In the east African country of Ethiopia, high-tech sugar production plants have been the focus of food-processing investments. These plants rely on diffusers—large, horizontal installations that extract sugar from sugar cane. Each diffuser can extract up to 12,000 tons of sugar per day.
Horizontal diffusers in sugar extraction typically measure 64 meters (m) long, 14 m wide and 8 m high. Twelve juice troughs are distributed along the length of the lower part. A chain conveyor above the troughs carries sugar cane at 0.6 m per minute after it has been shredded at the plant entrance. Water washes the cane in the cross-counter current, increasing the sugar content from one trough to the next.
"With an average sugar content of 12 percent, sugar cane is an ideal raw material for producing sugar," said Torsten Jüttner, technical project manager at BMA Automation GmbH in Braunschweig, Germany. His company specializes in the construction of sugar production plants, particularly in African countries.
"Almost a dozen of these plants are planned to be built within a decade," Jüttner said. "We've already received the orders for the first two factories, and we're in the implementation phase."
Compact Starters
For the first two plants, Beles 1 and 2, BMA implemented a modern automation approach. The industrial controls were organized through a standard configuration—an IO-Link, which is a point-to-point serial protocol to allow communication with sensors and/or actuators.
It decreased space requirements and installation costs and ensured ease of operation.
"The combination of compact starters for the electric drives and communication via IO-Link has proven to be the ideal solution here," said Han Janssen, who is responsible for hardware design at the Braunschweig operation.
The configuration saves up to 60 percent on installation and wiring for the plants. One plant includes 50 drives, 35 of which are actuated by compact starters. Twenty-eight electric motors turn the vertically oriented, 5-m spindles in the diffuser. These spindles break up the sugar cane to optimize the wash-out effect.
The 11-kilowatt (kW) drives consume 22.5 amperes (A) of power.
BMA Automation GmbH chose compact starters for sugar production plants in Ethiopia and installed them vertically in control cabinets.Vertical Mounting
Routing cabinets simplify cabling on the left and right of each control cabinet. This configuration works well with large and small drives alike. The compact starters are mounted vertically on the support systems in the control cabinets.
The vertical placement "not only saves space but also achieves a very clear overall layout," said Janssen.
Terminal blocks are not required, thanks to the central in-feed and compact starters located on the support system.
"The user in Ethiopia can also connect the motors much more easily and ergonomically during installation," said Janssen.
IO-Link communication can connect four compact starters into a single group. Three wires connect the first starter in the series to the IO-Link master, and pre-assembled flat cables connect the remaining three.
IO-Link masters can be plugged as boards into the distributed I/O system. Each board has four channels, and each channel can switch up to four drives—16 in total.Simple Configuration
The IO-Link master operates as a communication module with four IO-Link ports, each of which can connect up to four motor starters in group configuration. Thirty-five drives for pumps and spindles, with powers ranging from 0.2 to 11 kW, are controlled by three IO-Link masters.
"The system configuration could not be simpler—that is exactly what is often required in automation," Janssen said.
The distributed inputs/outputs (I/O) would have required 12 corresponding cards if composed with conventional digital I/O. This design would have fed only contactor control and alarms from the motor circuit breakers into the control system.
Simple programming in the engineering control software enables access to diagnostic information, including checkback signals, thermal overload trip and short-circuit trip. The LEDs on the front of each motor starter allow for visual fault diagnosis. The compact starters also indicate when contacts have reached the end of their service lives. Operators can plan replacements before downtime occurs.
Easy to Exchange
If an exchange is needed, a port configuration tool (POT) can release a specified removal diagnosis. The diagnosis determines whether the replacement starter's switching capacity and adjustment range match the old unit.
An error message will appear if using a compact starter with the wrong power range. Compact starters have an electronic overload trip with a wide-adjustment range, and trip classes 10 and 20 are integrated. The device has only five different versions, from 0.1 A to 32 A.
These advantages allow plant operators in Ethiopia to store fewer types of compact starters and replace faulty starters even during plant operation. When replacing a starter, the affected channel of the IO-Link master enters failure status. Not all the drives are switched off, but at most, only four are on one channel.
Cost-Savings Made Simple
Sugar plants Beles 1 and 2 in Ethiopia have experienced several advantages from their modern system solutions. Compact starters with IO-Link communication simplified the industrial controls configuration for the plant's sugar diffusers.
The design also saved space, reduced wiring costs and allowed for simplified installation and starter replacement.