what do we mean by term ' arming a BLDC' ??how important is it before every run of BLDC motor??
RC ESCs have to protect the user from severe injury that can result from unexpected
power-up of a prop motor (even small RC plane propellers can cut to the bone due to
the high speeds they travel at).
Thus the ESC will never just start up if the throttle setting is left on between
power-ups. Usually they just refuse to start-up if the throttle isn't set to off at
start up. Some require slightly more complicated arming sequences.
First guess is start with low duty cycle (throttle off) and wait a few seconds, then
gradually increase till start-up. Sudden large changes of duty-cycle may be filtered out
as erroneous (or RF interference), so always ramp up and ramp down the throttle
smoothly in case the ESC is paranoid like this.