Ritesh Kumar Keshri

Torque Ripple-Free Operation of PM BLDC Drives With Petal-Wave Current Supply

Further to the vector analysis in the stationary plane of the behavior of a permanent-magnet brushless dc (PM BLDC) drive, this paper proposes a method of synthesizing the current supply of the motor that ensures torque ripple-free operation of the drive. The synthesis is carried out analytically by the vector approach, and the resulting current vector is then expressed in motor phase coordinates. It comes out that the current vector has a petal-shape trajectory in the stationary plane. The operation of the drive with such a current supply is extensively examined; in particular, the torque capability for an rms value of the phase currents equal to the rated one, the requirements for the voltages to be applied across the motor terminals, and the base speed in correspondence to the supply voltage saturation are determined. At last, experimental traces obtained from an in-wheel PM BLDC drive used for the traction of light electric vehicles are included to corroborate the theoretical findings.

Analytical study of Torque vs. speed characteristics of PM brushless DC drives

PM brushless DC (BLDC) motors should be fed by square-wave currents synchronized with the back emfs to develop a constant torque with the required value. In practice, phase inductances and limited source voltage produce non ideal square-wave currents and unbalanced phase currents during commutations. Such phenomena affect the torque developed by the PM BLDC drives by deviating its value from the requested one and by giving rise to torque ripple. In this paper, an analytical study of the torque characteristics, namely motor torque and torque ripple, of PM BLDC drives is carried out as a function of the motor speed and is supported by experimental data. Torque characteristics are expressed in terms of a quantity distinctive of the motor, thus giving a generalized formulation to the results.

Sinusoidal Versus Square-Wave Current Supply of PM Brushless DC Drives: A Convenience Analysis

Permanent-magnet (PM) brushless direct current (BLDC) drives are utilized in a variety of applications because of their inherent features and would be even more utilized if their torque performance could be improved. Indeed, when supplied with square-wave currents, the torque-speed characteristic undergoes a drop at high speeds, and a significant torque ripple arises at both low and high speeds due to the commutation phenomena. In this paper, the sinusoidal current supply of the PM BLDC motors is investigated in depth, and an analytical formulation of the torque-speed characteristic, the torque ripple, and the base speed for such a supply are found. Based on the resulting equations, a thorough convenience analysis of the sinusoidal current supply is carried out with respect to the square-wave current in the presence of the commutation phenomena, which is hereafter termed as the real square-wave current supply. Simulation and experimental tests for a study case are given to corroborate the theoretical results. Generation of the sinusoidal current references using Hall sensors is also discussed.

Characteristics of Z-source inverter supply for permanent magnet brushless motors

Z-source inverters (ZSIs) supply ac loads from a dc source and boost the voltage of the dc source in a single stage. Such an ability is much needed in electric vehicles where the rated voltage of the traction motors is usually higher than the voltage generated by the onboard dc sources. Being the technological trend in the traction drives directed toward the employment of PM brushless motors, the use of a ZSI for their supply is a cuttingedge issue, which is investigated in this paper. The paper starts by formulating the equations of a ZSI in a suitable form. Then the characteristics of the ZSI supply for the two basic types of PM brushless motor, namely the dc and ac types, are assessed with regards to the switch solicitation and utilization. As a comparison, the characteristics of the traditional dc-dc boosted inverter supply are also given.

Integration of a Photovoltaic Panel with an Electric City Car

Abstract—Autonomy of light electric vehicles with limited mobility can be improved by assisting onboard energy sources, such as battery and ultra-capacitors, by solar energy. This article discusses the integration of a photovoltaic panel with an electric city car. The Photovoltaic Geographical Information Systems of Joint Research Center, Europe, is used for estimating the solar irradiance. Based on the estimations, a DC-to-DC boost converter topology is considered to interface the panel with the DC bus of the electric car. Experimental evaluation of the performance is carried out under a real climatic situation. An analytical loss model is used to comment on the associated losses and to explain the measured changes in gain and efficiency under varying irradiance. Acceptable extension in the autonomy of the electric city car is predicted from the results.

Hardware development of Voltage Source Inverter for Hybrid Electric Vehicle

The global desire to reduce the vehicle emissions and improve fuel economy accelerated the development of Hybrid Electric Vehicle (HEV). The technology advancements in the area of electric drive systems, battery technologies, fuel cells and the internal combustion engine (ICE) resulted in highly efficient HEV. In this paper the hardware details of three phase, 50Hz, 6KW, 180° conduction mode of Voltage Source Inverter (VSI) was explained. The output waveforms under various load conditions were presented and discussed.

Stationary plane based investigation of the behavior of PM BLDC drives

The paper investigates the behavior of permanent magnet (PM) brushless DC (BLDC) drives in the stationary plane. The vectors of the phase currents and back-emfs are first drawn under ideal square-wave current supply. Development of a constant torque from the motor is explicated with the help of the vector representation. Trajectories of the tips of the motor current and voltage vectors are then traced for various motor speeds taking into account the phase commutations. Torque developed by the motor and its ripple are determined from the vector tip trajectories. Theoretical findings are supported by simulation results obtained by using the data of a PM BLDC drive designed for the propulsion of electric vehicles.

Comparison of DBI and ZSI supply for PM brushless DC drives powered by fuel cell

Nominal voltage of the traction motors being used in electric vehicles is typically higher than the voltage generated by the onboard DC sources. Thus, motors of AC type require boost as well as inversion of available DC voltage. This can be done either by a DC-DC boosted inverter (DBI) or by the recently introduced Z-source inverter (ZSI). Since drives with PM brushless DC (BLDC) motor are largely utilized in the traction of light electric vehicles, it is of interest to carry out a comparative analysis of the two supplies when feeding such kind of motor. In this paper, DBI and ZSI supplies are designed for the study case of an electric city scooter propelled by a PM BLDC motor and powered by a fuel cell with the assistance of a battery. Ratings of the transistors and sizes of the passive components for the two supplies are determined as a function of the fraction of the fuel cell power to the nominal power of the traction motor. The design results are discussed.

Brushless DC drive operation during phase commutation under various switching patterns

The paper deals with the operation of a brushless DC drive during the phase commutation. At first, the various switching patterns that can be used to command the inverter are identified. It is demonstrated that the switching patterns are a combination of two basic commutation modes. For each mode, the current transients during the phase commutation are determined as well as two significant commutation-related quantities, namely the decay angle of the current in the outgoing phase and the maximum current excursion in the non-commutating phase. The results obtained for the two modes are then compared, showing that each switching pattern gives a brushless DC drive specific properties.

Inductive characteristics of asymmetrical coils for wireless power transfer

Inductive wireless power transfer (WPT) is being explored as a future solution for charging the electric vehicles. Coil coupling is the critical issue in WPT in which transmitting coil (TC) is buried under the ground and receiving coil (RC) is on the chassis of vehicle. In this paper cases of asymmetrical circular, spiral, and rectangular coils are considered for coupling. COMSOL Finite element analysis (FEA) is used to determine and comment on the inductive parameters with the base of analytics. It also includes discussion on parametric variations like inner diameter, coil gap distance, different number of turns on TC and RC. The outcomes are compared for to select coil structure for charging the electric vehicle.