S.N. Bhadra

Analysis of parallel-operated self excited induction generators

The paper presents an iterative solution for the problems related to steady state performance of self-excited induction generators operating in parallel. The analysis is based on voltage and current balance equations derived from an inverse-model for the steady state equivalent circuit of induction machines. The nonlinearity in the magnetization characteristics has been taken into account by piecewise linearisation. The proposed method is general and can be applied for analysis of any number of parallel connected machines. Theoretical predictions and experimental results are presented to study different performance characteristics of the system.

Excitation requirements for stand alone three-phase induction generator

Self excitation in induction machines depends on appropriate combination of speed, load and excitation capacitance. This paper presents direct methods derived from loop and nodal analyses to find different criteria for maintaining self-excitation. Unlike available techniques, the inverse-model for the steady state equivalent circuit has been used. This is found to be of much assistance in the analysis. Besides determination of speed-limits for fixed terminal parameters, and capacitance requirement under varying speed and load, a method to test the possibility of self-excitation for known speed, load and terminal capacitance has also been presented.

Analysis of parallel-operated self-excited induction generators

The paper presents an iterative solution for the problems related to steady state performance of self-excited induction generators operating in parallel. The analysis is based on voltage and current balance equations derived from an inverse-/spl Gamma/ model for steady state equivalent circuit of induction machines. The nonlinearity in the magnetization characteristics has been taken into account by piece-wise linearisation. The proposed method is general and can be applied for analysis of any number of parallel connected machines. Theoretical predictions and experimental results are presented to study different performance characteristics of the system.

Performance of parallel-operated self-excited induction generators with the variation of machine parameters

A stand alone system consisting of induction generators connected in parallel, has been considered in this paper. Detailed investigation of such system is carried out to find the influence of machine parameters on system performance. The inverse-/spl Gamma/ model of the per-phase steady state equivalent circuit has been used for the analysis. The nonlinearity imposed by the magnetization characteristics of the machines, calls for iterative technique for the solutions of equations derived from the inverse-/spl Gamma/ model. From the investigation it has been found that rotor resistance being the most sensitive parameter, needs careful selection/design. Influences of other parameter variations have also been presented.

An inverter-fed self-controlled commutatorless series motor with the field winding in the DC link

This paper examines the basic operation of a self-controlled synchronous motor driven by a three-phase MOSFET inverter with the field winding located in the DC link, yielding inherent series characteristics like a DC series motor. A new approach to the analytical and experimental study of the drive with the switches conducting for both 120/spl deg/ and 180/spl deg/ is presented, and typical results, both simulation and experimental, are shown and the performance characteristics compared. The effect of shifting the rotor position sensor is studied for both cases, as well as for four-quadrant operation. It is observed that the resulting drive system is simple, able to operate with reduced torque ripples and voltage spikes, and the characteristics of the drive are well suited for traction/transit propulsion applications and battery/flywheel energy storage systems.

Regenerative Braking Performance Analysis of a Thyristor-Chopper Controlled DC Series Motor

This paper presents a comprehensive analysis which predicts the performance of a thyristor-chopper controlled dc series motor during regenerative braking operation. The analysis takes into account all the possible modes of operation during this type of braking, the nonlinearity of the magnetization characteristics including the variation of the field inductance, and the effect of the commutating capacitor in the chopper circuit on the braking performance. It is shown from the computed results that above a critical speed, the value of the commutating capacitor sets a maximum value of mark/space ratio of the chopper regulator beyond which the regenerative braking operation fails. Typical test results on a practical system are shown to agree with the computed results.

Some studies on the parallel operation of self excited induction generators

The performance of parallel self-excited induction generators with common excitation capacitance under steady-state balanced conditions was investigated. The machines may be of different ratings and run at different speeds. Investigations cover maintaining constant terminal voltage and bus voltage regulation with fixed excitation capacitors under varying load and speed conditions. Limited experimental results are presented in support of the analysis. The algorithm based on the analysis is easy to implement.<<ETX>>

Controllable DC power from self-excited induction generator through series connected single phase force-commutated rectifiers

The generation of DC power by a capacitor self-excited induction generator is considered. The isolated phases of the induction generator feed the load through single-phase force-commutated rectifiers, which are connected in series. By controlling the ON-OFF instants of the switching devices the fundamental component of the rectifier input current is made to lag or lead the corresponding voltage, thereby producing reactive power, which either assists or opposes the VArs supplied by the existing capacitors. This is to maintain good DC voltage regulation under varying speed or load condition. Procedures are laid down to determine the capacitance requirement to maintain desired terminal voltage of the generator and the firing instants of the converter devices to meet the required output characteristics. Computed results are presented indicating the performance of the system. Limited experimental observations are also indicated.<<ETX>>

Performance of an inverter-fed self-controlled synchronous motor with series characteristics

The paper describes the operation of a synchronous motor in the self-controlled mode, yielding series characteristics. The drive consists of a single-quadrant transistor chopper and a three-phase transistor inverter feeding the armature of a synchronous machine. The field winding in series with an additional inductor, both clamped with a diode, forms the DC link choke. The switching signals for the inverter are derived from a rotor position encoder in a way to ensure an average orthogonal relationship between the field and the armature MMFs. The field winding in the DC link makes the excitation MMF proportional to the armature current resulting in series characteristics. Analytical treatment for the steady state performance of the drives as well as a digital computer simulation study for the dynamic behaviour of the scheme, under certain justifiable assumptions, is presented. An experimental model using a laboratory type synchronous machine is built and tested. Performance characteristics of the drive determined from the test results and predicted from the analyses resemble those of a DC series motor.<<ETX>>

A novel two phase self excited induction generator-series connected converter system as DC power supply

The paper presents a new DC power supply based on a two phase induction generator coupled to two series connected transistor power converters. The base drives of the transistors are adjusted so that the power converter can generate the required amount of VAr (lag/lead) to maintain a strictly constant output voltage. The results of studies show that more than the rated power can be extracted from the induction generator at some combinations of terminal capacitance and speed. The load and speed range of the proposed system are derived. For experimental verification, a laboratory type two-phase induction generator was chosen. The results are in good agreement with those obtained from analyses.<<ETX>>