Short answer, the motor tries to run at Kv*V, but it never can get there, due to losses. A perfect motor would actually run at Kv*V.
Long (more interesting!) answer follows. I warn you, I am going to be super verbose with this:
First, some quick core concepts:
1) Whenever the motor is turning, it generates a voltage (called back EMF, BEMF) of RPM divided by Kv.
2) The torque generated by the motor is proportional to the current running through it, and inversely proportional to the Kv.
Now, step by step, what is happening to a motor (The motor is lets say 1000 Kv with 10 volts across it) at zero load (obviously doesn't happen in reality) with a voltage across it, and then what happens when you add a load:
Basically, we enter this example some time after the zero-load motor has been started and it has spun up to speed and reached equilibrium (it would generally take only a fraction of a second to spin our motors up to like 99.99% speed by the way). It is therefore running at 10k RPM (10v*1000Kv). Why doesn't it go faster? Well, at 10K Rpm, we know from concept 1 it is generating that voltage (back EMF) of 10000/1000Kv = 10V. This voltage opposes the battery voltage of 10V, and therefore the total voltage across the windings is zero. Current does not flow when voltage is zero. And concept 2 says torque generated by the motor is proportional to current. No current flow, no torque. So the motor has no torque to accelerate further.
So what happens when a wizard appears and
...Continue Reading