Motor control circuits
Star-Delta Starting Circuit with Forward–Reverse Control
What is forward-reverse star-delta starting?
This control circuit combines star-delta starting with forward-reverse control. In both directions the motor starts in star and then switches to delta, so a large motor starts with a low current and can run in both directions.
Where is it used?
It is used on large cranes, heavy conveyors, large reversing mixers and mining and quarry machines. It is the choice for applications that need both high power and a change of direction.
Power circuit and control circuit
The power circuit has four contactors: forward, reverse, star and delta. The control circuit has these contactors, a timer relay, an overload relay and start-stop buttons. The contactors interlock each other for both direction and connection. Anyone who can work out this circuit can easily read the most complex contactor panels on site.
What to watch out for
Wait for the motor to stop completely before changing direction; reversing a running motor causes mechanical and electrical stress. Test every interlock one by one during commissioning.
Parts used
- Stop button (NC)
- S1, S3, S2
- Start button (NO)
- S2, S3
- Contactor coil
- K4, K1, K2, K3
Run it in the simulator.
This circuit is ready in the CoilPath library. Open it, press the buttons and follow the current. It also comes with a wiring view and a panel layout.