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

[ale0502]

I can measure the stator resistance with multimeter, I have several motors to test, the idea is to start with a little brushless hobby, and then skip a small 3 phase induction, to finally test my big motor to control. My idea was to do this to test and advance little by little.
I solder it, is a mix of your controller in a pcb manufactured by me connected to a piece of three-phase UPS, now I do not have photos, but in a while I take them and upload them to show you.
I checked the 6 outputs pwm leave the dspic and reach the optocouplers, the IGBT are connected and are shooting, I also have a bus capacitor.
I can see with the oscilloscope at the output (with the resistive load) is rare, it would seem that it is generating a very low frequency, I see that pwm of different DCs is generated and they change every one second approximately.
I already checked the throttle potentiometer read and I think it's fine, just like the current sensors and the encoder.

thank you

[MPaulHolmes]

You can't do the PI test with a resistive load, because the P and I values are related to the inductance and resistance of the stator coil. I would get maybe 48v, and then do
run-pi-test

and see what happens. A better way is to measure the stator resistance, and then use the following formula:

ki = 2000*3.14159*STATOR_RESISTANCE*CURRENT_SENSOR*192* 1702/(BUS_VOLTAGE*2048*10000)

For "CURRENT_SENSOR", you would use 100 if you are using a LEM Hass 100-s. This number is how many amps per 0.625 volts change in the current sensor.
So, if you are using a LEM Hass 50-s, it would be 50, a LEM Hass 300-s, you would use 300, etc... Tamura is the same way. However many amps per 0.625v is what you use.

Then, you could try Kp = 62*Ki all the way up to Kp = 100*Ki. To see what works best, you would type:

run-pi-test2

To see the actual convergence.

[ale0502]

Hi, what is promised is due, so here is an image of my staff.



Back to the equation of ki, my brushless motor has 0,6ohm of resistance and my little induction motor has 50ohm os resistance, when I calculated ki values, give me 1002 and 83000 respectly, there are numbers too big.

ki = 2000*3.14159*STATOR_RESISTANCE*CURRENT_SENSOR*192* 1702/(BUS_VOLTAGE*2048*10000)

STATOR_RESISTANCIA = 0,6 or 50
CURRENT_SENSOR = 200
BUS_VOLTAGE = 12

[Mrmacireland]

Dia duit ale
That sure is something to achieve and build at the end could you post a video of your controller in action on the bench driving the induction 3 phase motor mine is around 10 HP would that work for me?

[MPaulHolmes]

You can make the Kp and Ki values smaller if you increase the DC voltage. They should be below around 20,000, so I would increase the DC voltage to maybe 48 or 60v. Also, the LEM Hass 200-s has a resolution of -400 to 400 amp, but that wire would probably only carry maybe a few amps, so you won't get good resolution. You can wrap the wire several times through the current sensor window to increase the sensitivity. Another loop through makes it behave like a 100amp current sensor, with a range of -200 to 200. 4 passes through the current sensor windows make the range -100 to 100. etc... I would do that before attempting any PI testing.

[motorulf]

Originally Posted by MPaulHolmes

Sorry for the delay, I missed this message.
run-rotor-test did nothing?! It does take a long time to run, but yes, you are looking for best acceleration. 50-60 sounds reasonable. There is a range of values that work best. Big motors tend to be in the 25-80 range. 50-60 is fine. There is a way to compute the rotor time constant involving the stator inductance/resistance and mutual inductance, but the true value is going to be in the range of 50-60 anyway. All this is doing is figuring out what causes the best acceleration, so the "true" value isn't going to be better. Also, the true value varies a little bit with temperature, so you could compute 55, but while driving it will vary some anyway.

Yikes, -35degC is ridiculous. I've never been in anything like that!

Yes, i was waiting for it for 10 minutes, I could not notice it doing anything. I tried a couple of times.

Now i am working again, will be on tour for 4 months, no time to play with my electric car.

If any one is interested in the reverse function. I will try the diff utility in MPLABX and post the result.

[kalidasbala]

Originally Posted by motorulf

If any one is interested in the reverse function. I will try the diff utility in MPLABX and post the result.

I think many will be interested. Atleast I am interested to get the reverse functionality done - software controlled.

Btw, is there a formula to calculate the precharge resistor value? Also can I use an automotive relay (12v).

[kalidasbala]

Originally Posted by motorulf

Yeah, i am only using 25 volts right now, is that too low?

You are using 25v as HV and running a 208Vac 3PH motor? What kind of batteries are you using?

[MPaulHolmes]

Looking at the code, I think the current command of Id = 300 (normalized value) and Iq = 300 might not be enough to get your motor turning. I used that value on my smaller motor and it worked OK, but I think you might need to change yours to 500 or 600 or 1000 or whatever. It's in RunRotorTest(). I probably should change that to an actual current rather than the normalized so it would work with all motor sizes.

[motorulf]

OK, here are the DIFF-files for my reverse function hack.
I used source code from Jan-06-2017.
Paul, may i attach that version of source code here?

Diff.zip

It uses the ICSP header for input and the LED output as an indicator.
No settings for reverse-amps, so you get full power backwards.
Use this at your own risk!!




I forgot to add the resistance...
Put resistor values as suggested here, it worked good for me:

Originally Posted by thingstodo

I would add a couple of resistors on the board, and one in series with the switch, to limit the max current into the micro.

Perhaps a 22K from Vcc (whether that is 5V or 3.3V) or your top trace on the board to the PIC pin or middle trace on the board. A 10K resistor from the PIC pin, or middle trace on your board, to Gnd, the bottom trace on your board. This one is shown as 'some resistor. That sets up a voltage divider for about 1/3 of Vcc on the input pin, which should read as 0 or OFF.

The switch would go in series with a 2K2 resistor - top trace to your switch .. green wire ... which is now wired in parallel with the 22K resistor. That sets up the PIC pin for about 85% of Vcc and should read as 1 or ON.

These resistor values are ones that I typically use. They limit current under 3 mA and are easy to buy. I didn't look up the specs on the PIC, but I don't expect any issues with low current into the PIC pin.

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