The Value of Synchronous Motors in Mining Conveyors

As heavy-duty mining conveyor systems move heavier amounts of materials across greater distances, their performance becomes more essential and their uptime more critical. When designing a rugged conveyor system, it's important to consider the use of synchronous motors as they eliminate the need for gearboxes, increase uptime and reduce maintenance costs.

• Synchronous motors can supply the power and torque needed in heavy-duty applications.

• They operate at lower speeds than induction motors and can therefore drive the conveyor pulleys directly, without the need for gearboxes and couplings.

• Gearless operation makes the conveyor system much more reliable, reduces maintenance costs, and increases efficiency due to the elimination of friction losses.

Due to the unique nature of each mining conveyor system, the demands placed upon it, and its geographical location, the motor may need to be specially designed. During the design phase, there are typically five motor features to consider.

Bearings — In addition to the normal configuration of two sets of bearings, motors can be designed with one or even no bearings (bearingless or 'overhang' design). In the latter case, the conveyor pulley and rotor are mounted on the same long shaft. These special bearing configurations are preferred by some conveyor manufacturers to optimize the overall system. Reducing the number of bearings helps to increase reliability, but it can only be done if the conveyor itself is sufficiently robust and installed on a strong base.

Frame — The motor frame can be tailored for easier transportation in tunnels and other areas where space is restricted. This requires the motor manufacturer to calculate material strengths and ensure that the modifications are made safely without compromising the strength of the frame in critical areas.

Mounting — Motor mounting arrangements are designed on a case-by-case basis. One advantage of large synchronous motors over induction motors is that their larger air gap makes them more tolerant of rotor movement.

Protection Class — Ingress protection class (IP) is important in conveyor motors because mines are typically dusty, humid and corrosive environments. In synchronous motors with IP55 class, air entering the motor is filtered, and the frame is designed to avoid leaving any openings where unfiltered air could enter. A high IP class makes cleaning the external surface easier, with no risk of dirt being washed inside the housing and damaging the motor.

Excitation — Excitation for conveyor motors is usually supplied by direct current taken from the conveyor systems variable speed drives. The DC is fed to the rotor via brushes and slip rings, components that are sensitive to environmental conditions. The motor manufacturer should optimize the choice of brush material to ensure that brush wear is consistent and stable and that replacement needs can be anticipated well in advance.

Logistics and assembly should also be taken into account at the motor design stage. Transportation of large equipment items like motors involves special arrangements, particularly if the mine is in a remote location with limited access. This can be solved by transporting the rotor and stator separately to reduce the weight of the individual packages. Other items can also be designed to be removable to help with transportation.

Heavy-duty conveyor motors play a crucial role in any mines operations. It's important to choose the right motor manufacturer to partner with you on your system design and performance. The right partner should be capable of providing a customized motor for your system along with predictive maintenance and remote monitoring capabilities to ensure reliability and uptime.