RES-WFH Datasheet, PDF (1/2 Pages) Ohmite Mfg. Co. – Multiple resistors in one profile possible

WFH Series
Aluminum Housed Wirewound Power
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.
F e at u r e s
• Solder lug, wire, and “Fast-on” amp ter-
minations
• Multiple resistors in one profile possible
• Custom wire lengths available
S ERIE S S P ECI F ICATI O N S

Power Rating*
Type
(watts)
WFH90
90
WFH160
160
WFH230
230
WFH330
330
*at 40°C base plate temperature
Resistance Range
(Ω)
0.22Ω – 6.8K
0.47Ω-18K
0.82Ω-27K
1Ω - 39K
characteristics
Power rating 90W-330W
Resistance ±5%, ±10%
tolerance
Temperature Normal: 50ppm - 150ppm
Coefficients Low ohmic values: 400ppm
Dielectric 2500 VAC peak
strength
Working voltage 1200 VAC
Test voltage 6000 VAC
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 & -40˚C
Operating Temp.
Power Dissipation
350
300
WFH330
250
200 _WFH230
150
WFH160
100
50 ^WFH90
0
40°
60°
80°
100°
120°
Heat Sink Temperature, °C
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.
140°
Thermal Resistances
Thermal Resistance (°C/W) between different
measuring points
WFH90 WFH160 WFH230 WFH330
R_TH1 2
1
0.75 0.5
R_TH2 6.8
3.9
2.75 2
R_TH3 0.1
0.05 0.03
0.02
R_TH4 0.3
0.17
0.1
0.085
resistor
surface to
heat sink
R_TH4
aluminum
housing
to air
R_TH2
R_TH3
aluminum
housing to
heat sink
R_TH1
wire to
aluminum
housing
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.
1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax [phone] • www.ohmite.com • [e-mail]
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