Fabio Crescimbini

Application of direct drive wheel motor for fuel cell electric and hybrid electric vehicle propulsion system

This work presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquid-cooled axial flux permanent magnet machine designed to meet the direct drive requirements. Machine design implements techniques to increase machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. Machine design also optimizes the placement of the magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows very effective removal of machine power loss. Design details and experimental results are presented.

Study of bi-directional buck-boost converter topologies for application in electrical vehicle motor drives

The use of a bi-directional DC-DC converter in motor drives devoted to EVs allows a suitable control of both motoring and regenerative braking operations. In particular, during motoring operations of a battery-fed DC motor drive, a DC-DC converter is to be used to adjust the motor current in order to follow the torque reference signal. On the other hand, a bi-directional arrangement of the converter is needed for the reversal of the power flow, in order to recover the vehicle kinetic energy in the battery by means of motor drive regenerative braking operations. This paper deals with the study and comparison of two bi-directional buck-boost converter topologies. Each of them allows stepping the battery voltage level either up or down, according to motor drive modes of operation. For each converter topology computer simulations of modes of operation are presented together with experimental test results.

Multiple input DC-DC power converter for fuel-cell powered hybrid vehicles

Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with a multiple input DC-DC power converter devoted to combine the power flow of multi-source on-board energy systems. The proposed energy storage arrangement includes fuel cell generator, ultracapacitor tank, and battery system. Possibility of optimization of the output capacitors bank in relation to the RMS value of the current ripple is investigated.

Multi-stage axial-flux PM machine for wheel direct drive

The design of direct-drive wheel motors must comply with a diameter restriction due to housing the motor in a wheel rim, and must allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be one of the best candidates for application in electric vehicles as direct-drive wheel motors, as in comparison with conventional machines they allow designs with higher compactness, lightness and efficiency. The paper presents a newly-conceived AFPM which has multi-stage structure and water-cooled ironless stator. In the proposed new machine topology, the space formerly occupied by the toroidal core becomes a water duct, which removes heat directly from the interior surface of the stator winding. The high efficiency of the machine cooling arrangement allows long-term 100% overload operation and great reduction of the machine weight. The multistage structure of the machine is suited to overcome the restriction on the machine diameter and meet the torque required at the wheel shaft. The paper gives guidelines for the design of a multi-stage AFPM with water-cooled ironless stator, and describes characteristics of a two-stage prototype machine rated 220 Nm, 1100 RPM.

Performance of a 10 kW power electronic interface for combined wind/PV isolated generating systems

The hoped exploitation of pollution-free, low cost, renewable energy resources has always stirred up interest and inventiveness. The double-input single-output DC/DC power converter discussed in this paper, developed for combined wind-photovoltaic generating systems, aims to mitigate the output power fluctuations due to the intermittent nature of both solar and wind energy. Digital control of the whole apparatus also contributes to optimise the converter modes of operation, running both the energy input circuits at their maximum power level. The paper reports an overall description of the power interface characteristics and experimental results recorded in extensive laboratory tests of a 10 kW rated prototype.

Modular, axial-flux, permanent-magnet motor for ship propulsion drives

Original features such as compactness and lightness make slotless axial-flux permanent-magnet machines (AFPMs) eligible for application in large power motor drives devoted to the direct drive of ship propellers. This paper discusses characteristics of AFPMs designed for application in marine propulsion, and machine performances such as efficiency, weight and torque density are evaluated for a comparison with those of conventional synchronous machines. A newly-conceived modular arrangement of the machine stator winding is proposed and experimental results taken from a small-size machine prototype are finally shown.

Experimental study on reducing cogging torque and no-load power loss in axial-flux permanent-magnet machines with slotted winding

The axial flux permanent magnet machine (AFPM) topology is suited for direct-drive applications, and due to their enhanced flux weakening capability AFPMs having slotted winding are the most promising candidate for use in wheel-motor drives. In consideration of that, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having a slotted winding in order to achieve substantial reduction of cogging torque and power loss in the stator core. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve off-line modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.

Performance of coreless-winding axial-flux permanent-magnet generator with power output at 400 Hz-3000 rev/min

An axial-flux permanent magnet machine (AFPM) topology with a coreless winding is proposed for generator units required aboard ships, aircraft or hybrid-electric vehicles. In the proposed AFPM configuration, the winding consists of rhomboidal shaped coils encapsulated in fibre-reinforced epoxy resin. The coils have a double-layer arrangement to leave space for a cooling water duct being used to remove heat directly from the interior surface of the winding. The overall machine structure has high compactness and lightness, and because of the lack of the iron core generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. The paper discusses the basic design and construction of AFPM generators with coreless winding and experimental results taken from a 16 poles machine prototype rated 70 kW, 3000 rev/min are finally reported.

Control strategy for multiple input DC-DC power converters devoted to hybrid vehicle propulsion systems

Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with the control system of an original HEV propulsion system that includes fuel cell generator and storage energy system combining ultracapacitor tank and battery. The three on-board power sources supply the vehicle traction drive through a multi-input DC-to-DC power converter which provides the desired management of the power flows. In particular, in the proposed arrangement the ultracapacitor tank is used for leveling the battery load current during transients resulting from either acceleration or braking operation of the vehicle. The paper outlines the features of the control unit of the DC-to-DC power converter being used in the proposed propulsion system and describes the main characteristics of a 35 kW prototype developed to conduct laboratory experiments and validate the control strategy.

20 kW water-cooled prototype of a buck-boost bidirectional DC-DC converter topology for electrical vehicle motor drives

In brushless DC motor drives devoted to electric vehicles (EVs) a bi-directional DC-DC power converter can be used to control suitably both motoring and regenerative braking operations in order to improve the motor drive performance. In consideration of such an application, this paper deals with the experimental study of a buck-boost bi-directional DC-DC power converter topology which has been conceived for the use in EVs propelled by means of wheel-direct-coupling axial-flux PM motor drives. The paper discusses the power converter modes of operation and reports experimental results taken from a 20 kW water-cooled prototype of the proposed power converter topology.<<ETX>>