Compact permanent-magnet generator for hybrid vehicle applications

In hybrid electric vehicle (HEV) drivetrains 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 topology was selected for a 15-kW-at-4500-r/min-rated generator prototype that would be utilized in a demonstrator of an HEV drive train. This paper describes the original solutions adopted for the design of such an HEV generator and reports experimental results taken from the prototype machine.     

Nonconventional three-wheel electric vehicle for urban mobility

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     

Basic principle and design criteria of axial-flux PM machineshaving counterrotating rotors

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     

Low-cost compact permanent magnet machine for adjustable-speed pumpapplication

The variable-speed driven pump can result in significant energy conservation where reduced flow rates are required for long periods of time. In regard to adjustable-speed pump drives, one major contribution of this paper is the demonstration that a permanent magnet (PM) motor based on the slotless axial-flux permanent magnet machine (AFPM) topology can be a suitable candidate to advantageously compete with the induction motor for such a low-cost drive application. For the purpose of a cost comparison, the paper discusses 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     

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 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.     

Axial-flux permanent-magnet motor for direct-drive elevator systemswithout machine room

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     

Multistage axial-flux PM machine for wheel direct drive

The design of direct-drive wheel motors must comply with diameter restrictions due to housing the motor in a wheel rim and allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be the best candidate 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 a multistage structure and a water-cooled ironless stator. In the proposed new topology of the machine, 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 multistage AFPM with water-cooled ironless stator, and describes characteristics of a two-stage prototype machine rated 215 Nm, 1100 RPM     

Performance of coreless-winding axial-flux permanent-magnetgenerator with power output at 400 Hz, 3000 r/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 fiber-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 is compact and lightweight and, due to the lack of an iron core, generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. This paper discusses the basic design and construction of AFPM generators with coreless windings and experimental results taken from a 16-pole machine prototype rated 230 Nm, 3000 RPM are also reported     

Compact wheel direct drive for EVs

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     

Converter topology with load-neutral modulation for trapezoidal-EMFPM motor drives

The average torque of concentrated winding PM machines can be increased significantly by supplying current waveforms matching in full the trapezoidal back EMF. However, such current supply arrangements involve a large harmonic current flowing into the machine neutral. This paper presents an innovative converter topology to overcome the problem. This new configuration extends the standard layout of conventional PWM-VSI by adding a fourth branch devoted to control the voltage of the machine neutral. The inverter modes of operation resulting from the modulation of the machine neutral are discussed, and the paper reports the experimental results achieved from a converter prototype which has been constructed using IGBTs. Results show that the new inverter configuration allows significant benefits in the machine average torque, as well as the fact that the machine neutral modulation introduces an additional degree of freedom in the machine torque control