UBC Theses and Dissertations

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UBC Theses and Dissertations

Load sharing schemes in multiple induction motor drive applications using volts per hertz control Iyer, Jaishankar


Multi induction-motor (IM) drives are commonly used to share a mechanical load in a wide range of industrial applications. In many existing auxiliary applications, the traditional low-cost Volts-per-Hertz (V/F) drives are typically used in speed control mode to simultaneously operate several IMs. In multi-machine load-sharing applications, it is preferred to have number of identical IMs to share the load equally. Under ideal conditions, the identical IMs would operate with equal loading. However, in practice deviations of the load sharing among the IMs is possible due to many factors including variations in internal or external parameters and operating conditions of each individual IM. Such deviations may result in disproportionate sharing of the mechanical load and even overloading one or several machines while some machines may be under-loaded. The basic low-cost variable frequency drives (VFDs) with traditional open-loop V/F control scheme fail to share the load under such conditions. In this Thesis, two new methods are proposed to address the load sharing problems under an internal disturbances (such as rotor resistance variations) and external disturbances (such as wheel slippage due to snow/water/oil etc.). The new methods are shown to be effective in sharing the load under disturbances. Moreover, the proposed methodologies may be readily extended to an arbitrary number of motors driving a common mechanical load, and are easy to implement with traditional/existing low-cost VFDs, which may be advantageous for many existing or legacy applications.

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Attribution-NonCommercial-NoDerivatives 4.0 International