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The analysis of the transient overvoltages in a pulsewidth modulation (PWM) motor drive system comprises a wide frequency range, which starts with the low values corresponding to the motor speed, includes the switching harmonics, which can reach up to few hundreds of kHz, and also the cable resonance frequency, which value can be in the MHz range, depending on the cable length. In this context, this work presents a time domain methodology for cable modeling able to represent the cable parameters variation due to skin effect in this broad range of frequencies. The proposed technique reproduces accurately the wave propagation and reflection phenomena, thus showing to be very appropriate to transient overvoltage studies in PWM motor drives. A new alternative to represent the frequency-dependent cable earth-return path is also included, allowing the computation of the zero-sequence currents generated by the common-mode voltage produced by the inverter. Simulations using the proposed methodology are conducted and the obtained results are compared with measurements, showing good agreement. Index Terms--Cable modeling, common-mode currents, pulsewidth modulation (PWM) motor drive, skin effect, transient overvoltages.

This paper presents a new strategy for modeling the saturated induction machine. Saturation is considered by means of 'magnetic harmonic functions,' defined in the model and obtained experimentally, considering the fundamental and third harmonic of the spatial flux density distribution. It is shown that the distortions on voltage and current waveforms are due to harmonic content in the main flux, caused by saturation. Experimental and theoretical results for a capacitor self-excited induction generator are presented to show the validity of the proposed model. Index Terms--Induction generators, induction machines, iron saturation, modeling.

The paper proposes a current controlled inverter operating in zero voltage switching (ZVS) mode for an induction machine drive. Operation with no voltage stress in the dc link bus is achieved. Together with the soft switching operation, a fixed frequency bang-bang current control technique is also implemented to allow for an accurate shaping of sinusoidal currents to feed the motor. As a result, a ripple free torque profile in steady state operation is achieved. With the soft switching technique it is possible to operate conventional IGBTs at 40 kHz. A detailed analysis of the circuit operation is presented. The feasibility of the proposed scheme is experimentally verified on a prototype. Index Terms--AC motor drives, induction motors, insulated gate bipolar transistors, lossless circuits.