Avtron, Avtron Power Resistors

Tech Tip

OVERLOAD AND DERATING CHARTS FOR AVTRON POWER RESISTORS


GENERAL FORMULAS

OHM’S LAW
V = I x R    (Volts = Amps x Resistance)

POWER CALCULATIONS
P = V x I    (Power = Volts x Amps)
P = V2/R    (Power = Volts squared / Resistance)
P = I2 x R   (Power = Amps squared x Resistance)


SINGLE SHOT OVERLOADS (cool to ambient between cycles)

TIME ON MULT. AMPS BY MULT. WATTS BY
1 sec. 8.0 64
3 sec. 7.0 49
5 sec. 6.0 36
10 sec. 4.5 20
30 sec. 3.0 9.0
60 sec. 2.0 4.0


REPEATING DUTY OVERLOADS

NEMA CLASS ON TIME/OFF TIME MULT. AMPS BY MULT. WATTS BY
110 5 / 75 sec. 2.5 6.2
130 10 / 75 sec. 2.0 4.0
140 15 / 75 sec. 1.8 3.2
150 15 / 45 sec. 1.6 2.5
160 15 / 30 sec. 1.5 2.2
170 15 / 15 sec. 1.4 2.0
90 continuous 1.0 1.0


DERATING FOR AMBIENT TEMPERATURE

AMBIENT TEMP. MULT. AMPS BY MULT. WATTS BY
Up to 40 C 1.0 1.0
50 C 0.96 0.92
60 C 0.95 0.90
70 C 0.94 0.88
80 C 0.92 0.85
90 C 0.90 0.81
100 C 0.88 0.77
120 C 0.86 0.74
150 C 0.80 0.64


DERATING FOR ALTITUDE

ALTITUDE MULT. AMPS BY MULT. WATTS BY
0 - 6000’ 1.0 1.0
6000’ - 15000’ 0.86 0.75
above 15000’   consult factory


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avtron_tip (orig.-8/1/02)
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