SOLUTIONS - Moeller Electric Parts

SOLUTIONS18S + + + N E W S + + + N E W S + + + N E W S + + + N E W S + + + N E W S + + + N E W S + + + N E W SDeep WaterMoeller Field Service ensures correct controlresponse in deep wellWithout water, life is not possible. As groundwater onlyrarely contains any material concentrations that are harmfulto health, it is of particular importance for the drinkingwater supply. Air pollutants released into the ground or theexcessive spreading of fertilisers and pesticides, as well asharmful substances from contaminated sites can severelyreduce groundwater quality and can only be removed fromthe water with great difficulty. Preventative groundwaterprotection is therefore essential and is a key requirement formaintaining high quality potable water. Municipalities aretherefore specifically defining water protection areas withextensive protection requirements.The water supply department for theMontabaur collective municipality operatesa number of well systems in the south of theWesterwald. A new well system was put intooperation in the Montabaur water protectionarea of Höhe in 1991. A complete overhaulof the electrical installation was carried outin 2008. Up to 200,000 m 2 of potable wateris conveyed annually from a depth of 102 m,stored temporarily in a high-level tank, treatedand fed into the water supply network.Moeller supplied the entire control systemfor the water well system. A DF51-340-7K5frequency inverter controls the speed of thepump and thus regulates the water flow rate.The DF51 frequency inverter comes with anintegrated keypad with a four-digit 7-segmentdisplay, a serial interface and with digital andanalog inputs/outputs. Integrated electronicmotor protection, manual restart, DC braking,PID controller and PLC functions are alsoprovided. The actual value required for thecontrol system is received by the PID controllerfrom a flow meter.During the commissioning of the pump controlsystem, a satisfactory control response couldnot be achieved, even by changing severalcontrol parameters. According to the localelectrical fitter, the drive was “oscillating”between the minimum (20Hz) and themaximum (50Hz) frequency. The MoellerField Service was called upon to analysethe problem and rectify the fault. With itsspecialists, Moeller is always able to offer helpwhen system faults have to be examined andrectified. Alternatively, customers can carry outinteractive troubleshooting via the Internetor can access Moeller‘s Field Service databasedirectly.In the case of the pump control system,Moeller Field Service specialists werecalled to the installation. It wasn‘t clearwhether the cause of the fault was dueto an insufficiently parameterised PIDcontroller or was in the measuring systemfor the controlled variable. In the firststep the parameters of the PID controllerwere assigned very slow response settings.This allowed stable states to be achievedalthough the control system becameunstable as soon as flow disturbanceproduced by eddies in the pipe of the flowmeter could be heard. This added to thesuspicion that the actual value measuringwas possibly being corrupted by air presentin the pipe, thus causing an unstable PIDcontroller response. In the second step thecontrol system was examined more closely.The well is located at the highest point inthe entire system, consisting of the well, thepipe and the high-level tank. The high-leveltank, which serves as a storage for potablewater, is located at a lower point than thewell. This difference in height caused air inthe pipe system and therefore corrupted theflow rate readings.To rectify the error, the entry of air intothe flow rate measuring area had to beprevented. A fast solution that could beimplemented easily was found: Reduce thepipe cross section enough so that no aircould enter the section between the pumpand flow meter and thus corrupt the flowrate reading. In order to limit the flowrate to 25 m 2 per hour, the pipe valve wasclosed accordingly. The drive was also runat maximum speed for the first one to twominutes in order to remove any residual airfrom the measuring area. The result wasimpressive since now the control behaviouris continuously stable.Quicklink ID:MS1809For Moeller Electric Sales and Support call KMparts.com (866) 595-96169