# current control versus voltage control

Discussion in 'General Electronics Chat' started by kokkie_d, Oct 15, 2010.

1. ### kokkie_d Thread Starter Active Member

Jan 12, 2009
72
0
Hi,

In order to limit current rushing into a motor one can control the amount of current by limiting the voltage. i.e.
$
\frac{Vin - Vemf}{Ra} = I
$

So, in the beginning when there is no emf you start of a low voltage and slowly ramp up the voltage until you reach the final running voltage.
All the time the current will be as per equation.

And the otherway around you could aim for a fixed current which means that you have to keep increasing the voltage butthis could bring the voltage above its maximum.

That relationship is set; the armature resistance is fixed so the only way to control the current is via the voltage and similar the only way to control the voltage is via the current.

So, when people are talking about current control and voltage control for motors (and batteries) this is what they are talking about, right?
I mean current control is only realy useable until the voltage reaches its maximum and after that the voltage has to be kept stable and thus voltage control will be used.

The question: is this correct? or am I missing something?