Star Delta Starter Control Panel

Starting a motor seems easy until the large inrush current pulls voltage down on the feeder that supplies the motor. A properly designed and built Star Delta Starter Control Panel can make a big difference in how smoothly a motor is started and if the motor experiences repeated nuisance trips.

Our design process for these panels begins with a review of the motor rating, load inertia, duty cycle, and the capacity of the upstream circuit’s breakers to ensure that the transition from stars to delta is accomplished without torque shocks or inrush current spikes.

The power circuit uses contactors with the proper rating, mechanical and electrical interlocks to prevent overlap during the transition from star to delta. The timer logic is chosen based on the actual acceleration time rather than an arbitrary, fixed timer setting. Heavier applications (compressors, pumps and blowers) have adjustable timer provisions along with thermal protection rated based on the motors full load current.

The control wiring is routed to provide clear terminal segregation and to have a clear ferrule to eliminate any possibility of tracing the wires incorrectly as a result of troubleshooting during hours of production work. The door has lights indicating whether the motor is running in each of the modes - running, starting, tripping, or delta mode - to provide quick reference to the operator. The panels provide adequate distance between them and sufficient ventilation so that they can be cooled during the continuous startup of each panel.

The panels go through a dry run, which includes simulating a powered up start sequence, verifying all interlocks and performing fault condition simulations. The motor will start only using the very low initial current, which will provide maximum stability to the supply system, and then provide reduced mechanical shock to the motor when it is started while other motors are started on shift at the same time.