# trying to figure out power of a Sepex Motor



## mechano (Jun 1, 2015)

Hi All,

I have a 23 cm diameter Sepex motor I bought from junk yard, probably it is out of a forklift.
Sadly it has nothing written on it, power voltage amps. I want to figure out what kind of performance I can have.
Motor has its own cooling fan and it has 8 brushes.
The field winding has a 2.4 ohm resistance, I fed it with 24 volts and it draws around 10 amps. The armature has around 1.3 ohms (this is just multimeter measurement) 
The motor has its cables on it and the field winding has a cable like 5-6 mm in diameter whereas the armature has a cable like 15 mm in diameter.

In a sepex motor what kind of power is used in field winding? In the website of curtis controllers it is stated 800 Watts is typical ..

If this is a 48 Volt motor 2.4 ohm field resistance means 20 amps and this means 960 watts for field. Is this a wise approach?

If so what kind of power can I expect from a 960 watts field sepex motor??? 











Thanks for advices.


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## dcb (Dec 5, 2009)

maybe measure the field and rotor wire diameters and note the configuration to get a feel for the current capacity?


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## major (Apr 4, 2008)

The nominal field voltage is not the armature supply voltage for a "seperately" excited motor. It normally requires a few percent of input power for the field excitation at rated load. 

There are threads in which I have outlined how to test a SepEx motor to determine its field characteristics for the purpose of developing the field map for control. The search engine might find those for you. 

Regards, 

major


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## mechano (Jun 1, 2015)

major said:


> The nominal field voltage is not the armature supply voltage for a "seperately" excited motor. It normally requires a few percent of input power for the field excitation at rated load.
> 
> There are threads in which I have outlined how to test a SepEx motor to determine its field characteristics for the purpose of developing the field map for control. The search engine might find those for you.
> 
> ...


Hello Major, thanks for reply.
I thought a sepex motor is just a shunt motor so when you have a sepex controller you have the bonus to control the field.

I think the threat you mention is: http://www.diyelectriccar.com/forums/showthread.php?p=171434#post171434

What is the benefit of obtaining the "armature volts vs. field amps at a given rpm" graph?
How to interpret it?


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## major (Apr 4, 2008)

mechano said:


> Hello Major, thanks for reply.
> I thought a sepex motor is just a shunt motor so when you have a sepex controller you have the bonus to control the field.
> 
> I think the threat you mention is: http://www.diyelectriccar.com/forums/showthread.php?p=171434#post171434
> ...


Good find. There are some other threads where I help members use the curve, which is essentially the saturation curve of the motor's magnetic circuit, to develop the "field map" to program into the controller.
This allows one to take full advantage of the motor.


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