# Sepex control with Curtis 1204



## dcb (Dec 5, 2009)

Sure, your controller can only do 48 volts though, so it wont make much torque at higher rpm, and it can't do a lot of amps, so it is not the best choice (should be able to use 400+ amps with that es-10). basically get a 48v brushed ebike controller, or even this *might* be enough: http://www.ebay.com/itm/MAX-10-50V-...838871?hash=item21139ae457:g:LYsAAOSwHgVW8OYD

and you will have something sort-of-similiar to a gear selector. the motor can spin faster when the field is weaker, or it can make more torque when the field is stronger, or just find a spot you like and leave it.

Don't turn it all the way down (or up), maybe 1/3 power setting or so for starters. My best swag from reading the internet tea leaves is you don't want to put more than 30 amps into the field, and you don't want to stay at 30 amps for long.

If this doesn't make sense, then don't try it, or be willing to write it off as a learning experience.

If you need reversing, then it gets a little more complicated. There are ways to modify it to deliver a field current in proportion to the armature current, but again it gets complicated and I don't have any specifics for you.


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## Roro500 (Aug 25, 2016)

Hi dcb,
Thank you for the reply. I am trying to set this motor up to propel an old electric boat that is already rigged for 36V (battery bank) and has this curtis controller. Because it is a boat, I do not think that a torque is my great concern, but burning up a field coil in the motor certainly would
Because of the application, reversing is important. There is a whole bank of old relays in that boat that probably could be harvested for this purpose. It also has 5kOhm->0 throttle, which would be nice to reuse.
Are you aware of any diagrams showing how to connect Curtis to Sepex motor?


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## dcb (Dec 5, 2009)

no diagrams that I know of, it would go straight to the armature (A1?) and back to the other end of the pack or the contactor or whatev, and the cheap controller would go to a 30+ amp DPDT relay to F1 and F2 and back to the pack or contactor or whatev.

make sure the field has its own flyback diode or that it is integral with the cheap controller. It *might* not be enough induction for the controller too, kind of experimenting here.


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## major (Apr 4, 2008)

Hi Roro,

That controller will probably work to control the armature only (use A1 & A2), but it might have some issue due to load inductance. It is intended for a series wound motor and the inductance of the armature without the series field coils is much lower. Additional inductance could be added by coiling 4 or 5 loops of cable between controller and motor.

I found a PDF from Bradley Univ on Google detailing use of this motor. Sorry but I can't copy the link. Anyway it claims the SepEx field resistance is 1.3 ohms. So if you connect it as a shunt motor with field (F1 & F2) across a 36V source you will cook the field coils in short order ( over 1000 Watts in field alone). My guess is to keep field constant at around 8 or 9 A. So 12V to F1 & F2 would work. That is about 100 W on the field. Might still be a little high. If they get too warm, their resistance goes up and current goes down so may stabilize thermally. However RPM will increase due to field weakening.

Reverse by reversing current thru field. Shut armature off before and during field reversal. I think a boat should run fine like this. Just use the armature control for speed control leaving the field constant.

Regards,

major


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## Roro500 (Aug 25, 2016)

Hi major.
These were some very helpful suggestions. Saw the pdf from Bradley, they were using Altrax DCX600 to control it.
I would like to try your idea. What would you recommend to do to bring the field voltage down to 12V?

Thank you,
Roro


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## major (Apr 4, 2008)

Roro500 said:


> Hi major.
> These were some very helpful suggestions. Saw the pdf from Bradley, they were using Altrax DCX600 to control it.
> I would like to try your idea. What would you recommend to do to bring the field voltage down to 12V?
> 
> ...


For starters you could test using a separate 12V or even 3 Lithium cells for about 10V. If 12V tests out ok, a 36 to 12 Volt DC/DC converter should be commonly available. You might want an auxiliary 12V battery and converter for lights, horn, radio, etc anyway. You could use it for the field if it has enough capacity.


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## Roro500 (Aug 25, 2016)

Thank you for your help. Time to do some experiments. I will update once that happens.


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