Cane Shredder Liquid Resistance Starter with Slip Control and Current Limiting

November 6, 2024

PROJECT: Sugar Mill, Liquid Resistance Starter
INDUSTRY: Manufacturing
LOCATION: Queensland, Australia

The Customer

Wilmar Sugar and Renewables is Australia’s largest raw sugar manufacturer and a leader in renewable energy. Operating across eight sugar mills located in the Herbert, Burdekin, Proserpine and Sarina regions of Queensland, each mill operates 24/7 during the crushing season, typically from June to November.

Located near Brandon in the Burdekin region, Pioneer Mill crushes an average of 1.62 million tonnes of sugarcane a year, to manufacture about 260,000 tonnes of raw sugar. It also has Australia’s largest biomass generator.

Wilmar Sugar and Renewables has invested in high levels of innovative technology and automation to enhance safety, increase efficiency and optimise productivity, establishing the company among the most efficient in the world.

The Challenge

Wilmar Sugar and Renewables approached CSE Uniserve to replace their existing Liquid Resistance Starter (LRS) and its control, for the main 5,200kW sugarcane shredder motor at their Pioneer Sugar Mill.

Wilmar had concerns related to the age and performance of their existing LRS. It was requested that the replacement LRS provide enhanced control and protection to optimise the shredder performance and meet the requirements of the site power generation.

The Solution

To best address Wilmar’s requirements, CSE Uniserve supplied a tailored UniStarter® LRS with Rotor Slip and Rotor Current control, and alarms and trips, using CSE Uniserve’s LRS Rotor Current Monitoring System.

Typically, in sugarcane shredding applications, additional Rotor Slip is introduced to reduce the impact of uneven sugarcane feed clumps and subsequent current transients imposed on the shredder motor supply. The additional slip allows the shredder drum’s stored rotational kinetic energy to break through the clumps.

To precisely control the percentage of motor slip, CSE Uniserve’s Rotor Current Monitoring system continuously monitors and controls the resistance between the LRS’s electrodes, using PID control. Excessive stator current transients are then “clipped“, using high speed LRS electrode control, by responding to the Rotor Current Monitoring’s instantaneous RMS rotor current measurement.

Resultant energy losses produced during slip are removed from the LRS via manually selected duty/standby heat exchangers. Automatic changeover and alternating duty/standby pumps, provide for high reliability and continuous operation.

To streamline servicing requirements, the LRS is equipped with CSE Uniserve’s unique Anti-Evaporation Floating Panel. This floating panel eliminates the traditional anti-evaporation oil, thereby making the electrolyte tank emptying, internal inspection and servicing faster, cleaner and safer.

Following installation, CSE Uniserve engineers successfully commissioned the LRS and Slip Control system. The solution achieved the design brief with precise slip control, significantly reduced transients on the motor’s supply and mitigation of overcurrent conditions.

Key Solution Features

• Slip and resistance control with maximum slip control between 1.5%-5% (985-950rpm)
• Rotor Current Limiting at 110% at startup and 120% during operation
• Rotor current phase imbalance alarms
• Locked Rotor, Timed and Instantaneous Rotor overcurrent protection
• Automatically cycled or selected duty and standby Electrolyte Pumps
• Manually selected duty and standby Heat Exchangers