Re: dc motor details
Hi,
I try to give some (short) answers....
> What is the relationsip between the speed and torque?
For a given motor Torque curve can be plotted like a family of curve in a Speed/Current graph
> Without a control can torque stay constant?
Torque of course depends on motor load, so....
>With a control (dc drive) can torque stay constant at any speed?
No, for a given motor you have to plot the torque curve to see in wich way torque vary vith speed at a given current.
If you have a currrent limited generator to supply the motor you can have a torque limit (at a given speed).
If you use a current generator speed change with motor load.
>What is the purpose of using gear with a dc motor?
Motor optimization. If you use an increase ratio of course you can have higher speed (and lower Torque). I the opposite way you can have Higher torque with lower speed (gear efficency must also be take in count ).
>Can we achieve the same goal using a dc drive without a gearless motor >like a geared dc motor? (I mean at any speed can we obtain the same >torque as in the geared motor with a gearless motor?)
Of course no, you cannot have the same result in the full range of applications (otherwise why to spend money with gear?).