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Accurate Calculation of Braking Cycle of Wirewound Resistors
Feb 17, 2018

Accurate Calculation of Braking Cycle of Wirewound Resistors


    It turns out that the calculation of the braking cycle of a wire wound ripple brake resistor can sometimes easily be confusing. In fact, a 5% braking cycle means that the ripple resistor can dissipate 100% of the power in 12 seconds and then cool 228 Seconds. Of course, if the braking time is less than 12 seconds or the power consumption is less than 100%, the inverter will calculate the i2t of the ripple resistance.

     If the braking period is more than 5%, 440 allows to set a higher braking period, but in fact it is difficult to accurately calculate the braking situation. For example, a frequency converter brake for 5 seconds per minute, braking power 50%. In this case, it is generally recommended to select a slightly larger wire wound resistor than the theoretical calculation, and to set a higher brake cycle accordingly in parameter P1237.

     Suppose a 7.5kW ripple resistor frequency converter, brake 5 times a minute, every 2 seconds, braking power 50%. Braking 5 times per minute, each 2 seconds is equivalent to 40 seconds of braking within 240 seconds, and 50% of the braking power converted to time is 20 seconds. So you can calculate the braking cycle: 8%? 20/240, so the converted braking power is 625w, so select the 750w ripple resistance, while setting the brake cycle in P1237 10%.