Circuit 2 for synchronously controlling multiple motors with multiple frequency converters

Multiple frequency converters can be used to control multiple motors to run at the same or different speeds, or multiple motors
to run at different speeds, but the same proportion of acceleration and deceleration is required. There are two control methods:
    The circuit is shown in the figure. By adjusting the potentiometers of respective frequency converters respectively , you can adjust the speed of the corresponding motor
to achieve synchronous operation.