Nikos Margaris

Loss minimization in induction motor adjustable-speed drives

A loss model controller (LMC) for determining the optimal air-gap flux that minimizes the losses in scalar controlled induction motor drives is presented. The suggested LMC is simple, and its implementation does not affect significantly the cost and the complexity of the drive. Although the conception of the suggested LMC is based on the loss model of the induction motor, it is shown that its realization does not require knowledge of the loss model.

Loss minimization in scalar-controlled induction motor drives with search controllers

Loss minimization in scalar-controlled induction motor drives (IMD) with search controllers (SC) is investigated. The problems arising when the input power is used as the controlled variable are described. It is proved that better results are achieved if the stator current is used as the controlled variable.

Loss minimization in vector-controlled interior permanent-magnet synchronous motor drives

An efficiency optimization method for vector-controlled interior permanent-magnet synchronous motor drives is presented. Based on theoretical analysis, a loss minimization condition that determines the optimal d-axis component of the armature current is derived. Selected experimental results are presented to validate the effectiveness of the proposed control method.

Optimal efficiency control strategy for interior permanent-magnet synchronous motor drives

In this paper, the problem of efficiency optimization in vector-controlled interior permanent-magnet (PM) synchronous motor drives is investigated. A loss model controller is introduced that determines the optimal d-axis component of the stator current that minimizes power losses. For the implementation of the suggested controller, the knowledge of the loss model is not required since an experimental procedure is followed to determine its parameters. Furthermore, it is shown that the loss model of the interior PM motor can be used as a basis for deriving loss minimization conditions for surface PM synchronous motors and synchronous reluctance motors as well. Experimental results of an interior PM motor are presented to validate the effectiveness of the proposed method and demonstrate the operational improvements.

Loss minimization in surface permanent-magnet synchronous motor drives

The loss minimization in surface permanent-magnet synchronous motor drives is investigated. Based on theoretical analysis, a loss model controller is introduced to specify the optimal air-gap flux that minimizes losses. Theoretical results are verified experimentally. The proposed loss model controller is simple and does not adversely affect the cost and complexity of the drive. Implementation of the loss model controller does not require knowledge of the loss model. The suggested loss minimization method can be applied both in V/f- or current-controlled schemes.

Thermal and slip effects on rotor time constant in vector controlled induction motor drives

In this paper, the fast variation of rotor resistance due to winding temperature is shown. Thus, the rotor time constant in the vector controlled induction motor drives, in contrary to common belief, changes fast via temperature. Moreover, it depends on the motor slip. The slip dependency of rotor time constant is due to motor loss that is usually ignored. The iron and stray loss is introduced in the induction machine dynamic and static models and a new expression of the rotor time constant is derived, that contains the motor slip. Thus, the rotor time constant rapidly varies at load torque changes. A novel slip frequency calculation procedure is proposed that ensures the accurate and fast estimation of the valid machine rotor time constant. The above aspects have been verified by extensive simulation and experimental tests in a wide speed-torque range.

Loss minimization in DC drives

A method for determining the optimal DC machine excitation for loss minimization is presented. The proposed method may be implemented by using either analog or digital techniques. The method is simple, and its implementation does not affect significantly the cost, the complexity, and the dynamics of the DC drive. Thus, energy can be saved without sacrificing the quality of the DC drive. Even though the conception of the proposed method is based on the loss model of the DC machine, it is shown that its realization does not require knowledge of the loss model. >

Calculation and stability investigation of periodic steady states of the voltage controlled Buck DC-DC converter

A new method for investigating the complex dc-dc converters dynamics is suggested in this paper. The method is based on the formulation of a nonlinear difference equation with respect to the duty cycle. This equation embodies the nonlinear and discrete-time characteristics of dc-dc converters and allows both the calculation of normal and subharmonic steady states and their local stability analysis. The method is presented through the analysis of a voltage controlled Buck dc-dc converter.

Voltage Pump Phase-Locked Loops

This paper is concerned with the phase-locked loop with Voltage Pump Phase Frequency Detector (VPPFD) and resolves the differences in explanation about its somehow peculiar behavior appearing in the literature.

Magnetic and thermal performance of a synchronous motor under loss minimization control

The steady state magnetic and thermal performance of a wound-field cylindrical rotor synchronous motor under loss minimization control is investigated. The calculated magnetic field waveforms are presented and it is shown that loss minimization control decreases the magnetic saturation. It is also proved that although the optimal stator current is increased, the temperature is decreased in all parts of the motor. Theoretical and experimental results are presented to verify the operational improvements.