Ohmite’s new flat core winding technology allows for wirewound 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 mounting surface.
Features
- Solder lug, wire, and “Fast-on” amp terminations
- Multiple resistors in one profile possible
- Custom wire lengths available
Series Specifications
*at 40°C base plate temperature
Characteristics
Power Dissipation
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.
Thermal Resistance (°C/W) between different
measuring points
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.
Dimensions
(mm)
Amp terminal
Lug terminal
Wire terminal
Ordering Information
The following equations are applied in the dimensioning of the resistors at stationary load. If more information is required please consult Ohmite. It is assumed that the air around the resistors is stationary (worst case). See ohmite.com for more examples.
Thermal Management Guidelines
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:
TMAX = WMAX x (RTH + RTH3 + RTH1) + TAMB <220°C
B. The Temperature of the Heat Sink is known,
T = WMAX x RTH4 + TH
Check that:
TMAX = WMAX x (RTH1 + RTH3) + TH <220°C
2. WFH is mounted without a heat sink:
Check that:
TMAX = WMAX x (RTH1 + RTH2 ) + TAMB <220°C
Where:
WMAX = Maximum required load in resistor
TMAX = Maximum hot spot temperature requested in resistor (TMAX <220°C)
TAMB = Ambient temperature
RTH = Thermal resistance. Refer to table Thermal resistances
TH = Heat sink temperature (chassis).
T = Temperature on top of the Aluminum profile.
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