WIRE WOUND RESISTORS
SILICONE COATED TYPE
VHIA
TM
Voltage rating
The resistors shall have a rated DC, continuous
working voltage or an approximate sine-wave root
mean square (rms) working voltage at commercial
line frequency corresponding to the power rating as
determined by the following formula
E = PR
where,
E = rated DC or rms continuous working voltage.
P = Power rating in watts.
R = Nominal resistance in ohms.
Rated ambient temperature - 25°C
Full power dissipation at upto 25°C and linearly
derated down to zero dissipation at 275°C. [See
derating curve]
Resistor temperature rise as a function of applied
power
[see graph displayed below]
Resistance tolerances available
+10% [K], +5% [J], +3% [H] +2% [G], +1% [F],
[Test method no. 303 of MIL 202 F]
ELECTRICAL DATA/CHARACTERISTICS
DERATING CURVE
100%
83.5%
50%
0
Rated Dissipation [%]
25 70 100 200 275
0
Ambient Temperature [ C]
10 20 30 40 50 60 70 80 90 100
Percentage of nominal power
at an ambient temperature of 25°C
0
Temperature rise [ C]
275°
200°
°C
100°
Temperature rise curve
Dielectric withstanding voltage
Max. DR+(1%+R05). No flashover, mechanical
damage, arcing or insulation breakdown.
[Test method no. 301 of MIL 202 F]
Insulation resistance
> 1000 M (dry) > 100 M (wet)
[Test method no. 302 of MIL 202 F]
Short time overload
Max. DR+(2%+R05). No arcing, burning or charring.
[Test method - 5 secs at 5 times rated power for 3
watts and smaller; 5 secs at 10 times rated power
for 4 watts and larger]
ENVIRONMENTAL SPECIFICATIONS
Temp. co-efficient - < 1 ohm +150 ppm/ °C, < 50 ohms +80 ppm/ °C, above 50 ohms +60ppm/ °C [Test method
no. 304 of MIL 202 F].
[TCR figures given are based on the usage of normally selected cost effective resistance elements and can be
significantly lowered on request].
Moisture resistance Load life
Max. DR+[3% + R05]. Max. DR+[5% + R05 ohms].
No mechanical damage. No mechanical damage.
[Test method no. 106 E of MIL 202 F]. [Test method no. 108 A of MIL 202 F].
MECHANICAL SPECIFICATIONS
Pull test Solderability
No mechanical damage. Continuous and satisfactory.
[Force supplied from 2 to 4.5 Kgs depending on size]. [Test method no. 208 F of MIL 202 F].