Overload and Derating Charts for Avtron Power Resistors
Tech Tip
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 |
For further assistance, call a Galco Sales Representative today at
1-800-575-5562