# MES-DEA TIM600 explosion! Help!



## major (Apr 4, 2008)

Stiive said:


> Unfortunately when trying to spin the motor for the first time using the set-up instructions in the TIM600 inverter manual, there was a large explosion and flames from the inverter!


That's not good. Bummer 

I have used inverters, but not this one. You might want to try putting three 220V light bulbs, delta connected on the phase leads from the inverter. If you can then get into a V/Hz control mode, you should be able to operate it like a very expensive light dimmer . But even this will not protect from internal fault/failure, but would take the output out of the danger zone.

Have you tried to talk with the vendor or manufacturer?

Good luck,

major


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## coryrc (Aug 5, 2008)

Put a fast-action fuse, maybe around 10A, in the DC bus. You shouldn't need more for just testing. If it does blow, try 20 or 30A. But if at 30A with no-load it still blows, maybe you are doing something wrong.


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## steven4601 (Nov 11, 2010)

I do not know the mes dea inverter.

But from my limited knowledge, try to change the motor voltage all the way down. Also drop the allowed current way down. (20A should be enough to get the motor ticking over in neutral). Low frequencies & high voltages can saturate the motor iron. Current will shoot up very rapidly on saturation. 

Also prior to the above advice, the experiment with light-bulbs can be very valueable to verifying operation of the VFD itself. If its in sensorless vector mode it may stuble as it detects no inductive load/motor. 

Do you have a insulated portable scope or graphical digital multimeter? Like a Fluke 99 ?


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## etischer (Jun 16, 2008)

Perhaps you could open up the dead TIM and find out where the smoke came from. It may give you clues as to what went wrong.


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## 7circle (May 29, 2010)

Stiive said:


> Dear All,
> I am currently developing a formula spec electric car as part of a university project. Our team is using a MES-DEA TIM600 inverter and has recently plugged it up to our EVE M2-AC30-L motor.
> Unfortunately when trying to spin the motor for the first time using the set-up instructions in the TIM600 inverter manual, there was a large explosion and flames from the inverter! This was encountered when doing the test to verify the number of poles of the motor and check that the 3 phases were correctly wired in... The motor never spun.
> 
> ...



Just an update of what happen and where they got up to.

I was able to spend some time with the team at their workshop and looked over the system and motor and controller information.

The Motor data
Motor type: M2AC30L 
Service: S21H 
P: 30kW 
V: 210V 
I: 105A (Could be 108 ?)
RPM: 5000RPM 
Freq: 175Hz 
RPM Max is 7000RPM 

(This suggests V/Hz of 210/175 = 1.2 V/Hz)

And the Test report supplied with the Motor showing the same serial number has a table of RPM,TORQUE,POWER. Tested sing a TIM400 and 96 volt DC Supply.



> "speed":"torque":"power"
> 
> "rpm":"T (Nm)":"P (kW)"
> 
> ...


This data plotted looks like:









From this the V/Hz can be estimated assuming they ran at Peak power at Max Vac of Vdc/√2 = 96/√2 = 65 Vac

The Mech RPM 3000RPM so the Hz is Nmech x 2.¶/60 x 2/Poles [Edit: oops should be Hz = Nmech x 4/2 x 1/60 = 3000 RPM x 2/60 = 100Hz]
So 3000 x 2x3.142/60 x 2/4 = 157.1 assuming 4 pole [ Edit:100hz at 3000 RPM]

So V/Hz = 65/157.1 = 0.413 [Edit:65/1000=0.65V/Hz]

This much lower than the name plate data suggests. 

But also, in the graph you can see the rounded power curve indicating that at 3000 RPM to 5000 RPM the power doesn't drop off fast like in the store graph image:









So the inverter is over-volting the motor and increasing the frequency up to 5000 RPM but limiting the current to with in the controllers capability.

So considering the test data supplied wth the motor, if the Vac at 2500 RPM is estimated to be 1/2 the Vac at 5000 RPM
the Volts would be 65/2 VAc at 2500 RPM

So the V/Hz would be 32.5/ (2500 x 2.¶/60 x 2/4) = 32.5/65.4 = 0.496 V/Hz [Edit:Hz is 32.5/(2500/30)=0.39 V/Hz]

So what is the correct V/Hz to stop inductive saturation in the motor?
The inverter doesn't have a specific parameter for V/Hz it uses the Nominal Motor Parameter data entered in.

So using
Motor type: M2AC30L 
Service: S21H 
P: 30kW 
V: 210V 
I: 105A 
RPM: 5000RPM 
Freq: 175Hz 

Gives V/Hz = 210 / 175 = 1.2 V/Hz
But if the "V: 210V" is really Vdc 
then the max Vac would be 210/√2 = 148
So the V/Hz would be Ksat = 148/175 = 0.845 V/Hz

After much fiddling around the Nominal Values V/Hz of 0.62 was showing slight buzzing so backed off to have 0.6 V/Hz by setting the Vnom back to 105Vac the motor passed the C41 test checking motor UVW connection and encoder feedback and Number off poles.

The Motor data that passed C41 was:
Motor type: M2AC30L 
Service: S21H 
P: 30kW 
V: 210V (entered as 105Vac)
I: 105A 
RPM: 5000RPM (Stator = 5250 = Fnom x 60*2/Poles so Slip RPM is 250RPM)
Freq: 175Hz 
RPM Max is 7000RPM 
(Poles 4)
(Encoder 64Pulses/Rev with corrected AB connection)
(Note: V/Hz = Ksat = 105/175 = 0.6) 

So what is the Motor capability?
The test they did with a TIM400 using 96Vdc Supply showed 30kW
So if they ran at 3000 RPM and got 100Nm the Power would be 
P = T.w where w is the mechanical RPM in rad/sec w = N 2¶/60
Tw = 100 x (3000 x 2¶/60) = 31kW which makes sense.

The motor info on the shop.electro-vehicles.eu for the 
*M2-AC30-L*

http://shop.electro-vehicles.eu/shop/details.asp?prodid=EVE02&cat=0&path=47,60

This shop site data shows 59kW at 3000 RPM with 188Nm
This calc's to P = Tw = 188 x (3000 x 2¶/60) = 59kW

The site info has


> *Main Features:
> *Nominal voltage: 288VDC
> nominal speed: 3600 rpm
> top speed: 8000 rpm
> ...


This suggests V/Hz of 288/√2 / (3600 x 2¶/60 x 2/4) 
For V/Hz = 203 / 188.52 
giving = 1.07

Using the Vnom as Vdc rating is confusing as Vdc/√2 may not be the capability of the inverter. The PWM generation of 3 phase may be limited to less than the Vdc on √2 as there are Volt drops in the IGBTs and sage in the Bus due to large currents. So the Vac generated may not have been the best possible of 203 but only 190 say, 
then the V/Hz would be 190 / 205.2 = 0.99

If the Online Vnom was supposed to be VNom = 288Vac (not Vdc)

Then V/Hz would be 288/188 = 1.53 V/Hz

So the Motor data supplied doesn't line up with the observed V/Hz of 0.6.

But the Motor Passed the C41 test with using the Nominal Voltage of 105 Vac and Nominal freq of 175Hz.

So what happened next, the motor was run through the C42 test and passed. This was done with Nominal speed of 1000RPM. This was repeated a few times to check repeatability.

Then the Chain was attached to drive the axles with no wheels.

The speed was limited to 80% of 500 RPM instead of 5000 RPM or even 1000RPm, to keep speeds low and the ramp accel time for test was P121=4sec the default)

The C42 test runs through 
- phase 1 - with no movement 
- phase 2 - Motor moves at creep speed
- phase 3 - Motor spins up to 80% Nom Speed 
- phase 4 - Motor spins up to 80% 16 times

During the phase 3 the Motor Spun up to the reduced speed setting then after about 6 seconds, when the motor would start to slow down the Inverter failed (Another IGBT popped) and of the battery back fuses blew.

So what would cause this?

My thoughts are the there is an issue that running the inverter with a 82 cell Kokam pack, deceleration of the motor caused the return current (de-magnitization current) to over volt the IGBT capability of 650V (absolute max from the spec sheet found on line for the device).

This is protected by the Snubbers (WIMA FKP 1uF) and main Bus Capacitance 45uF x 6 = 275uF.

The Battery back can't be relied on the absorb this energy as the Safety contactors could be released or the Fuses could blow disconnecting it. 

So all spike protection needs to be linked to the Controller DC Bus to absorb Turn-Off spikes on the Bus.

As the inductor magnetic field decays the current freewheels via the IGBT diodes onto the BUS, charging the capacitance available. The snubbers are small at 3 x 1uF and the 275uF from the 6 x 45uF caps is small too.

This decay energy must go somewhere. And the bigger the bus capacitance or accumulator, the absorption of this energy will stop it shooting up beyond the IGBT limits.

If there was no BUS capacitance or battery connection then the motor terminal Voltage will go so high that an arc through the air will occur.
And the humidity in the last few days would not help either.
It would be better to be in an area with below zero temperatures causing humidity to negligible.

The first Controller failure was very dramatic and Arcing did occur causing melting of thick bus bars. 

So operating at lower battery voltages and with a motor with lower inductance and operating at lower currents would all help reduce the size Turn-Off voltage spike.

Often motor controller have Ultra fast Zener Diodes (Transorbs or other brands) across bus and to Motor Terminals. These are selected to turn on before the IGBT limit is exceeded. This would protect the IGBT by absorbing the energy released by the Motor and stray capacitance and magnetising energy.

Operating at below 300V would keep the Stray capacitance from over-volting the IGBT and would also allow more delta Voltage for the Capacitors to absorb the energy from the current charging the capacitor.

So adding a larger Bus cap externally like a 400V 450V surge 4700uF Electrolytic would provide a store for released energy from Bus Votlage at 82 x 4.2 = 344 to 450Vdc 

so U_C at 344Vdc is V^2 x C/2 = 278 Joules

And at 450Vdc is 475.875 Joules allowing (475 - 278=) 197 J to be absorbed. 

Compared to (275 + 3) uF on the Bus providing up to the 650V max of the IGBT limit would be 59.3 - 16.3 = 43 Joules.

The inductor energy of U_L = 1/2 L x I^2 could be used if the motor inductance could be evaluated.

If some of this sounds wrong please reply or PM stiive with any questions or recommendations or thoughts.

7¢, Ken


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## major (Apr 4, 2008)

Hi Ken,

Nice report  So I read it and then was going thru for a second read. I have to do some other things today, but I'll be thinking about this. Thanks 

Anyway for now, I noticed this:



7circle said:


> The Mech RPM 3000RPM so the Hz is Nmech x 2.¶/60 x 2/Poles
> So 3000 x 2x3.142/60 x 2/4 = 157.1 assuming 4 pole


When working with RPM, Pi does not enter into the conversion, like when using rad/sec.

Electrical frequency (Hz) = mechanical frequency (RPM) * (#pole pairs / 60 seconds per minute). So 3000 RPM is 100 Hz, synchronous frequency.

Hope to get back into this, perhaps this evening. Yeah, Saturday nights are real exciting around here 

major


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## 7circle (May 29, 2010)

Hi Major Thanks for that pick up on my Hz calc.

I stuffed to bits that made the calc look correctish...

I edited the post above.

The team still needs to sort out the problem.

So any comments woul dbe helpfull

A VDR was put across the DC bus terminals to kick in at 350V there were 3 in parallel to allow 300A at 710V. Just so they would nlt blow and make a mess inside the case.

A pair inseres of Electro Caps at 4700uF / 450 Surge where also linked in on short leads to the Bus terminals.

A precharge and post discharge circuits with 500 ohm where used as well.

The only changes I can think of still are to wire the batts to the Caps then to the bus, add VDRs or Tranzorbs to the phase terminals on the IGBT modules.

The inverter controller software lloks like it was setup to be used as a wind turbine controller, so there are extra parameters that make things extra confusing.

The Zebra battery backs that Mes-Dea build may have capacitors in them to help them operate. 

I am worried that the DC bus at 350 Vdc is just too high for the 600V IGBTs and using 290V pack would be a losser fit for the IGBT rating.

We could replace these IGBT with higher rated Modules.


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## major (Apr 4, 2008)

7circle said:


> We could replace these IGBT with higher rated Modules.


Hi Ken,

You could do this. Likely you have 600V rated modules now. And it is possible that 1200V modules would have the same form factor. They would have different characteristics so I am unsure that gate drivers, dead bands and such carry over without modifications. I did a rather large inverter years ago for a 350V battery and had to use 1200V modules because the high current devices were unavailable in 600V. I always thought that was a blessing in disguise because we had a poor bus design and some snubber problems, yet the IGBT modules held up.

I did not know this used the Zebra battery. Don't know much about that. Is it actually built to accept regen? And to get the inverter tuned and set up, can you not just turn regen off? Ones I've used can. Then they just coast. If for some reason, you get an overvoltage condition, the control faults out and shuts down and protects itself. I am surprised your inverter doesn't do this. Which leads me to believe this is not your real problem.

As far as capacitors go, all inverters of this nature of which I am aware will have sufficient DC bus capacitance internally. In my opinion, adding external capacitors and voltage suppression devices will do little good. Like putting band aids on the body without knowing where it is bleeding.

I am also wondering why the dealer or manufacturer has not been brought in to deal with this.



> I am worried that the DC bus at 350 Vdc is just too high for the 600V IGBTs and using 290V pack would be a losser fit for the IGBT rating.


I was recently working with an inverter using 600V modules and we took the battery up to 400Vdc. We had no problems, well, at least, not in that area  But does bring to mind a test. Can you borrow a lower voltage lead acid or lithium battery for a test?

Regards,

major


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## 7circle (May 29, 2010)

major said:


> ...I did not know this used the Zebra battery. Don't know much about that. Is it actually built to accept regen? And to get the inverter tuned and set up, can you not just turn regen off? Ones I've used can. Then they just coast. If for some reason, you get an overvoltage condition, the control faults out and shuts down and protects itself. I am surprised your inverter doesn't do this. Which leads me to believe this is not your real problem.
> 
> As far as capacitors go, all inverters of this nature of which I am aware will have sufficient DC bus capacitance internally. In my opinion, adding external capacitors and voltage suppression devices will do little good. Like putting band aids on the body without knowing where it is bleeding.
> 
> ...


We found the spec on the Modules fe Frontrunnners from a division of Fuitsu
http://www.fe-frontrunners.eu/Semi/Datenblatt/IGBT/2MBI600U2E-060a.pdf

The dealer has been communicated with by Stiive, but no solution found.

They tested the motor with a TIM400 at 96Vdc to 15kW and up to the RPM I showed in the above graph.

The Cart uses 82 30Ah Kokam Cells for a 82 x 3.6V = 295V Nominal and at full Charge at 82 x 4.2 = 344.4V

I can see that the chemistry could have confused the situation if LiIronPOOOO was used, max pack voltage would have been 82 x 3.2V/cell =262V. And Max at 3.65V/Cell is 299.3V

The Inverter Controller has a section P106 - P109 that are settings for DC Bus voltage that are Over 
P t 106 Minima tensione del Bus in continua 180.0÷500.0 400 Volt
P t 107 Massima tensione del Bus in continua 300.0÷1200.0 760 Volt
P t 108 Soglia freno ON 300.0÷1200.0 730 Volt
P t 109 Soglia freno OFF 300.0÷1200.0 710 Volt










So should the Inverter be rated to 400V if it uses 600V IGBTs?


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## major (Apr 4, 2008)

7circle said:


> So should the Inverter be rated to 400V if it uses 600V IGBTs?


If it is a decent inverter design, yes. Most industrial VFDs (inverters) rated for 230 Vac have an overvoltage trip point at 400 volt DC on the DC bus. And I said, I have just run an inverter to full current (400A) on 400 volt DC battery using PowerEx 400A, 600V modules.

I thought you said it had a Zebra battery. Now it is Kokam?

And on that parameter list, why would you have brake thresholds set into the 700s? Now, all inverter companies use different parameter names just to confuse users. So I don't know what I am looking at. But seems fishy to me.

major


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## 7circle (May 29, 2010)

I mentioned Zebra as I was wondering how they designed the system.
Mes-Dea Zebra batteries are mentioned in the Controller Manual.

THey are part of the product range of the MES-DEA
See company info here:
http://www.fuelcellmarkets.com/fuel...iew.aspx?articleid=10060&subsite=1&language=1

I believe the Battery Pack was built by the Swinburne UNI SAE team to suite the ability of the Controller and Motor.


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## 7circle (May 29, 2010)

Have you seen the Manual

The Parameters and Connector Tables were copied and pasted to build an english version that can be read outside the LabVIEW-RT software that is used to setup and configure the drive. The document is picture based so it cant be searched. Someone needs to copie and paste the text out of the fields one-by-one for 300 or so parameters.

You can only view the parameters once the Software has Linked to the TIM600.

So just loading the software on another PC to review the parameters wont help.

The software needs to reach version 2 level. not the 1.01 it is at currently.


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## Nathan219 (May 18, 2010)

I would lower the brake voltage to the maximum you would want the batteries to see. We have abused our TIM600 far beyond what you have been able to do without hurting the inverter. The 850V limit in the software is probably to allow the logic board of this inverter to control other power stages. Our inverter successfully stopped regen under full load when the battery voltage spiked then it re-engaged regeneration while still braking. We have found the inverter to be pretty reliable I would call you to talk things over if it were not and international call.


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## 7circle (May 29, 2010)

Nathan219 said:


> I would lower the brake voltage to the maximum you would want the batteries to see. We have abused our TIM600 far beyond what you have been able to do without hurting the inverter. The 850V limit in the software is probably to allow the logic board of this inverter to control other power stages. Our inverter successfully stopped regen under full load when the battery voltage spiked then it re-engaged regeneration while still braking. We have found the inverter to be pretty reliable I would call you to talk things over if it were not and international call.


What battery back do you use?

Type and No of cells?


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## Nathan219 (May 18, 2010)

96 CALB 100AH cells


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## 7circle (May 29, 2010)

Nathan219 said:


> 96 CALB 100AH cells


Okay so 96 x 3.2 = 307.2 Under Nominla loads
and 96 x 4.2V max = 403V

So What motor are you using?

If the motor has significantly less inductance then the peaks caused by the IGBT turn off will be much lower even with the standard capacitors on the bus being 1uF on each of the the IGBT +/- terminals and 45uF x 6 beside the IGBT's linked by wires.

http://www.fe-frontrunners.eu/Semi/Datenblatt/IGBT/2MBI600U2E-060a.pdf

The 7.2 Version is hard to find on the web

Here is an appended manual for TIM600 http://www.docstoc.com/docs/66919358/TIM600Handbook_72ENG-App-ENG-PARAMS


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## Nathan219 (May 18, 2010)

We are using the MES DEA 200-300 motor. it can push our car to over 130mph currently, we are installing larger fuses which should allow us to increase current safely.


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## Tesseract (Sep 27, 2008)

7circle said:


> If the motor has significantly less inductance then the peaks caused by the IGBT turn off will be much lower even with the standard capacitors on the bus being 1uF on each of the the IGBT +/- terminals and 45uF x 6 beside the IGBT's linked by wires....


The magnitude of the turn-off spikes depends only on the stray inductance between the capacitor, switch and diode (regardless of the converter topology, btw); the motor inductance actually has no effect here.

So it sounds like there might be way too much inductance between the bus capacitors and the IGBT modules, and those 1uF caps on top of each module might actually hurt here because they will form a high Q resonant circuit with the wiring to the other bus capacitors. Put a scope on the DC bus set and see how much ringing there is there - this might very well be the cause of the occasional explosion...


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## 7circle (May 29, 2010)

Thanks Tesseract (Jeff)

Stray inductance and stray capacitance are hard to quantify without looking at it closely on a scope. This still can be done accurately, but normally needed by a DIY conversion.

To help stop spikes MOV's were fitted (not VDRs ). Three K375 types that can take 100A at 700Vdc each to abasorb pulse energy where fitted on the Bus terminals.

The 20mmx8mm bus bars will cause some stray inductance on the DC side. 
With the three WIMA FKP 1uF on each IGBT pos and neg Screw head and the low ESR 6 x 45uF caps linked to the bus seperately. The internal setup has minimal inductance between the CAPs and the IGBT's.
The circuit was improved by reducing the battery side cabling to be shorter and closer. Before the shunt for DC side current measurement was removed reducing the cabling to be even tighter, there was lots of ringing and sag seen at the battery end of the connections.

A extranal capacitor was added with 300mm flying leads. I would prefer the battery to be wired to this capacitor then link to then link to the internal bus, but the cap was mainly added to capture the freewheeling currents when the diodes are conducting onto the bus pos/neg.

Even after this was improved and the circuit was linked up with direct connections to the battery pack and the "T" link to the 2250uF/800Vdc Cap, the IGBT's blew in a fully tested and working inverter, the W phase top and bottom that then popped the battery fuse as it should. 
So where are the spikes coming from?

I was more concerned with the phase terminals. They have freewheeling diodes to the Positve and Negative bus connections inside the modules, as per normal. When the IGBT turns OFF the Diode needs to turn ON and allow the current to freewheel through the motor inductance.

The AC side, the IGBT terminal that is connected to the motor phase, has no protection. Adding Capacitors would only cause current spikes, but perhaps more MOV's (Metal Oxide Resistors) would help protect them.

As the inverter apparently works fine with other motor battery combinations, and this system uses 30Ah Kokams, that have a large capacitive effect to the chassis, that may be contributing to the battery side capacitance. Perhaps this needs to be considered.

The DC Bus is floating ideally and is monitored by a special circuit for leakage to the chassis.

The Inverter case has thick earthing links to bare metal contact points that are not structural.

When someone asks me whats wrong that isn't too electrically minded I say it could be like buying an Amp and Speakers that blow the Amp because the speakers are too big. I hope I'm wrong.

I'm surprised someone who has the same motor controller setup has not commented on how they got their system running.

I still think the V/Hz for this motor needs to be below 0.6V/Hz.
The Motor name plate has 210V at 175Hz giving 1.2V/Hz that squeals like a pig (Swine) when C41 test is run even at a very low test current. Suggesting saturation.

The motor may have been damaged in transit and have a air gap or other issue.
But we have had the motor passing C42 with no chain running at over 2000RPM.

Hopefully a similar system can be compared to. The parameters can be saved and emailed to us if some one is up to it.


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## 7circle (May 29, 2010)

Tesseract said:


> The magnitude of the turn-off spikes depends only on the stray inductance between the capacitor, switch and diode (regardless of the converter topology, btw); the motor inductance actually has no effect here.
> 
> So it sounds like there might be way too much inductance between the bus capacitors and the IGBT modules, and those 1uF caps on top of each module might actually hurt here because they will form a high Q resonant circuit with the wiring to the other bus capacitors. Put a scope on the DC bus set and see how much ringing there is there - this might very well be the cause of the occasional explosion...


Why do you say "the motor inductance actually has no effect here."

If the batteries are disconnected during a fault so there is only (275+3)uF normally on the bus. 

This capacitance has to abosorb all the current to denergize the motor inductance and any stray inductance.

The problem appears to be occuring during decceleration of the motor too. Notmal ON and OFF switching didn't kill the IGBT's.
So stray inductance alone can't be the problem.

If the EV-E motor had 400A in a field winding the stored energy is U_L = L/2 x I^2 Joules

If the motor is wound for only 0.6V/Hz at 50Hz is can only cope with [email protected] capable of 200Nm of Torque to rated rpm. 










If the motor performance data included line current not just torque the stall pf could be measured and the inductance can be calculated.


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## Tesseract (Sep 27, 2008)

7circle said:


> The 20mmx8mm bus bars will cause some stray inductance on the DC side.


If the bus bars are not stacked on top of each other so their mutual inductance cancels out then a useful rule of thumb is to assign them approximately 20nH/in. (8nH/cm) of inductance. Note that the actual inductance of the wire/busbar/etc also depends on the ratio of width to height but that's why this is called a "rule of thumb"...  

Anyway, if this inverter is switching 100A in 100ns then every 20nH of inductance will _induce_ 20V of spike on top of the bus.

I am not familiar with the internal construction of this inverter so I'm not sure what you mean by "on the DC side", but that usually refers to _before_ the input capacitor and any inductance there is irrelevant because it is not within the switching loop - that is, the loop between capacitor, switch and diode - just as the motor is not within that loop.



7circle said:


> With the three WIMA FKP 1uF on each IGBT pos and neg Screw head and the low ESR 6 x 45uF caps linked to the bus seperately. The internal setup has minimal inductance between the CAPs and the IGBT's.


No, a laminated bus structure comprised of twin plates as thin and wide as possible connecting the IGBT modules directly to the input capacitor is the "minimal inductance" setup. What you are describing - so far as I can tell, mind you - is the _typical_ setup, minus the electrolytics whose ESR would actually serve a useful purpose here by dampening out any ringing from those 1uF FKP caps. In other words, using too-good film caps with a crappy bus design just makes life harder for the IGBTs.



7circle said:


> Even after this was improved and the circuit was linked up with direct connections to the battery pack and the "T" link to the 2250uF/800Vdc Cap, the IGBT's blew in a fully tested and working inverter, the W phase top and bottom that then popped the battery fuse as it should.
> So where are the spikes coming from?


Given what I just explained above can you see how "T-ing" in that capacitor could actually hurt, rather than help? 

That said, there are many ways to blow both legs of a half-bridge so you really need to get lucky with the scope to catch the destruction when it happens. It is often helpful to trigger on bus current when looking for shoot-through (ie - both legs turning on at the same time, either from actual gate drive overlap or because of avalanching).



7circle said:


> As the inverter apparently works fine with other motor battery combinations, and this system uses 30Ah Kokams, that have a large capacitive effect to the chassis, that may be contributing to the battery side capacitance. Perhaps this needs to be considered.


I have no idea what a capacitive effect to the chassis is... the more likely reason as to why Dow-Kokam cells blow up this inverter/motor combo is their exceptionally low internal resistance compared to virtually every other cell chemistry out there (except, maybe, flooded NiCd). Thus, if this inverter does have a problem with shoot-through then the Kokam cells might very well deliver a much higher short-circuit current than the IGBTs can withstand. The current-sensing and/or desaturation fault detection circuits should protect against this unless the cause of the shoot-through is avalanching...

Once again, I have not actually seen this inverter so this is all speculation. 



7circle said:


> ...
> This capacitance has to abosorb all the current to denergize the motor inductance and any stray inductance.


No, motor current decays through the freewheeling diodes - the input capacitance does not participate here at all. You should review how a buck converter works (a 3ph. inverter is basically 6 buck converters operating in sequence).


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## 7circle (May 29, 2010)

Thanks for feedback,

I'll see if i can post some more picks.

Considering the controller works with 315Vnom TS cells and a MES-DEA motor A200-250. 

The changes are Dw-Kokam and Motor then later external bus cap.

I'll sleep on the freewheelers. I'm not convinced that the diodes are the only path without the Caps.

Cheers Ken 7C


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## 7circle (May 29, 2010)

Tesseract said:


> ....No, motor current decays through the freewheeling diodes - the input capacitance does not participate here at all. You should review how a buck converter works (a 3ph. inverter is basically 6 buck converters operating in sequence).












If there is a fault and the IGBT Gate control is lost the IGBT are all left off.

As there would be currents in the motor inductance (shown on the left, but linked, say as star) The only path is via the diodes that would return current on to the bus until the inductive EMF is subdued.

I have seen the bottom set all turned on to plug the current and brake the motor. But if there is no gate drive available then Diode will conduct in th upper section and return current into the capacitor.

If someone can explain how the Caps are not involved I would appreciate your help.

7C


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## 7circle (May 29, 2010)

Here is the pic with the two phases with current (let the third be at zero at time of fault)










If there is some physical reason why the current won't continue to flow as shown can you explain why?


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## Anaerin (Feb 4, 2009)

7circle said:


> Here is the pic with the two phases with current (let the third be at zero at time of fault)
> 
> 
> 
> ...


Yes. When the current that is there drains to ground (Or from ground, in the case of -UDC) there will be no more current entering. The system will reach 0v.


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## 7circle (May 29, 2010)

Anaerin said:


> Yes. When the current that is there drains to ground (Or from ground, in the case of -UDC) there will be no more current entering. The system will reach 0v.


If there was a center connection to GND, your suggesting that the capacitors will be involved and one will charge up and the other discharge.

But I picked too general circuit. The EV has no center capacitor link to GND or Chassis.

The issue of the controller IGBT's failing, I am suggesting is caused by over voltage caused by a spike when the motor is coming to rest due to the current that is flowing in it when the fault occurred. This is worst case.

The system is also mainly failing due to the IGBTs going short. This occurs when we expect to see the motor being slowed in the ramp down phase of the C42 auto tune test.

The controller PWM and Bus bar inductance is operating with start up some ramp down. So stray inductance in the controller is not causing the failure, in my opinion.

This picture with more detail may help clarify.


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## Coulomb (Apr 22, 2009)

7circle said:


> Here is the pic with the two phases with current (let the third be at zero at time of fault)


With an AC controller, either the upper or lower transistors will be on. I find it hard to see which transistors are supposed to be on or off, so I represent the transistors as switches here:










I've arbitrarily let phases A and B be on in the upper circuit, and "on" here means the lower transistors are switched on (like with a DC controller). So conventional currents (positive to negative) flow as shown by the colored arrows.

In the lower circuit, I've switched phase A the other way; now the blue current flowing left to right has to flow via the upper transistor (and/or its parasitic diode), through the pack and capacitor (which will be the capacitor only if the pack disconnects), and the only place for it to go is via the lower phase B transistor, as shown in the lower part of the diagram.

This flows in the opposite direction to the current from phase B, which seems wrong to me. [ Edit: indeed, it is wrong; see next diagram on the following page. ]

I've very likely gotten something wrong here; anyone care to point out the error?

However, 7 circle's point that the capacitor is involved in the motor current loop seems unavoidable. Unless I've made an error there too... [ Edit: this is also wrong. ]

Finally, the blue current is trying to charge the pack/capacitor, so the phase A motor wire has to raise to slightly higher than the pack voltage to push current into the pack/capacitor. [ Edit: three errors in a row! ]


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## 7circle (May 29, 2010)

Hi Coulomb

The problem is all six IGBTs are off and the case could be that the controller/gate driver is disabled.

You diagram of switches doesn't show what happens when the diodes conduct it only describes the IGBT switch function.

So would you aggree that the total bus capacitance needs to absorb the demagnetisation energy of the motor inductance. If the motor has 500A flowing between two phases. This will cause the motor to continue to generate Bemf from the rotor motion too. So kinetic energy will also be transferred on to the Bus Capacitors until the induction motor moves into no-load.

The usual AC Hz operation is invalid as the systems looks like a transformer with inductance and resistance and a rotor motion causing a secondary flux variation.

With the battery pack isolated the capacitor voltage increase has to absorb all this energy and the some copper resistive loss.

I hope this clarifies *Tesseracts* suggestion


> "(a 3ph. inverter is basically 6 buck converters operating in sequence)"


Also the comment


> "No, motor current decays through the freewheeling diodes - the input capacitance does not participate here at all. "


 I hope this helps explain ho(w) the input capacitance is involved, as the diodes can't freewheel with(out) the current passing via the DC Positive and Negative rail.

7C


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## Coulomb (Apr 22, 2009)

7circle said:


> The problem is all six IGBTs are off and the case could be that the controller/gate driver is disabled.


Well, that's a fault condition. I don't know what happens then.



> Your diagram of switches doesn't show what happens when the diodes conduct it only describes the IGBT switch function.


Well, but as long as one of the transistors is on when the other is off, the diodes should never conduct (except for a new nanoseconds of dead time) without the transistor being across them. They will share the current, hopefully the conducting IGBTs will take the majority of the current. So I feel justified in treating the IGBT and diode as a switch.



> So would you agree that the total bus capacitance needs to absorb the demagnetisation energy of the motor inductance.


I agree it looks that way from my diagram and explanation. However, I'm told by people whose knowledge I respect that this is not the case, so I'm looking forward to seeing where I've gone wrong, if someone is kind enough to point out my error(s) in ways that I can understand.


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## Coulomb (Apr 22, 2009)

Coulomb said:


> I'm looking forward to seeing where I've gone wrong, ...


Arrgh. Silly me. I had it on my scratchy diagram all along, and didn't copy it properly to what I drew in MS paint.

Of course, the blue current doesn't attempt to charge the pack/capacitor, it takes the easier path via the upper transistor of phase C:










Sorry for the confusion.


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## Coulomb (Apr 22, 2009)

I note that the blue current going through the upper C phase transistor is going in the opposite direction for the parasitic (freewheeling) diode to conduct. So in the special case of the IGBT drive not working, then indeed the current would have to take the path I show in my first diagram, through the capacitors. I'd say that this would be highly undesirable, especially in controllers that don't have electrolytics (e.g. "unlectrolytic" film capacitors).

I think that the inductors would more or less parallel themselves, cancelling each others' currents, but via the capacitor, which could cop a huge spike of energy. I can imagine that the IGBTs could end up with a large reverse voltage from collector to emitter, and this could cause them to avalanche and short. But I'm just speculating there.

So if something caused your gate drive to fail (after it had started of course), that could cause one or more IGBTs to fail, and possibly damage the capacitors as well.


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## 7circle (May 29, 2010)

I arrowed my diagram wrong. The pink dashed was supposed to be the other way.

This site shows standard H bridge theory. It can be compared to 3 phases easily.

http://www.modularcircuits.com/h-bridge_secrets2.htm

Also IGBT shoot through needs to be considered.

Fixed sketch of circuit.









An inductors terminal voltage will change to allow the current to flow. 

So the Voltage will go to Bus Voltage plus two diode forward voltage drops. 

Say 350V + 1V + 1V = 352V. 

The current will dissipate into the charging capacitor. 

So U-L current flow/flux Energy will shift to U-C capacitances stored potential energy. 

The Motor type has a V/Hz of 0.6 so at 60Hz the voltage for no load is 30Vac 

So the turns will be low compared to a 415 at 50Hz 30kW motor . 
The 415 Nominal Motor needs 44A for 30kW at 0.95 pf. 

So if the ratio follows L_30/L_415 = 30/415 then the AC-30 motor will have 7.2% of the 415Vac motors inductance. 

So with 105A Nominal the Inductance has U-L=I^2.L/2 

So the low V/Hz motor has 41% (=0.072x[105/44]^2) of the energy stored at their Nominal currents. 

The Bus circuit needs to change from +105A to -105A. 
The stray inductance will try to hold the current at +105A. 

mmm. looks like the Bus Bar stray inductance will fight the reversal so the IGBT V-CE will shoot up. So need to look into dV/dt shoot through.


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## 7circle (May 29, 2010)

Summer break is over for the guys here in Oz, so testing on the TIM600's is going ahead.

If you have the MES-DEA/ZEBRA TIM-600 and the EV-E 30kW motor combo can you let us know.

The battery pack type and size would be helpful to know.


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## Stiive (Nov 22, 2008)

FYI, have added some more information on the aeva website located here:
http://www.aeva.asn.au/forums/forum_posts.asp?TID=2377&PN=4

I know believe the problems have been caused by misifiring IGBTs possible due to a build up in capacitance between the LV and HV system. Please check the thread for details


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