Like redpoint5, I don't have much expertise, but a lot of interest in the subject.
First I'd like to thank cajunfj40 for this EXTREMELY valuable and interesting thread.
I'd also like to thank thingstodo and MightyMirage for their expertise, experience, and contributions on this topic.
My specific interest in this topic is developing a system that uses multiple Toyota MGR's, or possibly the Prius motors. The new versions appear to be designed for higher voltages in about 2010 ( and have been tested by ORNL ) In these tests, the bus voltage (DC link voltage) was boosted to 650V at 5kHz, NOT using the boost converter. For the Prius, the BEMF was just over 500VRMS at 14000 rpm. This would imply a peak internal voltage of over 700V. With field weakening, ORNL was able to test the motor up to 13,000 rpm with a 650V bus. When the bus voltage was reduced to 500VDC, they were only able to run to motor up to 8000 rpm, and 5000 rpm at 225VDC.
For my project, I'd like to spin the motors as fast as ORNL did, - not limited by a low bus voltage - maybe sanity - LOL!
Because I don't know what I'm doing, I always spec components with significantly higher voltage ratings than the one I'm actually using. When one looks at a $$/kW perspective, generally higher voltage (lower current) components are lighter and less expensive.
One mystery to me is "why do certain plastics have significantly better voltage ratings as insulators than others?" For example, you can get big cables for cars, where they can handle hundreds of amps, but they are only rated for 60V.
You can then go to home depot and get a same guage wire with similar thickness insulation, and it will be rated for 600V.
- E*clipse