[Yabert]

I like your answer Major. It's realy clear!

But I'm interested to know one more thing about DC serie motor.

At a fix given current, maybe 1000A, what determines the capacity of a motor to sustain his max torque over the increasing rpm?

I read someting about resitivity of motor in ohm (mΩ) vs voltage given to the motor vs voltage produce by the motor, but it's not clear for me.

Also, the number of commutator segments can play a role?

Can you explain please.

I need to understand why a motor compare to another one fo the same voltage and the same Amp lose his max torque before the second.
Bellow, an exemple of torque lost at high rpm!

 

[Yabert]

Just out of interest, what units are you using for torque in the last line, GT?

You need to use Feet-lbs!

240 ft-lbs x 2500 rpm / 5252 = 114 hp

 

[Yabert]

It's always a pleasure to read your great explanation Major


If I understand correctly , for the same voltage, the same current and same quantity of bar in the armature, a motor with less resitivity will be capable to sustain his max torque to a higher RPM.

So, because the the copper has a very little resistivity, the most resistive part of a serie DC motor is probably the brush and the brush contact area on collector.
If it is true, a motor with very large brush can tolerate more current and can also give his max torque at higher RPM. And in this case, with same controller, a bigger motor can probably give his max torque at higher rpm than a comparable smaller motor. (Example: Warp 11" vs Warp 9")

Am I right?

 

[Yabert]

It seem you are right Major! (see picture). Maybe it's more 25 slots and 50 bars.

After all this learning (thanks), I have more ability to seach a powerfull forklift motor for an street EV aplication.



And after all this explanation I realise the best forklift motor for high torque at high rpm for a 1000A/156v configuration was the GE 11" motor I found few weeks ago.

Large diameter for high torque, large brush for high current and 49 big cumm bars for sustain high torque at high rpm.......
Unfortunately, it need new flange on both side and it's lot of money in material and machining.


So, one more time, thanks Major.... this thread can probably help many other guys to find the best forklift motor for street EV.

 

[Yabert]

.. they both have the SAME internal specs too..

Not exactly.............

GE 11": 49 bars and 4 big brush (4 poles).

Warp11: 25 bars and 8 brush (4 poles).

 

[Yabert]

You can see.....

Warp 11 have 25 slot in armature, but 49 bar comm.

I would like to know the difference rpm and torque of each motor at same voltage and current!..

 

[Yabert]

yabert i think I see from your photos...you have the one piece brush design i was told by the people at warfeild to MAKE SURE that this was upgraded to the 2 piece brush design...this would then be like the WARP 11.

Is it a big disavantage to have one big brush hold with two spring compare at 2 brush with one spring on each?
I assume the same area of brush contact (2x1 = 1x2).