Hi,
I am always wondering why does the DC motor need more current when the load added and draw the max current when it stalls.
These are my own opinion:
The DC motor that is usually used is 3-pole type. When the power is turned on, one of the coil is conducted and electromagnet created. Before the current rises to the max, the second coil is conducted and the first coil is no longer connected to the brushed due to the pushing of the magnetic field causing the changes of the brushes connection. Then the same thing happen to the 2nd and 3rd pole as the motor turns around. So this constant current is the current required by the DC motor without load.
When the load added, the speed becomes slower and hence, the conduct time of the coil is increased and the current has enough time to rise higher.
When the motor stalls, the brushed are connected to only one coil, and this is the max current required by the motor.
So basically the max current is defined as:
Imax = Vsupply/Rcoil
Vsupply = supplied voltage
Rcoil = coil resistance
Are the explanation correct?
Thanks