US 4,532,458 AGranted

Variable-speed electrical machines

AssigneeNational Research Development Corporation

InventorsStephen B. Kuznetsov, Eric R. Laithwaite

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Abstract

An arrangement to provide variation of the speed or other operating parameters of an electrical machine without connection to the rotor. The machine is of the induction type having a winding in separate parts to create a flux movable in the air-gap different speeds by the alteration of current in a part of the winding. In one example the current is altered by a variable impedance connected to one winding part, the other part being connected to an electrical supply. Another example, FIG. 6, shows two machines (NM.sub.1, NM.sub.2) arranged to drive a rail vehicle through smooth rail wheels attached to the machine rotor axles. A single, variable-frequency, inverter (NI) drives both machines and is connected to part (MP) of each machine winding. Other parts (AP) of each machine winding are connected together by a link (NC). In operation power (real or reactive) is transferred between the machines along the link to equalize the torque of the machines. Run-away of one machine while the other stalls is thereby avoided.

Claims4

Dependent claims

An alternating current electrical machine arrangement comprising:

a primary winding for connection to an alternating current electrical circuit of a predetermined frequency;
a secondary winding mounted in a spaced relationship with and for relative motion with respect to the primary winding an electrically isolated to define a flux permeable gap therebetween with relative motion between said primary and secondary windings coupling them by electromagnetic effects;
said primary and secondary windings formed of electrical conductors distributed in predetermined patterns along the extent of the flux permeable gap therebetween;
at least one of said predetermined patterns of electrical conductors having a non-regular and non-uniform portion along the flux permeable gap for creating and maintaining at least one transient of electromagnetic field conditions along at least portions of the flux permeable gap;
said at least one transient comprising a change from one effective field speed to another from point to point along the flux permeable gap;
said at least one of said predetermined patterns of conductors being provided by a winding including at least a first and a further separate part;
and
means to alter a current in a said first part of a winding whereby at least one of said effective field speeds is altered to vary the speed of the machine.

5 more elements

Dependencies are inferred from the claim text.