HIGH POWER-DENSITY, HIGH BACK EMF PERMANENT MAGNET MACHINE AND METHOD OF MAKING SAME
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.
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.