AC Tuning

AC, DC, amps, volts and kilowatt. It's all discussed in here
a4x4kiwi
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Post by a4x4kiwi »

I thought I would start a new topic here.

I have driven the ute for the first time up and down the driveway a few times. Yah. EV Grin. Image

I find that the throttle response is like controlling a stepper motor speed.

I also find I have to start very judiciously otherwise it bunny hops like crazy like a learner driver.

Tuarn, Do you know how to turn of deceleration regen so it coasts when you let off the throttle?

Thanks, Mal.

Here is my current configuration.

Setup 1 - Forward

ID          Name                     Value      
009          Display line 2          Feedback [unit]      
010          Display line 1.1     Dc link voltage      
011          Display line 1.2     Reference %
012          Display line 1.3     Output energy      
014          Local stop          Disable (0)          Prevents rapid deceleration.
102          Motor power          15.00      
103          Motor voltage          415      
105          Motor current          28.00      
106          Motor nom. speed     1450      
108          Stator resist          0.2641               From AMA
109          Stator react.          20.33               From AMA
113          Lo spd load comp     0      
114          Hi spd load comp     0      
115          Slip compensat.          0      
119          High start torq.     0.5      
123          Min.f. func.stop     0.1      
128          Mot.therm protec     Etr warning1      
200          Out freq rng/rot     132 hz bothirections      
205          Max. reference          132.000      
206          Ramp type          S2 (2)               Gives better low speed control.
207          Ramp up time 1          6.00               Economy
208          Ramp down time 1     3.00               Economy
209          Ramp up time 2          4.00               Power
210          Ramp down time 2     2.00               Power
221          Torq limit motor     348.5               drive Max.
222          Torq limit gener     66.6               10kW max regeneration
227          Warn. feedb. low     -4,500.000      
228          Warn. feedb high     4,500.000      
300          Digital input 16     Setup select LSB      
301          Digital input 17     No operation      
302          Digital input 18     Latched start      
303          Digital input 19     No operation      
305          Digital input 29     Ramp 2 (17)          Power / Economy switch
306          Digital input 32     No operation      
307          Digital input 33     Encoder feedback input A      
314          Ai [mA] 60 funct     No operation      
319          Ao 42 function          Fb min-max =0      
320          Ao 42 puls scale     66               Speedo Cal
321          Ao 45 function          Fb min-max =0      
322          Ao 45 puls scale     144               Tacho Cal (Check if should be 150 = 4500/60*2)
323          Relay 1-3 funct.     No operation      
325          Relay 1-3 off dl     0      
326          Relay 4-5 funct.     No operation      
329          Encoder pulses          40     Set for speed pickup
345          Enc loss timeout     0.2      
409          Trip delay torq.     60               Maximum
410          Inv.fault delay          35               Maximum
411          Switch frequency     14.0               Maximum           
415          Max. feedback          4,500.000          This value should be 10% higher than par. 205
416          Ref/feedb. unit          Rpm (3)      
422          U0 voltage (0hz)     7.3      
445          Flying start          Enable (1)      
446          Switch pattern          60° avm (0)      
457          Mains imbalance          Warning (1)      


Setup 2 - Reverse (Changes From Setup 1)

205        Max. reference        50.000           
303        Digital input 19       Reversing (1)



Silicon is just sand with attitude.

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acmotor
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Post by acmotor »

par 100,101 your not telling us ?
I know, just checking to see if we are paying attention !

I take it 100 speed closed loop and 101 high constant torque ?

222 Torq limit generator - reduce to zero if you want no regen controller will then coast when throttle removed.

... or select overvoltage control par 400

Try also 221 at lower values while you get the hang of it. Controller will delay the ramp when torque limit is reached.

S2 sine curve ? I find linear easier.

check 417- 421 speed PID
reduce gain

Clearly you can come back up the driveway faster than you can reverse out !!!

You can investigate torque mode next !

All good fun !
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a4x4kiwi
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Post by a4x4kiwi »

Hi Tuarn,

Thanks for the tips. 100 speed open loop and 101 Hi Const.(both defaults)

Hmm tried reducing 222 to 0. Will check again.
OK 221
Will try linear. I was trying to have the throttle less responsive at low speed to aid parking.

400 set to over voltage looks risky if the battery is fully charged and you are trying to slow down going down hill. "this is done by increasing the output frequency so as to use the energy from the intermediate circuit."

OK on PID.
Silicon is just sand with attitude.

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a4x4kiwi
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Post by a4x4kiwi »

I have uploaded a video with a smooth takeoff to my blog
Silicon is just sand with attitude.

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acmotor
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Post by acmotor »

But if you have encoder (pickup) working, why not closed loop ?
I was hoping you could get your 40ppr going then I would try my 8ppr again !

par 400 overvoltage control works not quite as the name suggests. It simply stops the regen from increasing the DC bus voltage above its present value. That is maybe 620V in your case ?

I like the vid. The motor bike was right on cue !

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a4x4kiwi
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Post by a4x4kiwi »

I am a little hesitant to use closed loop until I am in an open space so I can tweak things without crashing. If the encoder drops pulses (it should be ok now) the motor goes to maximum RPM. Parameter 361 Encoder loss threshold is by default 300% This could be lower to detect a faulty sensor. Say 120%

According to the docs 417-421 are for closed loop.

The motorbike in the video was very timely.
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acmotor
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Post by acmotor »

Yes, that is why I suggested them. I assumed you were in closed loop.

Have fun.
Keep us posted. Image
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Post by Sparky Brother »

Hey Mal

Congrats on your first ride! I just watched you video and just like you can not wipe the smile off my face! Actually my whole family watched it and they admit you`ve done more than well onya mate!
Last edited by Sparky Brother on Fri, 16 Jan 2009, 17:44, edited 1 time in total.
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Post by Mesuge »

a4x4kiwi wrote: The motorbike in the video was very timely.


Congratulations, looking very smooth.

Btw. this is at least second EV related video this week with similar
"Attack from the planet ICE" soundtrack, I think they do it on purpose..Image
Last edited by Mesuge on Sat, 17 Jan 2009, 15:50, edited 1 time in total.
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a4x4kiwi
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Post by a4x4kiwi »

I tried switching to speed closed loop control with some unusual results. Also to a single profile to assist testing and reduce the possability of errors by adjusting 2 profiles.

If I coast backwards, even though forward is selected it accelerates reverse. I could not test the opposite due to the slope of my driveway. If I do a perfect hand brake start, it goes forward.

Back to open loop for now. :(

I hope my VFD does not have some strange fault.

The diff has a lot of backlash so when you lift off the accelerator there is a real clunk and lurch intil the drive figures out -0 torque is being generated and lets go. I anticipate this to be less obvious at road speed.

As I think tuarn mentioned in the past, speed mode might take some getting used to.

Will have to try torque mode. Tuarn any tips before I configure this?
Last edited by a4x4kiwi on Mon, 19 Jan 2009, 03:33, edited 1 time in total.
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acmotor
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Post by acmotor »

Like any piece of 'software' you often think there is a bug or virus or corruption until finally you realise it is PEBCAC.

PEBCAC is the IT sign off on non faults i.e. 'problem exists between computer and chair' !
Customer does not know what it means but it sounds official.

I don't know if that helps, but VFD is most likely OK. It just works on logic, humans don't !

If you haven't been able to set up speed closed loop then don't try the torque closed loop unless you are looking for excitement !

Torque open loop just involves par 100 change.
Reverse becomes an issue as accel demand voltage needs to go -ve or use another setup with an offset in one of the presets.
You can select the feedback unit as Nm and scale the feedback.

You may need to increase the torque gain if the motor doesn't pull.

Torque open loop will not supply full start torque i.e. it will supply 100% not 300% or so.
Torque closed loop will supply full torque -beware !

The way I have got around this is to tell the open loop mode that the motor itself is 30kW and then it applies more torque. You need to manually intert the R, Xr values though.
As I have commented before... beware the automatic interaction between paramaters. A simple change back does not undo other auto changes e.g. changing motor size will change current and max torque settings.

Another thought in speed open loop is to reduce the slip compensation value into the -ve (can go to -500%).

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EV2Go
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Post by EV2Go »

Just like an ID Ten T error Image

I keep reading this thread hoping some form of intelligence transference might take place, but alas it hasn’t happened yet. Image
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Johny
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Post by Johny »

I don't think anyone but a Danfoss VFD devotee is going to follow this thread very well. When Mal gets it all going he is very good at documenting things so there will be a very helpful outcome which will translate in some way to other AC Industrial setups regardless of brand. (Sorry for the pressure Mal).
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EV2Go
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Post by EV2Go »

Thanks Johny I feel marginally less stupid knowing that. Image I don’t know if it is because the AC guys with their superior electrical knowledge discuss things at a much higher level that makes things sound more complicated than DC, or AC just is more complicated.

Apart from a few time when Jaron started talking electrical jibberish, I though the electrical system on Kearon’s DC - EvCapri seemed very straight forward and easy to follow.

We just bolted the Curtis in and it worked (after a minor electrical whoopsie) I am guessing a lot of this discussion is more about fine tuning like an aftermarket ECU, then it is about getting it going.
Last edited by EV2Go on Tue, 20 Jan 2009, 16:00, edited 1 time in total.
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Post by Electrocycle »

that's because AC people are trying to hack industrial gear to drive a car :P
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a4x4kiwi
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Post by a4x4kiwi »

@Tuarn. Thanks for the tip on the slip comp. i will give it a go next week when I am back form NZ.

@Johny, You are correct, most VFDs have similar features. No pressure here :)

@EV2Go. I guess AC configuration is a bit of a science in itself as I am learning. :)
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EV2Go
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Post by EV2Go »

Electrocycle wrote: that's because AC people are trying to hack industrial gear to drive a car :P


Thanks Andrew I lost sight of the obvious there for a sec.
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Post by Sparky Brother »

I for one count technical people into two groups:
1. Those who are curious to get to know how stuff work no matter of what trouble they get in with their wives
2. Those who like to follow well stumped tracks. As long as the majority is doing it this way I am on the safe side, they say.

Well Paul I recon you should let the AC People be. It`s their right to be wrong. Just read your own motto. Otherwise you just hit the wrong thread.


Cheers


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Post by EV2Go »

Problem is I fall into the category of people that can’t help themselves, I am compelled to pull it apart to see if I can make it work better, hence why I am revisiting the idea of AC. Seems like a crap load more work, but if there is a gain to be had, sometimes it just has to be done it is a compulsion.

I am wondering if I should do some kind of electrical course just to understand what I am contemplating getting myself into. So much to learn and so little time to do it...

Anyway don’t want to clutter up a useful thread with my ramblings...
Last edited by EV2Go on Wed, 21 Jan 2009, 15:09, edited 1 time in total.
a4x4kiwi
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Post by a4x4kiwi »

Latest results:

The good news. I think I am happy with open loop speed control now. After many hours diving up and down our short driveway, and logging 10kms! I found that the throttle response was too precise. After a lot of fiddling I lowered the switching frequency (I was curious about audible noise at a lower frequency) and the throttle response is much less agressive. Makes sense after you think about it for a minute. :)

The bad news. Closed loop and Torque open loop have been non starters. Perhaps you need many more that 40 pulses per revolution for closed loop to be useful. I still have a service call in with Danfoss as I would like to have the other control modes available.


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Post by Richo »

If a control loop is going at 16kHz.
The speed data maybe updated 1 every 30 loops.
and the motor is 1000RPM with 40 pulses per rev.
1000/60=16.666 rev / sec.
16.66x40=666 Pulses per sec. (666Hz)

Loop update rate 16000Hz/30=533Hz

So about one update per pulse.
At lower RPM it would be wose.

Maybe more pulses would be a good place to start.
So the short answer is NO but the long answer is YES.
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Post by Johny »

Mal the Lenze gives some parameters that can alter the speed control loop. I haven't seen any speed control gain adjustments in the params you have described but surely there are some - (I think I found some).

It sounds a bit close-to-the-wind that the switching rate is effecting the speed control. You have probably got red-eyes from searching the documentation but these stood out. Is Speed PID the correct term?

417 Speed PID proportional gain
418 Speed PID integration time
419 Speed PID differentiation time
420 Speed PID diff. gain limit
421 Speed PID lowpass filter time

They explain the set up procedure around there somewhere. I'm assuming here that the standard speed control is classified as a PID.
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Post by Johny »

BTW I was reading about this in Danfoss document MG52A302 page 90.
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Post by a4x4kiwi »

Thanks for the feedback guys.
Danfoss also suggests a proper encoder.

The parameters 417-421 are for the PID control mode where as at present I am working with speed open loop.
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acmotor
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Post by acmotor »

Mal,
Some more experiment with Danfoss pars.
Slip compensation reduced to -400% (default 100%, but I had been using 0%). This relaxed the tight control and made speed open loop more of a torque demand from the pedal.
I am running with 60% regen limit and that is quite comfortable.
The harder you drive (more heavy stop/go) the better the regen works.

There is more still to the shudder at start.
I note there is no shudder with any amount of accelerator applied when the handbrake is on (note handbrake is at rear of transfer case on suzi) (just a smooth groan from the emotor as it leans on the engine mounts). Shudder only comes in when power is going all the way to the wheels. There must be some control loop timing that is resonating with the drive train.
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