# Series VS SepEx



## major (Apr 4, 2008)

Georgia Tech said:


> I am SURE this has been discussed before, but I am trying to find out why most motors are series based instead of SepEx based. It seems SepEx has more advantages over the Series but most are using series motors, why??? Of course there’s the obvious reasons for the SepEx, that’s the regen braking. But I can't figure why most conversions are series. I mean it not tough to do, the controllers for the field are mere 50 amps at about 30 volts!!! From what I’ve read SepEx are more efficient, is this true? There is something MAJOR MAJOR I am missing here about this whole thing but I don't know what it is...Why are EV motors mostly Series?


Hey GT,

You ask a lot of questions

Short answer is availability of the motors and controllers. And the higher voltage/power SepEx motors need interpoles because brush advance is opposite for generator/motor. On the lower voltage systems you can get away without interpoles, so you see more vehicles like golfcarts and lift trucks using SepEx. And not a big difference in efficiency between the two, if any.

Regards,

major


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## frodus (Apr 12, 2008)

Couldn't have said it better major!

Lack of higher voltage motors and controllers is a major factor...things get complicated at higher voltages with regen on a sepex.... they have interpols, because the timing is advanced in the wrong direction during regen.


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## Georgia Tech (Dec 5, 2008)

thanks....


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## Georgia Tech (Dec 5, 2008)

major said:


> Hey GT,
> 
> You ask a lot of questions
> 
> ...


Yeah but I ask the REAL tough technical questions that no one thinks about!!


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## booksix (Aug 26, 2008)

I was wondering too... there are a few 8" sepex motors on ebay. So how are the controllers different (or what do they do different)?


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## Georgia Tech (Dec 5, 2008)

booksix said:


> I was wondering too... there are a few 8" sepex motors on ebay. So how are the controllers different (or what do they do different)?


Well one thing is that SepEx controllers have to control both the Armature Voltage and the current on the field coil. It offers more dynamic control over the motor that a series motor does not have. I did not realize there was somewhat of a limit in the voltage. this was the piece I was missing that I was looking for. SepEx motors as these two were saying is limited to 80 volts then this is a REAL issue when it comes to high power applications


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## booksix (Aug 26, 2008)

Ahh, that's what I was missing as well.


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