WFH Series Aluminum Housed Wirewound Power Ohmites 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. FeatureS Close mounting of heat sensitive components is possible Solder lug, wire, and Fast-on amp ter- due to only a slight rise of the temperature on the aluminum minations profile. Multiple resistors in one profile possible No heat sink compound is required because of large mount- ing surface. Custom wire lengths available SerieS SPeciFicatiONS Power Rating* Resistance Range Type (watts) () WFH90 90 0.22 6.8K WFH160 160 0.47-18K WFH230 230 0.82-27K WFH330 330 1 - 39K *at 40C base plate temperature cHaracteriSticS Power rating 90W-330W Power Dissipation 5%, 10% Resistance 350 This graph shows the maxi- mum wattage rating for each tolerance 300 possible resistor of standard WFH330 size corresponding to the Temperature Normal: 50ppm - 150ppm 250 heat sink temperature. It is Coefficients Low ohmic values: 400ppm 200 assumed that all resistors WFH230 are equally loaded. 150 Dielectric 2500 VAC peak WFH160 strength 100 WFH90 50 Working voltage 1200 VAC 0 Test voltage 6000 VAC 40 60 80 100 120 140 Heat Sink Temperature, C (wire terminal version only): XLPE, 600V, 125C, Lead wire 18 AWG stranded Thermal Resistances Insulation Silicone Rubber & Mica. The Silicone is Thermal Resistance (C/W) between different resistor measuring points surface to UL-recognised (UL 94 HB) to a working tem- aluminum heat sink perature of 220C. Temperatures of up to housing R to air TH 4 300C can be endured for shorter periods. WFH90 WFH160 WFH230 WFH330 R TH This may however cause an expansion of the R 2 1 0.75 0.5 2 TH 1 silicone rubber with a possibility of reducing R 6.8 3.9 2.75 2 TH 2 the dielectric strength. R R 0.1 0.05 0.03 0.02 TH 1 TH 3 R TH 3 wire to Min. Storage & -40C R 0.3 0.17 0.1 0.085 TH aluminum 4 aluminum housing to Operating Temp. housing heat sink 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. (continued) 1-866-9-OHMITE Intl 1-847-258-0300 Fax 1-847-574-7522 www.ohmite.com info ohmite.com 133 W/ResistorWFH Series Aluminum Housed Wirewound Power deSigN iNFOrmatiON The following equations are 1. WFH is mounted on a heat sink: applied in the dimensioning of A. The thermal resistance RTH of the heat sink is known, the resistors at stationary load. T = W x (R + R ) MAX TH4 TH If more information is required Check that: please consult Ohmite. It is as- T = W x (R + R + R ) + T <220C MAX MAX TH TH3 TH1 AMB sumed that the air around the B. The Temperature of the Heat Sink is known, resistors is stationary (worst T = W x R + T MAX TH4 H case). See ohmite.com for more Check that: examples. T = W x (R + R ) + T <220C MAX MAX TH1 TH3 H 2. WFH is mounted without a heat sink: Check that: T = W x (R + R ) + T <220C MAX MAX TH1 TH2 AMB Where: W = Maximum reguired load in resistor MAX T = Maximum hot spot temperature reguested in resistor (T <220C) MAX MAX The lower T the higher reliability and lifetime. MAX T = Ambient temperature AMB R = Thermal resistance. Refer to table Thermal resistances TH T = Heat sink temperature (chassis). H T = Temperature on top of the Aluminum profile. dimeNSiONS (mm) Type Watts A B L WFH90 90 70 39.7 53 10 WFH160 160 140 80 123 WFH230 230 210 2x 80 193 WFH330 330 280 2x 100 263 300 12.6 L 4.8 6.3 0.8 2.2 4.5 0.6 8 6 13.6 Amp 41 51 terminal Lug Wire 15 terminal terminal B A OrderiNg iNFOrmatiON Standard part numbers RoHS Compliant WFH90L4R7KE WFH160LR47KE WFH160L1K0JE WFH230L100JE WFH330L50RJE Tolerance WFH90L10RKE WFH160L1R0KE WFH160L5K0JE WFH230L150JE WFH330L75RJE Series Wattage Terminal Type Ohms J = 5% at 40 C L= lug terminals R47= 0.47 WFH90L25RJE WFH160L2R0KE WFH160L10KJE WFH230L250JE WFH330L100JE K = 10% base plate A= amp terminals WFH90L50RJE WFH160L10RKE WFH230L1R0KE WFH230L1K0JE WFH330L150JE temp. W= 30cm insulated wire cable 18AWG WFH90L100JE WFH160L27RJE WFH230L2R0KE WFH230L1K5JE WFH330L250JE WFH90L470JE WFH160L50RJE WFH230L5R0KE WFH230L2K5JE WFH330L1K0JE WFH90L750JE WFH160L75RJE WFH230L10RKE WFH330L1R0KE WFH330L5K0JE WFH90L1K0JE WFH160L100JE WFH230L27RJE WFH330L2R0KE WFH330L10KJE WFH90L2K7JE WFH160L150JE WFH230L50RJE WFH330L10RKE WFH90L5K0JE WFH160L250JE WFH230L75RJE WFH330L27RJE 134 1-866-9-OHMITE Intl 1-847-258-0300 Fax 1-847-574-7522 www.ohmite.com info ohmite.com