Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

Contents

2.6.3 Mains Drop-outDuring a mains drop-out, the frequency converter keepsrunning until the intermediate circuit voltage drops belowthe minimum stop level, which is typically 15% below thelowest rated supply voltage. The mains voltage before thedrop-out and the motor load determines how long it takesfor the frequency converter to coast.The frequency converter can be configured (14-10 MainsFailure) to different types of behaviour during mains drop-out,• Trip Lock once the DC link is exhausted.• Coast with flying start whenever mains return(1-73 Flying Start).• Kinetic back-up.• Controlled ramp-down.Flying startThis selection makes it possible to catch a motor that isspinning freely due to a mains drop-out. This option isrelevant for centrifuges and fans.Kinetic back-upThis selection ensures that the frequency converter runs aslong as there is energy in the system. For short mainsdrop-out, the operation is restored upon mains return,without bringing the application to a stop or losing controlat any time. Several variants of kinetic back-up can beselected.Configure the behaviour of the frequency converter atmains drop-out, in 14-10 Mains Failure and 1-73 Flying Start.2.6.4 Built-in PID ControllersThe 4 built-in proportional, integral, derivative (PID)controllers eliminate the need for auxiliary control devices.One of the PID controllers maintains constant control ofclosed-loop systems where regulated pressure, flow,temperature, or other system requirements must bemaintained. The frequency converter can provide self-reliant control of the motor speed in response to feedbacksignals from remote sensors. The frequency converteraccommodates 2 feedback signals from 2 different devices.This feature allows regulating a system with differentfeedback requirements. The frequency converter makescontrol decisions by comparing the 2 signals to optimisesystem performance.Use the 3 additional and independent controllers forcontrolling other process equipment, such as chemicalfeed pumps, valve control or for aeration with differentlevels.2.6.5 Automatic RestartThe frequency converter can be programmed to automat-ically restart the motor after a minor trip, such asmomentary power loss or fluctuation. This featureeliminates the need for manual resetting and enhancesautomated operation for remotely controlled systems. Thenumber of restart attempts as well as the durationbetween attempts can be limited.2.6.6 Flying StartFlying start allows the frequency converter to synchronisewith an operating motor rotating at up to full speed, ineither direction. This prevents trips due to overcurrentdraw. It minimises mechanical stress to the system sincethe motor receives no abrupt change in speed when thefrequency converter starts.2.6.7 Full Torque at Reduced SpeedThe frequency converter follows a variable V/Hz curve toprovide full motor torque even at reduced speeds. Fulloutput torque can coincide with the maximum designedoperating speed of the motor. This is unlike variabletorque converters that provide reduced motor torque atlow speed, or constant torque converters that provideexcess voltage, heat, and motor noise at less than fullspeed.2.6.8 Frequency BypassIn some applications, the system may have operationalspeeds that create a mechanical resonance. This cangenerate excessive noise and possibly damage mechanicalcomponents in the system. The frequency converter has 4programmable bypass-frequency bandwidths. These allowthe motor to step over speeds that induce systemresonance.2.6.9 Motor PreheatTo preheat a motor in a cold or damp environment, asmall amount of DC current can be trickled continuouslyinto the motor to protect it from condensation and a coldstart. This can eliminate the need for a space heater.2.6.10 Four Programmable Set-upsThe frequency converter has 4 set-ups that can beindependently programmed. Using multi-setup, it ispossible to switch between independently programmedfunctions activated by digital inputs or a serial command.Independent set-ups are used, for example, to changereferences, or for day/night or summer/winter operation, orProduct Overview Design Guide30 Danfoss A/S © 09/2014 All rights reserved. MG20N60222