RH, NH

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Vishay Dale

Revision: 26-Feb-16

3

Document Number: 30201

For technical questions, contact: ww2aresistors@vishay.com

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POWER RATING

Vishay RH resistor wattage ratings are based on mounting to the following heat sink:



RH005 and RH010:

4" x 6" x 2" x 0.040" thick aluminum chassis (129 sq. in. surface area)



RH025:

5" x 7" x 2" x 0.040" thick aluminum chassis (167 sq. in. surface area)



RH050:

12" x 12" x 0.059" thick aluminum panel (291 sq. in. surface area)



RH100 and RH250:

12" x 12" x 0.125" thick aluminum panel (294 sq. in. surface area)

AMBIENT TEMPERATURE DERATING

Derating is required for ambient temperatures above 25 °C, see the following graph.



Curves A, B, C apply to operation of unmounted resistors. Curve D applies to all types when mounted to specified heat sink.



A = RH005 and RH010 size resistor, unmounted



B = RH025 size resistor, unmounted



C = RH050, RH100 and RH250 size resistor, unmounted



D = All types mounted to recommended aluminum heat sink



REDUCED HEAT SINK DERATING

Derating is also required when recommended heat sink area is reduced.



A = RH005 and RH010 size resistor



B = RH025 size resistor



C = RH050, RH100 and RH250 size resistor



FREE AIR POWER RATING

GLOBAL



MODEL

RH005

NH005

RH010

NH010

RH025

NH025

RH050

NH050

RH100

NH100

RH250

NH250

W at 25 °C

4.5

7.5

12.5

20

40

100

AMBIENT TEMPERATURE IN °C

25

120

A

C

D

B

0

20

40

60

80

100

- 55 - 50

0

50

150

250

0

100

80

60

40

20

0

100

90

80

70

60

50

40

30

20

10

% OF RECOMMENDED HEAT SINK AREA

C

B

A