Michel Lecrivain

A new structure of a switching flux synchronous polyphased machine with hybrid excitation

The aim of this paper is to present the structure of a new flux switching synchronous machine with hybrid excitation. This machine uses the flux switching principle where all the active parts are located on the stator. The rotor is only a salient passive rotor and can be robust and made with a low cost technology. This new machine can be supplied with electricity by means of a traditional three phase voltage converter or can be associated with a diode rectifier. The hybrid excitation is an association of permanent magnets and a wound exciter.

Hybrid Excitation Synchronous Machines: Energy-Efficient Solution for Vehicles Propulsion

In this paper, the suitability of a class of electric machines for vehicle traction applications is discussed. These machines, which are known as hybrid excitation synchronous machines, combine permanent-magnet (PM) excitation with wound field excitation. The goal behind the principle of hybrid excitation is to combine the advantages of PM excited machines and wound field synchronous machines. It is shown that these machines have good flux weakening capability compared with PM machines, and that they constitute an energy-efficient solution for vehicle propulsion.

Control of a Hybrid Excitation Synchronous Generator for Aircraft Applications

This paper deals with the control of a hybrid excitation synchronous generator which is used to supply an isolated grid for aircraft applications. This grid is supposed to be a 270-V dc bus. Thus, a rectifier is required between the machine and the dc bus. A diode rectifier is preferred here due to its great reliability and because it is also a low-cost solution. A controller is then proposed in order to regulate the output dc voltage of the generator. It is finally validated by simulations and experimental results.

A new topology of hybrid synchronous machine

Permanent magnet (PM) synchronous machines are able to operate over a wide range of speeds at constant power through the use of control laws allowing for flux weakening. Generally, this is performed by applying a strong demagnetizing current in the d-axis, yet such an approach involves the risk of irreversible magnet demagnetization and, consequently, a reduction in machine performance. This paper presents a novel structure for a hybrid synchronous machine. Our solution provides good flux weakening without introducing the risk of magnet demagnetization. In order to explain the structures operating principle, we apply a model with a single elementary design; EMF measurements are then presented to demonstrate the possibilities of flux weakening, along with a series of simulations to show the contribution of hybrid excitation.

A Hybrid-Excited Flux-Switching Machine for High-Speed DC-Alternator Applications

This paper presents a new topology of hybrid-excited flux-switching machine with excitation coils located in stator slots (or inner dc windings). After describing the three-phase structure to be investigated, the working principle is discussed, and the main electromagnetic performances are simulated by finite-element (FE) analysis. It is demonstrated that the air-gap field can be easily controlled, which is interesting for variable-speed applications. Finally, a prototype having 12 stator poles and different rotor tooth numbers (10 or 14) was built. Experiments were performed, validating the FE simulations and the operation principle. Finally, the thermal behavior of the prototype machine is investigated through experiments. It is shown that, up to 12 000 r/min, the thermal stabilization is achieved, making this topology an excellent candidate for high-speed applications.

Influence of magnetic losses on maximum power limits of synchronous permanent magnet drives in flux-weakening mode

The aim of this paper is to present the structure of a new synchronous machine with stator ferrite permanent magnets and a salient passive rotor (a robust and low-cost technology) which, when supplied with current by a three-phase bridge converter, produces continuous torque. This feature serves to place our machine on a par with the best synchronous machines available (e.g. high-energy rotor magnets with flux concentration). Furthermore, the electrical characteristics of this machine make it possible to apply the well-known flux weakening technique, which enhances the performance of the entire energy-conversion system. In theory, an operating area at constant power with unlimited speed can be obtained merely by taking into account the ohmic tension drops in the coils. Experimental results demonstrate that taking both magnetic losses and windage losses into account is necessary in order to identify the maximum mechanical output power characteristics.

Hybrid Excitation Synchronous Machines: Energy Efficient Solution for Vehicle Propulsion

In this paper the suitability of a class of electric machines for vehicle traction application is discussed. These machines, known as hybrid excitation synchronous machines, combine a permanent magnet excitation with wound field excitation. The goal behind the principle of hybrid excitation is to combine advantages of PM excited machines and wound field synchronous machines. It is shown that these machines have good flux weakening capability compared to PM machines, and that they constitute an energy efficient solution for vehicles propulsion

Comparative Studies Between Classical and Mutually Coupled Switched Reluctance Motors Using Thermal-Electromagnetic Analysis for Driving Cycles

This paper presents copper and iron loss models of a classical switched reluctance motor (SRM) and a mutually coupled switched reluctance motor (MCSRM). The iron losses in different parts of machines are then detailed. Based on the power losses model, a lumped parameter (LP) transient thermal model during driving cycles is performed, the analytical results are validated by the finite-element (FE) transient thermal model. Special attention has been paid to model the salient rotor and a method to transform the salient rotor into a nonsalient one has been proposed. A comparison between the maximum temperatures obtained by using different heat source (average power losses or instantaneous power losses during driving cycles) is given. The experimental tests are also realized to verify the analytical and numerical results.

Homopolar and bipolar hybrid excitation synchronous machines

This paper presents a description and operating principle of different hybrid excitation synchronous machines. Four prototype machines of different power rating (3 kW and 15 kW) have been studied. These machines combine two flux sources: permanent magnets, located in the rotor, and field coils, located in the stator. Thanks to this particular configuration the air gap flux can be easily controlled, without any risk of magnets demagnetisation. Tests are performed on the prototype machines to asses their flux weakening capability. Three of prototype machines are modular and can be assembled to have a homopolar or a bipolar configuration. These two configurations are compared using experimental measurements. The advantages and drawbacks of each configuration are described

Modification in Rotor Pole Geometry of Mutually Coupled Switched Reluctance Machine for Torque Ripple Mitigating

This paper presents a new method to minimize the torque ripple of a 3-phase, 6-slot, and 4-pole mutually coupled switched reluctance motor (MCSRM 6/4). The difference between a MCSRM and a classical SRM is their winding configuration. In a MCSRM, the mutual inductances are no longer neglectable when compared to self inductance. On the contrary, due to mutual inductances, the MCSRM can produce higher average torque than a classical SRM. A literature review is firstly performed to identify the source of high torque ripple level of a MCSRM. Then, the method using punching holes in rotor poles to modify the waveforms of flux as well as derivatives of inductances with respect to rotor position (dL/d and dM/d ) is proposed. Using the 2-D finite-element method (FEM), the influence of dimensions of punching hole on the electromagnetic performances (average torque and torque ripple) is analyzed. The two MCSRM are supplied by three-phase sine wave currents, and comparisons in terms of average torque and torque ripple versus RMS current density are also carried out. In order to make sure that the presence of punching holes does not cause mechanical problems, some mechanical studies are performed. Finally, experimental tests are also realized to validate numerical results obtained by 2-D FEM.