# Another Motor theory question



## gerd1022 (Jun 9, 2008)

yeah im pretty sure that for a series motor, the stall torque is theoretically infinite. That is IF you had enough amps to feed it. In fact, awhile pack i did a simple excel chart of the warp 11 torque speed curve and put an equation to it. It came out to T = (1E+10)*RPM^-2.5469

so you can see, torque (in ft-lbs) goes to infinity when RPM goes to zero. This equation is from the data posted on the warp website for the 72 volt test. I also read somewhere that for series motors, T = K*i^1.5, where K is a motor dependent constant and i is current. 

so infinite torque would only require (inf/K)^2/3... not that bad!


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## Georgia Tech (Dec 5, 2008)

gerd1022 said:


> yeah im pretty sure that for a series motor, the stall torque is theoretically infinite. That is IF you had enough amps to feed it. In fact, awhile pack i did a simple excel chart of the warp 11 torque speed curve and put an equation to it. It came out to T = (1E+10)*RPM^-2.5469
> 
> so you can see, torque (in ft-lbs) goes to infinity when RPM goes to zero. This equation is from the data posted on the warp website for the 72 volt test. I also read somewhere that for series motors, T = K*i^1.5, where K is a motor dependent constant and i is current.
> 
> so infinite torque would only require (inf/K)^2/3... not that bad!


WOw simply mind boggeling!! As stupid as it might sound the heart and sole of why I like EVs is the motors, don't care too much for AC, at least not yet...I am a Motor nut through and through!!


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## ice (Sep 8, 2008)

Torque Constant, It is said that for each ampere of current, a fixed amount of torque is produced...


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## gerd1022 (Jun 9, 2008)

hey i just did a little more research on the matter, and at a certain point, the field coils become saturated, and their magnetic field reaches a limit. 

At this point, the motor will act as a permanent magnet motor, because only the armature current will vary the torque. This will make a limit on torque. Not sure at what current this saturation happens though.


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## Georgia Tech (Dec 5, 2008)

gerd1022 said:


> hey i just did a little more research on the matter, and at a certain point, the field coils become saturated, and their magnetic field reaches a limit.
> 
> At this point, the motor will act as a permanent magnet motor, because only the armature current will vary the torque. This will make a limit on torque. Not sure at what current this saturation happens though.


 
That was what I was talking bout...even if we reach saturation in the fields we will still continue to make torque well beyond saturation...


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## ice (Sep 8, 2008)

I had a question though, In a point of saturation in the fields what is the condition of the torque at this point?


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