Danfoss VLT 5000 Series Design Manual
Also see for VLT 5000 Series: ManualInstruction manualInstructionsOperating instructionsQuick setup
                                                                                                                                               | |
Contents
| 
EfficiencyTo reduce energy consumption it is very important tooptimize the efficiency of a system. The efficiency ofeach single element in the system should be as highas possible.Efficiency of VLT 5000 Series (ŋ VLT )The load on the frequency converter has little effect onits efficiency. In general, the efficiency is the same atthe rated motor frequency f M,N, regardless of whetherthe motor supplies 100% of the rated shaft torque oronly 75%, i.e. in case of part loads.This also means that the efficieny of the frequencyconverter does not change even if other U/f charac-teristics are chosen.However, the U/f characteristics influence the efficien-cy of the motor.The efficiency declines a little when the switching fre-quency is set to a value of above 4 kHz (3 kHz for VLT5005) (parameter 411). The rate of efficiency will alsobe slightly reduced if the mains voltage is 500 V, or ifthe motor cable is longer than 30 m.Efficiency of the motor (ŋ MOTOR )The efficiency of a motor connected to the frequencyconverter depends on the sine shape of the current. Ingeneral, the efficiency is just as good as with mainsoperation. The efficiency of the motor depends on thetype of motor.In the range of 75-100% of the rated torque, the effi-ciency of the motor is practically constant, both whenit is controlled by the frequency converter and when itruns directly on mains.In small motors, the influence from the U/f character-istic on efficiency is marginal; however, in motors from11 kW and up, the advantages are significant.In general, the switching frequency does not affect theefficiency of small motors. Motors from 11 kW and uphave their efficiency improved (1-2%). This is becausethe sine shape of the motor current is almost perfectat high switching frequency.Efficiency of the system (ŋ SYSTEM )To calculate the system efficiency, the efficiency ofVLT 5000 Series (ŋ VLT) is multiplied by the efficiencyof the motor (ŋ MOTOR ):ηSYSTEM = ηVLT × ηMOTORBased on the graph on this page, it is possible to cal-culate the efficiency of the system at different loads.VLT ® 5000 Design GuideMG.52.B2.02 - VLT ® is a registered Danfoss trademark 119Special conditions |
Related manuals for Danfoss VLT 5000 Series
manualsdatabase
Your AI-powered manual search engine