Danfoss VLT AQUA Drive Design Manual

Also see for vlt aqua: Instructions Design guide Instruction manual Operating instructions Design guide

Contents

However, the U/f characteristics influence the efficiency of the motor.The efficiency declines a little when the switching frequency is set to a value greater than 5 kHz.The efficiency will also be slightly reduced if the line voltage is 480 V, or if the motor cable is longerthan 98.43 ft. [30 m].Efficiency of the motor (ηMOTOR )The efficiency of a motor connected to the adjustable frequency drive depends on magnetizinglevel. In general, the efficiency is just as good as with line operation; however, it depends on thetype of motor.In the range of 75-100% of the rated torque, the efficiency of the motor is practically constant,both when it is controlled by the adjustable frequency drive, and when it runs directly on linepower.In small motors, the influence from the U/f characteristic on efficiency is marginal. However, inmotors from 15 hp [11 kW] and up, the advantages are significant.In general, the switching frequency does not affect the efficiency of small motors. The efficiencyof motors from 15 hp [11 kW] and up improves by 1-2%. This is because the sine shape of themotor current is almost perfect at high switching frequency.Efficiency of the system (ηSYSTEM )To calculate the system efficiency, the efficiency of VLT AQUA (ηVLT) is multiplied by the efficiencyof the motor (ηMOTOR ):ηSYSTEM ) = η VLT x ηMOTORCalculate the efficiency of the system at different loads based on the graph above.3.3. Acoustic noiseThe acoustic noise from the adjustable frequency drive comes from three sources:1. DC intermediate circuit coils.2. Integrated fan.3. RFI filter choke.Typical values are measured at a distance of 3.28 ft. [1 m] from the unit:Encapsulation At reduced fan speed (50%)[dBA] Full fan speed [dBA]A2 51 60A3 51 60A5 - 54B1 61 67B2 58 70C1 52 62C2 55 653. VLT AQUA Selection VLT® AQUA Drive Design Guide56 MG.20.N2.22 - VLT® is a registered Danfoss trademark.3