Arlo1 Inverter build for Emrax 268

Electric Motors and Controllers
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Wächter
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Arlo1 Inverter build for Emrax 268

Post by Wächter » Jan 24, 2018 5:29 am

This topic is about an inverter based on the "Hi power inverter for Nissan leaf motor. Dyno's 302.3hp p15" from Arlo1. (https://endless-sphere.com/forums/viewt ... 30&t=63982)

It will be used for an Emrax 268 (medium voltage) motor.
I'm finally in the stage were everything is complete and i can make the first tests.
Here are some pictures of the build process:

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The bus bars are water cut and the caps have 75uf each.
Right now i'm trying to figure out the right settings for the lebowski ic (latest 2.A1 firmware). The desat protection is tripping really fast. I started with the settings Arlo1 used in one of his videos.
I made a video where you can see the motor wiggling around for a few seconds and then desat is triggered:



I'm running a 380V system. I can also force the motor to spin up when i'm closing the throttle really fast but only for around 2 seconds.
I will now test various settings, but if anybody has a good idea which settings will possibly improve the performance i would be grateful to hear it :D . I also uploaded the settings hex file. This is where i'm starting off from.

And here is a picture of the inverter inside the car (just for testing :D):

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Attachments
Setting.txt
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Last edited by Wächter on Feb 10, 2018 4:48 am, edited 1 time in total.

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Lebowski
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Re: Arlo1 Inverter build for Emrax 268

Post by Lebowski » Jan 24, 2018 6:56 am

Looking at the settings, I would go through the setup menus starting from main menu option c. Looks like some settings come from Arlo1's motor (like the motor impedance) and his controller (like the current sensor offsets). Also, at the moment it is in sensorless so it cannot deal with a heavy load on startup (wheels off the ground should be OK, but to start with wheels on the ground you'll need hall sensored mode).

Just go through all menu's from c, use autocomplete where available.

Wächter
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Re: Arlo1 Inverter build for Emrax 268

Post by Wächter » Jan 24, 2018 10:30 am

Yes, the wheels are off the ground at the moment and i have the hall sensors ready to be connected to the brain board.
I stay in sensorless for now, because it is not possible to calibrate the hall sensors with the fast desat triggering.
The current sensor offset measurement is also triggering desat. Same for the motor impedance measurement. I had to reduce the current to around 10A to successfully complete the motor impedance measurement. I also tried putting the values from the motor manual in there (126/118 Ld/Lq uH and 11,5mOhm phase resistance) but that didn't changed much.
I will go though the menu's again and play with the settings.

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Lebowski
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Re: Arlo1 Inverter build for Emrax 268

Post by Lebowski » Jan 24, 2018 11:07 am

Did you check the polarity of the current sensors ? Are the current sensors associated with the correct outputs ?

Wächter
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Re: Arlo1 Inverter build for Emrax 268

Post by Wächter » Jan 24, 2018 11:34 am

Yes, the polarity of the current sensors is correct.
I also tested the inverter with a 12V battery at first. With 12V i was able to perform the current sensor calibration. I also could spin the motor without desat triggering. Now with 380V you can hear the calibrating noise for one moment and then it shuts off.

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Lebowski
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Re: Arlo1 Inverter build for Emrax 268

Post by Lebowski » Jan 24, 2018 1:15 pm

sounds like something is triggering the desat. Could be desat too sensitive or something wrong with the gate drive... Did you try the PWM test function (without motor connected) for 5, 50 and 95% dutycycle and check the waveforms on a scope for all 3 outputs ?

Wächter
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Re: Arlo1 Inverter build for Emrax 268

Post by Wächter » Jan 25, 2018 4:27 am

I only checked the pwm with 50% dutycycle and it looked ok. I will also check with 5% and 90% and i'm taking a look at which phase is causing the desat. maybe it's always the same.

Wächter
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Re: Arlo1 Inverter build for Emrax 268

Post by Wächter » Feb 11, 2018 9:59 am

Ok, all the phases are behaving the same way. So it's not like one igbt is causing desat all the time.
I checked the gate signals again. With 5%, 50% and 90% dutycycle.

50% dutycycle:
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5% dutycycle:
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90% dutycycle:
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I think they look okay. I also checked the fault signal.
As soon as i give a little bit of throttle you can see the desat triggering (No arduino attached, you can see the 25us the igbt driver is shutting the igbt down):
Image

Maybe there is something wrong with the desat circuit itself (false diode?)

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Lebowski
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Re: Arlo1 Inverter build for Emrax 268

Post by Lebowski » Feb 11, 2018 3:08 pm

Did you double check the polarity of the current sensors AND that the channels of the pwm outputs and current sensors match up ?

Wächter
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Re: Arlo1 Inverter build for Emrax 268

Post by Wächter » Feb 15, 2018 5:43 pm

Yes, i did that. The polarity is correct and the channels of the pwm output and the current sensor match up. There is one ribbon cable for each phase. Not really much that could go wrong on that part.
What is the relation of the current sensor with my desat problem? My understanding was that the desat circuit and the current sensor are not affecting each other. Please correct me if i'm wrong, maybe i miss out on something. And thank you for helping me on this problem :)

The motor spins when i disconnect the arduino (which is shutting down the brain in case of a desat fault).


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Lebowski
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Re: Arlo1 Inverter build for Emrax 268

Post by Lebowski » Feb 16, 2018 4:26 am

Well the current sensors have to match up with the motor phases. The controller IC gets very confused when it outputs a forward rotating voltage but sees a reverse rotating current (because 2 channels were swapped). In a situation like that it will have no control over the current and it will trip the desat (or blow the fuse).

What might be tripping the desat are the PWM frequency related currents. A low PWM frequency, combined with a high voltage and a low motor inductance will give very high PWM currents. The controller IC has no real control over this as the currents are dictated by the aforementioned parameters. Maybe you have much higher PWM currents than Arlo1, either due to more voltage or lower motor inductance.
What helps here is to increase the PWM frequency, but you must be sure of course that the output stage can take this (increased switching losses etc).

When you change the PWM frequency you need to re-autocomplete the PWM menu which changes the loop sample frequency. This parameter is used everywhere, meaning that you will need to re-do most of the menu's.... (redo the FOC measurement, re-set the erpm limits etc etc etc)

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