> *What exactly is the Work of Start Capacitor?*
>
>For single-phase motors normally have both the run and start capacitor.
>However, they work differently. The start capacitor produces a bolt of
>energy to the motor for it to run; while for run capacitor helps
>maintain the functioning of the motor when the start capacitor switches
>off. Start capacitor has the ability to store more charge than the run
>capacitor.
A pure single phase motor doesn't produce a rotating magnetic field. When power is applied, it might just start vibrating in place. You can then turn it manually and it will start rotating either CW or CCW, depending on in which direction you push it. After it starts rotating it will rotate in that direction until the power is cut.
This would be a bit hard, if you had to manually turn the motor once the power is applied.
A three phase motor produces a rotating magnetic field and the motor starts automatically in the same direction (unless two phase wires are swapped).
In practice a single phase motor is actually a two phase motor, in which the second phase is generated with a series capacitor (produces up to 90 phase shift) producing a rotating magnetic field and the motor starts in the same direction.
I have never heard of "run" capacitors. Are these connected between phase and neutral, then it would just be used for correcting the power factor, since the motor power factor can be quite bad when lightly loaded. However, the capacitor should not be too big, since it could overcompensate and cause problems to the network.
If it is between the hot end of the main winding and between the hot end of the start winding then it will constantly feed the second phase to the start winding. If you have installed some copper for the start winding, so why not use it also for normal operation (with reduced power)? But OTOH, why not make the secondary winding strong enough so that it can be constantly fed by the larger start capacitor ?