The paper derives a generalised operational equivalent circuit for induction machines starting from fundamental principles in any arbitrary rotating reference frame. Directly measurable parameters are used in this equivalent circuit. From this generalised model, the equations for any reference frame are derivable as particular cases. The model presented is versatile as it can be used for any operating condition and any asymmetrical connection or switching and for both three-phase and two-phase wound machines. The equivalent circuit provides space phase vectors and the relevant expressions can be used to develop software for online control of motors through field orientation. Different possible modes are considered in this paper to derive relevant equations from the general model to illustrate its potential.

A generalised operational equivalent circuit of induction machines for transient/dynamic studies under different operating conditions

This paper investigates the soft starter torque and flux control (STFC) algorithm for braking induction motors driven by them. In comparison to classic phase angle control approaches, the STFC algorithm considers the rotor flux during the firing pulse generation, additional to the grid voltage. The algorithm and the additional control structure is explained and discussed in detail. Different measurements compare the behaviour with a classic phase swap approach. A special focus lies on the requirements to the constellation of motor and load for a robust performance. A huge advantage of this new braking approach is that no additional equipment such as contactors or rectifiers is necessary, even for braking very high inertias.

Braking Induction Motors Using Soft Starter Torque and Flux Control Algorithm

Induction motor transients under `plugging' is investigated. A realistic plugging contractor is considered, which includes disconnecting the supply, `coasting'-a period when no voltage is applied, and applying a negative sequence voltage to cause braking. A mathematical model to simulate the plugging process is presented and used to predict the transient behaviour of an industrial induction motor under plugging operation, Corresponding results obtained experimentally are also presented and discussed. The effect of the timing of contractor operation on the braking performance is studied. Simulated results indicate that the braking time and peak braking torque are affected considerably by the instant when negative sequence voltage is applied.

http://ieeexplore.ieee.org/iel7/6449389/6451883/06591358.pdf

S. S. Murthy

Papers

Transient performance of induction motors under plugging operation