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Old 11-30-2016, 01:31 AM   #2901 (permalink)
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Not a production run but an experimentation for production run. The potential is very high when it comes to high end electric motorcycles and low end cars.

Thanks for the run time and your advice.

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Old 11-30-2016, 11:42 PM   #2902 (permalink)
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Originally Posted by johkim View Post
Hello!

I am completely new to the EV community, and have been reading a lot of information on EVs online for the last few days. I have an interest in cars in general, and currently drive a modded VW GTI

Not to bore you with too much of my own story, I was just wondering where I would go to learn more about inverters before coming back to this thread and also Paul's instructables. I am by no means a ME or an EE, just an ordinary guy (my background is in civil engineering!), but I dream of one day making my own EV hotrod.

(the reason why I'm asking about inverters is that AC motors, and batteries are something that I understand to some degree, including BMS, at least enough to read and learn, but inverters are quite a bit harder!)

Sorry if I've posted in the wrong section! I just got stuck here hahaha
I have not seen a primer for three phase AC inverters.

The wikipedia article is OK as far as it goes

https://en.wikipedia.org/wiki/Power_inverter

My poor and disjointed summary:
- The inverter turns on 2 or 3 transistors (IGBTs) in different combinations to get current running through the motor.
- How these pulses are controlled is the magic behind Paul's controller. A bunch of math is used to figure out the angle between where the rotor is and where the voltage applied to the motor should be in order to apply torque.
- How much torque you want is controlled by how hard you push the throttle.
- The controller makes that happen by varying the applied voltage and the phase angle that the voltage is applied at relative to what angle the rotor is at now. That is calculated ... hmm ... at least 8000 times per second but I think it is more like 20,000 times per second.
- The motor position is measured by the encoder (or a resolver that pretends it is an encoder). 64 pulses per rotation is OK. More is better. My testing started out with 1000 pulses per rotation and ended up with 64 pulses per rotation.

Paul has over-current measurements that shut down the controller in the case of a problem .. sort of hard-wired into the enable circuit that drives the transistors. The temperature sensors ... if I remember .. (doubtful) .. I think those are inputs to the controller.

Many plans on the internet have been published by people with limited experience. It is quite easy to burn up IGBT(s) by turning on the positive transistor before the negative transistor finishes turning off. Ask me how I know! These types of mistakes are expensive ... and it is not usually obvious what you did wrong, or what part of your code is responsible ... or if it was a bad solder joint ... or ... you get the idea.

Paul has done a good job of ensuring that these types of things do not happen - traces well separated, ground and power planes used, inductive loop areas minimized - and of shutting things down immediately if .. sh*t happens .. and there is a lot of current somehow going through one or more of the IGBTs.

I can point you to a few videos that begin with the three phase motor and continue on to the inverters, field oriented control, the theory involved, the math, etc. It is not like a video night. Several of the videos I had to watch maybe 10 or 12 times to get through all of the details ... and the info still does not make sense to me when I go through it! I end up going through it a couple of times each time I need to revisit a small chunk of it.

Paul sent me the links. If there is any interest, I can post them
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Old 12-01-2016, 03:21 AM   #2903 (permalink)
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Old 12-05-2016, 09:13 AM   #2904 (permalink)
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Paul?

I made encoder fitting and wiring. It is open collector output so i have to setup pullup resistors for A, B, Z signal lines. Can you tell me if it would be better to put pullups to inverter PCB or put them to encoder PCB? What would be best? Either way is fine here, i am just asking if there is a better way.

tnx

A
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Old 12-05-2016, 10:46 PM   #2905 (permalink)
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I think on the inverter board. IT's always nice for the micro to have a default value for something if a cable comes loose.
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Old 12-06-2016, 09:09 AM   #2906 (permalink)
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Volts / Hz code

Paul - I think this was discussed briefly a while ago, but I don't remember the result:

- do you have any code kicking around for simple voltage output based on frequency output (instead of torque?)

I'm looking for a 'limp home' mode. It seems that the encoder is like anything else in a car - it fails sometimes. I know that it is not efficient to run in Volts/Hz, and that the motor will heat a bit more, and that the torque will be reduced ... but it should get me home instead of sitting on the side of the road.
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Old 12-06-2016, 09:22 AM   #2907 (permalink)
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New AC Boards

BTW - I have not powered up the new AC boards yet. It looks like it will not happen until the new year.

I've chosen an Allen-Bradley 1333 AC Controller, 5 HP, 230V, that has a bad current sensor for my first AC Controller brain transplant. It looks like I can run the old controller (it runs for about 10 seconds before it faults out on the current sensor) to verify the caps and such are working OK. I do have a couple of the same model that have working current sensors if it makes more sense to try one of them first.

Disconnecting the old controller looks like removing ribbon connectors for the IGBTs and the current sensors

Connecting the new control board looks like plugging in ribbon connectors and one new current sensor. The voltages appear to match. I guess we'll see.

The controller is set up to run from single-phase 240V or 3 phase 208V input. The control board doesn't really care what voltage the DC bus is, right? It assumes a battery bank but it doesn't really CARE. As long as the controller has the isolated 24V input, the output drives IGBTs, and the hall effect current sensors accept 5V, Gnd and the signal comes back proportional to the current measured .... we're good?
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Old 12-06-2016, 12:18 PM   #2908 (permalink)
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Quote:
Originally Posted by thingstodo View Post
The controller is set up to run from single-phase 240V or 3 phase 208V input. The control board doesn't really care what voltage the DC bus is, right? It assumes a battery bank but it doesn't really CARE. As long as the controller has the isolated 24V input, the output drives IGBTs, and the hall effect current sensors accept 5V, Gnd and the signal comes back proportional to the current measured .... we're good?
Yes that's right. There's DC voltage monitoring now, but the only use of it at the moment would be to verify precharge. But I'm not even doing that right this second.

I have NOT added the V/Hz to this code yet. It's a good idea though. It's pretty easy to get working. IT was version 0.001 a few years ago. I just need a lookup table, and to race through the table at a given frequency, with all 3 phases 120deg apart from each other.
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Old 12-07-2016, 08:55 AM   #2909 (permalink)
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Yes that's right. There's DC voltage monitoring now, but the only use of it at the moment would be to verify precharge. But I'm not even doing that right this second.
Hmmm ... the existing pre-charge (when powered with AC) uses the brute-force method. The full wave bridge has a resistor in series, connected to the positive bus. When the DC bus voltage charges through that resistor and gets high enough for the DC/DC converter circuit to work properly, the micro powers up, and turns on the main contactor. That contactor bypasses the pre-charge resistor.

Since I'm not using that (old and inefficient) DC/DC converter, and since I will be using mostly whatever voltage pack I have available for testing ... maybe I can implement the DC voltage monitoring for pre-charge?

Quote:
I have NOT added the V/Hz to this code yet. It's a good idea though. It's pretty easy to get working. IT was version 0.001 a few years ago. I just need a lookup table, and to race through the table at a given frequency, with all 3 phases 120deg apart from each other.
Would it be a different call to a different library to put the PWM out to the IGBTs?

The method to switch to V/Hz from Field Oriented Control would take a bit of fool-proofing (we fools are very creative!) since I think your throttle is a torque command for FOC and it would be a frequency output in V/Hz?

I haven't seen code for the new board as yet. Is it time for a backup email or are you doing version control through git?
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Old 12-07-2016, 10:25 AM   #2910 (permalink)
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Quote:
Originally Posted by MPaulHolmes View Post
Yes that's right. There's DC voltage monitoring now, but the only use of it at the moment would be to verify precharge. But I'm not even doing that right this second.

I have NOT added the V/Hz to this code yet. It's a good idea though. It's pretty easy to get working. IT was version 0.001 a few years ago. I just need a lookup table, and to race through the table at a given frequency, with all 3 phases 120deg apart from each other.
I am down with some stomack flu, but at least i have time to think about...
Finally someone figured cruise control for this inverter! Which is what V/Hz is yes? Well sort off... I suggest the primary use of V/Hz would be to implement cruise control. You have PID regulation working. You frame it for V/Hz to move found one chosen frequency, fixed by a button switch (on dash) and PID would try to follow this frequency - speed control! Throttle would still be effective upwards from chosen speed, so you could tap the button with throttle and set a higher speed or just tap button with throttle loose and car would deccelerate some. To break the link would require pulse on brake switch line, you have this wired yes?

I have everything here in my head, except how to program it, i suck at programming PIC . Would you mind doing this?

Limp home mode could effect itself automaticaly if encoder signal would be lost. That way you could have some control if sensor was out. It happened to me with my controller. I use optical RPM sensor for arduino (a glorified mouse sensor) and it caught moisture and corrosion. I replaced it with better protected one but it stays a weak link im my car. My 5c...

Arber

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