Parallel and flux forced windings in discontinuous machines

Abstract

Linear Induction Motors commonly have the coils of each phase connected in series. The effect of this connection type is that equal currents flow throughout the phase winding, whilst the voltage across coil groups connected in series may vary significantly. As flux is proportional to voltage, the air gap flux may also significantly vary over the length of the machine. This can be an issue particularly where a conductive plate is traveling between a series of discontinuous machines at high speed, for example in electromagnetic launch systems. The plate entry into each discontinuous machine can cause significant drops in flux with a consequent large variation in thrust. With a machine using phase groups connected in parallel, the voltage is now forced whilst the current is variant. This has the effect of maintaining the air gap flux on entry and so producing a more consistent force profile, a significant benefit for high speed launch applications.

Vehicular suspension and propulsion using double sided linear induction machines

“…The air gap contains a conductive sheet secondary to generate force. These machine configurations are widely employed in linear form for applications such as transport, aircraft launch [9], industrial applications and amusement rides. One of the main benefits of the double sided configuration compared to the single sided configuration is that the conductive secondary when in the center of the air gap experiences no net normal force in relation to the primaries [7].…”