Danfoss VLT 2800 Series Operating Instructions Manual

Also see for VLT 2800 Series: Instruction manual Manual Quick guide Operating instructions General information

Contents

Danfoss VLT 2800 Series Operating Instructions Manual Manual pdf 54 page image

Enhanced Sleep ModeThe enhanced sleep mode has been developed towork under all conditions and to overcome problemswhen using pumps with flat pump curves or when suc-tion pressure varies. Enhanced sleep mode providesexcellent control for shutting down the pump at lowflow, thus saving energy.If operating with constant pressure control in the SYS-TEM, for instance a drop in the suction pressure willlead to an increase in frequency to maintain pressure.Consequently there is a situation, where the frequencywill vary independent of the flow. This can lead to in-appropriate activation of sleep mode or wake-up of thefrequency converter.Flat pump curves leads to a situation where there willbe little or no change in frequency in response to flowvariation. Consequently, the frequency convertermight not reach the sleep frequency when setting it ata low value.Enhanced sleep mode is based on power/frequencymonitoring and works in closed loop only. Stop due tothe enhanced sleep mode function is initiated underthe following conditions:• Power consumption is below the no/low flowpower curve and stays there for a certain time(parameter 462 Enhanced sleep mode timer)or• The pressure feedback is above the refer-ence when running at minimum speed andstays there for a certain time (parameter 462Enhanced sleep mode timer).If the feedback pressure falls below the wakeup pres-sure (Parameter 464 Wakeup pressure), the frequencyconverter restarts the motor.Dry Run DetectionFor most pumps, especially submersible bore-holepumps, it must be assured that the pump is stopped incase of dry run. This is assured by the Dry run detec-tion feature.How Does It Work?Dry run detection is based on power/frequency moni-toring and works in both closed and open loop.Stop (trip) due to dry run is initiated under followingconditions:Closed loop:• The frequency converter is running at maxi-mum frequency (parameter 202 Output fre-quency high limit, f MAX ) and• Feedback is below minimum reference (pa-rameter 204 Minimum reference, Ref,MIN) and• Power consumption is below the no/low flowpower curve for a certain time (parameter470 Dry run time out)Open loop:• Whenever the power consumption is belowthe no/low flow power curve for a certain time(parameter 470 Dry run time out) the frequen-cy converter will trip.The frequency converter can be set up for either man-ual or automatic restart after stop (parameters 405Reset function and 406 Automatic restart time).• Enhanced Sleep Mode and Dry Run Detec-tion can be enabled and disabled independ-ently. This is done in parameter 462Enhanced sleep mode timer and parameter470 Dry run time out.Centrifugal pumps with radial impellers show a clearone-to-one relation between power consumption andflow, which is utilized to detect a no or low flow situa-tion.It is only necessary to enter two sets of values for pow-er and frequency (min and max) at no or low flow. Thefrequency converter then automatically calculates alldata in-between those two sets of values and gener-ates the no/low flow power curve.If the power consumption falls below the power curve,the frequency converter enters Sleep-mode or tripsdue to dry run, depending on the configuration.VLT® 2800 SeriesMG.27.A2.02 - VLT ® is a registered Danfoss trademark 53Programming