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Concerning the application of slotless axial-flux PM motor (AFPMs) in electric vehicle drives, this article deals with the development of a 16-pole AFPM prototype which is used in the propulsion system of an electrical scooter. The proposed AFPM prototype has 45 Nm peak torque and 6.8 kg mass of active materials, and it is coupled directly to the scooter's rear wheel. In the following, the authors discuss the design and construction of the motor prototype and report experimental results taken from machine laboratory tests. Finally, they give details concerning the motor drive arrangement used in an electrical scooter prototype.

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 windings are the most promising candidates for use in wheel-motor drives. In consideration of this, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having slotted windings in order to achieve substantial reduction of both cogging torque and no-load power loss in the machine. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve offline 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.

The search for a compact, lightweight, and efficient energy storage system (battery and/or combination of other emerging technologies, including ultracapacitors, flywheel energy storage system, advanced batteries, and fuel cells) that is both affordable and has acceptable cycle life remains the major roadblock to large-scale production of EVs and HEVs. In this paper a multiple input DC-DC power converter (MI-PEC) devoted to combine the power flowing from combined on-board energy sources is presented; the proposed arrangement for the propulsion system includes electric generator (EG), ultracapacitor tank (UC) and battery systems.

This paper 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. The machine design implements techniques to increase the 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. The machine design also optimizes the placement of 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 the very effective removal of machine power loss. Design details and experimental results are presented

In hybrid electric vehicle (HEV) drive-trains an electrical generator is coupled onto the shaft of an internal-combustion engine (ICE) in order to process either the entire or a given fraction of the traction power required by the vehicle wheels. As such an ICE-driven generator is being confined within the vehicle hood and is exposed to heating resulting from ICE operation, high compactness, totally-enclosed construction and suitable machine cooling arrangement become challenging targets the generator design must, deal with. Due to unique characteristics such as higher torque per volume and higher efficiency compared to other machine topologies, the axial-field permanent magnet machine (AFPM) topology was selected for the development of a 15 kW @ 4500 rev/min rated generator prototype that would be utilized in a demonstrator of HEV drive train. This paper describes the original solutions adopted for the design of such a HEV generator and reports experimental results taken from the prototype machine.

This paper deals with design and construction of two twin prototypes of slotless axial-flux permanent-magnet motor drives jointly developed by SIMINOR Ascenseurs and the University of Rome for application in direct-drive elevator systems without a machine room. Each prototype of pulley-direct-drive motor is rated 5 kW, 95 rev/min, and has a shaft height of 380 mm and overall axial thickness of about 80 mm. Machine design based on unusual specification and original manufacturing solutions adopted for the proposed direct-drive elevator arrangement are discussed throughout the paper, including the leading dimensions and characteristics of the prototype motors. Finally, experimental results taken from the machine prototypes are reported.

This paper outlines the original solutions adopted for powering a nonconventional three-wheel electric vehicle. This is a lightweight vehicle for use in urban mobility with mission tasks such as 50 km/h cruising speed and 80 km range of autonomy. The propulsion system is based on a lead-acid battery-fed wheel direct drive. This is arranged with a 4.5 kW prototype of a slotless axial-flux permanent magnet machine, which has a total weight of 15 kg and is capable of 85 Nm continuous torque and 120 Nm peak torque over 2 min. The motor is totally enclosed in the single front wheel of the vehicle and fed through an IGBT bidirectional power converter, which allows the control of both motoring and regenerative braking operations. Design characteristics and experimental data taken from the prototype of wheel direct drive are given.

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.

The paper outlines the original solutions adopted for powering an original three-wheel electric vehicle. This is a lightweight vehicle for use in the urban mobility with mission tasks such as 50 km/h cruising speed and 80 km range of autonomy. The propulsion system is based on a lead-acid battery fed wheel direct drive. This is arranged with a 4.5 kW prototype of slotless axial-flux permanent magnet machine which has total weight of 15 kg and is capable of 85 Nm continuous torque and 120 Nm peak torque over 2 min. The motor is totally enclosed in the single front wheel of the vehicle and fed through an IGBT bidirectional power converter which allows the control of both motoring and regenerative braking operations. Design characteristics and experimental data taken from the prototype of wheel direct drive are given in the paper.

A variable-speed driven pump can result in significant energy conservation where reduced flow rates are required for long periods of time. Concerning adjustable-speed pump drives, one major contribution of this paper is to show that a permanent magnet motor based on the slotless axial-flux PM machine (AFPM) topology can be a suitable candidate to advantageously compete with the induction motor for such a low-cost drive application. To the purpose of a cost comparison, the paper discusses the design and construction of a prototype machine which has been conceived to replace a 1.2 hp induction motor being used in a standard adjustable-speed pump drive. Results taken from laboratory tests of the prototype machine are reported together with an assessment of the machine manufacturing cost.

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.

Axial-flux PM machines are particularly suitable for application in electrical drives devoted to ship propulsion, since they allow the elimination of the large-power gearbox used in conventional systems. In consideration of that, this paper deals with a novel slotless axial-flux PM machine topology which is characterized by the synchronous counterrotation of the two machine rotors. Such a new machine topology can find application in the direct driving of two counterrotating propellers, which may be used in ship propulsion systems to recover energy from the rotational flow of the main propeller slip stream. In this case, the use of an axial-flux machine having counter-rotating rotors allows an improvement in terms of weight and efficiency, since the epicyclic gear otherwise required for the motion reversal can be avoided. The paper discusses the stator winding arrangement which allows the opposite motion of the machine rotors and reports experimental results taken from a small-size machine prototype. >

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.

Wind and solar photovoltaic generating systems have advanced rapidly in recent years, but both suffer from the intermittent nature of their resource. A secure stand-alone power supply based on either requires a substantial energy store. Combining the two creates a supply with smaller storage requirement since the fluctuations have a statistical tendency to cancel. The system developed for a 10 kW application comprises wind and solar collectors, each of 5 kW rating, with a lead-acid battery for storage and a 10 kW PWM inverter for the final output. The wind turbine generator is a 5 kW, 200 RPM, direct-drive, permanent-magnet, axial-flux machine based on the 'Torus' configuration. The three-phase output is rectified to form a variable voltage DC link. The power converter uses two DC-DC power converters connected in series, each with a bypass diode which conducts continuously when the corresponding source is not available.