On 1 Jan 2018 at 10:03, evdragracer--- via EV wrote:

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I have 2 sepex vehicles.

A circuit diagram might be clearer, but hopefully words work OK:

On my tractor:

Keyswitch turns on field relay

field relay hooks up field to a 12V battery

The field lead is wrapped around a proximity reed switch (used in alarm 
systems to see if a door or window is closed, the switch changes state when 
a magnet gets close enough to it). The wraps of wire provide the "magnet" to 
close the reed switch.

Current in the field closes the proximity reed switch

The proximity reed switch turns on a contactor relay that feeds the armature 
through a big, high power current limiting resistor

The proximity reed switch also feeds a delay relay

After about 1 second the delay relay feeds a contactor that shorts the 
current limiting resistor

Don't forget to put a big diode on the field, otherwise you'll get a big arc 
when you shut off.

It is amazingly smooth, I can start in gear and the tractor takes off very 
smoothly. Idle RPM is about 3600 rpm. I get regen down hills. The tractor 
has a variable speed transmission so I don't need to change motor speed. If 
I did, I would put in a welder rheostat in series with the field.

I also have a car with a sepex. It has a Kelly 144V sepex controller. The 
controller needs to have been ordered with the appropriate current range for 
your field. My first motor had low field resistance, the Kelly worked well 
for that. For my new higher resistance field motor, I can't get the Kelly 
field current to go low enough, so I have to run in "Voltage Mode" for the 
field, which means no field weakening. It still works pretty well, but that 
cuts off my higher RPM. If I could get to the field current sense resistor I 
could fool it to work at lower field current (it's potted, I'm reluctant to 
remove the potting compound).

David Roden - Akron, Ohio, USA
EVDL Administrator

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