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Conformai mapping is a widespread mathematical technique to approach the electromagnetic study of electric machines. In its practical application, however, it is relatively easy to incur in errors which make results unreliable. In this paper, some fundamental but possibly deceitful facts in conformal mapping application are described, focusing in particular on: energy conservation in magnetostatic...
Cogging torque is a known disadvantage of surface permanent magnet (SPM) machines, especially if equipped with open stator slots. A possible strategy to reduce the cogging torque is to use suitably designed non-isotropic magnetic wedges. The design of such wedges for cogging torque minimization requires a genetic optimization approach. This has been done in previous works using Finite Element Analysis...
Induction motors are presently the most widespread kind of electric machinery used for industrial and general purpose applications. The parameters of their equivalent circuit model can be determined with a combination of magneto-static and time-harmonic Finite Element Analysis (FEA) simulations. This paper investigates how equivalent circuit parameters depend on current and frequency variations. Calculation...
In this paper two possible design alternatives are investigated for a high-power synchronous motor propulsion drive employing two voltage-source inverters for motor supply. The two arrangements are compared based on their steady-state behavior in both normal and faulty conditions (i.e. with one out-of-service inverter), predicted by time-stepping finite-element simulations. Simulation results found...
In three-phase induction machines, the non-sinusoidal winding distribution normally causes space harmonics in the air-gap field, with negative impacts on stray-load losses and parasitic torques. An appropriate coil pitch choice is a traditional design strategy to improve the air-gap field waveform. In this paper an alternative technique is investigated based on using stator coils with unequal size...
Salient-pole synchronous generators are conventional electric machines which have been widely studied over decades. Nevertheless, some aspects still constitute a challenge for designers and need to be approached with state-of-the-art modeling and computation techniques. An example is illustrated in this paper dealing with a 14 MVA synchronous generator. Different design solutions for its damper cage...
Split-phase machines are multi-phase machines whose stator phases are split into two or more three-phase windings. When all windings are equally loaded, the split-phase topology produces a better air-gap field than the usual three-phase one, with beneficial effects on rotor additional losses and torque quality. This does not occur when the windings are differently loaded, as typically occurs is split-phase...
In high-power electric drives the use of multiple three-phase stator windings, supplied by voltage-source PWM inverters, is a design strategy for power rating, performance and reliability enhancement. Possible drawbacks, highlighted in the literature, come from the high-frequency circulation currents that originate in motor phases due to PWM switching. When a synchronous machine is used as the motor,...
Multi-phase machines are of increasing importance in today's electric drives and generation systems. While in three-phase machines stator leakage flux phenomena are usually described with a single parameter, a higher number of independent leakage inductances is required as the number of phases increases. The impact of leakage inductances on multi-phase machine performance, especially in PWM inverter-supplied...
When an induction motor is supplied by a PWM voltage source inverter (VSI), flux pulsations due to voltage harmonics cause extra power dissipation for hysteresis and eddy-currents in the magnetic core. Based on the expected inverter output voltage spectrum, a finite element analysis method is discussed in this paper to predict supply-related additional core losses. The finite element motor model is...
This paper deals with the electrical modeling of synchronous machines equipped with more than one three-phase stator windings. First, the general model structure is derived in a stationary reference frame and transformed into the d-q coordinates. For both forms, a minimal common set of parameters is defined to fully characterize the stator portion of the model, which is the only one differing form...
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