Danfoss VLT AQUA Design Manual

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

Contents

2.7.6. Better controlIf a frequency converter is used for controlling the flow or pressure of a system, improved control is obtained.A frequency converter can vary the speed of the fan or pump, thereby obtaining variable control of flow and pressure.Furthermore, a frequency converter can quickly adapt the speed of the fan or pump to new flow or pressure conditions in the system.Simple control of process (Flow, Level or Pressure) utilizing the built in PID control.2.7.7. Cos φ compensationGenerally speaking, a frequency converter with a cos φ of 1 provides power factor correction for the cos φ of the motor, which means that there is noneed to make allowance for the cos φ of the motor when sizing the power factor correction unit.2.7.8. Star/delta starter or soft-starter not requiredWhen larger motors are started, it is necessary in many countries to use equipment that limits the start-up current. In more traditional systems, a star/delta starter or soft-starter is widely used. Such motor starters are not required if a frequency converter is used.As illustrated in the figure below, a frequency converter does not consume more than rated current.1 = VLT AQUA Drive2 = Star/delta starter3 = Soft-starter4 = Start directly on mainsVLT® AQUA Drive Design Guide 2. Introduction to VLT AQUA DriveMG.20.N3.02 - VLT® is a registered Danfoss trademark 192