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How do I calculate overload factor for a REO Braking Resistor?

How do I calculate overload factor for a REO Braking Resistor? image #1

REO braking resistors are designed for continuous 100% duty at the power on the rating label.

We usually define continuous duty as being energized at full power for 120 seconds.

Therefore if braking resistors are used for less than the full duty cycle time then they can be used at a higher power rating. The diagrams below show the multiplication factor that can be used to calculate the per¬mitted overload for a braking resistor.

For example:

We can use a typical air-cooled REO resistor for 12 seconds every 120 secs at 10 times its rated continuous duty. So if you need 25000 kW of braking then you can take a resistor that is continuously rated for just 2500 W, provided you adhere to the duty cycle.

These figures are given for the resistor operating in a 40 deg C ambient at 1000 m above sea level. Please contact us for information concerning derating.

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