Wirewound High Surge Resistors WHS Series · Enhanced surge & pulse energy capacity · UL94-V0 flameproof protection · Radial taped form available · Surface mount Z-form available · RoHS compliant with Pb-free terminations Electrical Data WHS2 WHS3 WHS5 WHS7 Power rating at 25ºC watts 2 3 5 7 5s overload rating at 25ºC watts 10 15 25 35 Short pulse performance See Pulse Performance graphs Resistance range ohms TCR 1R0-330R ppm/ºC Isolation Voltage volts Resistance Tolerance 200 250 350 % 500 <20R: 5 Standard Values 700 ≥20R: 1, 2, 5 E12 preferred Thermal Impedance ºC/watt Ambient temperature range 110 82 ºC 54 35 -55 to +155 No Limiting Element Voltage applies to this series; the Rated Voltage is √(P.R). Physical Data Dimensions (mm) & Weight (g) Type L max D max f min d nom PCB mount centres Min bend radius Wt. nom WHS2 9.0 3.6 19.80 12.70 0.50 WHS3 14.5 5.2 24.55 20.30 1.10 WHS5 16.5 7.0 23.55 WHS7 25.0 8.8 28.30 0.8 22.86 31.40 1.2 1.75 d D L f 4.40 Construction A high purity ceramic substrate is assembled with interference fit end caps to which are welded the terminations. The resistive element is wound on the substrate and welded to the caps. Flameproof silicone cement coating is applied priorto marking with indelible ink. The components are then leadformed if required and packed. General Note TT electronics reserves the right to make changes in product specification without notice or liability. All information is subject to TT electronics’ own data and is considered accurate at time of going to print. www.bitechnologies.com www.irctt.com www.welwyn-tt.com © TT electronics plc 08. 12 Wirewound High Surge Resistors WHS Series Terminations Material: Strength: Solderability: Hot tin dipped copper wire The terminations meet the requirements of IEC 68.2.21 The terminations meet the requirements of IEC 115-1 Clause 4.17.3.2 Marking WHS2, and WHS3 resistors are marked with four colour bands in conformance with IEC62. WHS5 and WHS7 resistors are legend marked with type reference, resistance value and tolerance. Solvent Resistance The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits. Flammability The resistor coating will not burn or emit incandescent particles under any condition of applied temperature or power overload. Performance Data Maximum Typical Load at rated power: 1000hrs @ 25°C ΔR% 5 +0.001Ω 3 Dry heat: 1000hrs @ 200°C ΔR% 5 +0.001Ω 3 Short term overload ΔR% 5 +0.001Ω 1 ΔR% 5 +0.001Ω Derating from rated power @25°C Climatic Zero at 280°C (See Thermal Performance graph). 2 Climatic category 55/200/56 TRC & Vibration ΔR% 5 +0.001Ω 1 Robustness & solder heat ΔR% 5 +0.001Ω 1 Long term damp heat (56 days) ΔR% 5 +0.001Ω 1 Pulse Performance Surge / Pulse Energy Capacity (single or low repetition rate, R < 5%) Energy (joules) 100 WHS7 WHS5 10 WHS3 1 WHS2 1 10 100 1000 Value (ohms) General Note TT electronics reserves the right to make changes in product specification without notice or liability. All information is subject to TT electronics’ own data and is considered accurate at time of going to print. www.bitechnologies.com www.irctt.com www.welwyn-tt.com © TT electronics plc 08. 12 Wirewound High Surge Resistors WHS Series s Peak Voltage Limit Peak Voltage (kV) (10 pulses at 30s intervals, R < 5%) Note the voltage shown is the nett voltage across the resistor. At low values, the generator open circuit voltage will be higher due to the generator's 2 ohm internal impedance. 10 1 0.1 1 10 100 1000 Value (ohms) Thermal Performance Body Temperature Rise 80 60 40 20 WHS5 WHS3 250 TemperatureRise Rise (°C) (°C) Temperature Proportion of Rated Power (%) 300 100 WHS7 WHS2 200 150 100 50 0 0 0 50 100 150 200 250 300 350 0 Ambient Temperature °C (°C) Am bient Tem perature 1 2 3 4 5 6 7 8 9 10 Power (W) Application Notes 1. If the resistors are to dissipate full rated power, it is recommended that the terminations should not be soldered closer than 4mm from the body. 2. Due to operating temperature limits imposed by some PCB materials, derating may be necessary. The surface temperature rise at the centre of the body is shown under Thermal Performance. 3. WHS2, WHS3, WHS5 resistors can also be supplied with goalpost or lancet pre-formed leads. Radial form is available on WHS2 and WHS3 only. WHS2, WHS3, and WHS5 are also available in an SMD format with Z formed leads and packed in blister tape. See the Z-form datasheet for details http://www.welwyn-tt.com/pdf/datasheet/Z-form.pdf General Note TT electronics reserves the right to make changes in product specification without notice or liability. All information is subject to TT electronics’ own data and is considered accurate at time of going to print. www.bitechnologies.com www.irctt.com www.welwyn-tt.com © TT electronics plc 08. 12 Wirewound High Surge Resistors WHS Series Radial Goalpost Lancet Z-form Packaging The standard packaging for WHS is taped. The critical dimensions are shown in Figure 1. The component wires will not protrude beyond the outside edge of the tapes. Taped product is then packed into boxes or onto reels. See Ordering Procedure for details. Alternative packaging is available by request. Pre-formed resistors are supplied loose packed in plastic bags or boxes. Dimensions mm b c WHS2 52 5 WHS3 67 10 WHS5 63 10 *WHS7 85 10 Figure 1 c *An offset lead length is available for WHS7 series. Consult factory for details 6 f1 f2 b 6 -f2 < 1.4mm Ordering Procedure Example: WHS2 at 100 ohms and 5% tolerance in ammo pack box of 2500 pieces WHS2 – 100R J A25 Type Value (use IEC62 code) Tolerance (use IEC62 code) F 1% G 2% J 5% Packing A25 A1 T075 T07 Tape Ammo WHS2 2500/box WHS3 1000/box WHS5 750/reel WHS7 700/reel Standard General Note TT electronics reserves the right to make changes in product specification without notice or liability. All information is subject to TT electronics’ own data and is considered accurate at time of going to print. www.bitechnologies.com www.irctt.com www.welwyn-tt.com © TT electronics plc 08. 12