WFH OHMITE | Alldatasheet

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1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com 133 WFH Series Aluminum Housed Wirewound Power Power rating 90W-330W Resistance tolerance ±5%, ±10% Temperature Coefficients Normal: 50ppm - 150ppm Low ohmic values: 400ppm Dielectric strength

2500 VAC peak

Lead wire (wire terminal version only): XLPE, 600V, 125C,

18 AWG stranded

Insulation Silicone Rubber & Mica. The Silicone is UL-recognised (UL 94 HB) to a working tem- perature of 220°C. Temperatures of up to 300°C can be endured for shorter periods. This may however cause an expansion of the silicone rubber with a possibility of reducing the dielectric strength. Min. Storage & Operating Temp. -40˚C Power Rating* Resistance Range Type (watts) (Ω) WFH90 90 0.22Ω – 6.8K WFH160 160 0.47Ω-18K WFH230 230 0.82Ω-27K WFH330 330 1Ω - 39K *at 40°C base plate temperature W/Resistor Heat Sink Temperature, °C 40° 60° 80° 100° 120° 140° 100 150 200 300 250 350 WFH330 WFH160 WFH230 WFH90 Power Dissipation Ohmite’s new flat core winding technology allows for wire- wound heatsinkable resistors affording a very low profile, and superior thermal transfer characteristics when compared to conventional aluminum housed wirewound resistors. Close mounting of heat sensitive components is possible due to only a slight rise of the temperature on the aluminum profile. No heat sink compound is required because of large mount- ing surface. This graph shows the maxi- mum wattage rating for each possible resistor of standard size corresponding to the heat sink temperature. It is assumed that all resistors are equally loaded. resistor surface to heat sink RTH4 RTH1 wire to aluminum housing aluminum housing to air RTH2 RTH3 aluminum housing to heat sink Thermal Resistances Thermal Resistance (°C/W) between different measuring points WFH90 WFH160 WFH230 WFH330 RTH1 2 1 0.75 0.5 RTH2 6.8 3.9 2.75 2 RTH3 0.1 0.05 0.03 0.02 RTH4 0.3 0.17 0.1 0.085 THIS PRODUCT IS DESIGNED FOR USE WITH PROPER HEATSINKING. Maximum base plate temperature of the resistor must be monitored and kept within specified limits to establish the power rating. Best technique is to attach a thermocouple to the side of the base plate of the resistor. Temperature of plastic housing or heat sink cannot be used to establish rating of the resistor.

FeatureS

  • Solder lug, wire, and “Fast-on” amp ter- minations
  • Multiple resistors in one profile possible
  • Custom wire lengths available cHaracteriSticS SerieS SPeciFicatiONS (continued)

1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com134 Series Terminal Type L= lug terminals A= amp terminals W= 30cm insulated wire cable 18AWG Tolerance J = 5% K = 10% Wattage at 40°C base plate temp. Ohms R47= 0.47Ω RoHS Compliant Standard part numbers WFH90L4R7KE WFH90L10RKE WFH90L25RJE WFH90L50RJE WFH90L100JE WFH90L470JE WFH90L750JE WFH90L1K0JE WFH90L2K7JE WFH90L5K0JE WFH160LR47KE WFH160L1R0KE WFH160L2R0KE WFH160L10RKE WFH160L27RJE WFH160L50RJE WFH160L75RJE WFH160L100JE WFH160L150JE WFH160L250JE WFH160L1K0JE WFH160L5K0JE WFH160L10KJE WFH230L1R0KE WFH230L2R0KE WFH230L5R0KE WFH230L10RKE WFH230L27RJE WFH230L50RJE WFH230L75RJE WFH230L100JE WFH230L150JE WFH230L250JE WFH230L1K0JE WFH230L1K5JE WFH230L2K5JE WFH330L1R0KE WFH330L2R0KE WFH330L10RKE WFH330L27RJE WFH330L50RJE WFH330L75RJE WFH330L100JE WFH330L150JE WFH330L250JE WFH330L1K0JE WFH330L5K0JE WFH330L10KJE The following equations are applied in the dimensioning of the resistors at stationary load. If more information is required please consult Ohmite. It is as- sumed that the air around the resistors is stationary (worst case). See ohmite.com for more examples. dimeNSiONS (mm)

OrderiNg iNFOrmatiON

4.8 0.6ø2.2 300 Wire terminal Lug terminal A B 6.3 5141 13.6 12.6 0.8ø4.5 L Amp terminal WFH Series Aluminum Housed Wirewound Power 1. WFH is mounted on a heat sink: A. The thermal resistance RTH of the heat sink is known, T = WMAX x (RTH4 + RTH) Check that: T MAX = WMAX x (RTH + RTH3 + RTH1) + TAMB <220°C B. The Temperature of the Heat Sink is known, T = W MAX x RTH4 + TH Check that: T MAX = WMAX x (RTH1 + RTH3) + TH <220°C 2. WFH is mounted without a heat sink: Check that: T MAX = WMAX x (RTH1 + RTH2 ) + TAMB <220°C Where: W MAX = Maximum reguired load in resistor TMAX = Maximum hot spot temperature reguested in resistor (TMAX <220°C) The lower TMAX the higher reliability and lifetime. TAMB = Ambient temperature RTH = Thermal resistance. Refer to table Thermal resistances TH = Heat sink temperature (chassis). T = Temperature on top of the Aluminum profile. Type Watts A B L WFH90 90 70 39.7 53 WFH160 160 140 80 123 WFH230 230 210 2x 80 193 WFH330 330 280 2x 100 263