RH, NH

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Vishay Dale

Revision: 22-Jun-12

3

Document Number: 30201

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

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