الفهرس | Only 14 pages are availabe for public view |
Abstract The research presented deals with a reliable and effieient solid-.tato inv~rter system loaded by an indu- vii ction motor. Experimental investigation as well as theoretieal analysis of the systGm have been carried out • .A d.c. link conver-t er has been d~signed and exe- cuted in the laboratory. The firing circuit has been specially constructed, it delivers hard drive pulses having a frequency which can be smoothly varied from about 15 to 2)0 HZ. Th~ fr·~qUf’ncyvariation is achieved by using an astable mult ivibrator. Frequency variation can be simply done by means afapotenti.0meter. This astable mu Lc i.v Lbrator is thermally stable and is not affected by load transients. Thyristor protection against high dV/dt as well as high di/dt and over-current have been taken into consid6ration. Oscillograms of t he d If’f’erx.n t variables in the system UDd~r investigation have b~en rpcorded. Extensive tests were perLormed for diffsr.0nt circuit conditions under steady end transient states. Bff~ct of the variation of circuit parameters upon the system behavf.oun is also studied Mathe.natical ans Lys,s of the basic circuit as well as of the modified cLrcu i t has been introduced. The mathematical expressions obtained yields a simplified digital computer model~ The analysis is concerned with single phase as well as with three-phase inverter cir~ caits. Digital computer simulation of the system has been executed. Three programs are presented for the three different cases which hai,;~bGCD tackled. These are, the basic circuit with passiva loads, the singl~-phase inve~. rter 10aded by a single phase Lnducti.on motor, and the three-phase inverter-motor set.· The numerical solution has been carried out on the leL 1900 series computer of ~o·Univ8rsity. The program caD execute six different operations. These are, the st art Lng condi t Lon.,the steady state performance, the spssd torque ch8r&cteris- .. tics, the step variation in toXqu8, the step variation in frequency, and the sudden opening in the load termi nals. In the solution of the syst;;:;m,.a g~od method has been adopted ~mich avoids the divergence in the solution of differential equations. How8vt-r, maximum saving for the computer running and storage times have been consi- dered. |