# understanding the specs of a sepex motor



## major (Apr 4, 2008)

Hi mec,

I'll insert some comments:



mechano said:


> Hi everyone, I have this sepex motor, I know there is not much love for sepex motors generally but it was $250 from local junk-yard.
> 
> The advertised power is 9,2kW @ 80V 136A on armature, and 2060 rpm.
> Rated field voltage is 32,6V and 9.3 Amps.
> ...


Just about. The numbers off a nameplate like this are most likely relative to the rated load. In this case 9.2kW and 136A Ia. At no-load, Va=80V with Vf=32.6V will likely yield RPM greater than 2060. 



mechano said:


> as 2060 rpm is very low for an EV conversion and available controllers are 80V maximum (curtis 1244 & kelly KDZ), is there a way of running this motor faster like lowering the field voltage (at least this is the theory)


Sure. Field weakening will increase RPM. But it is not a free lunch. Field weakening also reduces torque. Now you can make up torque with more armature current, but there will be limits. Your controller will have a current limit on armature current. This pretty much sets maximum power. Field weakening will not get you higher power than that limit. So you end up trading torque for RPM. This can work quite nicely for you if you can set up the controller to manage it. And that, from everything I've seen, is impossible with a Kelly. Curtis can effectively manage SepEx motors. 



mechano said:


> I haven't purchased a controller yet, I really like to use this motor for my 1966 VW bug.
> 
> Thanks for any help.


Again.... Avoid Kelly.

Good luck,

major


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## Duncan (Dec 8, 2008)

Hi Major
With a sepex could I use two controllers? 
One like an OpenRevolt for the armature current and a separate smaller one for the field coils?
Would the two controllers have to be in phase with each other or do the motor coils spread the signal such that it would not be needed?

Just out of curiosity


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## major (Apr 4, 2008)

Duncan said:


> Hi Major
> With a sepex could I use two controllers?
> One like an OpenRevolt for the armature current and a separate smaller one for the field coils?
> Would the two controllers have to be in phase with each other or do the motor coils spread the signal such that it would not be needed?
> ...


Hi Dunc,

Yeah. We had a member or two do this. The field filters its supply well so no need to synch PWM.

major


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## dcb (Dec 5, 2009)

re: sepex controller, there is some mapping to consider, iirc some just make the field current a specific fraction of the armature current, and it largely behaves like a series motor (though I don't think it has the same overload capacity). ah, here it is http://www.diyelectriccar.com/forums/showthread.php?p=333959#post333959

there are other modes of course, and mechman has lots of info on it here
http://electric-booger.blogspot.com/2013/01/motor-basics.html

but the other one of interest is "FOC" style, where you map the field for most torque per amp for better reduced power efficiency (you might have to intercept the main controller throttle too). At least that is my understanding, plus reverse and regen options. I think there are a lot of folks who appreciate sepex still.


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## mechano (Jun 1, 2015)

Hi major, do you have any experience or heard about sevcon gen4 Dc controller ?

72 V 450 amp Kelly is around $250, Curtis 1244 is like $1250.
I asked the price of Sevcon Gen4 DC 72V 550amp from local dealer, it is $780 which sound reasonable if it is a quality product like curtis.





major said:


> Hi mec,
> 
> I'll insert some comments:
> 
> ...


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## major (Apr 4, 2008)

mechano said:


> Hi major, do you have any experience or heard about sevcon gen4 Dc controller ?
> 
> 72 V 450 amp Kelly is around $250, Curtis 1244 is like $1250.
> I asked the price of Sevcon Gen4 DC 72V 550amp from local dealer, it is $780 which sound reasonable if it is a quality product like curtis.


Hi mec,

Not with Gen4 but prior Sevcon millipak. Those were good quality, performed to spec and Sevcon knew what they were doing. None of which can be said of Kelly. Kelly sucks. Curtis like Sevcon, maybe a bit easier to work with. Both Sevcon and Curtis require programmer or pc dongal. Go ahead with Kelly and it will end up in trash can. And Kelly never, ever refunds.

Good luck,

major


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## mechano (Jun 1, 2015)

I just received an email from the Sevcon dealer, 72 Volt version is not available, they only have 48V, they say 72V has never been produced yet 

The only other controller I can find is Navitas, any ideas about this:
http://www.evdrives.com/product_p/con-tsx500-72.htm

This guy had bad experiance with navitas sepex controller: http://www.evalbum.com/1772




major said:


> Hi mec,
> 
> Not with Gen4 but prior Sevcon millipak. Those were good quality, performed to spec and Sevcon knew what they were doing. None of which can be said of Kelly. Kelly sucks. Curtis like Sevcon, maybe a bit easier to work with. Both Sevcon and Curtis require programmer or pc dongal. Go ahead with Kelly and it will end up in trash can. And Kelly never, ever refunds.
> 
> ...


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