A 3-level Inverter based Induction Motor Drive for Cane Preparation in Sugar Industry

Abstract

The sugar making process has broadly four steps, namely, cane preparation, milling, clarification and crystallization. In a sugar factory, a share of around 25-30% of total installed power is in Cane Preparation station. The prime mover of cane preparatory devices is invariably a slip ring induction motor (SRIM). For providing load equalization and to mitigate the effect of high swing in load current a flywheel is installed at the far end of the shaft of the preparatory devices and, additionally, a residual resistance (also known as buffer/slip resistance in the industry) is left in-line in rotor circuit throughout the operation. Conventionally, the value of this buffer/slip resistance is kept such so that a 15% slip (or 7.5% slip at some of the installations) is realized at full load. This kind of set up results in huge power loss in cane preparation. In this paper, a simulation study of proposed 3-level inverter based induction motor drive is carried out and the performance is compared with the existing system having SRIM drive and with the recently introduced 2-level inverter based squirrel cage induction motor (SCIM) drive in the industry. The 3-level inverter based induction motor drive is presented for an Open-End Winding Induction Motor (OEWIM) for the application.