Marco Zimmer

Design of a 3 kW primary power supply unit for inductive charging systems optimized for the compatibility to receiving units with 20 kw rated power

This paper presents a power unit for use in the primary side of 3 kW rated inductive charging system. The objective is the design of 3 kW rated primary sides which are compatible to 20 kW rated secondary side receiving units inside electric vehicles. The motivation arises from the consideration that 3 kW and 20 kW charging stations should be kept compatible. Compatible especially in the way that vehicles with 20 kW rated receiving units should be able to use 3 kW charging stations. The basis for the design of the 3 kW system is a series-compensated secondary receiving coil without an additional DC/DC-converter stage between a B4 rectifier and battery with a rated power of 20 kW. The absence of a DC/DC stage allows lower weight and installation space in the vehicle, but the possibility for impedance matching is missing. The system behavior is investigated analytically, so that all currents and voltages, as well as the reactive power in both compensation networks can be calculated depending on the given systems parameter, such as the inductance of the secondary coil, the coupling factor, the operation frequency and the transferred power. It is shown that the operation point with the lowest reactive power, and thus least losses in the coils and compensation capacitors, strongly depends on the design of the receiving unit. Since the receiving unit is designed for a transferred power of 20 kW, an operation with 3 kW will result in a significantly lower efficiency. Therefore a solution is presented, to shift the ideal operation point of the secondary side system from 20 kW to a much lower value. That way, the 3 kW system is able to operate very close to the shifted ideal operation point.

A novel self oscillating power electronics for contactless energy transfer and frequency shift keying modulation

This paper deals with a combination of an inductive based contactless energy transfer system and a data transfer from the primary side to the secondary side of this system. Therefore, an extension of a self-oscillating power electronics offering the possibility to change the capacity of the resonant circuit during energy transmission is presented. An additional switchable capacitor in the compensation network leads to an immediate shift of the resonance frequency of the circuit. On the basis of this frequency shift a frequency shift keying modulation is implemented to encode binary data in the energy signal.

Dimensioning of a contactless energy transfer system for an electrical excited synchronous machine

This paper deals with the electrical design of a rotating contactless energy transfer system. The system replaces the slip rings of an electrical excited synchronous machine and transfers energy contactlessly onto the rotor of the synchronous machine. To operate this machine, the possibility to set the rotor current must be given. Therefore, a topology with an input voltage controlled output current source is designed. Furthermore, the required parameters of the contactless energy transfer system are calculated.

A scaled model for investigations of three-phase contactless energy transfer systems

This paper starts with the basics of contactless energy transfer systems for charging of electric vehicles and discusses reactive power compensation networks for single-phase and three-phase systems. After presenting a small scale model of a three-phase prototype with distributed windings, results from measurements and simulations will be described for further investigations.

Contribution to the system design of contactless energy transfer systems

This contribution propose a design procedure applicable to many kinds of wireless or contactless energy transfer systems. The design procedure is limited to near field wireless energy transfer systems in resonant operation. Therefore it is well applicable to systems with a primary side power oscillator or systems with a control strategy that forces an equal system behavior compared to a primary side power oscillator. In resonant operation the input impedance and voltage transfer function of different natural frequencies describe the system behavior and will be calculated analytically in this contribution. Not only the knowledge of these transfer functions but also the knowledge of basic magnetic properties lead to a readily applicable design procedure.

Design and construction of a novel rotating contactless energy transfer system for an electrical excited synchronous machine

This paper deals with the design and construction of a rotating contactless energy transfer system. The system is used to replace the slip rings of an electrical excited synchronous machine and transfer energy contactless on the rotor of the machine. Considering the application and the involved boundary conditions, three approaches with non distinctive magnetic flux guidance of the electromagnetic design are presented. Calculation and dimensioning of the system is done by electromagnetic and thermal 2D and 3D finite element simulation. Finally, the results are verified by prototypes, constructed for each presented approach.