Hello David,
There should be a main contactor which is normally on one side of the
battery pack power lead that is control by ignition switch. As a back up to
the ignition switch circuit that controls the main contactor and controller
circuit, I have the ignition switch back up with two more on console kill
switches.
Some motor controllers require a 12 volt ignition and 12 volt power control.
I also have a big red flag 12 volt shut down switch that kills the main 12
volt power.
For maximum safety, there should be two more contactors to kill the negative
and positive side of the battery pack. These are also control by two more
console switches and all three contactors are also control by ignition
switch and back up ignition switches.
These battery contactors are known as safety contactors, and they provide
isolation from the battery charger voltage, that may be higher than the
controller rating. Also, in some controllers, you may have a battery pack
line go directly to the motor, and when charging the battery, you may be
applying the higher charging voltage to the motor. I took out a accessory
drive motor one time, because there was only one contactor on one battery
line. This motor was arcing to ground cause by the inductive path of the
brush dust while the battery charger was on.
These large contactor's coils may draw up to 5 amps on 12 vdc and has taken
out driver circuits in a controller that may control a main contactor. It
is best to use a Zener Overvoltage Transient Suppressor across all the
contactor coils. I use NTE 4933 for 12 V circuits and NTE 4999 for 180 V.
To reduce my 12 volt load on these contactors, I use line voltage
contactors, meaning the contactor coils use the battery pack voltage to
operate these coils. Line voltage contactors design for a EV are size for
the battery pack, where they will take a overvoltage or more than the
equalize charging voltage of the battery and the contactor will stay open
even if the battery pack drops below the LOW VOLTAGE LIMIT SET BY THE
CONTROLLER. My 12 V ignition turns on 250 VDC relays that is rated for 10
amps and only use 0.1 amp on a 180 volt battery pack voltage to turn on
these contactors.
Roland
----- Original Message -----
From: "David Hrivnak" <
[email protected]>
To: <
[email protected]>
Sent: Wednesday, October 17, 2007 7:27 PM
Subject: [EVDL] Contractor/Manual disconnect/Naked?
> I am in the process of building my first EV. I will have 72V and will be
> using an Altrax 7245 controller and as such will pull up to 450 amps. As
> I
> am laying out the system it seems prudent to install an emergency cutoff
> or
> a contactor just in case there is a failure and I end up with a runaway
> electric motor.
>
>
>
> Do you think this is prudent to design in or do most EV'ers go "naked" so
> to
> speak with no emergency cut out? If you do have an emergency cut off do
> most use a manual kill switch or contactor? It looks like a contactor
> will
> be a lot easier to design in.
>
>
>
> Thank you
>
>
>
> David J. Hrivnak
>
> <http://www.hrivnak.com> www.hrivnak.com
>
> Personal Account WWJD?
>
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev