Magnetization Curve Identification of Vector-Controlled Induction Motor at Low-Load Conditions

Abstract

Original scientific paperIn many drives the induction motor torque is transferred to the load through complex mechanical connections which produce an initial load. In such cases, to identify the magnetization curve by the no-load test it is necessary to decouple the motor from the transfer gear what is expensively and time-consuming. In an attempt to avoid the motor mechanical decoupling in the case of hoist crane systems, in this paper a method is proposed for the magnetization curve identification of the indirect rotor flux oriented (IRFO) induction machine at low-load conditions. Two flux controllers with estimated feedback quantities are added to the basic structure of the IRFO control drive. One of these controllers is used to control desired operating point on the magnetization curve and the other for on-line adaption of the reference frame position. The proposed algorithm is implemented in a commercial drive as a part of the self-commissioning module. Afterward, the magnetization curve of the 22 kW induction motor was identified and compared with the one obtained by the no-load test. The method sensitivity to the load torque and the transient inductance has also been considered. Key words: Induction motors, Magnetization curve, Parameter estimation, Vector controlOdredivanje krivulje magnetiziranja vektorski upravljanog asinkronog motora kod malih opterećenja. Brojni su primjeri pogona u kojima se moment asinkronog stroja prenosi na radni mehanizam preko mehaničkih reduktora koji mogu predstavljati značajno opterećenje motoru i u režimu neopterećenog pogona. Da bi se u takvim slučajevima odredila krivulja magnetiziranja iz pokusa praznog hoda nužno je odspojiti motor od reduktora što je skupo i vremenski zahtjevno. U pokušaju da se izbjegne mehaničko odspajanje motora kod dizaličnih sustava, u ovom je radu predložena metoda za odredivanje krivulje magnetizranja vektorski upravljanog asinkronog motora kod malih iznosa opterećenja. Dva regulatora ulančenog toka s estimiranim veličinama u granama povratne veze dodani su osnovnoj strukturi vektorski upravljanog pogona. Jedan od regulatora koristi se za upravljanje željenom radnom točkom na krivulji magnetiziranja dok se drugi koristi za podešavanje referentnog položaja vektora toka rotora. Predloženi algoritam implementiran je u komercijalnom uredaju kao jedan od samopodešavajućih modula koji se koriste prilikom puštanja u rad pogona. Nakon toga je opisanim postupkom odredena krivulja magnetiziranja 22 kW asinkronog motora i usporedena s krivuljom dobivenom iz klasičnog pokusa praznog hoda. Takoder je razmotrena i osjetljivost metode na iznos momenta opterećenja i tranzijentnog induktiviteta.

Induction motor pre-excitation starting based on vector control with flux linkage deviation decoupling

“…Frequency conversion starts control on induction motors is becoming an important part of industry research. Generally, the induction motor starting performance is hoped that the torque responds rapidly to ensure the normal operation of machinery in the starting process, and the starting current is as small as possible to avoid the impact on the grid [1][2][3]. In actual application, especially to a large power induction motor, because of its large capacity and the moment of inertia is large, when the applied voltage is not suitable, it will produce a huge peak current.…”