Reflected wave transient voltages that are impressed on drive output cables and low voltage AC induction motors are normally simulated with steep fronted dv/dt pulse waveforms from PWM voltage source inverters. System simulation arises from a need to correlate reflected wave peak voltage and risetime with the dielectric insulation capability of both the motor and cable. To obtain reasonable results, accurate models of each component must be employed. This investigation concentrates on parameter identification for a high frequency resonant tank motor model from fractional to several hundred horsepower

Kerkman, Russ

Schlegel, Davia W

Skibinski, Gary

Wrate, Glenn T

English

Northern Michigan University: The Commons

Northern Michigan UniversityNMU CommonsConference Papers in Published Proceedings FacWorks5-1999Resonant Tank Motor Model For VoltageReflection Simulations With PWM DrivesDavia W. SchlegelRockwell Automation, dwschlegel@ra.rockwell.comGlenn T. WrateMilwaukee School of Engineering, gwrate@nmu.eduRuss KerkmanRockwell AutomationGary SkibinskiRockwell AutomationFollow this and additional works at: https://commons.nmu.edu/facwork_conferencepapersPart of the Electrical and Electronics Commons, and the Power and Energy CommonsThis Conference Paper in Published Proceedings is brought to you for free and open access by the FacWorks at NMU Commons. It has been acceptedfor inclusion in Conference Papers in Published Proceedings by an authorized administrator of NMU Commons. For more information, please contactkmcdonou@nmu.edu,bsarjean@nmu.edu.Recommended CitationSchlegel, Davia W.; Wrate, Glenn T.; Kerkman, Russ; and Skibinski, Gary, "Resonant Tank Motor Model For Voltage ReflectionSimulations With PWM Drives" (1999). Conference Papers in Published Proceedings. 70.https://commons.nmu.edu/facwork_conferencepapers/70IFFF IFMDC dim=w9/’30/9SResonant Tank Motor Model For Voltage Reflection SimulationsWith PWM DrivesD. Schlegel* G. Wrate** R. Kerkman* G. Skibinski** Rockwell Automation6400 W. Enterprise DriveMequon, WI 53092(414) 512-7088 (414) 512-8300 FaxAbstract: Reflected wave transient voltages that areimpressed on drive output cables and low voltage acinductionmotorsare normatlysimulatedwith steep fronteddvhil putse waveforms from PWM voltage source inverters.System ahmdation arises from a need to correlate reflectedwave peak voltage and risetime with the dielectric insulationcapability of both the motor and cable. To obtain reasonableresul~ accurate models of each component must heemployed. This investigation witl concentrate on parameteridentification for a hlgb frequency resonant tank motormodel from fractional to severat hundred horsepower.I. IntroductionThe increasing use and issues associated with PWMdrives has caused applications engineers to approachinstallations with caution. The use of accurate componentmodels provides the designer with a measure of comfort inthe systems performance. Numerous simulation packageshave become available over the years, such as TransientNetwork Analyzer’s (TNA’s) in the 1930’s, ElectroMagnetic Transients Program (EMTP) in the late 1970’s[1], PSpice in 1984 [2] and MATLAB in 1990 [3]. PSpiceis among the more popular simulation tools, due to itsavailability and numerous developed models. MATLABhas spawned SIMULINK, the object-oriented languageused in this paper.II. Drive System ModelAc drive systems have become increasingly complexand require simulations to aid their design. Thecomplexity of a simulation is dictated by the particularsubsystem analyzed. Evaluation of high frequency effectsnecessitates simulation times based on the smallesteigenvalues. The desired accuracy places constraints onthe simulation package and corresponding componentmodels. Recently, a SIMULINK based drive system toolwas proposed [4]. The simulation separated theapplication into three subsystems, drive (source), cable(transport delay), and machine (load). The transport delayfeature of the program was used to simulate the travelingwave propagation time fairy accurately. Cable skin andproximity effects of cable resistance may be modeledeasily. The source – using a step function - models theIGBT risetime from the drive. The motor was modeledwith a combination of motor surge impedance, statorresistance, high frequency capacitance and windinginductance. Many of the parameters of the system are not** Milwaukee School of Engineering1025 N. BroadwayMilwaukee, WI 53202readily known through published literature or are difficultto predict. Therefore, this investigation will concentrateon motor model parameter identification from fractionalto several hundred horsepower.III. Motor ModelThe adverse effects of steep voltage wavefronts onmachine windings have resulted in extensiveinvestigations into motor terminal overvoltages [5-10].IGBT based PWM voltage source inverters, with verysmall rise times, subject ac induction motors to extremevoltage stress thousands of times per second. Peak line-to-line terminal over-voltage (Vpk) at the receiving end of aninitially uncharged transmission line subjected to a singlePWh4 pulse with risetime (tr), is derived in [11].A. High Frequency Models of A C MotorsNumerous investigations into high frequency modelingof ac induction machines were recently reported [12-17].High frequency motor models may be subdivided into twobroad categories: Finite Element Analysis (FEA) andreduced order models. FEA models examine the machineon a per turn level [12], but they are complex andprimarily for motor design purposes. Reduced ordermodels are developed for simulation tools designed toexamine application specific problems [4,9, 14].B. Motor Model for Di#erential Reflected WaveSimulationsAs derived in [4,10], a differential or line-to-line motormodel for purposes of predicting the peak line-to-linemotor terminal voltage (Vt) is set forth in Fig. 1. Thecircuit topology, essentially a resonant tank, provides arelatively simple interface to transmission line models.cVt “R 2000 tFig. 1. Differential Mode Motor Model.L LFR L’0-7803-5293-9/99 $10.00 @ 1999 IEEE 463IEEE IEMDC digest 9/30/98The parameters are obtainable through systemidentification procedures and tabulated motor data. At lowfrequency, the motor behaves as an inductive dominantseries impedance (R + jo)L). At high frequent y, the motorbehaves as a capacitive dominant series impedance (R +1/jo)C). In Fig. 1, the low frequency inductance, LLF,(consistent with low frequency motor amlysis) is in serieswith the low frequency stator resistance, RLF. The highfrequency resistance, RZO, corresponds to the surgeimpedance of the machine and establishes the reflectioncoefficient, with the high frequent y capacitance, CHF,appearing as a short.C. LCR Measurements and Trends in Motor Impedanceand Phase Angle.A Hewlett Packard Impedance Amlyzer (HP4284),with a frequency range of 20 Hz to 1 MHz, was used tomeasure the impedance and phase angle of over 30 motorsacross a broad range of horsepower. The impedancemagnitude and phase angle changed with excitationfrequency. At low frequency, all the machines had an100000100001 hp1000E~100!Ag 1010110 100 1000 10000 100000 1000000Fraquency (Hz)Flg 2 hnpedance Magnitude for 1, IO, and 100 hp Motors~luo)EsQfm .g~ma 1 hpg to 3 hp15 h1 i) m tmmllmmm-!+4Fig. 3. Impedance Magnitude fix 1,3, 15, and 40 hp Motorsfmm the Sarrx Manufacturer.inductive dominant series impedance (R + jwL), whichturned into a capacitive dornimnt series impedance (R +l/j(oC) after a resonant maximum is exceeded. The phaseangle switched from inductive (positive) to capacitive(negative) at the resonant maximum point. Higherfrequency measurements were recorded to demonstrateadditional oscillations, but exceeded device limits. TheImpedance vs. Frequency plots for 1, 10, and 100 hpmachines from various vendors are shown in Fig. 2. Arange of motor horsepower impedance from a singlevendor is shown in Fig. 3.To veri~ the symmetry of the windings, the three motorphases were sequentially transposed and measured in eachgrouping. Identical motors were also measured. Whenplotted, both cases showed good agreement. Impedancevariations occurred within identical horsepower ratedmachines with different fiarne sizes. Fig. 4 indicates thestator dimensions and fmme material affect theimpedance. Fig. 5 shows impedance variations within asingle NEMA frame size from different vendors,indicating the manufacturing process effects.100000r10 100 1000 10000 100000 1000000 /Frequency (Hz)..—— JFig. 4. Impedance Magnitude for Three I hp Motorswith Different Frame Styles.1000O1/10 100 lm 1000O 1000OO looOOOoFraqwncy(t+z)Fig. 5. Impedance Magnitude for Three 10 hp MotorsFrom Different Vendors in the Same Frame.464. ..IEEEIEMDC digest 9/30/98Several trends are apparent from the data in Figs. 2-5.First, the low frequency portion (inductive branch) has asimilar slope across the range of motor impedance.Second, as motor horsepower increases, the low ffeqttencyimpedance value decreases. These provide hints about theR~~ and L~~ values. Third, the resonant maximum pointmigrates higher with increasing horsepower. Fourth, thehigh frequency portion (capacitive branch) has a dominantminor oscillation after the maximum point. These providehints about the Rm and CHFvalues. Ongoing work willdevelop equations to model RLF,LLF, CHF,and Rm as afunction of horsepower,D. ldenti~ing Motor Surge Impedance (Rm)Identifying Rw using tnverter Pulses: The apparent Rmobserved during the rising edge of the reflected wave frontwas measured under drive operation [4]. Fig. 9 of [4]shows how Rm varies with horsepower when measuredduring the pulse risetime. Motor surge impedance is notan absolute value, since 1 hp measured values varied from1,000 to 5,000 ohms depending on the manufacturer.Thus, rather than an absolute RW magnitude vs.horsepower line, there is probably a band for model use.!dentifiing Rm with LCR Analyzer: HP4284 test leadswere connected from parallel motor phases A & B tophase C to simulate the surge impedance observed duringa reflected wave transient. Motor surge impedance isinferred from the high frequency capacitive dominantimpedance. When the LCR readings are capacitive, thecorresponding resistance is the surge impedance.E. ldentt~ing High Frequency Capacitance (CHF)The high frequency capacitance, CHF,can be inferredfrom the high frequency capacitive dominant impedancethat occurs after the resonant maximum point. Thecapacitance is hard to quantify, due to the multitude ofwinding configurations possible [14].F. Identifying Low Frequency Inductance (LLF)The low frequency inductance, Lw, is consistent withtraditional motor loads used in low frequency simulations,where a series RL load is used. The Lw can be inferredfrom the low frequency inductive dominant impedance.G. Identifying Low Frequency Resistance (Rw)The low frequency resistance, RLF, is consistent withtraditional motor loads used in low frequency simulations,where a series RL load is used. The Ru can be inferredfrom the low frequency inductive dominant impedance.VI. ConclusionA high frequency resonant tank circuit motor model wasdeveloped for use in simulations of drive systems. LCRImpedance Analyzer measurements were recorded toverify the low frequency inductive impedance (R + j@L),a resonant maximum, and the high frequency capacitiveimpedance (R + 1/j@). The low frequency impedancewas developed into a series resistance (Ru) andinductance (LLF ), while the high frequency was developedinto a series surge impedance (Rm) and capacitance (CHF).The LCR impedance data was correlated and trends wereestablished to assist in model parameter identification.Ongoing work will develop empirically derived equationsfor RLF,LLF,CHF,and Rm as a function of horsepower.References[l] H. Domrnd, E[ectro-magne(ics Trunsierm Program & TheoryManual, Bonneville Power Administration, Portland,OR[2] MicroSim Pspice, MicroSim Corporation.[3] SIMULtNK with Matlab, The Mathworks, Inc.[4] G. Skibinski, R. Kerkman, D. hggate, J. Pankau, and D. Schlegel,“Reflected Wave Modeling Techniques for PWM AC MotorDrives”, tEEE APEC Conference, Anaheim, CA, Fcb 15-19 1998,pp. 1021-1029.[5] P. Van Paucke, R. Belmans, W. Gcysen, and E. Temier,“Overvoltages in Inverter Fed Jnduction Machines Using HighFrequency Power EkxXsonicComponents,” tEEE APEC ConferenceProceeding 1994, pp. 536-541.[6] T. Takahashi, M. Termcyer, T. Lowery, and H. Tsai, “Motor LeadLength ksues for IGBT drives”, IEEE Pulp and Paper ConferenceProceedings, 1995,pp. 21-27.[7] C. J. Melhom and L. Tang, “Transient Effects of PWM ASDS onStandard Squirrel Cage Induction Motors,” tEEE IAS Conference,C)rtando,FL Oct. 8-12, 1995, pp. 2689-2695.[8] B. Kawkabani, J.J. Simond, and F. Kehtari, “Voltage Peaks of LowVoltage Motors Due to PWM Inverter Supply,” EPE ConferenceProceedings 1995, SeviHa,pp. 465-469.[9] A. von Jouanne, P. Enjeti, and W. Gray, “The Effect of Long MotorLeads on PWM Irsverter Fed AC Motor Drive Systems,” tEEEAPEC Conference, Dallas, TX, March 6-9, 1995, pp. 592-597.[10] R. Kcrknum, D. fzggate, G. Skibinski, “Interaction of DriveModulation & Cable Parameters on AC Motor Tmnsients,” IEEEtAS Conference, San Diego, CA, Oct. 6-10, 1996, pp. 143-152.[11] G. Skibinski, “Design Methodology of a Cable Terminator toReduce Reflected Voltage on AC Motors”, IEEE MS Conference,San Diego, CA, October 6-10, 1996, pp. 153-161.[12] G. Suresh, Hamid A. Toliyat, Dudi A. Renduss% and Prasad N.Enjeti, “Ptwticting the Transient Effects of PWM VoltageWaveform on the Stator Whrdings of Random Wound tnductionMotors: tEEE APEC Conference, Atlanta, GA, Feb 23-27, 1997,pp. 135-141.[13] G. Grarrdi, D. Casadei, A. Massarini, “High Fmquency LumpedParameter Model for AC Motor Windings”, EPE Conference,Trondtilm, September 1997, pp. 2.578-2.583.[14] G. Grandi, D. Casad@ U. Reggiani, “Analysis of Common Modeand Differential Mode HF Cummt Components in PWM InverterFED AC Motors; IEEE PESC’98 Conference, Fukuoka, Japan,May 17-22, 1998, pp. 1146-1151.[15] A Consoli, G. Oriti, A. Testa, and A. L. Julian, “Induction MotorModeling for Common Mode and Differential Mode EmissionEvaluation,” IEEE IAS Conference, San Diego, CA, Oct. 6-101996, pp. 595-599.[16] David B. Hyypio, “ Effects of Risetime and Cable Length on MotorInsulation Degmdation Resulting from Operation on PWM VoltageSource tnverters,” tEEE International Electric Machines and DrivesConference, IEMDC Record, May 1997, pp. TCS-2. 1-TCS-2.3.[17] D. Hyypio, “Simulation of Cable and Winding mqonse to SteepFronted Voltage Waves”, IEEE tAS Conference, Orlando, Ft+ Oct.8-12, 1995, pp. 800-806.465.

Resonant Tank Motor Model For Voltage Reflection Simulations With PWM Drives

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Resonant Tank Motor Model For Voltage Reflection Simulations With PWM Drives

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