When the motor is connected across the American Horror Story 9th Anniversary 2011-2020 thank you for the memories shirt supply mains without load, then it will draw a small current from supply mains. Now question arises why small amount of current and why not high current? It is because when no load is connected on motor, torque requirement will be low. Now as torque requirement is low, speed will be higher as speed is inversely proportional to main flux and torque is directly proportional to main flux. So as speed will be higher, back emf will be higher i.e higher opposition to the flow of current from supply to motor and thus current will be less on no load condition.
So now as low current will flow through the field American Horror Story 9th Anniversary 2011-2020 thank you for the memories shirt winding as well as armature winding ( as it is series motor) so main flux produced will be lesser, as before saturation point current is directly proportional to flux. So as main flux is lower, speed will tend to increase. As speed increases, back ems also increases and thus current drawn from the supply will become more and more lower and thus main flux will also become more and more lower and thus speed will tend to increase more and more and this continues till armature of motor has attained speed which is so high that due to centrifugal forces set up in the rotating parts damages armature.