Electric machine with a damping device

Abstract

An electric AC machine includes a primary section and a secondary section. The primary section has a region facing the secondary section and a region facing away from the secondary section. The region facing the secondary section has windings adapted to receive an AC current. The winding of the primary section has at least one phase conductor which at least partially extends in or on the region of the primary section facing away from the secondary section, thereby producing a magnetic field that extends outside the secondary section. This arrangement can reduce overvoltages and eliminate voltage breakdowns at the star point of winding strands of a synchronous motor.

1 . An electric AC machine comprising a primary section and a secondary section, with the primary section having a plurality of windings adapted to receive an AC current and a short-circuited conducting loop with at least one winding.  
   
   
       2 . The electric AC machine of  claim 1 , wherein the plurality of windings has at least one phase conductor which extends at least partially next to the at least one winding of the short-circuited conducting loop.  
   
   
       3 . The electric AC machine of  claim 2 , wherein the at least one phase conductor and the at least one winding of the short-circuited conducting loop at least partially surround a body that conducts the magnetic flux or an air gap disposed on this body.  
   
   
       4 . The electric AC machine of  claim 1 , wherein the primary section includes a magnetic flux conducting means comprising a sheet metal laminate.  
   
   
       5 . The electric AC machine of  claim 4 , wherein the magnetic flux conducting means is formed in at least two parts, with a first of the two parts being formed by the sheet metal laminate and a second of the two parts being formed by a bridge, said sheet metal laminate and said bridge forming a cavity.  
   
   
       6 . The electric AC machine of  claim 5 , wherein the sheet metal laminate and the bridge form an air gap.  
   
   
       7 . The electric AC machine of  claim 1 , wherein the electric AC machine is a three-phase machine, wherein those phase conductors that have in normal three-phase operation a zero sum current are grouped and extend together with the at least one winding of the short-circuited conducting loop through a cavity.  
   
   
       8 . A method for operating an electric AC machine having a primary section, which includes windings of a phase conductor, and a secondary section facing away from the first section and including a short-circuited conducting loop with at least one winding, said method comprising the steps of: 
 feeding the phase conductor with AC current; and    disposing at least a section of the short-circuited conducting loop in close proximity of the phase conductor to form a damping magnetic field which extends outside the secondary section.