WFH Series

WFH Series
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.
F e at u r e s
•Solder lug, wire, and “Fast-on” amp terminations
•Multiple resistors in one profile possible
•Custom wire lengths available
S ERIE S S P ECI F ICATI O N S
Type WFH90
WFH160
WFH230
WFH330
Power Rating*
(watts) 90
160
230 330 Resistance Range
(Ω)
0.22Ω – 6.8K
0.47Ω-18K
0.82Ω-27K
1Ω - 39K
*at 40°C base plate temperature
characteristics
Power Dissipation
Power rating 90W-330W
Resistance ±5%, ±10%
tolerance
Dielectric 2500 VAC peak
strength
W/Resistor
300
Temperature Normal: 50ppm - 150ppm
Coefficients Low ohmic values: 400ppm
250
200
150
100
50
Working voltage 1200 VAC
0
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 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.
Min. Storage & -40˚C
Operating Temp.
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.
350
WFH330
WFH230
WFH160
WFH90
40°
60°
80°
100°
120°
Heat Sink Temperature, °C
140°
Thermal Resistances
Thermal Resistance (°C/W) between different
measuring points
resistor
surface to
heat sink
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
RTH4
RTH3
aluminum
housing to
heat sink
aluminum
housing
to air
RTH2
RTH1
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. (continued)
1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • [email protected]
133
WFH Series
Aluminum Housed Wirewound Power
d e s i g n i nfo r m a t i on
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.
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 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 = Heat sink temperature (chassis). TH
T
= Temperature on top of the Aluminum profile.
d i m e ns i ons
(mm)
Type WFH90
WFH160
WFH230
WFH330
Watts
A
B
L
90 70
39.7
53
160 140
330 280 230
ø4.5
L
210
80
123
2x 100
263
2x 80
10
193
300
12.6
6.3
0.8
ø2.2
4.8
0.6
8
13.6
6
Amp
terminal
41 51
Lug
terminal
15
Wire
terminal
B
A
o r d e r i n g i nfo r m a t i on
RoHS
Compliant
Series
134
Wattage
at 40°C
base plate
temp.
Tolerance
Ohms
Terminal Type
J = 5%
L = lug terminals R47= 0.47Ω K = 10%
A = amp terminals
W= 30cm insulated wire cable 18AWG
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
1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • [email protected]
WFH230L100JE
WFH230L150JE
WFH230L250JE
WFH230L1K0JE
WFH230L1K5JE
WFH230L2K5JE
WFH330L1R0KE
WFH330L2R0KE
WFH330L10RKE
WFH330L27RJE
WFH330L50RJE
WFH330L75RJE
WFH330L100JE
WFH330L150JE
WFH330L250JE
WFH330L1K0JE
WFH330L5K0JE
WFH330L10KJE