WMO-S

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 Resistance range Limiting element voltage TCR (25 to 75°C) Isolation Voltage Resistance tolerance Standard Values Thermal Impedance °C/watt °C 125 105 Ambient temperature range watts ohms volts ppm/°C volts % 250 5 E24 75 -55 to +155 63 42 250 300 350 350 500 ½ WMO1S 1 WMO2S 2 10R – 100K 350 500 WMO3S 3 WMO5S 5 Physical Data Dimensions (mm) and Weight (g) Type WMO½S WMO1S WMO2S WMO3S WMO5S L max. 7.5 10 12 16 26 D max. 3 4.5 5 5.5 8.5 D f min. 22 21 20 25 29 d nom. 0.6 0.7 0.7 0.8 0.8 PCB mounting centres Min. bend radius 0.6 1.05 1.05 1.2 1.2 Wt. nom. 0.22 0.42 0.63 1.0 3.7 12.7 15.2 17.8 20.3 30.5 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 Welwyn’s 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: info@welwyn-tt.com Website: www.welwyn-tt.com A subsidiary of TT electronics plc Issue B . 03.07 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 Short term (5s) overload Derating Temperature cycling Moisture resistance Resistance to solder heat Insulation resistance DR% DR% DR% DR% DR% GW 5 2 + 0.05W See derating curve 2 + 0.05W 5 1 >10 WMO-S Series Derating Curve 100 % of Rated Power at 70 ºC 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: info@welwyn-tt.com Website: www.welwyn-tt.com Issue B . 03.07 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. Radial Goalpost 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 B 52 5 52 5 Figure 1 52 5 67 10 85 10 B 6 f1 A f2 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%: T ype Value (use IE C62 code) T olerance (use IE C 62 code) J 5% P acking Code W MO 3 S – 1 K 5 J A 1 A5 A1 A05 Ammo Pack WMO1 2 S WMO1S, WMO2S, WMO3S WMO5S 5000 / Box 1000 / Box 500 / Box © Welwyn Components Limited Bedlington Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 Facsimile: +44 (0) 1670 829465 Email: info@welwyn-tt.com Website: www.welwyn-tt.com Issue B . 03.07