Ashoke K. Ganguli

Development, Analysis and Control of an axial flux Permanent Magnet Linear Oscillating Motor suitable for short strokes

Development, Analysis and Control of an axial flux Permanent Magnet Linear Oscillating Motor(PMLOM) along with a suitable speed and thrust control technique is described in this paper. Also its performance parameters, such as the force, current, Efficiency, Power factor etc. are experimentally assessed. The objective of this paper is to determine the forces for aluminium mover embedded with the rare earth permanent magnet experimentally and analytically through FEM software and develop a low cost solution for its control.

Modeling and estimation of core losses for doubly-fed wound rotor induction machine

Wound-rotor induction motor drive fed from inverters on both the stator and rotor side is discussed. The sensorless control scheme for the motor requires a V/f-type direct frequency control preferably on the rotor side, with either vector control or direct torque control on the stator side. Selection of any frequency for the rotor side inverter keeping the rotor flux constant is possible. This rotor frequency will decide the selection of the stator side frequency. In this paper, a study on core loss at different rotor injected frequencies is carried out at different loads. Also to operate the motor at an optimum efficiency during any loading condition, a method for correct selection of stator and rotor frequency is studied. It is also shown that core losses constitute a considerable amount of the total losses and hence should not be neglected for the sake of efficiency. Experimental results on a real machine are presented in support of the proposed concept.

Development of low cost single phase self excited wind generator using three phase machine

Conventional three phase induction generators connected to wind turbines are extensively used nowadays for providing grid connected as well as isolated loads. This paper presents an enhanced low cost single phase self excited induction generator (SEIG) using a three phase machine. Reactive power for such an induction generator is provided partially through a fixed capacitor and strategically through an inverter for constant voltage and frequency operation. This dc source is a photovoltaic (PV) module connected to the inverter input. Appropriate experimental and simulation results validate the proposed strategy.

An online core loss estimation technique for self-excited induction generator

A simple method for on-line calculation of core losses is developed. The method is based on the separation of core loss into hysteresis and eddy current components. The generated voltage of a self excited induction generator (SEIG) is neither purely sinusoidal nor its frequency is fixed. For the current analysis sinusoidal flux wave form is considered for simplicity. When the frequency of the generated voltage of SEIG increases, the core loss of the machine also increases. This increased core loss can make the machine overheated during its operation which may turn in to machine failure. So online monitoring of the core loss is required for reliable operation of the machine. The proposed model is simple and can be easily implemented with the help of an ordinary processor.

An improved control strategy of self excited induction generator taking magnetization nonlinearity

Self excited induction generators (SEIG) are being widely used in wind power generation, especially for supplying electric power in remote areas. The major problem of such generation is to maintain constant voltage and frequency under variable load and variable wind speed condition. In this paper a control strategy involving supply of reactive power to the generator partially through fixed capacitor bank connected at the stator terminals and switched dc power source is proposed for constant voltage and constant frequency operation. The dc source can be a battery charged from the generator during a light loaded condition. The method is simple and can be implemented through a low cost inverter of smaller size for supplying reactive power only and for a large change in operating condition another additional set of fixed capacitor can be switched to reduce the reactive power loading on the inverter. Suitable simulations and experiments are performed to validate the proposed concept.

A Photovoltaic-based Improved Excitation Control Strategy of Three-phase Self-excited Induction Generator Suitable for Wind Power Generation

Abstract—Self-excited induction generators are extensively used for wind power generation in remote and grid-isolated areas. It is challenging to maintain constant voltage and frequency under variable loads and variable wind speed conditions for such kinds of generators. This article proposes a hybrid reactive power control technique for induction generators through a fixed capacitor bank connected at the stator terminals and a strategically switched inverter source. The inverters DC bus is connected to a photovoltaic panel and a storage battery. This scheme provides stable voltage output with changing loads and widely varying wind speeds. The capacitor provides the bulk excitation current for the induction generator, while the inverter provides the additional reactive current desired to regulate the generator output voltage under variable wind speeds and variable loads. Suitable simulations and experiments validate the proposed concept.

A modified non-dissipative LC snubber circuit for MOSFET based fly-back converters

High frequency converters with different switching topologies are now being widely used over a wide range of applications, which mainly includes different types of power supplies. Snubber circuit design for high frequency-switched converters using MOSFET as a power device assumes different dimension as regards the minimisation of the power dissipation in the snubber resistance. This paper shows a different mode of operation to reduce the clamp voltage across the device used in fly-back type converter. The LC snubber circuit is almost lossless and of energy regenerative type. A reduced clamp voltage is required not only for device protection, but also to reduce the cross regulation effect in multiple output converters. Simulations and experimental results validate the concept.

A simple approach to rotor flux estimation without integration for a DSP based speed sensorless vector control of induction motor

In this paper a simple field orientation control scheme for induction motor is described. The principle is based on the idea of a simplified equivalent circuit of the machine and the orientation of the fluxes, currents and voltage vectors. Here the determination of stator flux avoids integration, which is increasingly difficult when the speed reference becomes lower down to almost zero. In order to estimate the stator flux, a simple algorithm based on the principle of orthogonality of stator flux and stator induced e.m.f. vectors is used. The proposed control technique is validated by some simulation results and also experiments were conducted which showed conformity to the theoretical basis and simulation results.