Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[nlc]

Originally Posted by nlc

I also understood the FOC, but don't want for know to try by myself

I omitted to say that for now I understood the FOC principle on PMAC motor but not completely on induction motor !!
On PMSM motor, the rotor flux comes from permanent magnets, it's easy to know the rotor flux position with hall sensors or encoder to adapt the stator flux position, but on induction motor the rotor flux is generated by induced current in the squirel cage. What I don't understand is how this induced rotor flux cannot be naturally 90° oriented relative to stator flux !?

When we look on the induction motor slip/torque characteristic, we can see that when we apply torque on the motor, the slip increases, torque increases, but when we request to much torque, when the slip increases, torque decreases, there is a maximum torque point on the curve.

So I believe the IFOC job is to alway apply the good voltage and frequency on the stator to alway have the appropriate slip and alway have the user requested torque positioned on the maximum torque point of the curve ? Am I right ?

[SakkeP]

[QUOTE=MPaulHolmes;284860]OK, maybe $450. They are $6.51 each in quantity 1. But 229 amps!


There isn't anti-parallel diode ?

[nlc]

Hummm, you are right !!

[MPaulHolmes]

Holy crap! Finland 1, USA 0. THank you!!!! May Moomintroll Live forever!

nlc, I should have said I understand the process for permanent magnet synchronous too. haha. The space vector modulation was always confusing to me until a couple days ago, but I still need to understand exactly how they compute the rotor flux angle in the ACIM case. My understanding is that if you command too much torque things will get jacked up. that's my technical understanding for ACIM at this point.

[nlc]

Yesterday evening I read the ST documentation of their V2.0 library for ACIM motor. FOC principle is the same as PMAC, the only diffrence comes from the software block which manage the rotor flux position : for PMAC the rotor flux position can be established with hall, encoder or estimated with a sensorless algorithm. In ACIM, the rotor flux position is estimated with a software block which use the measured rotor speed, the measured Iqs and Ids (from measured phase current and Clarke+Park tranformation), and motor characteristics.

Thus it seems that for ACIM it's very important to have a perfect knowledge of motor characteristics. For example, the IFOC ST library for ACIM needs :

#define ROTOR_TIME_CONSTANT

Define here (in μs), the rotor open circuit time constant of the motor τ r:

τ r = Lr/rr = (Lm + Llr) / rr

#define POLE_PAIR_NUM

Define here the stator winding pole pair number;

#define RATED_FREQ

Define here (in 0.1Hz) the right-hand boundary of the constant torque region (see
Figure 6): in that region we have rated current, rated flux, rated torque, rated power

#define NOMINAL_FLUX
Define here the required magnetizing current im (positive, peak value), expressed in q1.15 format

#define NOMINAL_TORQUE
Defines the maximum value for the motor’s rated torque expressed in q1.15 format.

#define FLUX_REFERENCE_TABLE: this look-up table (256 signed 16-bit values)
provides reference values of current ids (expressed in q1.15 format), according to
increasing stator frequencies (see Section 4.5.4 on page 70);
TORQUE_REFERENCE_TABLE: this look-up table (256 signed 16-bit values) provides saturation values of current iqs (expressed in q1.15 format), according to increasing stator frequencies (see Section 4.5.4 on page 70).

[TadhBijou]

Hello, I must say I am happy to see that this project is going to get to the production phase soon.
Thank you to all of you who contributed your knowledge into it.

This thread is really inspiring to me and I will soon start my electric car modding project.

Any way, I wanted just to say hello to every body and big thanks, especially to MPaulHolmes and nlc.

[shenta]

Great Job done by NLC, I am working also on STM32 with Hub Motor, but with FOC3.0 Library. My current wave form is some what more different than ur, and it swin like crazy on some angle... Again it may be problem of my motor, I will post some picture soon.

[nlc]

I work with FOC library V3.0 too. Don't hesitate to post screenshot, now I know in detail how this library works.

First step is to have a screenshot of backemf(scope between 2 phases and you turn the motor by hand), if it is not a true sinus the FOC algorithm cannot work correctly.

[MPaulHolmes]

I just got 300v worth of Sealed lead acid batteries. That should allow for 220v AC or something like that. They should be here some time next week. 25 12v batteries. ya! Also, Rod Hower from the EVTech list is sending me a bunch of TO-247 igbts to blow up. I'm going to do a small prototype before scaling it up. Since I'm broke, the power board will be something done on the mill. The plan is to do a driver board for the low side, driver board for high side, and then control board. low side on bottom, high side stacked on that, and then control on top of that. There's a pcb company here that will do $33 per board with no setup fee, so I'm going to use them. Just one board of each one, so no screw ups allowed!

[sawickm]

Originally Posted by MPaulHolmes

The plan is to do a driver board for the low side, driver board for high side, and then control board. low side on bottom, high side stacked on that, and then control on top of that.

Hi Paul,

I sounds like your AC Controller will be packaged similar to your new DC Controller (your PCB stacking concept). Are the driver PCBs going to be compatible for the AC & DC Controllers? Could you use the same driver PCB for the AC & DC Controllers? Or are they completely different circuits? Is it compatible with IGBTs or MOSFETs or both?

How is the testing of your new DC Driver PCB going

-Mark