Rice mill control board with soft starters, near Fuman

The brief

A rice mill with seven motors, all started direct on line from an open board. When the whitener started, the site voltage dipped far enough to drop the elevators at times, leaving paddy piling up on the husker. At least one motor went for rewinding every season, and the bill carried a reactive penalty.

How it was done

1. 01 Starting and running current measured on every motor, and site power factor logged during working hours
2. 02 Soft starters with bypass contactors on the whitener and husker; direct starting with motor circuit breakers on the small motors
3. 03 Start sequence from the end of the line backwards, with interlocks so that if an elevator stops, the machine feeding it stops too
4. 04 Phase loss, sequence and imbalance relay on the incomer, and emergency stop buttons along the line
5. 05 Closed IP54 enclosure with fan and filter, installed in a room separate from the dusty mill floor
6. 06 Stepped capacitor bank with regulator, sized from the measurements
7. 07 Terminations torqued with a torque wrench, conductors numbered and the drawing fixed inside the door

The outcome

The large motors now start without a noticeable dip, and the elevators no longer drop out when the whitener starts. In the season after the work no motor went for rewinding, and the reactive penalty came off the bill.