Area Title Functions1 Mains input • 3-phase AC mains power supplyto the frequency converter.2 Rectifier• The rectifier bridge converts theAC input to DC current to supplyinverter power.3 DC bus • Intermediate DC bus circuithandles the DC current.4 DC reactors• Filter the intermediate DC circuitvoltage.• Prove mains transient protection.• Reduce RMS current.• Raise the power factor reflectedback to the line.• Reduce harmonics on the ACinput.5 Capacitor bank• Stores the DC power.• Provides ride-through protectionfor short power losses.6 Inverter• Converts the DC into a controlledPWM AC waveform for acontrolled variable output to themotor.7 Output to motor • Regulated 3-phase output powerto the motor.Area Title Functions8 Control circuitry• Input power, internal processing,output, and motor current aremonitored to provide efficientoperation and control.• User interface and externalcommands are monitored andperformed.• Status output and control can beprovided.Table 2.3 Legend to Illustration 2.9The frequency converter rectifies AC voltage from mainsinto DC voltage, after which this DC voltage is convertedinto an AC current with a variable amplitude andfrequency.The frequency converter supplies the motor with variablevoltage/current and frequency, which enables variablespeed control of 3-phased, standard asynchronous motorsand non-salient PM motors.The frequency converter manages various motor controlprinciples such as U/f special motor mode and VVC+. Short-circuit behavior of the frequency converter depends on the3 current transducers in the motor phases.InrushR inrLoad sharing -Load sharing +LC Filter -(5A)LC Filter +(5A) BrakeResistor130BA193.14ML2 92L1 91L3 9389(+)88(-)R+82R-81U 96V 97W 98P 14-50 Rfi FilterIllustration 2.10 Frequency Converter StructureProduct Overview Design GuideMG20N602 Danfoss A/S © 09/2014 All rights reserved. 192 2
