Locomotive horsepower

[beaulieu]

Alan and Eric, did you see that Alstom for the new AGV (TGV successor) is going to permanent magnet synchronous traction motors? They used 2 sets of these under the coaches on the world record TGV run. Also what is the difference between voltage source invertors as used by most of the worlds 3-phase AC drive systems and the current source invertors used by Alstom in the SNCF Sybic locomotives and first generation TGVs?

[Railway Man]

Alan and Eric, did you see that Alstom for the new AGV (TGV successor) is going to permanent magnet synchronous traction motors? They used 2 sets of these under the coaches on the world record TGV run. Also what is the difference between voltage source invertors as used by most of the worlds 3-phase AC drive systems and the current source invertors used by Alstom in the SNCF Sybic locomotives and first generation TGVs?

What's the significance of this?

RWM 

[beaulieu]

Alan and Eric, did you see that Alstom for the new AGV (TGV successor) is going to permanent magnet synchronous traction motors? They used 2 sets of these under the coaches on the world record TGV run. Also what is the difference between voltage source invertors as used by most of the worlds 3-phase AC drive systems and the current source invertors used by Alstom in the SNCF Sybic locomotives and first generation TGVs?

What's the significance of this?

RWM 

Significant reduction in size and unsprung mass, for a given horsepower rating. 

[Railway Man]

Significant reduction in size and unsprung mass, for a given horsepower rating. 

I take it the technology wasn't feasible until recently.

 

[erikem]

Significant reduction in size and unsprung mass, for a given horsepower rating. 

I take it the technology wasn't feasible until recently.

 

Taking a bit of an educated guess here...

There are two areas of recent technological advances. One is in permanent magnet material, I'm assuming that the motors are using NdFeB material (or SmCo, which is really expensive). The other presumably being high voltage devices - it has been only recently where IGBT's have been avaliable with 3KV and higher ratings. The higher voltage ratings are more important for synchronous motors as the terminal voltage will be vary directly with motor speed.

I've heard one prediction of a 25% increase in motor power rating by replacing the induction motor squirrel cage with a permanent magnet rotor. In addition, there are some new permag motor designs where the magnetic field is parallel with the motor shaft as opposed to the traditional design with the fields perpendicular to the shaft. In the new designs, the rotor looks more like the rotor on a disc brake, with the windings sort of resembling the calipers of the disc brake. The magnetic circuit is much more compact in this design, resulting in marked weight savings (potentially much larger than a permag rotor retrofit to an AC induction traction motor).

Not sure about what's going on with the current source inverter versus the voltage source inverter.  

[beaulieu]

Significant reduction in size and unsprung mass, for a given horsepower rating. 

I take it the technology wasn't feasible until recently.

 

Taking a bit of an educated guess here...

There are two areas of recent technological advances. One is in permanent magnet material, I'm assuming that the motors are using NdFeB material (or SmCo, which is really expensive). The other presumably being high voltage devices - it has been only recently where IGBT's have been avaliable with 3KV and higher ratings. The higher voltage ratings are more important for synchronous motors as the terminal voltage will be vary directly with motor speed.

I've heard one prediction of a 25% increase in motor power rating by replacing the induction motor squirrel cage with a permanent magnet rotor. In addition, there are some new permag motor designs where the magnetic field is parallel with the motor shaft as opposed to the traditional design with the fields perpendicular to the shaft. In the new designs, the rotor looks more like the rotor on a disc brake, with the windings sort of resembling the calipers of the disc brake. The magnetic circuit is much more compact in this design, resulting in marked weight savings (potentially much larger than a permag rotor retrofit to an AC induction traction motor).

Not sure about what's going on with the current source inverter versus the voltage source inverter.  

The Big 3 European  train builders (Alstom, Bombardier, and Siemens), all use 6Kv IGBTs in their latest models. What surprised me about the AGV bogies (trucks) used under the record-setting TGV is that the motors did not appear to take up very much space between the sideframes, yet each motor was rated at 1MW (1340hp).