Refrigeration, air-conditioning and cooling technology - 2007.pdf

PLH_KKK_32_85.QXP 25.05.2007 10:11 Uhr Seite 52FUSE PROTECTION OF PUMPS AND REFRIGERATING MACHINESPower supplyPower supplies from the public mains powersupply are subject to certain constraints whichare taken into account in the design of drivesand control units. Voltage drops can occur dueto lines being too long or too thin, which canlead to output deficits and overheating. Controllines and power lines are to be laid separatelydue to induction processes. Systems are to beprotected against overvoltage (e.g. lightning)and to be switched off in the event of undervoltage.Surge arresters and mains monitoringrelays with all-pole insulation of the power supplyprovide solutions.If self-powered systems, mains replacement operationor converter operation are planned, thefollowing conditions must be met:• All Wilo pumps are designed to run on Europeanstandard voltage 230/400 V (±10 %) inaccordance with DIN IEC 60038. They havebeen marked with the CE marking in accordancewith the EU machine directive sinceJanuary 1, 1995. When pumps are utilised in installationswith pumping media temperaturesabove 90°C, a corresponding heat-resistantconnection line must be used.When operating Wilo pumps with control unitsor module accessories, it is essential to adhereto the electrical operating conditions as set outin VDE 0160. When operating glandless andglanded pumps in conjunction with frequencyconvertermodels not supplied by Wilo, it is necessaryto use output filters to reduce motor noiseand prevent harmful voltage peaks and to adhereto the following limit values:• Glandless pumps with P 2 and glandedpumps with P 2 1.1 kW rate of voltagerise du/dt < 500 V/µs, voltage peaks û < 850 V.Installations with large cable lengths (l > 10 m)between converter and motor may cause increasesof the du/dt and û levels (resonance). Thesame may happen for operation with more than4 motor units at one voltage source. The outputfilters must be selected as recommended by theconverter manufacturer or filter supplier, respectively.The pumps must be operated at a maximumof 95 % of their rated motor speed if thefrequency converter causes motor losses. If glandlesspumps are operated on a frequency converter,the following limits may not be fallen shortof at the connection terminals of the pumps:U min = 150 V, f min = 30 HzThe service life and operational reliability of acirculating pump depend to a great extent onthe choice of the correct motor protection device.Motor protection switches are unsuitablefor utilisation in conjunction with multi-speedpumps due to their different nominal currentratings at different speed settings which requirecorrespondingly different fuse protection.All glandless circulating pumps are either• blocking-current proof• provided with internal protection againstunacceptably high winding temperatures• provided with full motor protection throughthermal winding contact and separate relay• provided with full motor protection and builtintrip mechanism (for series, see cataloguedata).• No further motor protection by the customeris required except where this is stipulated forblocking current-proof motors and motorswith internal protection against unacceptablyhigh winding temperatures by the energy supplycompany.Standard glanded pumps are to be protected byonsite motor protection switches with a nominalcurrent setting. Full motor protection is onlyachieved, however, when a thermal winding contactor a PTC thermistor detector is additionallymonitored.If the glanded pump is equipped with a controlmounted to the motor housing, it is equippedwith full motor protection from the manufacturer.The protective measure of protective groundingis to be used for frequency converter controllerswith three-phase current connections. Residualcurrent protective equipment in accordancewith DIN VDE 0664 is not permitted. Exception:Selective universal-current-sensitive residualcurrent circuit breaker (recommended nominalresidual current ∆ = 300 mA).Maximum back-up fuses are to be providedaccording to the onsite installation and theinstalled devices in accordance with DIN/VDE.The maximum permissible cable/wire cross-sectionis to be taken from the catalogues. The ambientoperating conditions are to be taken intoconsideration in selecting the cables. Specialconditions, such as water-pressure tightness orshields, etc. might be required.52 Subject to change without prior notice 02/2007 WILO AG