Electrical Schematic – Motor Starting System – Soft Starter Starting/Slackening


This is an effective starting system (C Fig.7) for starting and stopping a motor smoothly (see the section on electronic speed controllers for more details).
It can be used for:
– current limitation,
– torque adjustment.
Control by current limitation sets a maximum current (3 to 4 x RC) during the starting stage and lowers torque performance. This control is especially suitable for “turbomachines” (centrifugal pumps, fans).
Control by torque adjustment optimises torque performance in the starting process and lowers mains inrush current. This is suited to constant torque machines.
This type of starter can have many different diagrams:
– one-way operation
– two-way operation
– device shunting at the end of the starting process
– starting and slackening several motors in cascade