Flameproof Metal Oxide Resistors WMO-S Series Cost effective Small size for power rating Good pulse handling capability Flameproof protection Electrical Data WMO½S Power rating @70°C watts Resistance range ohms Limiting element voltage volts TCR (25 to 75°C) ppm/°C Isolation Voltage volts Resistance tolerance WMO1S ½ 1 250 300 WMO3S WMO5S 2 3 5 10R 100K 500 350 350 350 250 500 5 % E24 Standard Values Thermal Impedance WMO2S °C/watt Ambient temperature range 105 125 75 63 42 -55 to +155 °C Physical Data Dimensions (mm) and Weight (g) Type L max. D max. f min. d nom. PCB mounting centres WMO½S WMO1S Min. bend radius Wt. nom. 7.5 3 27 0.6 10 4.5 27 0.7 12.7 0.6 0.22 15.2 1.05 0.42 WMO2S 12 5 28 0.7 17.8 1.05 0.63 WMO3S 16 5.5 28 0.8 20.3 1.2 1.0 WMO5S 26 8.5 38 0.8 30.5 1.2 3.7 D d L f General Note Welwyn Components reserves the right to make changes in product specification without notice or liability. All information is subject to Welwyns own data and is considered accurate at time of going to print. © Welwyn Components Limited Bedlington Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: [email protected] Website: www.welwyn-tt.com A subsidiary of TT electronics plc Issue A . 11.06 WMO-S Series Construction The resistive film is deposited onto a high purity ceramic rod. End caps are force fitted and termination wires are welded to the end caps. The element is adjusted to the required resistance value by a helical cut. Finally a cement protection is applied to the resistor body prior to marking with indelible ink. Marking WMO-S resistors are colour coded with four bands indicating value and tolerance in accordance with IEC62. 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 under any condition of applied temperature or component overload. Performance Data Maximum Load at Rated Power: 1000hrs @ 70°C DR% Short term (5s) overload DR% 5 2 + 0.05W See derating curve Derating Temperature cycling DR% 2 + 0.05W Moisture resistance DR% DR% 5 Resistance to solder heat 1 >10 GW Insulation resistance WMO-S Series Derating Curve % of Rated Power at 70 ºC 100 45 0 70 155 235 Ambient temperature (ºC) © Welwyn Components Limited Bedlington Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: [email protected] Website: www.welwyn-tt.com Issue A . 11.06 WMO-S Series 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. An estimate of the temperature rise to be expected can be calculated using the thermal impedance figures given under Electrical Data. 3. WMO-S resistors can also be supplied with radial, goalpost or lancet pre-formed leads. Consult Factory for details. Goalpost Radial Lanset Packaging Our standard packaging for WMO-S is taped and boxed. The critical dimensions are shown in Figure 1. The component wires will not protrude beyond the outside edge of the tapes. Pre-formed resistors are supplied loose packed in plastic bags or boxes. Dimensions mm WMO½S WMO1S WMO2S WMO3S WMO5S A 52 52 52 67 85 B 5 5 5 10 10 Figure 1 B 6 f1 f2 A 6 Body location f1-f2 < 1.4mm Ordering Procedure Specify type reference, value and tolerance as shown in this example of WMO3S at 1.5KW, 5%: W MO 3 S 1 K 5 J A 1 T ype Value (use IE C62 code) T olerance (use IE C 62 code) J 5% P acking Code A5 A1 A05 Ammo Pack WMO1 2 S 5000 / Box WMO1S, WMO2S, WMO3S 1000 / Box WMO5S 500 / Box © Welwyn Components Limited Bedlington Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: [email protected] Website: www.welwyn-tt.com Issue A . 11.06