Quote:
Originally Posted by P-hack
ran some simulations for 36hp @ 510v/70a. (510 because svpwm, hmm sounds like hubeners pack)
freq: 20k
battv: 144
batt/inductor avg A: 260 (160min/355max, triangular)
min inductor to avoid discontinuous mode: ~ 26uh
peak/avg switch current ~355/190
duty cycle %66
I think this is how the prius (mgr perhaps) 25kw boost does it too, doesn't run all the time, beefy inductor with few turns and large conductor, beefy igbt switch, available at a junkyard near you  (The whole inverter can be something of a 50kw-75kw bargain with a custom logic board.)
It would allow operation at v/hz < battv/510 with minimal losses, or something like that, below a certain rpm. |
That looks more meaningful than the 50% duty.
If one was to boost accordingly to the RPM it would make the inverter software very neat. Basically the V/Hz ratio and hence torque would be pretty much constant at all revs, which would save you of the nonlinear torque curves above nameplate.
Here is how I think this could be implemented:
Set the V/Hz ratio to 4V/Hz, for example. Run the booster regardless. If the result was under the battery voltage, the inductor would never run as the comparator would keep the IGBT off and only battery voltage would be used.
As soon as the output voltage was lower than the target (and this could be because the V/Hz ratio was too low or the battery was sagging too much) force the booster to regulate the output voltage. This could be to anywhere between 150 and 600V, depending on motor frequency.
This is transparent to the controller. Normally one would simply loose torque above nameplate, now the output becomes linear. 50% throttle = ~ 50% torque.
One less programming nightmare!
The only thing the boost controller would require is a signal from the motor encoder/tachogenerator.