# [EVDL] How To Burn Up Your DC Motor



## EVDL List (Jul 27, 2007)

I'm glad my Zilla has stall detect. its kicked in a couple times pulling
onto a trailer 


> "Bruce Lawton" <[email protected]> wrote:
> 
> > Maybe this is common knowledge for this group, but I recently learned how
> > to burn up my motor.
> ...


----------



## EVDL List (Jul 27, 2007)

Bummer. Does your EV still have the tranny or are you direct drive?

BTW the parking brake went overcenter on my EV once -- I couldn't get the p=
arking brake to release. I was able to drive it off the trailer and into my=
garage against the parking brake without drama. That was with 48V on my Ko=
stov sepex, the "controller" was just a switch... No Amp limit! Since there=
was no PWM there was no current multiplication, though.



________________________________
From: Bruce Lawton <[email protected]>
To: [email protected] =

Sent: Saturday, April 21, 2012 4:50 PM
Subject: [EVDL] How To Burn Up Your DC Motor
=

Maybe this is common knowledge for this group, but I recently learned how t=
o burn up my motor.

I was returning home, thinking about the prospect of working on the car and=
bumping the accelerator. I was working under the dash recently, on the hea=
ter core. If it were in gear and on, who would win: the motor or the parkin=
g brake? Some of you see where this is headed. I parked the car in the gara=
ge, set the brake and pressed the accelerator for at least 2 seconds, proba=
bly 4 or 5 seconds. The battery delivered 25A during this. The brake won, I=
turned everything off and went inside. The next day, as the car began to r=
oll, there was a tick-tick sound. I'd overheated the commutators and lifted=
4 bars. A LOT of motor amps had heated it when it wasn't turning.

The Zilla has stall protection; my Soliton apparently does not.

Lesson learned. :-\

BTW, Steve and Audrey from Green Shed Conversions drove up from Florida on =
short notice and brought a spare motor so I could show the car for Earth Da=
y. Wow! Kudos and a big thank you!

Bruce

_______________________________________________
| 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120422/04461c89=
/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)

Bruce,
Wow, that is indeed fast - are you sure it was only 2 sec that you used
full throttle? 25A from the batteries can easily turn into about 500A
motor current if the impedance of the loop controller - motor is low enough.
I have occasionally tested my EV pack by loading the motor while on parking =

brake - apparently the fact that I had an AC (induction) motor saved me
because I just heard a swishing sound of a slow rotating (slipping)
magnetic field at full power, but no harm was done to the field windings
(this AC motor was also water cooled - still I did not dare to run the
test longer than half a minute at a time with cooling periods)

In your case it sounds like the brushes and especially the contact area wit=
h the comm
heated up (that is one place where there is resistance and thus voltage dro=
p)
which managed to over-heat the comm bars due to the absence of cooling,
I take it that your motor has only an internal fan, not an external blower?

Indeed - lesson learned. I expect that the old motor is salvageable,
if needed by installing a new comm but probably by repairing the
damage that was done to the comm and rebanding it.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 =


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behal=
f Of David Dymaxion
Sent: Sunday, April 22, 2012 12:57 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

Bummer. Does your EV still have the tranny or are you direct drive?

BTW the parking brake went overcenter on my EV once -- I couldn't get the p=
arking brake to release. I was able to drive it off the trailer and into my=
garage against the parking brake without drama. That was with 48V on my Ko=
stov sepex, the "controller" was just a switch... No Amp limit! Since there=
was no PWM there was no current multiplication, though.



________________________________
From: Bruce Lawton <[email protected]>
To: [email protected]
Sent: Saturday, April 21, 2012 4:50 PM
Subject: [EVDL] How To Burn Up Your DC Motor
=

Maybe this is common knowledge for this group, but I recently learned how t=
o burn up my motor.

I was returning home, thinking about the prospect of working on the car and=
bumping the accelerator. I was working under the dash recently, on the hea=
ter core. If it were in gear and on, who would win: the motor or the parkin=
g brake? Some of you see where this is headed. I parked the car in the gara=
ge, set the brake and pressed the accelerator for at least 2 seconds, proba=
bly 4 or 5 seconds. The battery delivered 25A during this. The brake won, I=
turned everything off and went inside. The next day, as the car began to r=
oll, there was a tick-tick sound. I'd overheated the commutators and lifted=
4 bars. A LOT of motor amps had heated it when it wasn't turning.

The Zilla has stall protection; my Soliton apparently does not.

Lesson learned. :-\

BTW, Steve and Audrey from Green Shed Conversions drove up from Florida on =
short notice and brought a spare motor so I could show the car for Earth Da=
y. Wow! Kudos and a big thank you!

Bruce

_______________________________________________
| 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120422/04461c89=
/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

_______________________________________________
| 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)

Bruce Lawton wrote
> ... I parked the car in the garage, set the brake and pressed the
> accelerator for at least 2 seconds, probably 4 or 5 seconds. The battery
> delivered 25A during this. The brake won, I turned everything off and went
> inside. The next day, as the car began to roll, there was a tick-tick
> sound. I'd overheated the commutators and lifted 4 bars. A LOT of motor
> amps had heated it when it wasn't turning.
> 
> The Zilla has stall protection; my Soliton apparently does not....
> 

As of version 1.5.1 of the Soliton code that is correct - we do not prevent
you from pushing current through the motor even when stalled. 

We did contemplate adding this function at one time but did not because it
has a high annoyance potential (ie - stall detect triggering while trying to
drive up onto a trailer would infuriate me - I certainly wouldn't be
"thanking my controller" for its overzealousness), and, frankly, we feel it
is the motor manufacturer's responsibility to provide adequate
specifications and warnings for their products, rather than it be entirely
up to use to protect their products from abuse.

I should also point out that you are the only person I am aware of that has
damaged a motor by stalling it in the 3.5 years we've been selling Soliton
controllers, so I'd say this is a very rare problem. In contrast, we have
destroyed 7 motors ourselves by pushing too much current through them for
too long but I rather suspect that no one wants us to lower our current
ratings or otherwise thermally-cripple our controllers to protect against
that kind of abuse...

But if protecting against a stall seems really important to people -
particularly people that already own our controllers - then we'll add it to
the 1.6 release of the code.

We are about to roll out an intermediate version, 1.5.2, to correct the bug
in the start button function (failing to idle the motor) and add a couple of
minor functions: block throttle when signal is above calibrated range and a
somewhat convoluted reverse switch function to protect against reversing the
field polarity when the motor is already spinning. Coincidentally, both
functions are being added because someone did something dumb with their
controllers.



--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4580199.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)

Can the stall protection be configurable,
so you have it default "off" but if someone
needs it, it can be configured "on" and that
person must take care when loading the car on
a trailer that he may instantly lose traction
and catapult backwards due to this feature?
(the safe way would be to use a winch or at least
a protection that can be ratcheted so the car
does not uncontrolledly leave the trailer...)

I deal with products being deployed in a
wide variety of environments with conflicting
needs on a daily basis, so this is one of the
escapes - keep it compatible (default = old behavior)
and allow it to be "upgraded" to the new feature...

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Jeffrey Jenkins
Sent: Monday, April 23, 2012 5:23 PM
To: [email protected]
Subject: Re: [EVDL] How To Burn Up Your DC Motor


Bruce Lawton wrote
> ... I parked the car in the garage, set the brake and pressed the 
> accelerator for at least 2 seconds, probably 4 or 5 seconds. The 
> battery delivered 25A during this. The brake won, I turned everything 
> off and went inside. The next day, as the car began to roll, there was

> a tick-tick sound. I'd overheated the commutators and lifted 4 bars. A

> LOT of motor amps had heated it when it wasn't turning.
> 
> The Zilla has stall protection; my Soliton apparently does not....
> 

As of version 1.5.1 of the Soliton code that is correct - we do not
prevent you from pushing current through the motor even when stalled. 

We did contemplate adding this function at one time but did not because
it has a high annoyance potential (ie - stall detect triggering while
trying to drive up onto a trailer would infuriate me - I certainly
wouldn't be "thanking my controller" for its overzealousness), and,
frankly, we feel it is the motor manufacturer's responsibility to
provide adequate specifications and warnings for their products, rather
than it be entirely up to use to protect their products from abuse.

I should also point out that you are the only person I am aware of that
has damaged a motor by stalling it in the 3.5 years we've been selling
Soliton controllers, so I'd say this is a very rare problem. In
contrast, we have destroyed 7 motors ourselves by pushing too much
current through them for too long but I rather suspect that no one wants
us to lower our current ratings or otherwise thermally-cripple our
controllers to protect against that kind of abuse...

But if protecting against a stall seems really important to people -
particularly people that already own our controllers - then we'll add it
to the 1.6 release of the code.

We are about to roll out an intermediate version, 1.5.2, to correct the
bug in the start button function (failing to idle the motor) and add a
couple of minor functions: block throttle when signal is above
calibrated range and a somewhat convoluted reverse switch function to
protect against reversing the field polarity when the motor is already
spinning. Coincidentally, both functions are being added because someone
did something dumb with their controllers.



--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn
-Up-Your-DC-Motor-tp4577309p4580199.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

_______________________________________________
| 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)

I would suggest an "override" feature that could be triggered by a
momentary switch that the operator has to push if he wants to do something
out of the norm, like drive the EV up onto a trailer. During normal
operation, there would be normal stall protection. Voila, the best of both
worlds.




> Cor van de Water <[email protected]> wrote:
> 
> > Can the stall protection be configurable,
> > so you have it default "off" but if someone
> ...


----------



## EVDL List (Jul 27, 2007)

Mark Warner wrote
> 
> I would suggest an "override" feature that could be triggered by a
> momentary switch that the operator has to push if he wants to do something
> out of the norm, like drive the EV up onto a trailer. During normal
> operation, there would be normal stall protection. Voila, the best of both
> worlds.
> 

This isn't practical because the owner would have to 1) foresee the need to
override stall detection in the first place; 2) install a switch to do so;
3) remember to use the switch when the motor is inadvertently stalled!

Also, this still wouldn't have protected the OP from damaging his motor, as
he *intentionally* stalled it.






--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4580642.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)

The Leaf seems to have a bit of this problem. If parallel parking on a
hill, and you're using the brake, I think it's ignoring the accelerator
pedal till you take you foot off the brake. This results in a small surge
causing a small bump into the vehicle in front (or back). Not sure of the
best way to solve this, but something to think about.

Peri 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Mark Warner
Sent: 23 April, 2012 7:02 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

I would suggest an "override" feature that could be triggered by a momentary
switch that the operator has to push if he wants to do something out of the
norm, like drive the EV up onto a trailer. During normal operation, there
would be normal stall protection. Voila, the best of both worlds.




> Cor van de Water <[email protected]> wrote:
> 
> > Can the stall protection be configurable, so you have it default "off"
> > but if someone needs it, it can be configured "on" and that person
> ...


----------



## EVDL List (Jul 27, 2007)

> Jeffrey Jenkins wrote:
> 
> > This isn't practical because the owner would have to
> > 1) foresee the need to override stall detection in the first place;
> ...


----------



## EVDL List (Jul 27, 2007)

Lee Hart wrote
> 
> ...
> To avoid having it suddenly cut all power, it could be configured like 
> an RPM limiter or current limiter, which back off the power gradually 
> rather than suddenly cut out completely.
> 

Great idea... but how much current should I allow through the motor when it
is stalled? And how much time should I let pass between tach pulses before
activating the stall detection function in the first place? What about if
the commutator is already hot? What about different size motors - surely a
big GE 11" can take more stall current than a little 6.7 incher?!

Etc. and so on.






--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4581224.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)

It seems like some reasonable percentage (15-25%?) of your motor
current limit would be a good stall current, or else add that as a
configurable value: "Stall current limit" next to the stall detect
enable checkbox.

The time between tach pulses probably won't be too critical - if a
brush covers 3 comm bars, one comm bar overheats in two seconds and
the motor had 37 comm bars, then even three RPMs (one rotation in 24.6
seconds) would be sufficient to prevent stall failure. But since you
can't reasonably measure three RPMs fast enough to protect the
commutator, one pulse per second would give you fast enough response
and limit "nuisance trips" to only be possible below 30 RPMs (if you
have two pulses per rotation).

I don't think you need special code to handle an already hot
commutator: you don't reduce the drive current limit for a hot
commutator either. That would fall under your examples of
over-limiting it and causing problems.

I'm not one of your customers; I'm just brainstorming what controller
behavior would be a decent compromise between reasonable effort to
implement, protecting the motor, and avoiding nuisance trips.

-Morgan LaMoore

On Mon, Apr 23, 2012 at 12:56 PM, Jeffrey Jenkins


> <[email protected]> wrote:
> >
> > Lee Hart wrote
> >>
> ...


----------



## EVDL List (Jul 27, 2007)

Peri Hartman said: 
> The Leaf seems to have a bit of this problem. 
> If parallel parking on a hill, and you're using the brake,
> I think it's ignoring the accelerator pedal till you take
> you [sic] foot off the brake. This results in a small
> surge causing a small bump into the vehicle in front
> (or back). Not sure of the best way to solve this,
> but something to think about.

Hi Peri,
I doubt that this is a stall detect feature, it sounds to
me like they made sure to never get the problem that Toyota
struggled to dismiss - the unintended acceleration. 
This problem cannot occur if the brake overrides the 
accelerator, which is what I see in your description. 
This was actually already present on the Prius (you could 
hit both accelerator and brake, though there was some effect,
the engine would still rev up higher at standstill, which can 
be (mis-)used to fast-charge the battery pack.

When I made a short trip in a Leaf thanks to a local owner
who let me, I forgot to check if it has a hand (parking) brake
because that is the usual way to manage movements on an incline
so you do not need to move your foot between throttle and brake
(or worse - drive with 2 feet).
There was a reason that my driving instructor referred to those
two pedals as "water and fire".

Another observation - parallel parking, if performed with
enough space between two other vehicles, can be done in
one single movement, so you do not need to alternate
between acceleration and brake, unless there is limited space
and you need to make it a 2-point manouvre, then I was taught
to use the hand (or parking) brake on an incline, which should
avoid the accelerator override - though I did not test it.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

_______________________________________________
| 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)

Yes, one could use the parking brake - it is strictly physical brakes. I
haven't tried it for parking and my foot is plenty fast enough on hills not
to need it. 

The reason I haven't tried the parking brake for parallel parking is that it
is controlled by a servo, not by a lever. So you cannot feel when it is
engaging or disengaging. Thus, and I may be wrong, it seems it would be
hard to know how much and when to push the accelerator. I'll try it and
see.

Parking is tight in the city, so one movement parking is usually not
possible. Sometimes it takes 4 or 5 times back and forth. Don't always
have to park on a 20% grade, though.

Peri

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Cor van de Water
Sent: 23 April, 2012 12:13 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

Peri Hartman said: 
> The Leaf seems to have a bit of this problem. 
> If parallel parking on a hill, and you're using the brake, I think 
> it's ignoring the accelerator pedal till you take you [sic] foot off 
> the brake. This results in a small surge causing a small bump into 
> the vehicle in front (or back). Not sure of the best way to solve 
> this, but something to think about.

Hi Peri,
I doubt that this is a stall detect feature, it sounds to me like they made
sure to never get the problem that Toyota struggled to dismiss - the
unintended acceleration. 
This problem cannot occur if the brake overrides the accelerator, which is
what I see in your description. 
This was actually already present on the Prius (you could hit both
accelerator and brake, though there was some effect, the engine would still
rev up higher at standstill, which can be (mis-)used to fast-charge the
battery pack.

When I made a short trip in a Leaf thanks to a local owner who let me, I
forgot to check if it has a hand (parking) brake because that is the usual
way to manage movements on an incline so you do not need to move your foot
between throttle and brake (or worse - drive with 2 feet).
There was a reason that my driving instructor referred to those two pedals
as "water and fire".

Another observation - parallel parking, if performed with enough space
between two other vehicles, can be done in one single movement, so you do
not need to alternate between acceleration and brake, unless there is
limited space and you need to make it a 2-point manouvre, then I was taught
to use the hand (or parking) brake on an incline, which should avoid the
accelerator override - though I did not test it.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

_______________________________________________
| 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



_______________________________________________
| 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
> 
> The perfect is the enemy of the good. You'll do nothing if you try for 
> perfection. Aim for good instead.  

I admit I'm often guilty of that. In this case, though, I'm mainly trying to
avoid instilling a *false* sense of security. I distinctly remember George
Hamstra telling me that "hill holding" was really hard on the motor, but I
only vaguely remember any numbers (this conversation took place over 4 years
ago).


Lee Hart wrote
> 
> As a first try: Assume the RPM sensor produces something like 4-8 pulses 
> per revolution, and your current limit is set to 1000a. When you apply 
> current to the motor, if there are no RPM pulses for 1 second, start 
> ramping down the current limit. Ramp it down 100a every 0.1 second, so 
> at 1.9 seconds it will be down to 100a current limit.

Sounds reasonable for a WarP-9. I think it might be dangerous to extrapolate
too far afield, though. For example, a Kostov 9" motor certainly can't take
1000A for 1 second when stalled. A GE 13", however, might just be able to
take the full 3000A output of a Soliton Shiva before the comm explodes. All
I know for sure is that obtaining good data on this is *expensive*. 

I appreciate the suggestion all the same. I'll give it some (unpaid) thought
and see if I can come up with a way around the various issues. That said,
adding Yet Another Warning to the Fine Manual might be in order.





--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4581831.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)
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==


----------



## EVDL List (Jul 27, 2007)

The parallel parking discussion raises another difference between the Leaf and an i-MiEV. The i allows some preload of the motor while still on the brake, such as when starting motion while pointed uphill. Also,when 'idling' in drive at 1-2 mph, a definite 'cogging' can be felt.

Lee raised in this thread that it's bad for a synchronous motor to be powered forward while rotating in reverse, IIRC. A real common occurrance could be when shifting from Reverse to Drive in a fixed gear, synchronous AC-motored EV like the i, such as when backing out of the driveway or starting on a hill. On the scale of Makes a bit of Heat to Really Bad for the Motor, how bad would the practice of shifting to Drive while rolling in Reverse be? There is no lockout to prevent this action on the i. 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120425/9b9aff48/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)

It's closer to "makes a bit of heat", and the controller software
should make sure that the amount of heat is acceptable.

Lee's comment on not motoring forward while going in reverse was about
AC induction motors, not synchronous (PM) motors.

With an AC drive, the peak current through a phase (transistor and
winding) is 1.4 times higher than the RMS current. So if you have a
synchronous motor stalled so that one phase is at peak current, that
phase will see twice as much power dissipation as usual, which could
overheat it.

The same thing can happen with an AC induction motor if it is moving
backwards at exactly the slip speed; in that case, one phase sees DC
and could see a DC current of 1.4 times the RMS design value.

If the inverter software limits the current in such situations to less
than 70% of the normal continuous current limit, then that should
limit the current to the normal ratings and avoid overheating
everything. I would hope that the car companies thought about these
situations and protected against them in software.

With a 3-phase drive, stalling puts 1.4 times normal current though a
phase, leading to twice normal resistive power dissipation. With a
commutator, assuming the brushes cover 1/4-1/3 of the commutator bars
at any given time, stalling leads to 1.73-2 times the normal current
through the comm bars as well as vastly reduced cooling, leading to
3-4 times the power dissipation with nowhere to get rid of the heat
and less mass to absorb the heat.

So stalling is much harder on a commutator than it is on a 3-phase AC motor.

-Morgan LaMoore



> Jay Donnaway <[email protected]> wrote:
> > The parallel parking discussion raises another difference between the Lea=
> f and an i-MiEV. The i allows some preload of the motor while still on t=
> he brake, such as when starting motion while pointed uphill. Also,when '=
> ...


----------



## EVDL List (Jul 27, 2007)

I have frequently thrown the gears in the opposite
directoin of movement and taken off without trouble,
both with my Prius (PM AC motors) and the EV Electricar
(Hughes AC induction motor).
I never managed to keep the field stalled...
=

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 =


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behal=
f Of Morgan LaMoore
Sent: Wednesday, April 25, 2012 10:00 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

It's closer to "makes a bit of heat", and the controller software should ma=
ke sure that the amount of heat is acceptable.

Lee's comment on not motoring forward while going in reverse was about AC i=
nduction motors, not synchronous (PM) motors.

With an AC drive, the peak current through a phase (transistor and
winding) is 1.4 times higher than the RMS current. So if you have a synchro=
nous motor stalled so that one phase is at peak current, that phase will se=
e twice as much power dissipation as usual, which could overheat it.

The same thing can happen with an AC induction motor if it is moving backwa=
rds at exactly the slip speed; in that case, one phase sees DC and could se=
e a DC current of 1.4 times the RMS design value.

If the inverter software limits the current in such situations to less than=
70% of the normal continuous current limit, then that should limit the cur=
rent to the normal ratings and avoid overheating everything. I would hope t=
hat the car companies thought about these situations and protected against =
them in software.

With a 3-phase drive, stalling puts 1.4 times normal current though a phase=
, leading to twice normal resistive power dissipation. With a commutator, a=
ssuming the brushes cover 1/4-1/3 of the commutator bars at any given time,=
stalling leads to 1.73-2 times the normal current through the comm bars as=
well as vastly reduced cooling, leading to
3-4 times the power dissipation with nowhere to get rid of the heat and les=
s mass to absorb the heat.

So stalling is much harder on a commutator than it is on a 3-phase AC motor.

-Morgan LaMoore



> Jay Donnaway <[email protected]> wrote:
> > The parallel parking discussion raises another difference between the Lea=
> f and an i-MiEV. The i allows some preload of the motor while still on t=
> he brake, such as when starting motion while pointed uphill. Also,when '=
> ...


----------



## EVDL List (Jul 27, 2007)

> On 25 Apr 2012 at 11:29, Morgan LaMoore wrote:
> 
> > With an AC drive, the peak current through a phase (transistor and
> > winding) is 1.4 times higher than the RMS current. ...
> ...


----------



## EVDL List (Jul 27, 2007)

EVDL Administrator wrote
> 
> ...They're not the same thing. 1.4 times higher is equivalent to 2.4
> times as 
> high as. 

I'm not following your parsing here.... Peak current is 1.414 times higher
than RMS. RMS is 0.707 times peak. Not sure what grammar rule gets you to
2.4x.

(NB - the peak and RMS refer to the low frequency sinusoidal current through
the AC motor, not the high frequency PWM'ed voltage that results in said low
frequency current.)


--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4587622.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)

This is an argument for keeping the tranny. With the torque multiplication of the gears, you need about 1/2 the current to pull onto a trailer (compared to a single gear system), meaning 1/4 the heating. The motor will also be spinning about twice as fast once moving, spreading the load better amongst the commutator bars.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120425/83510145/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)

> Morgan LaMoore wrote:
> >> With an AC drive, the peak current through a phase (transistor and
> >> winding) is 1.4 times higher than the RMS current. ...
> >>
> ...


----------



## EVDL List (Jul 27, 2007)

> On 25 Apr 2012 at 11:35, Jeffrey Jenkins wrote:
> 
> > I'm not following your parsing here.... Peak current is 1.414 times higher
> > than RMS. RMS is 0.707 times peak. Not sure what grammar rule gets you to
> ...


----------



## EVDL List (Jul 27, 2007)

EVDL Administrator wrote
> 
> If you said that peak current is 1.414 times higher than RMS, it would
> mean 
> that peak current is the original RMS value PLUS 1.414 times the original 
> RMS value - that is, 2.414 times as much.
> 
> The problem is that a lot of people say "higher than" when they really
> mean 
> "as high as." But not everyone does. Because of this, "higher than" will 
> always be ambiguous.

I get the distinction you are trying to make, but I think you are
misapplying it. Your interpretation would be correct if the phrasing was,
"peak current is 41.4% higher than RMS." When the word, "times," is
included, however, the meaning of the phrase changes from addition to
multiplication. E.g. - "peak current is 1.414 times higher than RMS."


EVDL Administrator wrote
> But I'm probably tilting at windmills. :-\ 

Aye, Don Quixote - put down your sword... ;-)



--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4588460.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
> 
> Morgan's explanation was excellent. I would only add that at stall the 
> winding *sits* at a DC current that is 1.4 times the RMS AC current that 
> would have flowed if the motor were turning to produce that same torque. 
> But in this DC case, one inverter transistor (out of the six) is 
> carrying *all* that current at a 100% duty cycle. The transistors would 
> normally be on only half the time (50% duty cycle) when producing AC, so 
> this is double its normal peak, i.e. 2 x 1.4 = 2.8 times the normal AC 
> RMS current.
> 

I think both you and Morgan are making some assumptions here that may or not
apply.

If the inverter employs FOC then the stator phases will still be rotating
electrically at the maximum slip frequency when the rotor is stalled
otherwise the rotor won't be exerting any torque. 

A minor point of correction is that all of the switches in an inverter are
pulse-width modulated, even if tasked with delivering an effective DC
current to just one phase, so they are never 100% on. In some ways this is
worse, though, as it means there are switching losses on top of the
conduction losses.


--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4588480.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 25 Apr 2012 at 17:43, Lee Hart wrote:
> 
> > "1.4 times higher" and "1.4 times as high" mean the same thing --
> > multiplying something by 1.4.
> ...


----------



## EVDL List (Jul 27, 2007)

> Christopher Zach wrote:
> Lee Hart wrote:
> >> For an induction motor, worst case is with the rotor rotating
> >> *backwards* as the slip speed when the motor is commanded to produce
> ...


----------



## EVDL List (Jul 27, 2007)

Lee Hart wrote
> 
> For a PM motor, worst case is at stall, which requires DC current in a 
> phase winding.
> 
> For an induction motor, worst case is with the rotor rotating 
> *backwards* as the slip speed when the motor is commanded to produce 
> forward torque. This situation requires DC on a phase winding.

Gotcha. It was ambiguous before (a genuine ambiguity, and not a manufactured
one... ahem) whether this was a PMSM or ACIM and whether the motor was
stalled and the inverter was still trying to exert force, or the motor was
rotating slightly backwards while the inverter was "stalled" trying to hold
the rotor still.


Lee Hart wrote
> 
>> A minor point of correction is that all of the switches in an inverter
>> are
>> pulse-width modulated, even if tasked with delivering an effective DC
>> current to just one phase, so they are never 100% on. In some ways this
>> is
>> worse, though, as it means there are switching losses on top of the
>> conduction losses.
> 
> That's true, though the duty cycle will be essentially 100% for one 
> transistor, and 1% for its twin.

Are you referring to "six-step" PWM? I ask because the modulation strategy
in the inverter dictates the maximum output voltage that can be delivered to
any one phase, even if that phase is supposed to be supplied with a DC
current. Six-step PWM can go all the way to 100% of the DC bus voltage, but
every other modulation strategy requires turning the switches off for some
percentage of time (10% to 30% being typical, depending on the strategy).





--
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/How-To-Burn-Up-Your-DC-Motor-tp4577309p4589601.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 <[email protected]> wrote:
> >> A minor point of correction is that all of the switches in an inverter are
> >> pulse-width modulated, even if tasked with delivering an effective DC
> >> current to just one phase, so they are never 100% on. In some ways this is
> ...


----------



## EVDL List (Jul 27, 2007)

I expect that in a *stalled* motor, there is no back EMF
and thus the output *voltage* of the (AC) controller is
very low, because it will run either artificially limited
or at max motor current - which will command a low voltage
into the motor without back EMF. At high RPM the back EMF
will increase, so the required motor voltage will increase,
but if I am not mistaken I remember that a "full throttle"
(max motor amps at 250A from my AC controller) would draw
only 25A from the pack, so apparently the AC voltage that
could increase to about 160V RMS (312V nominal pack) was
around 16V RMS at that time.
This means that even if it would produce DC (it did not,
as I have ACIM and you could hear the swish-swish from
the motor due to the rotating -slipping- field) then
at a *stalled* motor and field the DC peak would be about
57% duty cycle (the companion transistor delivering 43%)

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Morgan LaMoore
Sent: Thursday, April 26, 2012 6:27 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

On Wed, Apr 25, 2012 at 7:11 PM, Lee Hart <[email protected]>


> wrote:
> >> A minor point of correction is that all of the switches in an
> >> inverter are pulse-width modulated, even if tasked with delivering an
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> Cor van de Water wrote:
> > I expect that in a *stalled* motor, there is no back EMF
> > and thus the output *voltage* of the (AC) controller is
> > very low
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> > ...
> > With a PM AC (synchronous) motor, worst case is also at stall. Again,
> > you have to maximum DC current to one phase winding. Again, the inverter
> ...


----------



## EVDL List (Jul 27, 2007)

Partial retraction of my statement:

The Leaf does, indeed, creep forward (or backwards) while pressing the brake
and accelerator at the same time. I tried it a few times on some hills.
Very nice behavior. I don't know if they have any sort of limiting to
prevent overheating and I don't plan on experimenting to find that out 

I have not tried parallel parking on a steep hill yet, though. There was
something happening that made it tricky but apparently it isn't the
brake-accel interoperation. More info if I discover something.

Peri

-----Original Message-----
From: Peri Hartman [mailto:[email protected]] 
Sent: 23 April, 2012 7:49 AM
To: 'Electric Vehicle Discussion List'
Subject: RE: [EVDL] How To Burn Up Your DC Motor

The Leaf seems to have a bit of this problem. If parallel parking on a
hill, and you're using the brake, I think it's ignoring the accelerator
pedal till you take you foot off the brake. This results in a small surge
causing a small bump into the vehicle in front (or back). Not sure of the
best way to solve this, but something to think about.

Peri 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Mark Warner
Sent: 23 April, 2012 7:02 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] How To Burn Up Your DC Motor

I would suggest an "override" feature that could be triggered by a momentary
switch that the operator has to push if he wants to do something out of the
norm, like drive the EV up onto a trailer. During normal operation, there
would be normal stall protection. Voila, the best of both worlds.




> Cor van de Water <[email protected]> wrote:
> 
> > Can the stall protection be configurable, so you have it default "off"
> > but if someone needs it, it can be configured "on" and that person
> ...


----------

