Switched Reluctance Drives Limited

Nidec Sr Drives, Ltd

Norman Neilson Fulton

Peter Richard Mayes

Phillip George Dickinson

Paul Andrew Sykes

Paul Greenhough

Thilak Raj Durairaj

Ernest J Buchan

A rotating electrical machine has a rotor composed of laminations having salient poles. The poles have one or more holes which are positioned so as to reduce the peak stress experienced by the laminations when the rotor is rotating. The holes are chosen according to a disclosed design procedure which gives a reduction in peak stress for a given limit on the output of the machine.

Reducing stress in electric-machine rotors by optimizing holes

A drive system has a number of electrical machines. One machine operates as a generator supplying an output to a DC link, which in turn supplies one or more machines operating as motors to drive loads. The motors are supplied through power converters. The total capacitance of the DC link is minimized and the link kept in a stable condition by preventing it falling to a hazardous level. One embodiment prevents the phase currents adding in such a manner as to reduce the DC link voltage. Another embodiment employs freewheeling in the phase currents to prevent the DC link voltage falling below a predetermined threshold.

Operating electrical machines from a DC link

A rotor for a switched reluctance machine has its main magnetic circuit provided by two mouldings of soft magnetic composite. The mouldings are substantially identical and fit together to form a magnetic circuit which, by virtue of its design, has a very low inductance in the unaligned position. The portions of the magnetic circuit lie beyond the active length of the rotor poles and the flux path is described in three dimensions.

Rotor for a switched reluctance machine

A coil former allows transposition between layers of turns in a coil to be accomplished without damage. The transpositions can be made in a short side of the coil. The former has finned portions which guide the wire into the correct locations during winding. When the coil is wound, the former is disassembled and the end portions are pulled towards the center of the former and turned through 90&deg; to be removed. A method of using the former is described.

Apparatus and method for winding electrical coils

Multi-phase switched reluctance machines use a phase excitation sequence that avoids consecutively exciting adjacent phases and so leads to reduced torque ripple. Corresponding methods are also provided.

Operation of switched reluctance machines

An electrical machine such as a switched reluctance motor includes a stator including a stator body, a plurality of poles each having an energizing coil, and a rotor. Portions of the coils are retained in channels between adjacent poles and by a wedge tied at each end to projections extending from the stator body. The manner of retaining the wedge avoids disturbance of the flux linkage in the stator poles and allows improved locating and retaining of the coils in the channels between stator poles.

Stator for an electrical machine including retainer for stator coils

A stator for electric machine, in particular a switched reluctance machine, has a non-circular, for example, square, outer profile and a set of equi-angularly spaced stator poles which are angularly arranged to be intermediate radially thickest and thinnest parts of the ring to avoid the poles coinciding with vibrational antinodes of the outer ring. In a particular embodiment the outer profile is square and the stator poles are angularly offset from a line of symmetry drawn through the center of the square at right angles to one pair of opposite sides.

Stator for electric machine and lamination thereof

A single-phase switched reluctance motor is disclosed. The motor includes a stator having a plurality of projecting poles and a rotor rotatably disposed adjacent to the stator. The stator and rotor poles may be formed from laminations of ferromagnetic material. Energizing coils are wound around one or more of the stator poles. When the coils are energized, the rotor develops torque. In one embodiment, the motor includes a motor starting mechanism which sets the rotor into motion before the stator coils are energized so that the rotor is never static in a preferred position. In another embodiment, the motor includes a rotor positioning mechanism which positions the rotor in a preferred starting position before the stator coils are energized.

Apparatus and method for starting a single-phase variable reluctance

A method and apparatus for increasing the starting torque of a two-phase switched reluctance motor is disclosed. The method involves the use of a specially constructed rotor position transducer with two sensing devices, each associated with one phase winding of the two-phase motor. The signals from the rotor position transducer are provided to a motor controller that energizes each winding whenever energization of the winding will produce torque in the desired direction.

Method and apparatus for increasing the starting torque of a two-phase

A reluctance machine comprises a rotor, defining rotor poles and a stator defining stator poles. Each stator pole pair, creating a flux path through the rotor includes only one winding mounted on one of the stator poles. The invention is particularly applicable to a machine having a four-pole field pattern and an odd number of phases. The coils are placed on alternate stator poles such that the space between stator poles can be used exclusively for a single winding. The single winding is made larger to compensate for the lack of a winding on its associated pole.

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Harrogate, United Kingdom

Norman Neilson Fulton