Danfoss VLT DriveMotor FCP 106 Design Manual

Also see for VLT DriveMotor FCP 106: Operating instructions Operating instructions Operating instructions Design guide Design guide

6.10 dU/dtShaft output power[kW (hp)]Motor cable length[m (ft)]Mains voltage[V]Rise time[μs]Vpeak[kV]dU/dt[kV/μs]0.55 (0.75) 0.5 (1.6) 400 0.1 0.57 4.50.75 (1.0) 0.5 (1.6) 400 0.1 0.57 4.51.1 (1.5) 0.5 (1.6) 400 0.1 0.57 4.51.5 (2.0) 0.5 (1.6) 400 0.1 0.57 4.52.2 (3.0) <0.5 (1.6) 400 1) 1) 1)3.0 (4.0) <0.5 (1.6) 400 1) 1) 1)4.0 (5.0) <0.5 (1.6) 400 1) 1) 1)5.5 (7.5) <0.5 (1.6) 400 1) 1) 1)7.5 (10) <0.5 (1.6) 400 1) 1) 1)Table 6.10 dU/dt, MH1–MH31) Data available at future release.6.11 EfficiencyEfficiency of the drive (ηVLT)The load on the drive has little effect on its efficiency. Ingeneral, the efficiency is the same at the rated motorfrequency fM,N, even if the motor supplies 100% of therated shaft torque or only 75%, that is if there is part loads.This also means that the efficiency of the drive does notchange even if other U/f characteristics are selected.However, the U/f characteristics influence the efficiency ofthe motor. The efficiency declines a little when theswitching frequency is set to a value of above 5 kHz. If themains voltage is 480 V, the efficiency is also slightlyreduced.Drive efficiency calculationCalculate the efficiency of the drive at different loadsbased on Illustration 6.6. Multiply the factor in this graphwith the specific efficiency factor listed in the specificationtables.1.00.990.980.970.960.950.930.920% 50% 100% 200%0.94Relative Efficiency130BB252.111.01150%% Speed100% load 75% load 50% load 25% loadIllustration 6.6 Typical Efficiency CurvesExample: Assume a 22 kW (30 hp), 380–480 V AC driveruns at 25% load at 50% speed. The graph shows 0.97,whereas rated efficiency for a 22 kW (30 hp) drive is 0.98.The actual efficiency is then: 0.97 x 0.98 = 0.95.Efficiency of the motor (ηMOTOR)The efficiency of a motor connected to the drive dependson the magnetizing level. In general, the efficiency is asgood as with mains operation. The efficiency of the motordepends on the motor type.In the range of 75–100% of the rated torque, the efficiencyof the motor is practically constant. The constant efficiencyapplies both when a drive controls the motor, and whenthe motor runs directly on mains.In small motors, the influence from the U/f characteristicon efficiency is marginal. However, in motors from 11 kW(15 hp) and up, the advantages are significant.In general, the switching frequency does not affect theefficiency of small motors. Motors from 11 kW (15 hp) andup have their efficiency improved (1–2%). Thisimprovement is due to an almost perfect sine shape of themotor current at high switching frequency.Efficiency of the system (ηSYSTEM)To calculate the system efficiency, the efficiency of thedrive (ηVLT) is multiplied by the efficiency of the motor(ηMOTOR):ηSYSTEM = ηVLT x ηMOTORSpecifications VLT® DriveMotor FCP 10658 Danfoss A/S © 12/2018 All rights reserved. MG03M30266