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Failsafe Moulded Wirewound Resistors

Specifications

The unique feature of this series of wire wound resistors is their case size. To make more compact resistors, IRC developed the BWH series and the BWF series which are rated at 2 watts, however they're encapsulated in a 1 watt case size. The same applies for the BW20 series and the BW20F series which are rated at a 1 watt rating encapsulated in a ½ watt case size.

Case sizes:

Note: After IRC was bought out by TRW/TT Electronics the BWH, BWF, BW20 and the BW20F series were discontinued. TRW/TT Electronics released a new series of resistors that serve as drop in replacements for the older series. To cross reference the older series to the new series click here.

resistor-breakdown

1.Resistive Element:
Every type of wire wound resistor has a resistive alloy winding on a braided fiberglass substrate. To increase processibility and protect the resistive element, these resistors are coated in a silicone coating.

2.Encapsulation:
This type of resistor is encapsulated in a compressed molded phenolic plastic material. Any part number ending with the letter “F”, simply means that there is a flame retardant coating applied to the resistive element. Which provides flammability protection when a destructive load may occur.

3.Termination:
This series of wirewound resistors are terminated using a copper flashed steel lead with an alloy coating, which is then welded to a cap made out of the same material.

Moulded Wirewound Resistors Specifications
Series Resistance Range Power Rating Case Size
SPH .01 ohm to 2400 ohms 2 Watt at 70°C
1 Watt at 115°C
Derating to 0 at 160°C
2 Watt rated with 1 Watt dimensions
SPF 0.1 ohm to 1000 ohms 2 Watt at 70°C
1 Watt at 115°C
Derating to 0 at 160°C
2 Watt rated with 1 Watt dimensions
SP20 0.1 ohm to 1200 ohms 1 Watt at 50°C
0.75 Watt at 70°C
Derating to 0 at 160°C
1 Watt rated with 1/2 Watt dimensions
SP20F 0.1 ohm to 1000 ohms 1 Watt at 50°C
0.75 Watt at 70°C
Derating to 0 at 160°C
1 Watt rated with 1/2 Watt dimensions
BWH .01 ohm to 2400 ohms 2 Watt at 70°C
1/2 Watt at 137°C
Derating to 0 at 150°C
2 Watt rated with 1 Watt dimensions
BWF 0.1 ohm to 1000 ohms 2 Watt at 70°C
1/2 Watt at 137°C
Derating to 0 at 150°C
2 Watt rated with 1 Watt dimensions
BW20 0.1 ohm to 1200 ohms 1 Watt at 50°C
0.25 Watt at 125°C
Derating to 0 at 160°C
1 Watt rated with 1/2 Watt dimensions
BW20F 0.1 ohm to 1000 ohms 1 Watt at 50°C
0.25 Watt at 125°C
Derating to 0 at 160°C
1 Watt rated with 1/2 Watt dimensions

Ordering Information For The SPH/SPF, SP20/SP20F, BWH/BWF, BW20/BW20F Series Resistors.

An example: SPF - 150 - 5%

SPF - 150 - 5%
| | |
Series Resistance Tolerance
1 2 3

1. Series

Current TRW/TT Electronics Part Numbers.

  • SPH
  • SPF
  • SP20
  • SP20F

Obsolete IRC Part Numbers.

  • BWH
  • BWF
  • BW20
  • BW20F

Note: F = Flame resistance coating applied.

2. Resistance
Resistance is expressed in Ω (ohms), use a decimal point and as many digits as required.

3. Tolerance
Tolerance is expressed as a percentage.

  • ±2%
  • ±5%
  • ±10%

Cross-Reference Case Sizes and Series

Cross-Reference Table
Series Drop in Replacement MIL-R-11 Equivalent
(Carbon Comp.)
EIA RS-344 Equivalent
SPH/SPF BPH/BWF RC32/RC42 CRU2
SP20/SP20F BW20/BW20F RC20/RCR20 CRU1
BPH/BWF BPH/BWF RC32/RC42 CRU2
BW20/BW20F SP20/SP20F RC20/RCR20 CRU1

Browse our Failsafe Moulded Wirewound Resistors Inventory

Failsafe Moulded Wirewound Resistors can be found in audio equipment such as guitar amplifiers, power amplifiers, and preamplifiers.