Series DC emergency braking possibility for two added parts.

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Series DC emergency braking possibility for two added parts.

Dennis Miles
I thought of this Sunday night and I would prefer asking you-all for a
comment or two before experimenting and destroying a motor. Or putting some
fast wear on brushes.
I propose using a high current relay (Contactor) under control of a dash
mounted switch with a protective cover, to "Short out the armature
connections" from one to the other, leaving the field connected to the
motor controller output, then, in case of a hydraulic braking system
failure (I have experienced one before and using the mechanical "Emergency
brake" is very hard to control to a safe stop.)  Instead I would in case of
foot brake failure merely lift the accelerator pedal to cut power to the
motor, but the car does not slow down, so with the above parts added, open
cover and flip switch activating the relay(Contactor) to short out the
armature, then slowly press the accelerator producing "Plug Braking" action
but with motor controller allowing a measure of control and thus bring the
EV to a safe stop. Pullover into a safe location and call a flatbed truck
car hauler to carry the EV home to the shop and fix the hydraulic brakes. I
do not think this would be a safe method for everyday use but I have 4-way
flashers and I use them only once a year or less. But. when needed they are
there.
--
Regards,
*     Dennis *(EVprofessor)* Miles*
  *(863)944-9913* (phone noon to midnight E.S.T.)
*    reply to [hidden email]*
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Re: Series DC emergency braking possibility for two added parts.

Roland Wiench
Hello Dennis,

My first EV back in 76 made by the Electric Fuel Propulsion Co. in Troy,
Mich. use a Cable Form motor controller made for industrial electric
machines normally in the 144 volt range.  It was modified for 180 vdc using
large heat sinking resistors to reduce the 180 volt battery pack to 144
volts.

This unit initially came with dynamic braking which is reversing the
direction of the motor using a 4 pole 600 amp contactor or using two 2-pole
contactors that is mechanically and electrically interlock together. Also
there was another 600 amp contactor that switch in a very large 0.25 to 0.50
power resistor that is use for resistance braking which I still have today.
This resistor measures about 18 inches long and is a 12 inches square. This
resistor is normally use in load banks for testing electrical machines.

Same type of unit is use for reversing a EV using a smaller 3 inch diameter
resistor that is 16 inches long.  Also the free wheeling diode had to be
switch out and another one switch in the reverse direction.

They first tested this dynamic braking setup in full violent emergency stop
mode.  There is actually a settings mode in the accelerator control that is
label violent, high, standard and soft accelerator and braking.

They first tested this braking action in violent which broke out a threaded
bolt section in the motor coupler.  In the most violent mode, the positive
voltage is disconnected from the motor communtator and the negative voltage
is disconnected from the motor field.

Then the positive voltage is connected to the field and the negative
connected to the communtator.  The field and communtator is still connected
in series.

In the not so violent mode using the normal or softer braking mode, the
resistor is inserted in the negative voltage between the negative of the
controller and the communtator.  The resistor is so large, that it had to be
hang below the front bumper.  On a braking test from 92 mph, it glow red
which I though it make a good heater source.

Never use it, need a larger EV to be able to install all this equipment.

Roland








----- Original Message -----
From: "Dennis Miles" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Monday, September 24, 2012 2:12 AM
Subject: [EVDL] Series DC emergency braking possibility for two added parts.


> I thought of this Sunday night and I would prefer asking you-all for a
> comment or two before experimenting and destroying a motor. Or putting
> some
> fast wear on brushes.
> I propose using a high current relay (Contactor) under control of a dash
> mounted switch with a protective cover, to "Short out the armature
> connections" from one to the other, leaving the field connected to the
> motor controller output, then, in case of a hydraulic braking system
> failure (I have experienced one before and using the mechanical "Emergency
> brake" is very hard to control to a safe stop.)  Instead I would in case
> of
> foot brake failure merely lift the accelerator pedal to cut power to the
> motor, but the car does not slow down, so with the above parts added, open
> cover and flip switch activating the relay(Contactor) to short out the
> armature, then slowly press the accelerator producing "Plug Braking"
> action
> but with motor controller allowing a measure of control and thus bring the
> EV to a safe stop. Pullover into a safe location and call a flatbed truck
> car hauler to carry the EV home to the shop and fix the hydraulic brakes.
> I
> do not think this would be a safe method for everyday use but I have 4-way
> flashers and I use them only once a year or less. But. when needed they
> are
> there.
> --
> Regards,
> *     Dennis *(EVprofessor)* Miles*
>   *(863)944-9913* (phone noon to midnight E.S.T.)
> *    reply to [hidden email]*
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL:
> http://lists.sjsu.edu/mailman/private/ev/attachments/20120924/74591896/attachment.html
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
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>

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Re: Series DC emergency braking possibility for two added parts.

Dennis Miles
Thanks, Roland,
    You have had so many interesting EV adventures and your sharing them
with us is wonderful. I always read your posts.
    I expect trying my simple short out the armature method could easily
"Smoke"the armature unless braking was very gently applied but smoke is
better than a collision with another vehicle or a big tree. (Both in repair
dollars and minimizing injury of occupants.)
Regards,*     Dennis *(EVprofessor)* Miles*
  *(863)944-9913* (phone noon to midnight E.S.T.)
*    reply to [hidden email]*
+++++++++++++++++++++++++++++++++++++++
On Mon, Sep 24, 2012 at 12:33 PM, Roland Wiench <[hidden email]> wrote:

> Hello Dennis,
>
> My first EV back in 76 made by the Electric Fuel Propulsion Co. in Troy,
> Mich. use a Cable Form motor controller made for industrial electric
> machines normally in the 144 volt range.  It was modified for 180 vdc using
> large heat sinking resistors to reduce the 180 volt battery pack to 144
> volts.
>
> This unit initially came with dynamic braking which is reversing the
> direction of the motor using a 4 pole 600 amp contactor or using two 2-pole
> contactors that is mechanically and electrically interlock together. Also
> there was another 600 amp contactor that switch in a very large 0.25 to
> 0.50
> power resistor that is use for resistance braking which I still have today.
> This resistor measures about 18 inches long and is a 12 inches square. This
> resistor is normally use in load banks for testing electrical machines.
>
> Same type of unit is use for reversing a EV using a smaller 3 inch diameter
> resistor that is 16 inches long.  Also the free wheeling diode had to be
> switch out and another one switch in the reverse direction.
>
> They first tested this dynamic braking setup in full violent emergency stop
> mode.  There is actually a settings mode in the accelerator control that is
> label violent, high, standard and soft accelerator and braking.
>
> They first tested this braking action in violent which broke out a threaded
> bolt section in the motor coupler.  In the most violent mode, the positive
> voltage is disconnected from the motor communtator and the negative voltage
> is disconnected from the motor field.
>
> Then the positive voltage is connected to the field and the negative
> connected to the communtator.  The field and communtator is still connected
> in series.
>
> In the not so violent mode using the normal or softer braking mode, the
> resistor is inserted in the negative voltage between the negative of the
> controller and the communtator.  The resistor is so large, that it had to
> be
> hang below the front bumper.  On a braking test from 92 mph, it glow red
> which I though it make a good heater source.
>
> Never use it, need a larger EV to be able to install all this equipment.
>
> Roland
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Dennis Miles" <[hidden email]>
> To: "Electric Vehicle Discussion List" <[hidden email]>
> Sent: Monday, September 24, 2012 2:12 AM
> Subject: [EVDL] Series DC emergency braking possibility for two added
> parts.
>
>
> > I thought of this Sunday night and I would prefer asking you-all for a
> > comment or two before experimenting and destroying a motor. Or putting
> > some
> > fast wear on brushes.
> > I propose using a high current relay (Contactor) under control of a dash
> > mounted switch with a protective cover, to "Short out the armature
> > connections" from one to the other, leaving the field connected to the
> > motor controller output, then, in case of a hydraulic braking system
> > failure (I have experienced one before and using the mechanical
> "Emergency
> > brake" is very hard to control to a safe stop.)  Instead I would in case
> > of
> > foot brake failure merely lift the accelerator pedal to cut power to the
> > motor, but the car does not slow down, so with the above parts added,
> open
> > cover and flip switch activating the relay(Contactor) to short out the
> > armature, then slowly press the accelerator producing "Plug Braking"
> > action
> > but with motor controller allowing a measure of control and thus bring
> the
> > EV to a safe stop. Pullover into a safe location and call a flatbed truck
> > car hauler to carry the EV home to the shop and fix the hydraulic brakes.
> > I
> > do not think this would be a safe method for everyday use but I have
> 4-way
> > flashers and I use them only once a year or less. But. when needed they
> > are
> > there.
> > --
> > Regards,
> > *     Dennis *(EVprofessor)* Miles*
> >   *(863)944-9913* (phone noon to midnight E.S.T.)
> > *    reply to [hidden email]*
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
> >
> http://lists.sjsu.edu/mailman/private/ev/attachments/20120924/74591896/attachment.html
> > _______________________________________________
> > | Moratorium on drag racing discussion is in effect.
> > | Please take those discussions elsewhere.  Thanks.
> > |
> > | REPLYING: address your message to [hidden email] 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 [hidden email] 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
>



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|
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Re: Series DC emergency braking possibility for two added parts.

EVDL Administrator
In reply to this post by Roland Wiench
On 24 Sep 2012 at 10:33, Roland Wiench wrote:

> My first EV back in 76 made by the Electric Fuel Propulsion Co. in
> Troy, Mich. use a Cable Form motor controller ... in the 144 volt
> range.  It was modified for 180 vdc using large heat sinking resistors
> to reduce the 180 volt battery pack to 144 volts.

I didn't and don't agree with a lot of what Bob Aronson did and does, but
that doesn't seem like him at all.  Why waste all that energy as heat when
he could have just used a 144v battery?  Or am I missing something here?

David Roden - Akron, Ohio, USA
EVDL Administrator

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email address from the webpage http://www.evdl.org/help/ .
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_______________________________________________
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| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
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Re: Series DC emergency braking possibility for two added parts.

Roger Stockton
David Roden wrote:

> On 24 Sep 2012 at 10:33, Roland Wiench wrote:
>
> > My first EV back in 76 made by the Electric Fuel Propulsion Co. in
> > Troy, Mich. use a Cable Form motor controller ... in the 144 volt
> > range.  It was modified for 180 vdc using large heat sinking resistors
> > to reduce the 180 volt battery pack to 144 volts.
>
> I didn't and don't agree with a lot of what Bob Aronson did and does, but
> that doesn't seem like him at all.  Why waste all that energy as heat when
> he could have just used a 144v battery?  Or am I missing something here?

I'm not familiar with the Cableform controllers, but it is possible that the resistors were required only to drop the voltage to the controller logic, and were not actually in the path of the power flow from the battery to the motor.

Cheers,

Roger.


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
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Re: Series DC emergency braking possibility for two addedparts.

Roland Wiench
In reply to this post by Dennis Miles
Hello David,

You are assuming that the main power circuit voltage to the controller is
reduce in voltage, no it is not, only the control voltage is drop.

The Cable Form controllers uses the pack voltage for the control voltage
too.  The controller in the 144 volt form still use some power resistors to
step down to a lower control voltage.  Cable Form added another 100 ohm and
50 ohm power resistor to step down the 180 volt pack voltage for the
existing control voltage circuit.

They do not use any 12 volt control voltage in this controller.  The Cable
Form controller still work until the battery voltage got below 150 volts and
the Cable Form contactors that I still use today will work even if the main
battery voltage got down to 11.5 volts!

Today, I am using a Café Electric 1000 amp controller which the contactor
output circuit operates a 12 volt glass enclose plug in relay that turns on
a 180 volt pack voltage fuse with a 1-amp Limitron Busman fuse which turns
on the Cable Form main contactor.  These contactor coils have a voltage
range of 150 to 250 vdc range on turn on and down to 11.5 vdc on turn off.

If the voltage ever got down that low, and the contactor goes off the line,
the contactors will not come on until the main battery voltage rises to 150
volts, which is the Low Voltage Cutoff setting of this controller.

Roland




----- Original Message -----
From: "EVDL Administrator" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Monday, September 24, 2012 12:47 PM
Subject: Re: [EVDL] Series DC emergency braking possibility for two
addedparts.


> On 24 Sep 2012 at 10:33, Roland Wiench wrote:
>
> > My first EV back in 76 made by the Electric Fuel Propulsion Co. in
> > Troy, Mich. use a Cable Form motor controller ... in the 144 volt
> > range.  It was modified for 180 vdc using large heat sinking resistors
> > to reduce the 180 volt battery pack to 144 volts.
>
> I didn't and don't agree with a lot of what Bob Aronson did and does, but
> that doesn't seem like him at all.  Why waste all that energy as heat when
> he could have just used a 144v battery?  Or am I missing something here?
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> Note: mail sent to "evpost" and "etpost" addresses will not
> reach me.  To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] 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 [hidden email] only.
| Multiple-address or CCed messages may be rejected.
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Re: Series DC emergency braking possibility for two added parts.

Dennis Miles
In reply to this post by Roland Wiench
Roland, am I confused? you said, *"In the most violent mode, the
positive voltage is disconnected from the motor commutator and the negative
voltage is disconnected from the motor field.*
*Then the positive voltage is connected to the field and the
negative connected to the commutator.  The field and commutator is still
connected in series."*
That being the situation the motor would continue to run in the same
direction, to reverse a series motor one reverses either the field OR the
armature but not both... (I didn't teach that wrong for twenty years, did
I?)
Could anyone tell me if they have tried the circuit as I described it for
controlled motor braking?
Regards,*     Dennis *(EVprofessor)* Miles*
  *(863)944-9913* (phone noon to midnight E.S.T.)
*    reply to [hidden email]*
+++++++++++++++++++++++++++++++++++++++++
On Mon, Sep 24, 2012 at 12:33 PM, Roland Wiench <[hidden email]> wrote:

> Hello Dennis,
>
> My first EV back in 76 made by the Electric Fuel Propulsion Co. in Troy,
> Mich. use a Cable Form motor controller made for industrial electric
> machines normally in the 144 volt range.  It was modified for 180 vdc using
> large heat sinking resistors to reduce the 180 volt battery pack to 144
> volts.
>
> This unit initially came with dynamic braking which is reversing the
> direction of the motor using a 4 pole 600 amp contactor or using two 2-pole
> contactors that is mechanically and electrically interlock together. Also
> there was another 600 amp contactor that switch in a very large 0.25 to
> 0.50
> power resistor that is use for resistance braking which I still have today.
> This resistor measures about 18 inches long and is a 12 inches square. This
> resistor is normally use in load banks for testing electrical machines.
>
> Same type of unit is use for reversing a EV using a smaller 3 inch diameter
> resistor that is 16 inches long.  Also the free wheeling diode had to be
> switch out and another one switch in the reverse direction.
>
> They first tested this dynamic braking setup in full violent emergency stop
> mode.  There is actually a settings mode in the accelerator control that is
> label violent, high, standard and soft accelerator and braking.
>
> They first tested this braking action in violent which broke out a threaded
> bolt section in the motor coupler.  In the most violent mode, the positive
> voltage is disconnected from the motor communtator and the negative voltage
> is disconnected from the motor field.
>
> Then the positive voltage is connected to the field and the negative
> connected to the communtator.  The field and communtator is still connected
> in series.
>
> In the not so violent mode using the normal or softer braking mode, the
> resistor is inserted in the negative voltage between the negative of the
> controller and the communtator.  The resistor is so large, that it had to
> be
> hang below the front bumper.  On a braking test from 92 mph, it glow red
> which I though it make a good heater source.
>
> Never use it, need a larger EV to be able to install all this equipment.
>
> Roland
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Dennis Miles" <[hidden email]>
> To: "Electric Vehicle Discussion List" <[hidden email]>
> Sent: Monday, September 24, 2012 2:12 AM
> Subject: [EVDL] Series DC emergency braking possibility for two added
> parts.
>
>
> > I thought of this Sunday night and I would prefer asking you-all for a
> > comment or two before experimenting and destroying a motor. Or putting
> > some
> > fast wear on brushes.
> > I propose using a high current relay (Contactor) under control of a dash
> > mounted switch with a protective cover, to "Short out the armature
> > connections" from one to the other, leaving the field connected to the
> > motor controller output, then, in case of a hydraulic braking system
> > failure (I have experienced one before and using the mechanical
> "Emergency
> > brake" is very hard to control to a safe stop.)  Instead I would in case
> > of
> > foot brake failure merely lift the accelerator pedal to cut power to the
> > motor, but the car does not slow down, so with the above parts added,
> open
> > cover and flip switch activating the relay(Contactor) to short out the
> > armature, then slowly press the accelerator producing "Plug Braking"
> > action
> > but with motor controller allowing a measure of control and thus bring
> the
> > EV to a safe stop. Pullover into a safe location and call a flatbed truck
> > car hauler to carry the EV home to the shop and fix the hydraulic brakes.
> > I
> > do not think this would be a safe method for everyday use but I have
> 4-way
> > flashers and I use them only once a year or less. But. when needed they
> > are
> > there.
> > --
> > Regards,
> > *     Dennis *(EVprofessor)* Miles*
> >   *(863)944-9913* (phone noon to midnight E.S.T.)
> > *    reply to [hidden email]*
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
> >
> http://lists.sjsu.edu/mailman/private/ev/attachments/20120924/74591896/attachment.html
> > _______________________________________________
> > | Moratorium on drag racing discussion is in effect.
> > | Please take those discussions elsewhere.  Thanks.
> > |
> > | REPLYING: address your message to [hidden email] 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 [hidden email] 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
>



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|
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Re: Series DC emergency braking possibility for two addedparts.

Roland Wiench
In reply to this post by Dennis Miles
Hello Dennis,

I should have said, the armature is still in series with the field which is
reverse connected to the armature by the use of the 2 pole double throw
contactor. Anyway you knew that.

My motor manual actually shows four different modes of connections that are
use for braking.  The slow retarding braking removes the positive and
negative voltage from the motor and connects the positive terminal to a
large resistance that is connected to the negative terminal of the motor.

Roland


----- Original Message -----
From: "Dennis Miles" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Monday, September 24, 2012 8:30 PM
Subject: Re: [EVDL] Series DC emergency braking possibility for two
addedparts.


> Roland, am I confused? you said, *"In the most violent mode, the
> positive voltage is disconnected from the motor commutator and the
> negative
> voltage is disconnected from the motor field.*
> *Then the positive voltage is connected to the field and the
> negative connected to the commutator.  The field and commutator is still
> connected in series."*
> That being the situation the motor would continue to run in the same
> direction, to reverse a series motor one reverses either the field OR the
> armature but not both... (I didn't teach that wrong for twenty years, did
> I?)
> Could anyone tell me if they have tried the circuit as I described it for
> controlled motor braking?
> Regards,*     Dennis *(EVprofessor)* Miles*
>   *(863)944-9913* (phone noon to midnight E.S.T.)
> *    reply to [hidden email]*
> +++++++++++++++++++++++++++++++++++++++++
> On Mon, Sep 24, 2012 at 12:33 PM, Roland Wiench <[hidden email]> wrote:
>
> > Hello Dennis,
> >
> > My first EV back in 76 made by the Electric Fuel Propulsion Co. in Troy,
> > Mich. use a Cable Form motor controller made for industrial electric
> > machines normally in the 144 volt range.  It was modified for 180 vdc
> > using
> > large heat sinking resistors to reduce the 180 volt battery pack to 144
> > volts.
> >
> > This unit initially came with dynamic braking which is reversing the
> > direction of the motor using a 4 pole 600 amp contactor or using two
> > 2-pole
> > contactors that is mechanically and electrically interlock together.
> > Also
> > there was another 600 amp contactor that switch in a very large 0.25 to
> > 0.50
> > power resistor that is use for resistance braking which I still have
> > today.
> > This resistor measures about 18 inches long and is a 12 inches square.
> > This
> > resistor is normally use in load banks for testing electrical machines.
> >
> > Same type of unit is use for reversing a EV using a smaller 3 inch
> > diameter
> > resistor that is 16 inches long.  Also the free wheeling diode had to be
> > switch out and another one switch in the reverse direction.
> >
> > They first tested this dynamic braking setup in full violent emergency
> > stop
> > mode.  There is actually a settings mode in the accelerator control that
> > is
> > label violent, high, standard and soft accelerator and braking.
> >
> > They first tested this braking action in violent which broke out a
> > threaded
> > bolt section in the motor coupler.  In the most violent mode, the
> > positive
> > voltage is disconnected from the motor communtator and the negative
> > voltage
> > is disconnected from the motor field.
> >
> > Then the positive voltage is connected to the field and the negative
> > connected to the communtator.  The field and communtator is still
> > connected
> > in series.
> >
> > In the not so violent mode using the normal or softer braking mode, the
> > resistor is inserted in the negative voltage between the negative of the
> > controller and the communtator.  The resistor is so large, that it had
> > to
> > be
> > hang below the front bumper.  On a braking test from 92 mph, it glow red
> > which I though it make a good heater source.
> >
> > Never use it, need a larger EV to be able to install all this equipment.
> >
> > Roland
> >
> >
> >
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Dennis Miles" <[hidden email]>
> > To: "Electric Vehicle Discussion List" <[hidden email]>
> > Sent: Monday, September 24, 2012 2:12 AM
> > Subject: [EVDL] Series DC emergency braking possibility for two added
> > parts.
> >
> >
> > > I thought of this Sunday night and I would prefer asking you-all for a
> > > comment or two before experimenting and destroying a motor. Or putting
> > > some
> > > fast wear on brushes.
> > > I propose using a high current relay (Contactor) under control of a
> > > dash
> > > mounted switch with a protective cover, to "Short out the armature
> > > connections" from one to the other, leaving the field connected to the
> > > motor controller output, then, in case of a hydraulic braking system
> > > failure (I have experienced one before and using the mechanical
> > "Emergency
> > > brake" is very hard to control to a safe stop.)  Instead I would in
> > > case
> > > of
> > > foot brake failure merely lift the accelerator pedal to cut power to
> > > the
> > > motor, but the car does not slow down, so with the above parts added,
> > open
> > > cover and flip switch activating the relay(Contactor) to short out the
> > > armature, then slowly press the accelerator producing "Plug Braking"
> > > action
> > > but with motor controller allowing a measure of control and thus bring
> > the
> > > EV to a safe stop. Pullover into a safe location and call a flatbed
> > > truck
> > > car hauler to carry the EV home to the shop and fix the hydraulic
> > > brakes.
> > > I
> > > do not think this would be a safe method for everyday use but I have
> > 4-way
> > > flashers and I use them only once a year or less. But. when needed
> > > they
> > > are
> > > there.
> > > --
> > > Regards,
> > > *     Dennis *(EVprofessor)* Miles*
> > >   *(863)944-9913* (phone noon to midnight E.S.T.)
> > > *    reply to [hidden email]*
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