E.R.C. da Silva

Fault detection of open-switch damage in voltage-fed PWM motor drive systems

This paper investigates the use of different techniques for fault detection in voltage-fed asynchronous machine drive systems. With the proposed techniques it is possible to detect and identify the power switch in which the fault has occurred. Such detection requires the measurement of some voltages and is based on the analytical model of the voltage source inverter. Simulation and experimental results are presented to demonstrate the correctness of the proposed techniques. The results obtained so far indicate that it is possible to embed some fault-tolerant properties for the voltage-fed asynchronous machine drive system.

Fault-tolerant voltage-fed PWM inverter AC motor drive systems

This paper shows how to integrate fault compensation strategies into two different types of configurations of induction motor drive systems. The proposed strategies provide compensation for open-circuit and short-circuit failures occurring in the converter power devices. The fault compensation is achieved by reconfiguring the power converter topology with the help of isolating and connecting devices. These devices are used to redefine the post-fault converter topology. This allows for continuous free operation of the drive after isolation of the faulty power switches in the converter. Experimental results demonstrate the validity of the proposed systems.

A General PWM Strategy for Four-Switch Three-Phase Inverters

A general pulsewidth modulation (PWM) method for control of four-switch three-phase inverters is presented. The proposed vector PWM offers a simple method to select three or four vectors that effectively synthesize the desired output voltage, even in presence of voltage oscillations across the two dc-link capacitors. The method utilizes the so called space vector modulation, and includes its scalar version. Different vector combinations are compared. The effect of Wye and delta motor winding connections over the pulse width modulator is also considered. The common mode voltage generated by the four-switch three-phase converter is evaluated and compared to that provided by the standard six-switch three-phase inverter. Simulation and experimental results are presented to demonstrate the feasibility of the proposed approach

Current control of unbalanced electrical systems

The vector modeling approach is employed to describe the behavior of unbalanced three-phase (three-wire), unbalanced two-phase and single-phase systems. In the case of single-phase systems, a fictitious circuit is introduced in order to create the vector model. Continuous-time and discrete-time current controllers based on the vector approach are presented. The current control scheme is based on two controllers, one for the positive sequence and another for the negative sequence. The controllers are implemented in the synchronous reference frame and in the stationary reference frame. In the stationary reference frame, the use of the same integral gains for both controllers simplifies the equations of the control law especially for single-phase systems. Simulation and experimental results obtained with a pulsewidth modulation voltage-source inverter supplying unbalanced systems are presented.

Vector control strategies for single-phase induction motor drive systems

This paper discusses vector control strategies for single-phase motor drive systems operating with two windings. A model is proposed and used to derive control laws for single-phase motor drive systems. Such model is also employed to introduce the double-sequence controller. Simulation and experimental results are provided to illustrate the operation of the proposed drive systems.

Rotor-flux-oriented control of a single-phase induction motor drive

This paper investigates the vector control of a single-phase induction motor drive to implement low-cost systems for low-power applications. The static power converter side is implemented using a single-phase rectifier cascaded with a four-switch inverter. The vector control is based upon field orientation concepts that have been adapted for this type of machine. Simulation and experimental results are provided to illustrate the system operation.

Induction motor drive system for low power applications

This paper investigates the utilization of three configurations of induction motor drives to implement low cost systems for low power applications. The static power converter side is implemented by using a single-phase rectifier cascaded with a four-switch inverter (FSI). Three types of induction machines are supplied with the static power converter. In the first scheme, a standard three-phase induction machine is employed. In the second, the load is a three-phase induction machine where only two windings are used. In the third, a standard two-phase induction machine is employed. Simulation and experimental results are provided to illustrate the operation of the systems.

Vector and scalar control of a four switch three phase inverter

This paper investigates the PWM operation of a four switch three phase inverter (FSTPI), in the case of digital implementation. Different switching sequence strategies for vector control are described and a digital scaler method is also presented. The influence of different switching patterns on the output voltage symmetry, current waveform and switching frequency are examined. The results obtained by employing the vector and scalar strategies are compared and a relationship between them is established. This comparison is based on analytical study and is corroborated by the computer simulations and by the experimental results. The vector approach makes it easy to understand and analyse the FSTPI, as well the choice of a PWM pattern. However, similar results may be obtained through the scalar approach, which has a simpler implementation. The experimental results of the use of the FSTPI and digital PWM to control an induction motor are presented.

A feasible loss model for IGBT in soft-switching inverters

This paper presents a feasible loss model to estimate IGBT losses in a soft switching operation. The loss model is developed based on the experimental determination of the power losses. This paper investigates the power losses in IGBTs as a function of the circuit and its operation parameters, in order to help the device selection for a given application. In addition, it compares the losses produced by hard-switched and quasisquare-wave inverters for different currents. The study takes into account conduction losses, switching losses (turn-on and turn-off losses) and losses in the passive components.

A Novel Monitoring of Load Level and Broken Bar Fault Severity Applied to Squirrel-Cage Induction Motors Using a Genetic Algorithm

This paper deals with the diagnostic of the signature of rotor broken bars when an induction machine is fed or not by an unbalanced line voltage. These signatures are given by the complex spectrum modulus of line current. In order to make the diagnostic, a genetic algorithm is used to keep the amplitude of all faulty lines. Moreover, a fuzzy logic approach allows us to conclude to the load level operating system and to inform the operator of the rotor fault severity. Several experimental results prove the performance of this method under various load levels and various fault severities. Notwithstanding, this approach requires a steady-state operating condition. The conclusion resulting from this paper is highlighted by experimental results which prove the efficiency of the suggested approach.