High power-density, high back emf permanent magnet machine and method of making same

Abstract

An electric drive system includes a permanent magnet machine having a rotor and a stator and a power converter electrically coupled to the permanent magnet machine and configured to convert a DC link voltage to an AC output voltage to drive the permanent magnet machine. The power converter includes a plurality of silicon carbide switching devices having a voltage rating that exceeds a peak line-to-line back electromotive force of the permanent magnet machine at a maximum speed of the permanent magnet machine.

What is claimed is: 
     
         1 . An electric drive system comprising:
 a DC link;   a permanent magnet machine comprising a rotor and a stator; and   a power converter coupled between the permanent magnet machine and the DC link, the power converter comprising a plurality of silicon carbide (SiC) switching devices having a voltage rating that exceeds a voltage of the DC link when the permanent magnet machine operates in an uncontrolled generation mode.   
     
     
         2 . The electric drive system of  claim 1  wherein the voltage rating of the plurality of SiC switching devices is at least three kV. 
     
     
         3 . The electric drive system of  claim 1  wherein the plurality of SiC switching devices comprise SiC MOSFETs. 
     
     
         4 . The electric drive system of  claim 1  further comprising:
 a power source coupled to the DC link; and 
 a controller programmed to disconnect the power source from the DC link based on a detected line-to-line back emf of the permanent magnet machine. 
 
     
     
         5 . The electric drive system of  claim 1  further comprising:
 a DC power source; 
 a bi-directional DC-to-DC power converter configured to boost an output voltage of the DC power source and supply the boosted output voltage to the DC link; and 
 an input filter capacitor coupled between a positive DC rail and a negative DC rail of the DC link. 
 
     
     
         6 . The electric drive system of  claim 1  wherein the power converter comprises a multi-phase power converter. 
     
     
         7 . The electric drive system of  claim 1  wherein the permanent magnet machine comprises a traction motor. 
     
     
         8 . A vehicle drive system comprising:
 an alternator; and   a power converter coupled to the alternator, the power converter comprising a plurality of gate driven silicon carbide (SiC) switching devices having a voltage rating that exceeds a peak line-to-line back electromotive force (emf) of the alternator.   
     
     
         9 . The vehicle drive system of  claim 8  wherein the peak line-to-line back emf of the alternator is defined at a maximum speed of the alternator. 
     
     
         10 . The vehicle drive system of  claim 8  further comprising a power source coupled to the to the power converter through a DC link. 
     
     
         11 . The vehicle drive system of  claim 10  further comprising at least contactor configured to disconnect the power source from the DC link. 
     
     
         12 . The vehicle drive system of  claim 11  wherein the at least one contactor comprises a first contactor positioned on a positive rail of the DC link and a second contactor positioned on a negative rail of the DC link. 
     
     
         13 . The vehicle drive system of  claim 10  further comprising a controller programmed to disconnect the power source from the DC link if a detected line-to-line back emf of the alternator is within a threshold percentage of the voltage rating of the power source. 
     
     
         14 . The vehicle drive system of  claim 10  wherein the power source is a DC power source. 
     
     
         15 . The vehicle drive system of  claim 14  further comprising a bi-directional DC-to-DC voltage converter coupled between the DC power source and the DC link. 
     
     
         16 . The vehicle drive system of  claim 8  wherein the alternator is coupled to a heat engine. 
     
     
         17 . The vehicle drive system of  claim 8  wherein the plurality of gate driven SiC switching devices comprise SiC MOSFETs. 
     
     
         18 . A power converter for use in a drive system of a hybrid electric vehicle, the power converter comprising a plurality of silicon carbide (SiC) switching devices having a voltage rating of at least three kV. 
     
     
         19 . The power converter of  claim 18  wherein the SiC switching devices comprise SiC MOSFETs. 
     
     
         20 . A power converter for use in a drive system of a hybrid electric vehicle, the power converter comprising a plurality of switching devices, each of the plurality of switching devices consisting of a silicon carbide (SiC) MOSFET and an anti-parallel diode.