Operating Instruction - Frequency Inverter 230V / 400V ... - opis.cz

17.4.1 Dimensioning of Brake ResistorThe following values must be known for dimensioning:− Peak braking power P b Peak in W− Resistance Rb in Ω− Duty cycle DC in %• Calculation of peak braking power P b PeakPb Peak2 2( n − n )J ⋅1=182⋅tb2P b Peak = Peak braking power in WJ = Moment of inertia of drive system kgm 2n 1 = Speed of drive system before the braking operationin min -1n 2 = Speed of drive system after the braking operationin min -1= Braking time in st b• Calculation of resistance R bURb=P2d BCb PeakR bU d BCP b Peak= Resistance in Ω= Switch-on threshold in V= Peak braking power in WThe switch-on threshold U d BC is the DC link voltage at which the brake resistor isswitched on. The switch-on threshold can be set, as described above, via parameterTrigger Threshold 506.Caution!The resistance of the brake resistor must not be less than the minimumvalue R b min -10%. The values for R b min are listed in chapter "TechnicalData".If the calculated resistance R b of the brake resistor is between two standard seriesvalues, the lower resistance is to be selected.• Calculation of duty cycle DCtD C =btcycleDCt bt cycle= Duty cycle= Braking time= Cycle timeExample:t b = 48 s, t cycle = 120 st tbD C =b= 0.4 = 40 %t cycletcycleIn the case of infrequent short braking operations, typical values of the duty cycle DCare at 10 %, for long braking operations (≥ 120 s) typical values are at 100%. In thecase of frequent deceleration and acceleration operations, it is recommended that theduty cycle DC be calculated according to the above formula.The calculated values for P b Peak , R b and DC can be used by the resistor manufacturersfor determining the resistor-specific permanent power.Warning!The brake resistor is to be connected according to the specifications andinstructions in chapter "Connection of a Brake Resistor".02/06 165