《清华大学电力电子与电机集成第二章》由会员分享，可在线阅读，更多相关《清华大学电力电子与电机集成第二章（43页珍藏版）》请在金锄头文库上搜索。
1、TsinghuaTsinghua Univ. DEEAUniv. DEEAChapter TwoAnalysis of Inverter-driven Motor1TsinghuaTsinghua Univ. DEEAUniv. DEEA“In fact, with the inverter as the power supply, the operational conditions of an induction machine are much different from the conventional supply with fixed voltage and frequency,
2、 which implies that the design of induction machines should be reconsidered to make them more suitable for the inverter-driven variable speed systems. ”IEEE Transaction on Energy ConversionChapter Two: -Inverter-driven MotorTsinghuaTsinghua Univ. DEEAUniv. DEEA2-1 Influence of Inverter on the Motors
3、?The mechanical characteristics ? Two key points: There are different combinations of U1and f1for a fixed running point. A speed may have different torque with different T-s curve.3 3)()(22 212 2 11 22 11llem xxsrrfsrpUm T +=TsinghuaTsinghua Univ. DEEAUniv. DEEA2-1 Influence of Inverter on the Motor
4、s?The mechanical characteristics ? Under certain running operations, the T-s curve could move with the increasing or decreasing frequency along with the speed-axis. In this way, the maximum start-up torque could be obtained by decreasing the frequency.4 4TsinghuaTsinghua Univ. DEEAUniv. DEEA2-1 Infl
5、uence of Inverter on the Motors?The distribution of the electromagnetic field5 5111144. 41 fE WKw=EM distribution with closed-loop controlOpen-loop distributionTsinghuaTsinghua Univ. DEEAUniv. DEEA2-1 Influence of Inverter on the Motors?The harmonics of voltage and current6 6三电平明显优于两电平的电压、电流波形比较Tsin
6、ghuaTsinghua Univ. DEEAUniv. DEEA2-1 Influence of Inverter on the Motors7 7TsinghuaTsinghua Univ. DEEAUniv. DEEA2-1 Influence of Inverter on the Motors?The controllable current and flux ? D-axis: magnetizing axis; Q-axis: torque axis ? Constant flux density ? Idsfor whole magnetizing field ? Ir= Iqr
7、and Idr= 08 8Without vector controlWith vector controlTsinghuaTsinghua Univ. DEEAUniv. DEEA?Sizing equation for conventional machine design ? Five equations:2-2 Sizing Equation for Inverter-driven Motor9 96 110)/2(44. 4=goiwBPLDKfWEcos100011=UImP4102=egLBiDQImA112=oi pD=(1) Back-emf equation:(2) Out
8、put power equation:(3) Flux equation:(4) Surface current density equation:(5) Pole pitch equation:TsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing equation for conventional machine design1010sinPCLD=2910cos6 . 8=ABKKCgweDi: stator inteiral diameter L: effecti
9、ve length of stator Bg: flux density in airgap P: rated output power ns: rated speed C: machine constant : efficiency cos: rated power factor Ke: back-emf coefficient Kw: winding coefficient A: surface current density0.930.6T200A/cm cos0.850.950.85egwKBAKTsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizi
10、ng Equation for Inverter-driven Motor? The motor design is for a range operation, not only for a rated point ? The motor running is not only for a high efficiency, also for a high power factor ? The flux distribution of the motor must fit with the current wave to reduce the harmonics ? The motor des
11、ign should match well with the inverter and its control ? Some of the motor performances could be replaced by certain control1111TsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing Equation for Electronic Machines121211 1 1 12cumW IJQ A=),(2321321rhhhbbbfAAs=2 2
12、3321()22sAbbhr=+Frequency equation:Stator current density equation:Slot area of stator:Round slot area:120osPnf =TsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing Equation for Electronic Machines1313111111(/ 2)/(/)(/ 2)/(/)(/ 2)/()giotsoycsBDL PBt Q L KPBhL K=
13、 () ()()1111111/gtsigycosiBBt Q KDBBhP KD=Flux density equations in parts:Flux density in airgapFlux density in teethFlux density in coreKs: flux coefficientTsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing Equation for Electronic Machines1414111/scucuAAK=Rati
14、o of areas in copper and slot:()() ()() ()112121112131111232111 11 11111 11 12222iocoicigi t tsigi cy oysDhhtbQDhrtbQDDhhhrhD BDtGQ B KQD BDhGP BK+=+ +=+ =+=11 112,gg ty tsoysBBGGB KPB K=Where,TsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing Equation for Elec
15、tronic Machines1515()()()()221 111111112 111121111 1122 111112148soityitoityioioQADDGGDGhhQQQQDDGGQQa Db D Dc D =+ =+ + +()()()()()()()()2221 11111 111221 1111 11221112 1112112 1114824481tyttytytytiQaGGGGGQQQQbGGGGQQQcQQGhhDhhQQ =+= +=+= +Stator slot area:TsinghuaTsinghua Univ. DEEAUniv. DEEA2-2 Sizing Equation for Inverter-driven Motor?Sizing Equation for Electronic Machines1616Solution: 10 11 11/2.7 10coss cu igweP nQ AJ D LB xKxK=Definition:11io
