30

31

WFH Series

Aluminum Housed Wirewound Power

F E A T U R E S

• Solder, wire and “Fast-On”

Termination

• More resistors in one profile pos-

sible

• Custom wire lengths available

S P E C I F I C A T I O N S

Power rating: 90W-330W

Resistance tolerance: ±5%, ±10%

Temperature Coefficients:

Normal: 50ppm - 150ppm

Low ohmic values: 400ppm

Dielectric strength: 2500 VAC

peak

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 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.

Power

Resistance

Rating*

Range

Dimension (mm)

Type

(watts)

(Ω)

A

B

L

WFH90

90

0.22Ω – 6.8K

70

39.7

53

WFH160

160

0.47Ω-18K

140

80

123

WFH230

230

0.82Ω-27K

210

2x 80

193

WFH330

330

1Ω - 39K

280

2x 100 263

*at 40°C base plate temperature

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

0.8

ø4.5

L

Amp

terminal

Heat Sink Temperature,

°C

40

°

60

°

80

°

100

°

120

°

140

°

100

150

200

300

50

250

350

0

WFH330

WFH160

WFH230

WFH90

P O W E R D I S S I P A T I O N

O R D E R I N G I N F O R M A T I O N

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= 0.47

Ω

RoHS

Compliant

S T A N D A R D P A R T N U M B E R S F O R W F H S E R I E S

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 sensi-

tive 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.

This graph shows the maximum wattage rating for each possible resistor

of standard size corresponding to the heat sink temperature. It is as-

sumed that all resistors are equally loaded.

resistor

surface to

heat sink

wire to

aluminum

housing

aluminum

housing

to air

aluminum

housing to

heat sink

T H E R M A L R E S I S T A N C E S

Thermal Resistance (°C/W) between different

measuring points

WFH90 WFH160 WFH230 WFH330

1

0.75

0.5

3.9

2.75

2

0.05

0.03

0.02

0.17

0.1

0.085

D E S I G N I N G

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:

Check that:

B. The Temperature of the Heat Sink is known,

Check that:

2. WFH is mounted without a heat sink:

Check that:

Where:

= Thermal resistance. Refer to table Thermal resistances

= Heat sink temperature (chassis).

T

= Temperature on top of the Aluminum profile.

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

Check product availability at

www.ohmite.com