Originally Posted by
Tinymind
It seems that the +/- 270v 'DC' is of course actually AC, the square wave being very much easier, and cheaper, to generate electronically from rectified frequency wild AC.
They seem to be using this level of control to give high power motors, I assume they are induction, higher starting torque with the initial lower frequency.
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The schematics above make me believe it's 270 V DC, coming from the ATRUs. Reason may be for the same amount of elec energy in comparison to 28 V DC the wires are much thinner (less weight and cost).