1) The document describes wire wound fusible resistors that function as regular resistors under normal conditions but fuse under excessive loads, providing overcurrent protection. 2) These resistors have enhanced surge voltage immunity and are available in various wattage ratings and resistance values. 3) Key specifications include temperature coefficient, short time overload rating, dielectric withstand voltage, fusing characteristics, and electrical performance standards.

1. 20111
8
WIRE WOUND FUSIBLE RESISTOR - HIGH SURGE IMMUNITY
INTRODUCTION:
The WWFHS series wire wound fusible high surge immune resistors are manufactured
to perform as a regular resistor under normal conditions and as a fuse under excessive
load. These fusible resistors have high surge voltage immunity.
In WWFHS series, for resistors up to 5W, the resistance value is color coded with 3
bands plus a tolerance band. An additional white band indicates that the resistor is
fusible. For resistors 6W and above, the value is printed on the resistor.
* Certified to UL 1412
Note: Resistance range mentioned above is standard range. Please contact us for any
specific resistance value outside the specified range. Also for any specific lead length.
SPECIFICATIONS
Type No. Wattage
Dimensions in mm Range
in
Ohms
[Ω]
Tolerance
Dielectric
withstanding
Voltage
D L H d
WWFHS 1*
WWFHS 2 M 1W / 2W 3.20 ± 0.5 9 ± 0.5 26 ± 2.0 0.55 ± 0.05 10 150 5% 350 V
WWFHS 2*
WWFHS 3 M 2W / 3W 4.25 ± 0.5 11 ± 1.0 26 ± 2.0 0.65 ± 0.05 10 150 5% 500 V
WWFHS 3
WWFHS 4 3W / 4W 5.00 ± 0.5 15 ± 1.0 26 ± 2.0 0.75 ± 0.05 10 150 5% 500 V
WWFHS 5
WWFHS 6 M 5W / 6W 6.00 ± 0.5 18 ± 1.0 30 ± 2.0 0.75 ± 0.05 10 150 5% 500 V
WWFHS 5 B
WWFHS 6 B
WWFHS 7 B
5W / 6W / 7W 7.00 ± 0.5 21 ± 1.0 38.5 ± 2.0 0.75 ± 0.05 10 150 5% 500 V
WWFHS 6
WWFHS 7
WWFHS 8
6W / 7W / 8W 8.00 ± 1.0 25 ± 1.0 38 ± 3.0 0.80 ± 0.05 10 150 5% 500 V
WWFHS 9
WWFHS 10
9W / 10W 8.00 ± 1.0 30 ± 1.0 38 ± 3.0 0.80 ± 0.05 10 150 5% 1000
TECHNICAL SPECIFICATIONS
PARAMETER UNIT RESISTOR CHARACTERISTICS
Temperature Coefficient ppm/°C ± 200
Short Time Overload
- 5 times of rated wattage for 5 sec for up to 3w
10 times of rated wattage for 5 sec. above 3w
Maximum Working Voltage V
Operating Temperature Range °C Characteristic V = -65 to +350
Power Rating - *Refer Power Derating Curve

2. 20111
8
* Please contact us for specific surge voltage requirements.
Eg: WWFHSR1005R68C0350 = 1W 5% 68E Wire Wound Fusible Resistor – High Surge
Immunity with 3.5KV Surge
The surge handling capability is based upon applying an exponential open circuit voltage
waveform according to specification IEC 61000-4-5(1.2 µs/50 µs) as shown below at an
ambient temperature of 25°C.
FUSING CHARACTERISTICS
RESISTANCE RANGE FUSING POWER FUSING TIME TCR
10E to 150E Rated Power x 32 < 60 seconds ± 200 ppm/°C
ELECTRICAL PERFORMANCE
Tests Condition Spec.
Surge Immunity Test 5 pulses at 2 Ohms impedance in asynchronous mode 2.5KV *
ResistanceTemp.Coeff. -55 °C ~ 200 °C ± 200 ppm/°C
Short Time Overload
5 times of rated wattage for 5 sec for up to 3w
10 times of rated wattage for 5 sec. above 3w
± 2%
Insulation Resistance 500 V Megger 1,000 MΩ
Load Life 70°C on-off cycle 1,000hrs. ± 3%
PART NUMBER INFORMATION
Watts Type
Wire Wound
Fusible Resistors
High Surge
Immunity
Size
R = Standard
M = Miniature
B = Special
Rated
Power
100 = 1W
200 = 2W
300 = 3W
500 = 5W
600 = 6W
700 = 7W
800 = 8W
900 = 9W
10W = 10W
Tolerance
1 = 1%
5 = 5%
Units
R = Ohms
K = Kilo Ohms
M = Mega Ohms
Resistance
Value
(Decimal value
is optional)
Surge
C0250 = 2.5 KV
C0300 = 3 KV
…….
C2000 = 20 KV
WWFHS R 100 5 R 68 C0350
HIGH VOLTAGE SURGE

3. 20111
8
The recommended storage conditions are in between 10°C and 30°C (room temperature)
at a relative humidity in between 35 % and 75 %. Do not store them within the vicinity of
any corrosive gases such as hydrogen sulphide, sulphurous acid, chlorine or ammonium.
10 11 12 13 15 16 18 20 22 24 27 30
33 36 39 43 47 51 56 62 68 75 82 91
STANDARD RESISTANCE VALUES
E24 Series
DERATING
STORAGE CONDITIONS
040220
Rev 04