm 500 500 500 LTRIM CRIMPED AND TRIMMED LEAD Mechanical Dimensions * To order this crimped and trimmed lead style, the standard radial type model number "LA" is changed to the model number "LC".This option is supplied in bulk only. OD A STANDARD MODEL ORDER AS V130LA20C V130LC20C 25.4 (1.00) Ob Example: * For 10 1mm lead spacing on 20mm units only; append standard model numbers by adding "X10" suffix. e e1 E Example: VARISTOR MODEL SIZE SYMBOL VRMS VOLTAGE MODEL A 10mm 14mm MIN MAX 13.5 (0.531) 20 (0.787) 17.5 (0.689) 26.5 (1.043) 12.5 (0.492) 13.5 (0.531) 17 (0.669) 17.5 (0.689) 23 (0.906) 6.5 (0.256) 8.5 (0.335) 6.5 (0.256) 8.5 (0.335) 2.5 (0.098) 5.5 (0.216) 2.5 (0.098) 4.5 (0.177) - 7.3 (0.287) - 7.3 (0.287) - 7.3 (0.287) - 11 (0.433) - 11 (0.433) 0.76 (0.030) 0.86 (0.034) 0.76 (0.030) 0.86 (0.034) MAX ALL 12 (0.472) 16 (0.630) OD ALL 10 (0.394) e ALL e1 130 - 320 >320 E 130 - 320 >320 Ob ALL MIN 20mm MAX MIN 6.5 (0.256) 8.5 (0.335) 5.5 (0.216) 2.5 (0.098) 5.5 (0.216) 9.0 (0.354) 4.5 (0.177) 9.0 (0.354) 0.76 (0.030) STANDARD MODEL ORDER AS V130LA20C V130LC20C * For other lead style variations to the above, please contact Littelfuse. 0.86 (0.034) Dimensions are in millimeters (inches) 1. 10mm lead spacing also available. See additional lead style options. 2. 7mm and 12mm devices also available upon request. Contact factory for details. 54 w w w. l i t t e l f u s e . c o m Varistor Products High Energy Radial Lead RoHS C-III Varistor Series Pb Additionally, all 20mm C-III devices are listed to the "Permanently Connected" category (10kA) of UL1449, by Underwriter's Laboratories, Inc. Ordering Information C-III series Varistors are shipped standard in bulk pack with straight leads and lead spacing outlined in the package dimensions on page 413. Contact your Littelfuse sales representative to discuss the non-standard options outlined below. For Lead-free and RoHS compliant parts add the letter `P' after the base part number and before any option as shown in the ordering example below. ex: V150LS20CP V300LS40CPX745 As a measure of the inherent device capability, samples of the 20mm V130LA20C devices were subjected to a worst case repetitive transient surges test. After 100 pulses, each of 3kA, there was negligible change in the device characteristics. Changes in the clamping voltage, measured at 100 amps, of less than 3% were recorded (Figure 9). Samples of the 14mm Series V175LA20C were subjected to repetitive surge occurrences of 750A. Again, there was negligible changes in any of the device characteristics after 2000 pulses (Figure 10). In both cases the inherent device capability is far in excess of the expected worst case scenario. 2 300 P: LEAD-FREE AND RoHS COMPLIANT OPTION RELATIVE ENERGY INDICATOR (One or Two Digits) 250 200 150 100 0 SERIES DESIGNATOR/ LEAD STYLE DESIGNATOR LC = Crimped and Clipped LS = Straight LT = Crimped LU = Under Crimped VARISTOR PRODUCTS VARISTOR VNOM AT 1mA (V) V XXX LA XX C P + Optional Suffix VM(AC) 130V to 1,000V V130LA20C Other Options Base Part # 100 200 300 400 500 600 700 TIME (HOURS) 800 900 1000 1100 The C-III series of metal oxide varistors was designed for use on the AC line. The varistor is connected across the AC line and is biased with a constant amplitude sinusoidal voltage. It should be noted that the definition of failure is a shift in the nominal varistor voltage (VN) exceeding 10%. Although this type of varistor is still functioning normally after this magnitude of shift, devices at the lower extremities of VN tolerance will begin to dissipate more power. Because of this possibility, an extensive series of statistically designed tests were performed to determine the reliability of the C-III type of varistor under AC bias combined with high levels of temperature stress. To date, this test has generated over 50,000 device hours of operation at a temperature of 125oC, although only rated at 85oC. Changes in the nominal varistor voltage, measured at 1mA, of less than 2% have been recorded (Figure 8). Transient Surge Current/Energy Transient Capability The transient surge rating serves as an excellent figure of merit for the C-III varistor. This inherent surge handling capability is one of the C-III varistor's best features. The enhanced surge absorption capability results from improved process uniformity and enhanced construction. The homogeneity of the raw material powder and improved control over the sintering and assembly processes are contributing factors to this improvement. In the low power AC mains environment, industry standards (UL, IEC, NEMA and IEEE) all suggest that the worst case surge occurrence will be 3kA. Such a transient event may occur up to five times over the equipment life time (approximately 10 years). While the occu rences of five 3kA transients is the required capability, the rated, repetitive surge current for the C-III series is 80 pulses for the 20mm units and 40 pulses for the 500 V130LA20C 3kA (8/20s) 450 400 350 (RATED FOR 80 PULSES) 300 0 10 20 30 40 50 60 70 80 NUMBER OF SURGES 90 100 110 120 FIGURE 9. TYPICAL REPETITIVE SURGE CURRENT CAPABILITY OF C-III SERIES MOVs CLAMPING VOLTAGE AT 750A AC Bias Reliability CLAMPING VOLTAGE AT 3kA FIGURE 8. HIGH TEMPERATURE OPERATING LIFE 125 oC FOR 1000 HOURS AT RATED BIAS 600 V175LA20C 750A (8/20s) 550 500 450 400 350 300 (RATED FOR 1600 PULSES) 0 200 400 600 800 1000 1200 1400 1600 2000 NUMBER OF SURGES FIGURE 10. TYPICAL REPETITIVE SURGE CURRENT CAPABILITY OF C-III SERIES MOVs w w w. l i t t e l f u s e . c o m 55