Most industrial motors have windings wired out to the junction box allowing 230 or 460 volt operation. Is your motor originally 460v and you are converting it to 230? Could you do two deltas instead of two stars to reduce the voltage to 133?
I think that's what he's doing now.
It's a 460 V motor, with all winding in series star. By putting it in parallel star, it becomes a 230 V motor. By getting at the internal star point and converting to parallel delta, it becomes a 230/√3 = 133 V motor.
[ Edit: This is wrong! I was confusing Dahlander connections, which change the motor from 4-pole to 2-pole, with series/parallel connections. The Dahlander parallel star configuration (and parallel delta also) are both
inverse parallel. In other words, the windings are in parallel, but with the opposite polarity to standard, so that the windings oppose each other. I don't pretend to understand this, but I know enough to know that the above is wrong. Dahlander configurations are always for a
fixed voltage, so the "high speed" connection is
still 460 V. ]
So if it's a 4 pole with nominal 1450 RPM @ 460 V in series star, it becomes 1450 RPM @ 230 V or 2900 RPM @ 460 V in parallel star. In parallel delta, it becomes 2500 RPM @ 230 V or 5000 RPM @ 460 V in parallel delta.
huub3 said:
Related to the wiring of the motor, I was not planning to do switching. I want to go direct drive
Alas, direct drive is where switched windings (series/parallel or star/delta) becomes useful. It gives a kind of "electrical gearbox" for a vehicle that no longer has a mechanical gearbox. Hence, we were planning on a star/delta switch for our MX-5 when we were thinking of losing the gearbox.
This becomes more important if your motor or controller are not very powerful. 75 kW peak might be marginal for direct drive. Remember that for direct drive, you need the torque and current at low speeds for acceleration, hill climbing, and gutter climbing, and sheer speed at the top end. By making the motor only get to full power at 5000 RPM, as this rewind will do, you'll get really great performance at the top end (full torque to 5/6 of top speed, assuming you balance the motor for 6000 RPM), but taking off/hill climbing/gutter climbing will be like doing thise things in top gear in a V8. It will do it, kind of, but how many V8 cars don't have a gearbox?
You will be able to get to all the connections, so you will be able to do series/parallel switching (equivalent to about 2nd and 4th on a 5 speed manual transmission) with 9 wires and a box full of contactors.
See for example here:
http://www.aeva.asn.au/forums/forum_posts.asp?TID=1574&PID=19215#19215. In fact, TJ seems to be implying that you didn't need to open the motor to get to the internal star point! I'd have to think about how that is done. I'm pretty sure it is on the AEVA forums somewhere.
Series parallel switching is more important for the Civic, as it has an ironless radial flux motor; these can't be field- or flux-weakened.
For direct drive, I think it would be better (if you don't do series/parallel switching, or even if you do) to have the speed where you run out of voltage (not really "nominal speed" any more; I suppose it's "new base speed") about the middle of the motor's speed range. Then each winding gets the maximum current your controller can supply, so the motor has twice the torque up to half speed. After that, you get approximately constant power from new base speed to maximum speed, effectively giving you a gearbox. So then the average torque and hence average power is higher when accelerating from stop to maximum motor speed. This tips the balance towards low speed driving, where you need the most torque, and you spend most of your time. You still get nearly full power available on the freeway.
Sorry to contradict your assumptions, but I think that a bit of a rethink may be in order.