Tab 36

Adjustable Frequency DrivesCPX9000 Drives36.7One-Line Diagram for Harmonic Analysis____Volts____VoltsUtility SideTransformer____Volts____kVA____Isc____ImpedanceCustomerGenerator____Volts____kVA____Isc____ImpedanceTerms●PCC (Point of CommonCoupling) is defined as theelectrical connecting pointbetween the utility andmultiple customers per thespecifications in IEEE 519●POA (Point of Analysis)is defined as where theharmonic calculationsare takenAn oscilloscope can makeall measurements at thePCC or POA do an on-siteharmonic evaluation.PCCUtility SideGeneratorSet____Volts____VoltsCustomerTransformer____Volts____kVA____Isc____ImpedanceHarmonic ReductionMethods to Meet IEEE 5191. Line ReactorA line reactor is a three-phaseseries inductance on the lineside of an AFD. If a linereactor is applied on all AFDs,it is possible to meet IEEEguidelines where 10–25% ofsystem loads are AFDs,depending on the stiffness ofthe line and the value of linereactance. Line reactors areavailable in various values ofimpedance, most typically1–1.5%, 3% and 5%.Source ASource BACMotorACMotorACMotorACMotorACMotorACMotorTotal Linear Motor Loads ____AMPSTotal Non-Linear Drive Loads ____AMPSThe best way to estimate AFD harmonic contribution to an electrical system is to perform a harmonic analysis based on known systemcharacteristics. The one-line in this figure would provide the data to complete the calculations.Line ReactorAdvantages● Low cost● Can provide moderatereduction in voltage andcurrent harmonics● Available in various valuesof impedance● Provides increased inputprotection for AFD and itssemiconductors from linetransientsAFDMotorDisadvantages● May not reduce harmoniclevels to below IEEE 519-1992 guidelines● Voltage drop due to IR loss363636363636363636363636363636363636363636363636363636363636Volume 6—Solid-State Motor Control CA08100007E—April 2011 www.eaton.comV6-T36-195