DC MOTOR

I think to state it is alternating is too simple.

It is not direct constant but it does not "flip" the zero current line either, it does only alternate in one direction.

The frequency on a DC drive depends on the design and may alter while the motor is running I believe so you could not give that as a fixed entity.

Hi Jafar,

any good motor supplier will give you not only the resistance but also the inductance.

Your feeling is ok, you need it to calculate the current rise- and fall-time after switching
the voltage (either by external power supply or by the commutator).

And you need it to determine the energy stored in the inductance, as this has to be treated properly at switching: not to damage neither commutator nor switch.

RHABE

jafar; your motors are also generators because of the counter emf perry