Reliability and safe operations! This is what customers are looking for when choosing a WEG product. Cimar, a cement company located in Maranhão, needed higher plant reliability and less maintenance costs. With this goal in mind, they chose a WEG new M Mining motor 3,400 kW, 6 poles, 6,600 V, 60 Hz, designed with a new brush lifting system to replace an existing motor from another manufacturer with fixed brushes.
Cimar now owns a motor with the best technology available on the market for slip ring motor with motorized brush lifting system, in addition of having WEG after sales support, a reference in the Brazilian market. “The change to a WEG motor moved us from a very risky condition and brought us, after the installation process, only positive points, bringing back 100% reliability to our most important asset, which is the Ball Mill. We had a very short downtime window to complete the installation and we did not have the expertise in installing a motor of this size. All the planning done by WEG and the leadership in the execution of the services during downtime brought us the confidence and guarantee that it would be executed on the expected time and with quality”, explains Roberlito M. Silva, Production Manager at Cimar.
WEG has developed a fully custom interchangeable motor for Cimar, adding the new brush lifting system of the M Mining line, delivering to the customer an up-to-date product with all the differentials mentioned above. The mill is one of the main equipment in a cement plant and if the equipment is out of operation, it can result in substantial production loss. Due to the customer's production requirements, plant downtime needed to be minimized. Thus, all start-up and commissioning activities of the machine were carried out in less than 24 hours.
Advantages of the motorized brush lifting system
The new brush lifting system is the evolution of the already established WEG brush lifting system, with the incorporation of the operating logic, fault investigation capabilities, operation monitoring via HMI simplifying and reducing the costs of motor installation, operation, and maintenance. In order to carry out the operation logic in a simpler way, its operation is via PLC. Monitoring of the operation and eventual faults is made available via the integrated PLC's display so that the user has full control over the performance of this system.
Slip ring rotor motors are recommended for applications that have high inertia loads, for example, mills, fans, and crushers. For these types of motors, the brush lifting system consists of starting the machine with the brushes in contact with the slip rings, connecting the rotor to the rheostat. After the start process is complete, the rings are shorted and the brushes are lifted via the drive system. Thus, the slip ring rotor motor starts to work in a similar way to a squirrel cage motor, combining the reliability and simplicity of maintenance of a squirrel cage motor with the robustness of the slip ring rotor motor.
The need for maintenance compared to a fixed brush system reduces considerably, due to the brushes being lifted after the motor starts, in addition to allowing the elimination or reduction of several variables, such as:
Suitability of the brush to the environment (humidity, patina formation)
Brushes wear (very low or high temperature, ring roughness and spring pressure)
Brushes Compartment cleaning
Cooling
“The brush lifting system is the main advantage of the WEG motor, which avoids constant wear of the brushes and the collector ring, thus reducing the number of stops for brushes measuring and replacing and increasing the service life of the machine as a whole. In addition, having a Brazilian motor was another extremely positive point, since the previous motor was an imported unit”, comments Roberlito M. Silva.
The lifting set has a gearbox driving the operation, adding robustness, reliability, and simplicity to the system. The brush holder works with constant pressure springs and has three inspection points, allowing agility and visibility in preventive, predictive or corrective maintenance. The internal position of the lifting mechanism is read by means of inductive sensors and they have a system that indicates their operating status.
