Ohmite WFH Series Data Sheet
WFH Series
W/Resistor
Heat Sink Te mperature, °C
40° 60° 80° 100° 120° 140°
100
150
200
300
50
250
350
0
WFH330
WFH160
WFH230
WFH90
resistor
surface to
heat sink
R
TH
4
R
TH
1
wire to
aluminum
housing
aluminum
housing
to air
R
TH
2
R
TH
3
aluminum
housing to
heat sink
Aluminum Housed Wirewound Power
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.
SERIES SPECIFICATIONS
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
FEATURES
• Solderlug,wire,and“Fast-on”ampter-
minations
• Multipleresistorsinoneprofilepossible
• Customwirelengthsavailable
Power rating
Resistance
tolerance
Temperature
Coefficients
Dielectric
strength
Working voltage
Test voltage
Lead wire
Insulation
Min. Storage &
Operating Temp.
132
CHARACTERISTICS
90W-330W
±5%, ±10%
Normal: 50ppm - 150ppm
Low ohmic values: 400ppm
2500 VAC peak
1200 VAC
6000 VAC
(wire terminal version only): XLPE, 600V, 125C,
18 AWG stranded
Silicone Rubber & Mica. The Silicone is
UL-recognised (UL 94 HB) to a working temperature 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.
-40˚C
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.
Power Dissipation
Thermal Resistances
Thermal Resistance (°C/W) between different
measuring points
WFH90 WFH160 WFH230 WFH330
R
2 1 0.75 0.5
TH
1
R
6.8 3.9 2.75 2
TH
2
R
0.1 0.05 0.03 0.02
TH
3
R
0.3 0.17 0.1 0.085
TH
4
This graph shows the maximum wattage rating for each
possible resistor of standard
size corresponding to the
heat sink temperature. It is
assumed that all resistors
are equally loaded.
(continued)
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
4.8
6
0.6
ø2.2
300
10
Wire
terminal
Lug
terminal
A
B
6.3
51
41
15
13.6
12.6
8 ±1
16 max.
0.8
ø4.5
L ±2
Amp
terminal
WFH Series
Aluminum Housed Wirewound Power
DESIGN INFORMATION
(mm)
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.
Type Watts A B L ±2
WFH90 90 70 39.7 53
WFH160 160 140 80 123
WFH230 230 210 2x 80 193
WFH330 330 280 2x 100 263
1. WFH is mounted on a heat sink:
A. The thermal resistance RTH of the heat sink is known,
B. The Temperature of the Heat Sink is known,
2. WFH is mounted without a heat sink:
Check that:
T
MAX
Where:
W
= Maximum reguired load in resistor
MAX
T
= Maximum hot spot temperature reguested in resistor (T
MAX
The lower T
T
= Ambient temperature
AMB
RTH = Thermal resistance. Refer to table Thermal resistances
= Heat sink temperature (chassis).
T
H
T = Temperature on top of the Aluminum profile.
DIMENSIONS
= W
MAX
T = W
MAX
x (R
TH4
+ RTH)
Check that:
T
= W
MAX
T = W
MAX
x (RTH + R
MAX
x R
TH4
+ TH
TH3
+ R
Check that:
T
= W
x (R
+ R
MAX
MAX
TH1
x (R
+ R
TH2
) + T
TH1
the higher reliability and lifetime.
MAX
) + TH <220°C
TH3
<220°C
AMB
TH1
) + T
AMB
<220°C
<220°C)
MAX
rev 10/19-1
ORDERING INFORMATION
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
133
WFH230L100JE
WFH230L150JE
WFH230L250JE
WFH230L1K0JE
WFH230L1K5JE
WFH230L2K5JE
WFH330L1R0KE
WFH330L2R0KE
WFH330L10RKE
WFH330L27RJE
WFH330L50RJE
WFH330L75RJE
WFH330L100JE
WFH330L150JE
WFH330L250JE
WFH330L1K0JE
WFH330L5K0JE
WFH330L10KJE
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