In lab,when we conducted experiment on DC shunt motor speed control using armature control,
The motor had no load connected to it and the field was kept constant.
Also the motor was started using three point starter
The observations are after the motor was in running condition.
what we observed is this:
1)As Va decreases,(i.e. by increasing the Ra connected in series with the armature),
N decrease.
2)Also what we found was Ia also decreased as Va was decreased
Now Ia,depends on the load connected to the motor,right?
There is no external load,also the field is constant,so should'nt the Ia have been constant too?as T=KtxφxIa ,as T is constant Ia should have been constant..rather than graduallly decreasing...
I forgot to note to take the name plate readings of the motor but I will send them by tomorrow.Have attached the readings.