Tab 36

Adjustable Frequency DrivesCFX9000 Drives36.64. Clean Power DrivesWhen the total load iscomprised of non-linear loadsuch as drives, and the ratiois l sc /I L , the greatestharmonic mitigation isrequired. Under theseconditions, the currentsdrawn from the supply needto be sinusoidal and “clean”such that systeminterference and additionallosses are negligible. Eaton’sCPX9000 clean powerdrive uses a phase-shiftingauto-transformer withdelta-connected winding thatcarries only the ampere-turnscaused by the difference inload currents. This results innine separate phases. In thistype of configuration, theBasic 18-Pulse Rectifier with Phase-Shifting Auto-Transformer1233-PhaseAC Input8C796A1N100 hp 480V Drive with 18-Pulse RectifiersCurrentAmps2001000–100–200518-Pulse SCRBridge RectifierConverter Section218-PulsePhase-ShiftingAuto-Transformer1233 454 6Time789Diode RectifiersBusCapacitorstotal kVA rating of thetransformer magnetic systemwas only 48% that of themotor load. A traditionalisolated transformer system,with multipulse windings,would require the full kVArating to be supported, whichis more common in an MVstep-down transformer.Pre-chargeCircuit(–) DCDynamic BrakingTransistorInverter Section(+) DCThe integrated 18-pulse cleanpower drive, with near sinewave input current and lowharmonics will meet therequirements of IEEE 519-1992 under all practicaloperating conditions. Thecomparisons with six-pulsepassive filter and 12-pulsesystems are shown on PagesV6-T36-161, V6-T36-163 andbelow.Output TransistorsIGBT Section100 hp 480V Drive with 18-Pulse Rectifiers18-Pulse Clean PowerCurrent harmonicsI 1 = 100% I 11 = 0.24% I 19 = 1.00%I 5 = 0.16% I 13 = 0.10% I 23 = 0.01%I 7 = 0.03% I 17 = 0.86% I 25 = 0.01%Power = 100 hpH c = 5.9 AmpsAdvantages●Effectively guaranteescompliance with IEEE 519-1992● Provides increased inputprotection for AFD and itssemiconductors from linetransients●Up to 4 times the harmonicreduction of 12-pulsemethods●Smaller transformer thanisolation transformer usedin 12-pulse converter●Minimizes ripple current incapacitors, doublingexpected capacitor lifeACMotorDisadvantages●Not as cost effective assome other methods atsmall (