V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Resistors - Solutions for Your Application Pulse Handling Capabilities of Vishay Dale Wirewound Resistors INTRODUCTION Power wirewound resistors have steady-state power and voltage ratings which indicate the maximum temperatures that the units should attain. For short durations of 5 seconds or less, these ratings are satisfactory; however, the resistors are capable of handling much higher levels of power and voltage for short periods of time (less than the cross-over point). For instance, at room temperature the RS005 has a continuous rating of 5 W, but for a duration of 1 ms the unit can handle 24 500 W, and for 1 μs the unit can handle 24 500 000 W. The reason for this seemingly high power capability is the fact that energy, which is the product of power and time, is what creates heat; not just power alone. Vishay Dale can provide solutions for your application if provided with information detailed on page three. Resources • Datasheet: RS style wirewound fuse resistor - www.vishay.com/doc?30232 • For technical questions contact [email protected] • Sales contacts: http://www.vishay.com/doc?99914 One of the World’s Largest Manufacturers of Discrete Semiconductors and Passive Components Capabilities VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Resistors - Solutions for Your Application Short Pulses (Less Than the Cross-Over Point Time Duration) For short pulses, it is necessary to determine the energy applied to the resistor. For pulses less than the cross-over point, Vishay Dale engineering assumes all of the pulse energy is dissipated in the resistance element (wire). In order for the resistor to maintain its performance characteristics over the life of the product, Vishay Dale bases analysis and recommendations on the amount of energy required to raise the resistance element to + 350 ºC with no heat loss to the core, coating, or leads. The cross-over point is the time where significant energy starts to be dissipated not only in the wire itself but is now being dissipated into the core, leads, and encapsulation material. This is the point where the pulse is no longer considered a short pulse, but is now considered a long pulse. The pulse handling capability is different for each resistor model and value, as it is based on the mass and specific heat of the resistance element. Once the power and energy have been defined, Vishay Dale can determine the best resistor choice for the application. Cross-Over Point An example of an RS005 500 Ω resistor at room temperature: Required information: ER = Energy rating of a given model, resistance value, and ambient temperature. Provided by Vishay Dale, ER = 6.33 J. PO = The overload power capability of the part at 1 s. The overload power capability of an RS005 for 1 s, 10 x 5 W x 5 s = 250 Ws/1 s = 250 W Cross-over point (s) = ER (J)/PO (W) 6.33 J/ 250 W = 0.0253 s. The cross-over point for the RS005 500 Ω resistor at room temperature is approximately 25.3 ms. Long Pulses (Cross-Over Point to 5 Seconds) For long pulses, much of the heat is dissipated in the core, leads, and encapsulation material. As a result, the calculations used for short pulses are far too conservative. For long pulse applications, the short time overload ratings from the datasheets are used. Note that repeated pulses consisting of the short time overload magnitude are extremely stressful and can cause some resistor styles to fail. • To find the overload power for a 5 s pulse, multiply the power rating by either 5 or 10 as stated on datasheet • To find the overload power capability for 1 s to 5 s, convert the overload power to energy by multiplying by 5 s, then convert back to power by dividing by the pulse width in seconds • For pulse durations between the cross-over point and 1 s, use the overload power computed for 1 s Example 1. What is the overload power for an RS005resistor? From the datasheet, the RS005 is rated at 5 W and will take 10 times rated power for 5 s: 10 x 5 W = 50 W 2. What is the energy capability of the RS005 for 5 s? For 5 s, the energy capability is: 50 W x 5 s = 250 W·s or J 3. What is the overload power capability of the RS005 for 1 s? For 1 s, the overload power capability is 250 W·s / 1 s = 250 W 4. What is the energy capability of the RS005 for 0.5 s? For 0.5 s, the energy capability is 250 W x 0.5 s = 125 W·s or J Capabilities 2/8 VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Information Required to Determine Pulse Capability Resistors - Solutions for Your Application Type of Pulse • Single Square Wave –– Resistor value and tolerance? –– Voltage or current? –– Duration? –– Repeated? –– Maximum ambient temperature? –– Is there any other power applied during the pulse? • Capacitor Discharge –– Resistor value and tolerance? –– Capacitance? –– Charge voltage? –– Repeated? –– Maximum ambient temperature? –– Is there any other power applied during the pulse? • Exponential Decay/Lightning Surge –– Resistor value and tolerance? –– Rise time? –– Peak voltage? –– Time to ½ voltage? –– Maximum ambient temperature? –– Is there any other power applied during the pulse? • Repetitive Pulse –– Resistor value and tolerance? –– Voltage or current? –– On time - off time? –– Number of repetitions? –– Maximum ambient temperature? –– Is there any other power applied during the pulse? Pulse applications often fall into one of three categories: square wave, capacitive charge/discharge, or exponential decay. An example of the pulse energy calculation for each of these will be shown in the following sections. Square Wave A constant voltage or current is applied across a resistor for a given pulse duration. E = Pt 2 P = V or I2R R V or I Where: E =Energy (watt-seconds, W·s, or Joules, J) P = Pulse power (watts, W) t = Pulse duration (seconds, s) V = Pulse voltage (volts, V) R = Resistance (ohms, Ω) I = Pulse current (amps, A) Example A single square wave pulse with an amplitude of 100 VDC for 1 ms is applied to a 10 Ω resistor. What is the pulse energy? t P= V2 = (100 V)2 = 1 kW 10 Ω R E = Pt = 1 kW x 1 ms = 1 W·s or J Capacitive Charge/Discharge A capacitor is charged to a given voltage and then discharged through a wirewound resistor. E= CV2 2 Where: E =Energy (W·s or J) C =Capacitance (farads, F) V = Peak voltage (V): VDC or VRMS × 2 V Example A 2 µF capacitor is charged to 400 VDC and discharged into a 1 kΩ resistor. What is the pulse energy this will produce? 2 E = CV = 2 Capabilities 2 µF x (400 V)2 2 = 0.16 W·s or J 3/8 VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Exponential Decay/Lightning Surge Resistors - Solutions for Your Application The application reaches a peak voltage and decreases at a rate proportional to its value. This is typically modeled by DO-160E WF4 or IEC 6100-4-5 and represents a lightning surge. Peak E= V ) (( + V2 x τ -2xR ) ( x e - 2 x (t3 - t1) τ )) -1 Where: E =Energy (W·s or J) V = Peak voltage (V): VDC or VRMS × 2 R = Resistance (Ω) t1= Time to peak voltage (s) t2= Time to 50 % of peak voltage (s) t3= Time to negligible voltage (s)* τ =Exponential rate of decay 50 % 0 ( 1 x V2 x t 1 3 R t1 t2 ..t3 t *N ote that if no t3 is provided, it is assumed to be greater than 20 times t2 Example Following DO-160E WF4, the peak voltage is 4 kV over a 100 Ω resistor, with the corresponding times: t1 = 1.2 µs t2 = 50 µs t3 = not provided; for the calculation it will be 20 x 50 µs = 1 ms τ=- E= (t2 - t1) (50 µs - 1.2 µs) == 70.4 µs ln (0.50) ln (0.50) ( 1 (4 kV)2 x x 1.2 µs 100 Ω 3 Capabilities ) (( + (4 kV)2 x 70.4 µs - 2 x 100 Ω ) ( x e - 2 x (1 ms - 1.2 µs) 70.4 µs 4/8 )) -1 = 5.51 W·s, or J VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Resistors - Solutions for Your Application Equally Spaced Repetitive Pulses When calculating pulse handling capability for repetitive pulses, the average power as well as the individual pulse energy must be considered. This is because the average power establishes some average heat rise on the part, which uses up some percentage of the part’s energy capability. That portion of the energy not used by average power is then available to handle the instantaneous pulse energy. When the two percentages (average power to rated power and pulse energy to pulse handling capability) are added together, they must not exceed 100 % of the part’s overall rating. Example The following example is provided based upon an equally spaced repetitive square wave pulse. Where: V = Pulse voltage (V) l = Pulse current (A) t = Pulse width (s) T =Cycle time (s) P = Pulse power (W) PAvg =Average power (W) E =Energy (W∙s or J) V or l t T 2 1. The pulse power, P = V or I2R, is calculated for a single pulse R Pt 2. The average power is calculated as follows: PAvg = T 3. Calculate the pulse energy: E = Pt 4. Calculate the percentage of average power to rated power (PR): Percentage (power) = PAvg x 100 PR 5. V ishay Dale engineering can provide the pulse handling capability (ER) given a resistor model, resistance value, and ambient temperature 6. Calculate the percentage of pulse energy to pulse handling capability: Percentage (energy) = E x 100 ER 7. Add the percentages in (4) and (6). If the percentage is less than 100 %, the resistor chosen is acceptable. If the percentage is greater than 100 %, a resistor with a higher power rating or higher pulse handling capability should be selected. Contact Vishay Dale engineering to determine the best resistor choice for your application. Example A series of equally spaced square wave pulses with an amplitude of 200 VDC, a pulse width of 20 ms, and a cycle time of 20 s, is applied to an RS007 100 Ω resistor at an ambient temperature of 25 °C. 2 2 1. The pulse power is: P = V = (200 V) = 400 W R 100 Ω 400 W x 0.02 s Pt 2. The average power is: PAvg = = = 0.4 W 20 s T 3. The pulse energy is calculated: E = Pt = 400 W x 0.02 s = 8.0 W∙s, or J 4. The RS007 resistor has a rated power (PR) of 7 W. The percentage of average power to rated power is calculated: PAvg 0.4 W X 100 = X 100 = 5.7 % 7.0 W PR 5. The pulse handling capability (ER) provided by Vishay Dale engineering at an ambient temperature of 25 °C is 15.3 J 6. The percentage of pulse energy to pulse handling capability is calculated: E x 100 = 8.0 J x 100 = 52.3 % 15.3 J ER 7. The percentages calculated in (4) and (6) are added: 5.7 % + 52.3 % = 58 % Since this percentage is less than 100 % of the overall rating, the RS007 style resistor will sufficiently handle the pulse. Capabilities 5/8 VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Vishay Dale Resistors - Solutions for Your Application Non-Inductive Resistors Non-inductive power resistors consist of two windings, each of which is twice the finished resistance value. For this reason, the energy capability will nearly always be greater than a standard wound unit. To calculate the energy capability needed for non-inductive styles, compute the energy per ohm (J/Ω) by dividing the energy by four times the resistance value. Example What is the energy per ohm pulse handling capability required to handle a 0.2 J pulse applied to a 500 Ω resistor? The energy per ohm needed is: 0.2 J E = = 100 x 10 -6 J/Ω 4R 4 x 500 Ω This can be provided to Vishay Dale engineering in order to find the best product for the application. Voltage Limitations Short pulses – No overload voltage rating has ever been established for wirewound resistors when pulsed for short durations. Sandia Corporation has performed a study on our NS and RS resistors using 20 µs pulses. This study indicates that this type of unit will take about 20 kV per inch as long as the pulse handling capability is not exceeded. Long pulses – For pulses between the cross-over point to 5 s, the recommended maximum overload is √10 times the maximum working voltage for the 4 W size and larger, and √5 times the maximum working voltage for sizes smaller than 4 W. Fusible Resistors If the goal of the application is for the resistor to fuse open under a specific condition, Vishay Dale offers fusible resistors. Reference page seven for common RS fuse resistor types, or click the following link for the entire datasheet: www.vishay.com/doc?30232. Capabilities 6/8 VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS RS Style Wirewound Fuse Resistor Vishay Dale Dale RS Style Wirewound Fuse Vishay Resistor Vishay Dale Fast-Acting, MoldedStyles, Styles, Custom Custom Designed Designed For Fast Acting, Molded For Your Your Application Application Resistors - Solutions for Your Application Features Fast Acting, Molded Styles, Custom Designed For Your Application • • • • • • • TYPICAL ELECTRICAL SPECIFICATIONS Low temperature coefficient (down to 30 ppm/°C) FEATURES High temperature silicone molded package •FEATURES Low temperature (derated to 200 °C)coefficient (down to 30 ppm/°C) Available • High temperature silicone molded package Available • (derated Low temperature coefficient to 30 ppm/°C) Performs function of resistor(down and series fuse and provides to 200 °C) Available High temperature silicone molded package predictable fusing times •• Performs function of resistor and series fuse and provides (derated to 200 °C) predictable fusing times Complete • Performswelded functionconstruction of resistor and series fuse and provides • Complete construction predictablewelded fusing times No flaming oror distortion of conditions •• No flaming distortion ofunit unitunder under fusing fusing conditions Complete welded construction Ideal squib applications and protection of of •• Ideal for Squib circuit and protection No for flaming or circuit distortion ofapplications unit under fusing conditions devices semiconductor devices • semi-conductor Ideal for Squib circuit applications and protection of semi-conductor devices • Negligible noiseand andvoltage voltagecoefficient coefficient Negligible noise • Negligible noise and voltage coefficient TYPICAL ELECTRICAL SPECIFICATIONS The following are offered as examples of reliable designs. Hundreds of possible combinations are available for meeting your requirements. Thefactory following offered asaddress examples reliable Hundreds of possible combinations are available for meeting your requirements. Contact byare using email inof the footerdesigns. of this page, for assistance. Higher wattages available. Contact factory by using email address in the footer of this page, for assistance. Higher wattages available. 1.0 W CONTINUOUS POWER (1) FUSING PARAMETERS 1.0 W CONTINUOUS POWER (1) FUSING PARAMETERS TOLERANCE GLOBAL HISTORICAL RESISTANCE TYPICAL CONTINUOUS CROSSOVER TOLERANCE GLOBAL HISTORICAL FUSING RESISTANCE ±% MODEL MODEL RANGE Ω FUSING FUSING TYPICAL CONTINUOUS CROSSOVER TIME CURRENT VALUE ±% MODEL MODEL CURRENT RANGE Ω CURRENT FUSING CURRENT VALUE A ms TIME A Ω A ms A Ω RS01A...209 RS-1A-209 0.5 4 49 500 5, 10 0.10 100.0 RS01A...209 RS-1A-209 0.5 4 49 - 500 5, 10 0.10 100.0 RS01A...118 1.01.0 99 6.8 5, 10 10 0.25 16.0 RS01A...118 RS-1A-118 RS-1A-118 6.8--185 185 5, 0.25 16.0 RS01A...212 1.25 88 4.7 5, 10 10 0.30 11.11 RS01A...212 RS-1A-212 RS-1A-212 1.25 4.7--107 107 5, 0.30 11.11 RS01A...213 1.51.5 1515 3.5 5, 10 10 0.35 8.16 RS01A...213 RS-1A-213 RS-1A-213 3.5--68 68 5, 0.35 8.16 RS01A...143 2.02.0 1515 2.2 5, 10 10 0.40 6.25 RS01A...143 RS-1A-143 RS-1A-143 2.2--35 35 5, 0.40 6.25 RS01A...214 2.52.5 2323 1.7 5, 10 10 0.45 4.94 RS01A...214 RS-1A-214 RS-1A-214 1.7--23 23 5, 0.45 4.94 RS01A...162 RS-1A-162 RS-1A-162 1.1--12 12 5, 0.55 3.31 RS01A...162 3.03.0 4848 1.1 5, 10 10 0.55 3.31 RS01A...208 RS-1A-208 RS-1A-208 0.72--6.44 6.44 5, 0.75 1.78 RS01A...208 4.04.0 4747 0.72 5, 10 10 0.75 1.78 RS01A...207 RS-1A-207 RS-1A-207 0.35--2.17 2.17 5, 1.0 1.01.0 RS01A...207 6.06.0 7070 0.35 5, 10 10 1.0 RS01A...215 RS-1A-215 RS-1A-215 0.29--1.61 1.61 5, 1.25 0.64 RS01A...215 8.08.0 4848 0.29 5, 10 10 1.25 0.64 RS01A...173 RS-1A-173 RS-1A-173 10.0 0.23--1.16 1.16 5, 1.50 0.44 RS01A...173 10.0 5050 0.23 5, 10 10 1.50 0.44 RS01A...216 RS-1A-216 RS-1A-216 15.0 0.19--0.82 0.82 5, 1.75 0.33 RS01A...216 15.0 3535 0.19 5, 10 10 1.75 0.33 RS01A...217 RS-1A-217 20.0 46 0.12 - 0.42 5, 10 2.0 0.25 RS01A...217 RS-1A-217 20.0 46 0.12 - 0.42 5, 10 2.0 0.25 Note Note (1) The Continuous Current Rating applies only to values equal to or less than the Crossover Value. The Continuous Power Rating applies only (1) The Continuous Current Rating applies only to values equal to or less than the Crossover Value. The Continuous Power Rating applies only to values equal to or higher than the Crossover Value. to •values equal that to orthe higher thancompromise the Crossover Value.between resistive and fusing functions sometimes makes certain exact combinations Be aware inherent involved • Be aware that the However, inherent in compromise involved between resistive fusing of functions sometimes makes certain exact combinations unattainable. nearly all cases, this does not prevent the and production a functional, reliable fuse resistor thoroughly capable of unattainable. However, in nearly all cases, this does not prevent the production of a functional, reliable fuse resistor thoroughly capable of meeting application requirements. meeting application requirements. GLOBAL PART NUMBER INFORMATION GLOBAL PART NUMBER INFORMATION Global Part Numbering example: RS01A402R0JS70209 Global PartRNumbering example: S 0 1 RS01A402R0JS70209 A 4 0 R S 0 1 GLOBAL MODEL (See Typical Electrical GLOBAL MODEL Specifications Global A 4 VALUE 0 2 2 R R TOLERANCE R = Decimal VALUE 15R00 = 15 Ω J = ± 5.0 % TOLERANCE K = ± 10.0 % Historical PartRS-1A-209 Numbering example: RS-1A-209 402 402ΩΩ 5 % S70 RS-1A-209 J J S S 7 7 0 0 PACKAGING R = Decimal J = ± 5.0 % (See Typical ModelElectrical column for 15R00 = 15 Ω K = ± 10.0 % Specifications Global options) Model column for options) Part Numbering example: RS-1A-209 402 Ω 5 % S70 Historical HISTORICAL MODEL 0 0 RESISTANCE VALUE 402 Ω E70 = Lead (Pb)-free, tape/reel PACKAGING E12 = Lead (Pb)-free, bulk E70 = Lead (Pb)-free, tape/reel S70==Lead Tin/lead, tape/reel E12 (Pb)-free, bulk B12 = Tin/lead, bulk S70 = Tin/lead, tape/reel B12 = Tin/lead, bulk 2 2 0 0 9 SPECIAL (DashSPECIAL Number) (up to 3 digits) (Dash From 1 -Number) 999 to 3 digits) as(up applicable From 1 - 999 as applicable 5% S70 TOLERANCE CODE PACKAGING 5% 9 S70 If a MODEL listed in TYPICAL ELECTRICAL SPECIFICATIONS table does not meet your requirements, then please include the following HISTORICAL RESISTANCE VALUE information. ItMODEL will enable us to choose the best design for your application.TOLERANCE CODE PACKAGING 1. Operating wattage or current, ambient temperature and required resistance stability. (% ΔR/1000 h) If a MODEL listed in TYPICAL ELECTRICAL SPECIFICATIONS does “blow” not meet your requirements, then please include the following 2. Fusing wattage or current and maximum “blow” time. Also,table minimum time, if applicable. information. It will enable us choose the best design for your application. 3. Nominal resistance andtomaximum allowable resistance tolerance, (5 % to 10 % preferred). 1. Operating wattage or current, ambient temperature and required resistance stability. (% ΔR/1000 h) 4. Maximum allowable physical size. 2. Fusing wattage or interrupted. current and maximum “blow” time. Also, minimum “blow” time, if applicable. 5. Voltage to be 3. Nominal resistance and maximum allowable resistance tolerance, % application. to 10 % preferred). 6. Frequency of power source, wave form and a brief description of (5 your 4. Maximum allowable physical size. 5. Voltage to be interrupted. 6. Frequency of power source, wave form and a brief description of your application. Document Number: 30232 Capabilities Revision: 12-Jan-11 For technical questions, contact: [email protected] 7/8 www.vishay.com VMN-PL0396-1302 1 Document Number: 30232 For technical questions, contact: [email protected] www.vishay.com This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO Revision: 12-Jan-11 1 SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000 V i s h ay I n t e r t e c h n o l o g y, I n c . WIREWOUND RESISTORS Resistors - Solutions for Your Application Vishay Dale Worldwide Sales Contacts The Americas EUROPE United states Germany Vishay Americas One Greenwich Place Shelton, CT 06484 United States Ph: +1-402-563-6866 Fax: +1-402-563-6296 Vishay Electronic GmbH Dr.-Felix-Zandman-Platz 1 95100 Selb Germany Ph: +49-9287-71-0 Fax: +49-9287-70435 Asia france singapore Vishay intertechnology Asia Pte Ltd. 37A Tampines Street 92 #07-00 Singapore 528886 Ph: +65-6788-6668 Fax: +65-6788-0988 Vishay S.A. 199, bd de la madelEine 06003 nice, cedex 1 France Ph: +33-4-9337-2727 Fax: +33-4-9337-2726 p.r. China united kingdom Vishay China Co., Ltd. 15D, Sun Tong Infoport Plaza 55 Huai Hai West Road Shanghai 200030 P.R. China PH: +86-21-5258 5000 FAX: +86-21-5258 7979 Vishay Ltd. Suite 6C, Tower House St. Catherine’s Court Sunderland Enterprise Park Sunderland SR5 3XJ UNITED KINGDOM Ph: +44-191-516-8584 Fax: +44-191-549-9556 japan VISHAY JAPAN CO., LTD. Shibuya Prestige Bldg. 4F 3-12-22, Shibuya Shibuya-ku Tokyo 150-0002 Japan Ph: +81-3-5466-7150 fax: +81-3-5466-7160 Capabilities 8/8 VMN-PL0396-1302 This document is subject to change without notice. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000