# [EVDL] My controller Sploded! and I was left with a box of charcoal :-(



## EVDL List (Jul 27, 2007)

Hi folk's,

I took my Ghia (ELEC KAR) out for a spin Saturday to make sure it was ready for St. Patty's day next week-end. Since I had a potted GE 2 wire non-linear control, I bumped up the PWM to be 80% still in PWM into the full on bypass contactor (activated by a full throttle microswitch). I've always had a bypass contactor on my controllers since the 70's so they'd run cooler and if the controller failed I could get to the next exit. But the bypass has always came on at 100% duty cycle.

Anyway as I was driving I tried going into bypass which was fine, full power, but when I came out of bypass I heard the plasma fuzz of the contactor (since the controller was still at 80% duty cycle). There was a stop sign ahead so I slowed down & stopped. then when I restarted slowly there was a snap, crackle, pop! After towing it back home (after a long hike to get my tow truck) I found that the dual IR 406CNQ200 (400A flywheel diodes X2) were shorted (across the motor). So when the IGBT's refired, they did so into a dead short. The dual 600A CM600HA-24H IGBT's gate resistors were blown open and most of the components on the gate driver board (and 08' microcontroller) popped their tops.

I'm curious as to why this happened. The full on bypass contactor should behave just like a parallel IGBT of fet even if the controller was still PWMing. And upon release the one shot back emf pulse shouldn't have fried the diodes, but it did. I noticed on the GE base controller I used, they had 800A of diodes (2 in parallel) and I usually use 1200A (3 in parallel to match the 1200A IGBT's of MOSFET's). I wonder if this was the main culprit although I ran the vehicle before in full bypass *but at 100% duty cycle* and had no problem. 

I overnighted from KTA-EV a Curtis 1231C- 8601 96-144V (for a 120V system) and I noticed in the manual no bypass contactor used. I wonder if the heat reduction in bypass (and ability to make it to the next exit should the controller open up) is worth the risk now. I haven't had trouble in the past with this method alothough I've been careful to make sure it's at a 100% duty cycle when the bypass contactor clicks full on & offas in the www.evalbum.com/1273 and the www.evalbum.com/2749 .

Have a renewable energy day,
Mark
www.reevadiy.org 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120312/c867bed8/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Mark Hanson-2 wrote
> ...The full on bypass contactor should behave just like a parallel IGBT of
> fet even if the controller was still PWMing. And upon release the one
> shot back emf pulse shouldn't have fried the diodes, but it did.

The likely culprit here is the energy stored in the unclamped inductance
between the internal switch (e.g. - IGBT) and the external bypass contactor,
rather than the bump in freewheeling current from when the bypass contactor
turns off. As long as the IGBT is on whenever the external bypass contactor
switches states the stray inductance in the loop between the internal IGBT
and the external contactor is irrelevant, but if the IGBT happens to be off
when the bypass contactor is turned off then the energy stored in the
inductance of that loop will ring with the output capacitance of the IGBT,
potentially to a voltage high enough to avalanche the Collector-Emitter
junction. IGBTs are supremely tough devices when it comes to tolerating
overloads, even short circuits, but like most semiconductors they are quite
vulnerable to overvoltage.



Mark Hanson-2 wrote
> I overnighted from KTA-EV a Curtis 1231C- 8601 96-144V (for a 120V system)
> and I noticed in the manual no bypass contactor used. 

Except for the old GE SCR-based controllers (e.g. - the EV-1), I'm not aware
of any other commercially produced motor controller that explicitly allows
using a bypass contactor. Even if it could be guaranteed that the bypass
contactor would only turn on and off whenever the IGBT (et al.) was on that
still takes control of the motor current away from the device ostensibly
controlling the motor!

-Jeffrey Jenkins


--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/My-controller-Sploded-and-I-was-left-with-a-box-of-charcoal-tp4465937p4495821.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Jeffrey, It is such a pleasure to hear from someone who knows how these
components actualy work, Hey, perhaps that is why the EVNETICS controllers
work so well.!

Side note to Otmar, using state of the art design like you is why the
"Zilla" is so much better than the Curtis and other "classic" motor
controllers.
Regards,
*Dennis Lee Miles* (Founder)
*"Electric Car Service Shop"*
*[ the Forgotten Infrastructure ]*
+++++++++++++++++++++++++
On Thu, Mar 22, 2012 at 11:22 AM, Jeffrey Jenkins <[email protected]


> > wrote:
> 
> >
> > Mark Hanson-2 wrote
> ...


----------



## EVDL List (Jul 27, 2007)

FYI,
GE made several MOSFET and IGBT based controls that used bypass contactors and 
went on thousands
of forklifts and hundreds on EV's. I'm not saying technically one way or the 
other there was benefits to doing this,
just wanted to set the record straight that they were not used on the EV1 SCR 
control exclusively!
I wrote software back in the day (1995) for a dual motor forklift that had 
bypass, regen and field weakening for two
series motors whose duty cycle and other functions where controlled by the steer 
angle sensor, that was a major pain in the
ass for an otherwise simple series motor control!


----- Original Message ----
From: Dennis Miles <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thu, March 22, 2012 8:48:08 PM
Subject: Re: [EVDL] My controller Sploded! and I was left with a box of charcoal 
:-(

Jeffrey, It is such a pleasure to hear from someone who knows how these
components actualy work, Hey, perhaps that is why the EVNETICS controllers
work so well.!

Side note to Otmar, using state of the art design like you is why the
"Zilla" is so much better than the Curtis and other "classic" motor
controllers.
Regards,
*Dennis Lee Miles* (Founder)
*"Electric Car Service Shop"*
*[ the Forgotten Infrastructure ]*
+++++++++++++++++++++++++
On Thu, Mar 22, 2012 at 11:22 AM, Jeffrey Jenkins <[email protected]


> > wrote:
> 
> >
> > Mark Hanson-2 wrote
> ...


----------



## EVDL List (Jul 27, 2007)

Hi Jeff etc,

It was the flywheel diodes that shorted *not* the IGBT's. When I pressed the peddle the second time after the contactor zorched, then the IGBT's fired into a dead nuts short and backflashed through the gate resistors. But in testing the IGBT's they appear to be neither shorted or open. When you say inductance, I think you mean the 150uH of the motor, the cable inductance is negligible and from the forensic testing it appears my problem was from overcurrenting the freewheel diodes when the contactor released while there was *no* PWMing going on. *Previously* a weeks earlier the controller worked *fine* when the IGBT's were kept on at 100% duty cycle above 500A battery current. But when I fooled with the software to allow PWMing during bypass (to linearize the pot response) *that's* when the kaboom happened.

BTW, the parade with the Curtis 1231C control went well.

Best Regards,
mark
www.reevadiy.org 

Message: 3
Date: Thu, 22 Mar 2012 08:22:14 -0700 (PDT)
From: Jeffrey Jenkins <[email protected]>
Subject: Re: [EVDL] My controller Sploded! and I was left with a box
of charcoal :-(
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii


Mark Hanson-2 wrote
> ...The full on bypass contactor should behave just like a parallel IGBT of
> fet even if the controller was still PWMing. And upon release the one
> shot back emf pulse shouldn't have fried the diodes, but it did.

The likely culprit here is the energy stored in the unclamped inductance
between the internal switch (e.g. - IGBT) and the external bypass contactor,
rather than the bump in freewheeling current from when the bypass contactor
turns off. As long as the IGBT is on whenever the external bypass contactor
switches states the stray inductance in the loop between the internal IGBT
and the external contactor is irrelevant, but if the IGBT happens to be off
when the bypass contactor is turned off then the energy stored in the
inductance of that loop will ring with the output capacitance of the IGBT,
potentially to a voltage high enough to avalanche the Collector-Emitter
junction. IGBTs are supremely tough devices when it comes to tolerating
overloads, even short circuits, but like most semiconductors they are quite
vulnerable to overvoltage.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120323/9421a69b/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Think the IGBT collector is still clamped by the free wheel diodes, even
when the bypass contactor turns off. This will prevent the collector-emitter
voltage exceeding the voltage on the supply caps? To blow the diodes you
need either to exceed the voltage rating or the current rating, or possible
overheat them. Since the node between the IGBT and the diode is constrained
in voltage to the supply range it should not be possible to kill either by
overvoltage unless the supply is overvoltage. 
Maybe the current limit does not work when the bypass contactor is
in, then when the contactor drops out the diodes have to catch the voltage
spike and to do this carry the full current that the contactor was carrying,
which may exceed the current limit of the controller and thus the rating of
the diodes.
In my work we design a range of products that have a 6A 1000V wire
lead diode, (P600M) that runs at 400A for 100uS every second. We have tested
them to over 1000A like this without problem. Under these conditions the
voltage drop across the conducting diode is 40V, so they share quite well
too. Just to give some idea of what you need to do to kill the diodes.



> Jeffrey Jenkins wrote:
> The likely culprit here is the energy stored in the unclamped
> inductance between the internal switch (e.g. - IGBT) and the external bypass
> contactor, rather than the bump in freewheeling current from when the bypass
> ...


----------



## EVDL List (Jul 27, 2007)

gtyler54 wrote
> 
> Think the IGBT collector is still clamped by the free wheel diodes, even
> when the bypass contactor turns off.

How do the anti-parallel diodes clamp the inductance in the wiring between
the internal IGBT(s) and the external bypass contactor? Not possible, hence
why I called such inductance "unclamped".



gtyler54 wrote
> In my work we design a range of products that have a 6A 1000V wire
> lead diode, (P600M) that runs at 400A for 100uS every second. We have
> tested
> them to over 1000A like this without problem. Under these conditions the
> voltage drop across the conducting diode is 40V, so they share quite well
> too. Just to give some idea of what you need to do to kill the diodes.

That's a tremendous amount of overcurrent for a brief period of time; try
applying the same multiplier of overvoltage across that diode and see how
long it lasts.



--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/My-controller-Sploded-and-I-was-left-with-a-box-of-charcoal-tp4465937p4500413.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Mark Hanson-2 wrote
> 
> ... 
> It was the flywheel diodes that shorted *not* the IGBT's. 

Then the diodes avalanched before the IGBTs - that's certainly possible.


Mark Hanson-2 wrote
> But in testing the IGBT's they appear to be neither shorted or open. 

For the sake of clarity and precision, if the IGBTs test fine you should
say, "the IGBTs do not appear shorted when the gate is shorted to the
emitter, nor do they appear open when the gate is biased on".


Mark Hanson-2 wrote
> When you say inductance, I think you mean the 150uH of the motor, the
> cable inductance is negligible

No, I did not mean the motor inductance. In fact I specifically referred to
the inductance in the wiring between the internal IGBTs and the external
bypass contactor so there should be no confusion in this.

The inductance of said wiring will likely be close to 20nH/in unless you
took care to maximize the cancellation of flux from the forward and return
currents. Energy will be stored in the inductance according to the eq.
0.5LI^2 and if that energy exceeds the single-pulse avalanche rating of the
IGBT (or the FWD) then it will be destroyed when the bypass contactor opens
up - after all, an inductor will create whatever voltage is necessary, of
either polarity, to prevent a discontinuity in current flow.


Mark Hanson-2 wrote
> and from the forensic testing it appears my problem was from
> overcurrenting the freewheel diodes when the contactor released while
> there was *no* PWMing going on. *Previously* a weeks earlier the
> controller worked *fine* when the IGBT's were kept on at 100% duty cycle
> above 500A battery current. But when I fooled with the software to allow
> PWMing during bypass (to linearize the pot response) *that's* when the
> kaboom happened.

I already explained why the unclamped inductance of the bypass wiring does
no harm as long as the IGBT is on when the bypass is opened - this provides
a ready pathway for the energy stored in the unclamped inductance to
freewheel through the closed IGBT.

It is, of course, entirely possible that the motor current during bypass
grew to such a huge extent that it blew the freewheeling diodes when the
bypass was opened, but that is much less likely in my experience as most
semiconductors can tolerate a huge overcurrent for a brief period;
overvoltage is an entirely different matter, as if it is high enough it will
trigger avalanche conduction which causes the affected junction to act very
much like an arc (ie - current flow is sustained at well below the avalanche
trigger voltage).



--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/My-controller-Sploded-and-I-was-left-with-a-box-of-charcoal-tp4499969p4501268.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Lee Hart wrote
> 
> Jeffrey, I'm having trouble seeing how the bypass contactor could break 
> down the transistors or diodes from over-VOLTAGE.
> 
> Any good controller has its transistors-diodes-capacitors in a tight 
> loop to minimize inductance.

Well there you go... the bypass contactor is like another transistor, except
that it isn't in a tight loop with an anti-parallel diode or the input
capacitor.




--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/My-controller-Sploded-and-I-was-left-with-a-box-of-charcoal-tp4499969p4501957.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Lee Hart wrote
> ...
>> Well there you go... the bypass contactor is like another transistor,
>> except
>> that it isn't in a tight loop with an anti-parallel diode or the input
>> capacitor.
> 
> That would mean that the contactor sees a big voltage spike when it 
> opens (due to the inductance of long leads connecting it to the 
> controller. But contactors are able to cope with very high voltage 
> transients for brief periods of time.
> ...
> 

Ok, I think I see where we are misunderstanding each other...

If I understand your position correctly, you suppose that the freewheeling
diode will shunt the energy stored in any stray inductance between it and
the bypass contactor back to the supply if the other switches are already
off, causing, at most, a brief bump in voltage across the capacitor.

My supposition is that the stray inductance in the bypass contactor wiring
will oppose the smooth transfer of motor current from switch (bypass
contactor in this instance) to freewheeling diode, just as it would if the
inductance were from a sloppy layout of the wiring between the semiconductor
switches, diode and input capacitor, and while the transfer of current is
being opposed the voltage across the contactor and switches will rise.
Enough stray inductance with enough current flowing through it prior to
opening the bypass contactor and the voltage will spike high enough to
avalanche the switch and/or its anti-parallel diode before the freewheeling
diode begins conducting. For extra excitement, you can add in the
complication of the stray inductance ringing with the output capacitance of
the semiconductor switches.

The devil is in the details. What you can get away with at 5, 50 or even
500W can murder all sorts of things at 100-1000kW.



--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/My-controller-Sploded-and-I-was-left-with-a-box-of-charcoal-tp4499969p4503120.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere. Thanks.
|
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

On Sun, Mar 25, 2012 at 8:01 AM, Jeffrey Jenkins


> <[email protected]>wrote:
> 
> > My supposition is that the stray inductance in the bypass contactor wiring
> > will oppose the smooth transfer of motor current from switch (bypass
> ...


----------

