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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 1Dr. Eulitz Rev 1 This presentation gives a short explanation of harmonics and reactive power consumption of 6-pulse converters A rectifier with a 6-pulse thyristor bridge is a typical non-linear load For the explanation we use an ideal converter model which is connected to an infinite inductive load. The resulting direct current is ideal smoothed

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 2Dr. Eulitz Rev 1 Net-current I N with ideal smoothed direct current I d V1V2V3 UdUd V4V6V5 IdId IdId -1,5 -0,5 0 0,5 1 1,5 U L1 U L2 U L3 U L1 U L2 U L3 -1,5 -0,5 0 0,5 1 1,5 I L1

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 3Dr. Eulitz Rev 1 Fundamental wave of rectangular current -0,5 0 0,5 1 -1,5 -0,5 0 0,5 1 1,5 I L1 I'=I 1 I1I1

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 4Dr. Eulitz Rev 1 Addition 1 th,5 th harmonic of rectangular current -1,5 -0,5 0 0,5 1 1,5 -0,5 0 0,5 + -0,5 0 0,5 1 I'=I 1 +I 5 I L1 I1I1 I5I5

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 5Dr. Eulitz Rev 1 Addition 1 th,5 th,7 th harmonic of rectangular current -0,5 0 0,5 + -0,5 0 0,5 1 -1,5 -0,5 0 0,5 1 1,5 -0,5 0 0,5 I'=I 1 +I 5 +I 7 I L1 I1I1 I5I5 I7I7

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 6Dr. Eulitz Rev 1 Addition 1 th,5 th,7 th,11 th harmonic of rectangular current -1,5 -0,5 0 0,5 1 1,5 0 0,5 -0,5 0 0,5 1 -0,5 0 0,5 -0,5 0 0,5 + I'=I 1 +I 5 +I 7 +I 11 I L1 I1I1 I5I5 I7I7 I 11

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 7Dr. Eulitz Rev 1 Addition 1 th,5 th,7 th,11 th,13 th harmonic of rectangular current 0 0,5 -0,5 0 0,5 -0,5 0 0,5 -1,5 -0,5 0 0,5 1 1,5 -0,5 0 0,5 + I'=I 1 +I 5 +I 7 +I 11 +I 13 I L1 I5I5 I7I7 I 11 I 13 -0,5 0 0,5 1 I1I1

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 8Dr. Eulitz Rev 1 Distortive reactive power Harmonics do not participate in transmission of active power They generate harmonic reactive power Distortive reactive power

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 9Dr. Eulitz Rev 1 Typical harmonics of 6-pulse bridge connected converters I /I 1 in % Applicable for: DC-dives Diode supply units Thyristor supply units Slip-power reclamation drives Thyrisor-controlled motor

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 10Dr. Eulitz Rev 1 Influence of firing angle Changes of the firing angle cause also a phase shift of the harmonics. (Related to the fundamental wave of the voltage) The active power consumption of thyristor rectifiers also depends on the firing angle

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 11Dr. Eulitz Rev 1 Firing angle = 40 ° UNUN V1V2V3 UdUd V4V6V5 IdId U L1 U L2 U L3 UdUd = 40 °

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 12Dr. Eulitz Rev 1 Net current I N at firing angle = 40 ° V1V2V3 UdUd V4V6V5 IdId IdId -1,5 -0,5 0 0,5 1 1,5 U L1 U L2 U L3 U L1 U L2 U L3 -1,5 -0,5 0 0,5 1 1,5 U L1 I L1

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 13Dr. Eulitz Rev 1 Fundamental wave of rectangle current at variable firing angle - control reactive power -1,5 -0,5 0 0,5 1 1,5 U L1 I L1 ° I1I1 0 0,5 1 1 U d <0 inverter U d >0 rectifier

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 14Dr. Eulitz Rev 1 Estimation of DC-drive‘s reactive power consumption Converter’s apparent power at net-connection S L U d, I d motor connection of converter Active power consumption at net- and motor-connection are identically Motor-voltage U d can be calculated from motor speed, Motor-current I d from motor-torque (Attention in field weakening mode!)

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 15Dr. Eulitz Rev 1 Estimation of bus bar-drive‘s reactive power consumption The intermediate DC-voltage circuit can only transmit active power! The reactive power for the induction machines is stored in the backup capacitors. This means for the active power at the net connected converter: for diode supply unit for thyristor supply unit (mainly caused by the safety margin)

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Harmonics and reactive power ABB Automation File: netzrück-2.ppt 16Dr. Eulitz Rev 1 This presentation does not explain: Effects of commutation commutating reactive power Influence of ripple Statistic effects with many installed drives Influence of rectangle currents‘s edge steepness More information on harmonics, reactive power and reactions on system in the Power NetAnalysis engineer’s training course

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