FlowrateDistribution Valve regulation Frequencyconvertercontrol% Duration Power Consump-tionPower Consump-tion[m3/h] [h] [kW] [kWh] [kW] [kWh]350 5 438 42.51) 18.615 42.51) 18.615300 15 1314 38.5 50.589 29.0 38.106250 20 1752 35.0 61.320 18.5 32.412200 20 1752 31.5 55.188 11.5 20.148150 20 1752 28.0 49.056 6.5 11.388100 20 1752 23.02) 40.296 3.53) 6.132Σ 1008760 – 275.064 – 26.801Table 2.2 Result1) Power reading at point A12) Power reading at point B13) Power reading at point C12.1.6 Improved ControlUsing a frequency converter to control the flow orpressure of a system improves control.A frequency converter can vary the speed of the fan orpump, obtaining variable control of flow and pressure.Furthermore, a frequency converter can quickly adapt thespeed of the fan or pump to new flow or pressureconditions in the system.Obtain simple control of process (flow, level or pressure)utilising the built-in PI control.2.1.7 Star/Delta Starter or Soft StarterWhen large motors are started, it is necessary in manycountries to use equipment that limits the start-up current.In more traditional systems, a star/delta starter or softstarter is widely used. Such motor starters are not requiredif a frequency converter is used.As illustrated in Illustration 2.8, a frequency converter doesnot consume more than rated current.Full load% Full load current& speed5001000 0 12,5 25 37,5 50Hz2003004006007008004321175HA227.101 VLT® AQUA Drive FC 2022 Star/delta starter3 Soft starter4 Start directly on mainsIllustration 2.8 Start-up Current2.2 Description of OperationThe frequency converter supplies a regulated amount ofmains AC power to the motor to control its speed. Thefrequency converter supplies variable frequency andvoltage to the motor.The frequency converter is divided into 4 main modules:• Rectifier• Intermediate DC bus circuit• Inverter• Control and regulationIllustration 2.9 is a block diagram of the internalcomponents of the frequency converter. See Table 2.3 fortheir functions.Illustration 2.9 Frequency Converter Block DiagramProduct Overview Design Guide18 Danfoss A/S © 09/2014 All rights reserved. MG20N60222
