Inertia switch

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Inertia switch

Steve Clunn-2
 <[hidden email]> wrote:
> Typical way to use that switch is to wire it in the circuit that
 engages the pack contactor coil (so, a 12V circuit!).
 If the switch opens after an accident, the high voltage from
 the pack is interrupted because the contactor(s) drop out.<

Some controllers and most contactors aren't happy being opened under
load . I've been hooking the Inertia switch to turn off the key input
to controller . I'm a little worried about a pot hole in the road
tripping the switch and blowing a controller.
Steve Clunn
Tomorrow's Ride...Today
www.Greenshedconversions.com
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Re: Inertia switch

corbin dunn

On Feb 25, 2013, at 6:41 AM, Steve Clunn <[hidden email]> wrote:

> <[hidden email]> wrote:
>> Typical way to use that switch is to wire it in the circuit that
> engages the pack contactor coil (so, a 12V circuit!).
> If the switch opens after an accident, the high voltage from
> the pack is interrupted because the contactor(s) drop out.<
>
> Some controllers and most contactors aren't happy being opened under
> load .

Really? which ones? Most should handle this okay. I know the Netgain brand controllers are fine.

> I've been hooking the Inertia switch to turn off the key input
> to controller .

I think that defeats the purpose of the inertia switch. What if the controller got messed up or confused in a crash, and didn't respond to the key-on being turned off?

It is much safer to have it open the contactor.


> I'm a little worried about a pot hole in the road
> tripping the switch and blowing a controller.

I hit a *big* pothole and had it happened to me. My controller didn't blow; the car just stopped.

corbin


> Steve Clunn
> Tomorrow's Ride...Today
> www.Greenshedconversions.com
> _______________________________________________
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>

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Re: Inertia switch

Jeffrey Jenkins
In reply to this post by Steve Clunn-2
Steve Clunn-2 wrote
Some controllers and most contactors aren't happy being opened under
load ....

It's perfectly okay to wire the inertia switch in series with the 12V supply to a Soliton controller (ie - the IGN terminal) and any controller with (still functioning) input capacitors will have no problem if the supply is interrupted under load.

Note that there are some controllers without any significant amount of input capacitance, like the old GE EV1 and EV100 types, that very well could be damaged by interrupting power to them while under load.

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Re: Inertia switch

Roger Stockton
Jeffrey Jenkins wrote:

> Note that there are some controllers without any significant amount of
> input capacitance, like the old GE EV1 and EV100 types, that very well
> could be damaged by interrupting power to them while under load.

I can't say that it isn't possible to damage the GE EV1 by repeatedly interrupting power to them while under load, but I can say with certainty that it is possible to interrupt power to it while under load without damaging it in the least.  I have done this with mine.

It seems to me that any competently designed controller ought to tolerate sudden removal of input power while under load, as this is a completely foreseeable event (e.g. battery pack fuse opens, or interconnect fails, etc.).

As to the role of the inertia switch, it seems to me that in addition to disabling the controller (potentially a controller that has lost its mind, and so cannot be relied upon to respond to a keyswitch or other logic input), another important role is to disconnect the traction pack to minimise the risk of traction voltage getting onto the chassis or elsewhere in the event of a serious accident (which is really the only time the inertia switch should be tripped).

Cheers,

Roger.

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Re: Inertia switch

Lee Hart
In reply to this post by corbin dunn
>>> Typical way to use [the inertia switch] is to wire it in the
>>> circuit that engages the pack contactor coil (so, a 12V
>>> circuit). If the switch opens after an accident, the high voltage
>>> from the pack is interrupted because the contactor(s) drop out.

Steve Clunn<[hidden email]>  wrote:
>> Some controllers and most contactors aren't happy being opened
>> under load.

Things obviously last longer when *not* asked to break high current.
However, it is sometimes necessary to do it anyway (such as in an
accident, or to stop a runaway controller).

corbin dunn wrote:
> Really? which ones? Most should handle this okay. I know the Netgain
> brand controllers are fine.

It isn't brand-specific; it is circumstance-specific.

Most controller skimp on the size of their input capacitors. They depend
on the battery to handle at least some of the inductive energy that
"kicks" the voltage up when the controller shuts off.

If the controller is operating at high current, and the battery suddenly
goes away, the voltage on the capacitors and transistors will spike up
much higher than normal. If the EV has a large design margin (like 250v
parts with a 150v pack), it will survive. But if the controller has 200v
parts and the pack is 144v (and at 180v because it was just charged),
there is not enough safety margin and the controller can blow.

>> I've been hooking the Inertia switch to turn off the key input to
>> controller.

> I think that defeats the purpose of the inertia switch.

The inertia switch is supposed to *absolutely* shut things down in case
of an accident. But one possible reason for an accident can be a runaway
controller! So, it is best if the inertia switch shuts everything off
that it can (controller *and* contactors).

--
*BE* the change that you wish to see in the world. -- Mahatma Gandhi
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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Re: Inertia switch

Cor van de Water
I don't have an inertia switch,
but I have had the IGBT of my controller go short-circuit,
which would cause a run-away situation, if not for the
controller monitoring the current and simply dropping
the contactor when it noticed that the current was above
the critical threshold, so all I noticed of the IGBT failing
was a short clunk in the drivetrain and the power dropping out.
The controller also protected from starting again, because it
monitors the controller output *before* closing contactors
through a high resistance voltage divider. If the output of
the controller (with the motor contactor unengaged) is not
near half the pack voltage then it assumes that either the
transistor or the freewheel diode is shorted, or another
reason that the output is not floating, such as a defective snubber
and it will not close the contactor, only throw an error code.
Very useful. Thanks, Rod!
 
Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Lee Hart
Sent: Monday, February 25, 2013 3:25 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Inertia switch

>>> Typical way to use [the inertia switch] is to wire it in the circuit

>>> that engages the pack contactor coil (so, a 12V circuit). If the
>>> switch opens after an accident, the high voltage from the pack is
>>> interrupted because the contactor(s) drop out.

Steve Clunn<[hidden email]>  wrote:
>> Some controllers and most contactors aren't happy being opened under
>> load.

Things obviously last longer when *not* asked to break high current.
However, it is sometimes necessary to do it anyway (such as in an
accident, or to stop a runaway controller).

corbin dunn wrote:
> Really? which ones? Most should handle this okay. I know the Netgain
> brand controllers are fine.

It isn't brand-specific; it is circumstance-specific.

Most controller skimp on the size of their input capacitors. They depend
on the battery to handle at least some of the inductive energy that
"kicks" the voltage up when the controller shuts off.

If the controller is operating at high current, and the battery suddenly
goes away, the voltage on the capacitors and transistors will spike up
much higher than normal. If the EV has a large design margin (like 250v
parts with a 150v pack), it will survive. But if the controller has 200v
parts and the pack is 144v (and at 180v because it was just charged),
there is not enough safety margin and the controller can blow.

>> I've been hooking the Inertia switch to turn off the key input to
>> controller.

> I think that defeats the purpose of the inertia switch.

The inertia switch is supposed to *absolutely* shut things down in case
of an accident. But one possible reason for an accident can be a runaway
controller! So, it is best if the inertia switch shuts everything off
that it can (controller *and* contactors).

--
*BE* the change that you wish to see in the world. -- Mahatma Gandhi
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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Re: Inertia switch

corbin dunn
In reply to this post by Lee Hart

On Feb 25, 2013, at 3:24 PM, Lee Hart <[hidden email]> wrote:

>>>> Typical way to use [the inertia switch] is to wire it in the
>>>> circuit that engages the pack contactor coil (so, a 12V
>>>> circuit). If the switch opens after an accident, the high voltage
>>>> from the pack is interrupted because the contactor(s) drop out.
>
> Steve Clunn<[hidden email]>  wrote:
>>> Some controllers and most contactors aren't happy being opened
>>> under load.
>
> Things obviously last longer when *not* asked to break high current.
> However, it is sometimes necessary to do it anyway (such as in an
> accident, or to stop a runaway controller).
>
> corbin dunn wrote:
>> Really? which ones? Most should handle this okay. I know the Netgain
>> brand controllers are fine.
>
> It isn't brand-specific; it is circumstance-specific.
>
> Most controller skimp on the size of their input capacitors. They depend on the battery to handle at least some of the inductive energy that "kicks" the voltage up when the controller shuts off.
>
> If the controller is operating at high current, and the battery suddenly goes away, the voltage on the capacitors and transistors will spike up much higher than normal. If the EV has a large design margin (like 250v parts with a 150v pack), it will survive. But if the controller has 200v parts and the pack is 144v (and at 180v because it was just charged), there is not enough safety margin and the controller can blow.
>
>>> I've been hooking the Inertia switch to turn off the key input to
>>> controller.
>
>> I think that defeats the purpose of the inertia switch.
>
> The inertia switch is supposed to *absolutely* shut things down in case of an accident. But one possible reason for an accident can be a runaway controller! So, it is best if the inertia switch shuts everything off that it can (controller *and* contactors).

Good point! I should have been more clear: I have mine wired up in exactly this way. The switch cuts off the 12v key-on input into the controller, and the 12v power into one contactor.

corbin


>
> --
> *BE* the change that you wish to see in the world. -- Mahatma Gandhi
> --
> Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
>

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Re: Inertia switch

Cor van de Water
If you think that the spike from killing the power by dropping the
contactor will kill your electronics, then you can design a circuit
that protects against that. Even thoug the current is high, it will
not last long so while the instantaneous power might easily kill
sensitive electronics, the total energy that you need to dissipate
is not very high.
Well-chosen Gas Discharge Tube or snubber circuits can probably
take care of protecting your downstream electronics from the
effect of sudden interrupted contactor.
Of course, the contactor itself will not survive repeated
interruptions under power, so by definition it should be a
rare occasion that you drop the contactors anyway.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of corbin dunn
Sent: Monday, February 25, 2013 7:51 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Inertia switch


On Feb 25, 2013, at 3:24 PM, Lee Hart <[hidden email]> wrote:

>>>> Typical way to use [the inertia switch] is to wire it in the
>>>> circuit that engages the pack contactor coil (so, a 12V circuit).
>>>> If the switch opens after an accident, the high voltage from the
>>>> pack is interrupted because the contactor(s) drop out.
>
> Steve Clunn<[hidden email]>  wrote:
>>> Some controllers and most contactors aren't happy being opened under

>>> load.
>
> Things obviously last longer when *not* asked to break high current.
> However, it is sometimes necessary to do it anyway (such as in an
> accident, or to stop a runaway controller).
>
> corbin dunn wrote:
>> Really? which ones? Most should handle this okay. I know the Netgain
>> brand controllers are fine.
>
> It isn't brand-specific; it is circumstance-specific.
>
> Most controller skimp on the size of their input capacitors. They
depend on the battery to handle at least some of the inductive energy
that "kicks" the voltage up when the controller shuts off.
>
> If the controller is operating at high current, and the battery
suddenly goes away, the voltage on the capacitors and transistors will
spike up much higher than normal. If the EV has a large design margin
(like 250v parts with a 150v pack), it will survive. But if the
controller has 200v parts and the pack is 144v (and at 180v because it
was just charged), there is not enough safety margin and the controller
can blow.
>
>>> I've been hooking the Inertia switch to turn off the key input to
>>> controller.
>
>> I think that defeats the purpose of the inertia switch.
>
> The inertia switch is supposed to *absolutely* shut things down in
case of an accident. But one possible reason for an accident can be a
runaway controller! So, it is best if the inertia switch shuts
everything off that it can (controller *and* contactors).

Good point! I should have been more clear: I have mine wired up in
exactly this way. The switch cuts off the 12v key-on input into the
controller, and the 12v power into one contactor.

corbin


>
> --
> *BE* the change that you wish to see in the world. -- Mahatma Gandhi
> --
> Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA
> (http://groups.yahoo.com/group/NEDRA)
>

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Re: Inertia switch

Jeffrey Jenkins
In reply to this post by Roger Stockton
Roger Stockton wrote
Jeffrey Jenkins wrote:

> Note that there are some controllers without any significant amount of
> input capacitance, like the old GE EV1 and EV100 types, that very well
> could be damaged by interrupting power to them while under load.

I can't say that it isn't possible to damage the GE EV1 by repeatedly interrupting power to them while under load, but I can say with certainty that it is possible to interrupt power to it while under load without damaging it in the least.  I have done this with mine.
Sure, if the semiconductor switch is still conducting (either on purpose, or because it has failed short) then the energy stored in the stray inductance of the battery circuit will be dissipated in the motor. If the switching device has been commanded off or failed open, however, and there is little or no input capacitance, then the battery circuit stray inductance will create whatever voltage is necessary to maintain a continuous flow of current, which basically means the semiconductor switch will be forced on via avalanching. If the battery circuit inductance and/or the current is low enough, and/or the avalanche energy rating of the switch is high enough, then the switch will survive this abuse, though possibly with some long term degradation in current gain for bipolar transistor/SCR devices.

In any event, I agree that it is entirely foreseeable that a fuse will blow, a contactor will open under load, etc., but I don't mistake that for being a "normal" or "everyday" occurrence. Generally speaking, you size the fuse to protect the insulation on wires from overheating, so if the fuse blows consider that a none-too-subtle hint.

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Re: Inertia switch

Roger Stockton
Jeffrey Jenkins wrote:

> In any event, I agree that it is entirely foreseeable that a fuse will
> blow, a contactor will open under load, etc., but I don't mistake that
> for being a "normal" or "everyday" occurrence. Generally speaking, you
> size the fuse to protect the insulation on wires from overheating, so
> if the fuse blows consider that a none-too-subtle hint.

Agreed, this should certainly not be a frequent occurrence.  My point is simply that if the fuse opening, which is what it is intended to do and which by definition will happen under load, and this normal (though infrequent) event takes out the controller, then the controller was not well designed.

Cheers,

Roger.

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Re: Inertia switch

Lee Hart
Roger Stockton wrote:
> Agreed, this should certainly not be a frequent occurrence.  My point
> is simply that if the fuse opening, which is what it is intended to
> do and which by definition will happen under load, and this normal
> (though infrequent) event takes out the controller, then the
> controller was not well designed.

I also agree. Or, the controller was mis-applied (used at too high a
voltage, or too much inductance in the battery cables, etc._

--
If you want to build a ship, don't drum up people to collect wood
and don't assign them tasks and work. Rather, teach them to long
for the endless immensity of the sea. -- Antoine de Saint-Exupery
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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Re: Inertia switch

Roger Stockton
Lee Hart wrote:

> I also agree. Or, the controller was mis-applied (used at too high a
> voltage, or too much inductance in the battery cables, etc._

Yes, absolutely; it is not the designer's fault if the user misapplies the product, such as using it at higher than rated voltage.

I think the cable inductance is probably the real thorny issue.  The controller designer must assume some reasonable amount of inductance if they are to design in protection or margin, however, the actual inductance in a particular installation/application could vary significantly from their assumptions.

Does the manufacturer state a maximum battery wiring inductance value that the user must observe, in the same way as they would an input voltage range?  Even if they do, how does the hobbyist determine if they are within spec or not?

Cheers,

Roger.

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Re: Inertia switch

Cor van de Water
In reply to this post by Jeffrey Jenkins
FYI,
My GE EV100 controller has 3 large (3" dia) Electrolytic
capacitors bolted to a bus bar above the IGBT.
Lower voltage models often have only 2 caps,
but due to the higher voltage (150V caps IIRC)
the capacitance of each is lower so they mounted one more.
The lower voltage model have 2 caps of 16,000uF 60V (90V surge)
so I would not say that they go without any significant amount
of input caps. On the contrary!

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Jeffrey Jenkins
Sent: Tuesday, February 26, 2013 4:19 AM
To: [hidden email]
Subject: Re: [EVDL] Inertia switch

Roger Stockton wrote

> Jeffrey Jenkins wrote:
>
>> Note that there are some controllers without any significant amount
>> of input capacitance, like the old GE EV1 and EV100 types, that very
>> well could be damaged by interrupting power to them while under load.
>
> I can't say that it isn't possible to damage the GE EV1 by repeatedly
> interrupting power to them while under load, but I can say with
> certainty that it is possible to interrupt power to it while under
> load without damaging it in the least.  I have done this with mine.

Sure, if the semiconductor switch is still conducting (either on
purpose, or because it has failed short) then the energy stored in the
stray inductance of the battery circuit will be dissipated in the motor.
If the switching device has been commanded off or failed open, however,
and there is little or no input capacitance, then the battery circuit
stray inductance will create whatever voltage is necessary to maintain a
continuous flow of current, which basically means the semiconductor
switch will be forced on via avalanching. If the battery circuit
inductance and/or the current is low enough, and/or the avalanche energy
rating of the switch is high enough, then the switch will survive this
abuse, though possibly with some long term degradation in current gain
for bipolar transistor/SCR devices.

In any event, I agree that it is entirely foreseeable that a fuse will
blow, a contactor will open under load, etc., but I don't mistake that
for being a "normal" or "everyday" occurrence. Generally speaking, you
size the fuse to protect the insulation on wires from overheating, so if
the fuse blows consider that a none-too-subtle hint.





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Re: Inertia switch

Jeffrey Jenkins
In reply to this post by Roger Stockton
Roger Stockton wrote
...Does the manufacturer state a maximum battery wiring inductance value that the user must observe, in the same way as they would an input voltage range?  Even if they do, how does the hobbyist determine if they are within spec or not?...
The hobbyist can estimate the worst-case inductance of a wire in free space (that is to say, the wire is separated more than 10 diameters from its return conductor) at around 1uH per meter; placing the forward and return conductors next to each other, or even twisting them, will dramatically reduce the inductance. Since energy stored in an inductor is 0.5LI^2 and energy stored in a capacitor is 0.5CV^2, if you equate the two* you'll see that it doesn't take much capacitance to deal with any reasonable amount of inductance in the battery circuit of most EVs. Do I specify this in the Soliton manual? No. I do recommend that the forward and return cables in the battery circuit be run together for this reason, as well as to reduce EMI emissions, but I don't explicitly warn people that too much inductance on the battery side of the controller will hurt it. I *do* warn about insufficient inductance on the motor side of the circuit, but that is mainly to protect PM motors from the effects of high ripple current (catastrophic demagnetization and/or hysteresis loss heating). NB - I don't know of any other manufacturer that provides a minimum inductance for the motor specification, even though it is probably the most important spec to the controller.

* - e.g., 1000A through 10uH of inductance = 5J = 100V across 1000uF of capacitance
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Re: Inertia switch

Jeffrey Jenkins
In reply to this post by Cor van de Water
Cor van de Water wrote
FYI,
My GE EV100 controller has 3 large (3" dia) Electrolytic
capacitors bolted to a bus bar above the IGBT.
Lower voltage models often have only 2 caps,
but due to the higher voltage (150V caps IIRC)
the capacitance of each is lower so they mounted one more.
The lower voltage model have 2 caps of 16,000uF 60V (90V surge)
so I would not say that they go without any significant amount
of input caps. On the contrary!
Ok, my mistake. It's been a long time since I looked at the EV1 and EV100, and, to be honest, I'm not too interested in what GE was doing 30+ years ago... :D


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Re: Inertia switch

Lee Hart
On 2/26/2013 3:13 PM, Jeffrey Jenkins wrote:

> Cor van de Water wrote
>> FYI,
>> My GE EV100 controller has 3 large (3" dia) Electrolytic
>> capacitors bolted to a bus bar above the IGBT.
>> Lower voltage models often have only 2 caps,
>> but due to the higher voltage (150V caps IIRC)
>> the capacitance of each is lower so they mounted one more.
>> The lower voltage model have 2 caps of 16,000uF 60V (90V surge)
>> so I would not say that they go without any significant amount
>> of input caps. On the contrary!
>
> Ok, my mistake. It's been a long time since I looked at the EV1 and EV100,
> and, to be honest, I'm not too interested in what GE was doing 30+ years
> ago... :D

The GE EV-1 is an SCR controller. It has no input capacitance, but SCRs
do have the advantage that if you exceed their breakdown voltage they
simply turn on. The SCR itself won't be harmed by an overvoltage
transient when a fuse or contactor opens, though other circuitry might be.

The GE EV-100 is an IGBT controller. As Cor mentioned, it does have
input capacitors.

--
Anyone can make the simple complicated. Creativity is making the
complicated simple. -- Charles Mingus
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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Inertia switch

R Willis
In reply to this post by corbin dunn
ok i have a question on this if you were to use a contactor on the
line for the fuel pump
circuit and if there is a accident it shut all power off  to the drive train
as well it can also be used to stop a run away as well  ?

we are now the proud owner of a 2013 Wrangler 9 KM on it and going electric !
we plan to leave in the computer and use all the sensors on the change over
let the fun begin !!!!



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