WEG has unveiled its new M Mining series of slip-ring motors that, it says, are intended for dusty environments in the iron ore or cement sectors.
Available in frame sizes IEC 355 to IEC 1000, the new M Mining slip-ring motors cover the power range from 250 kW-10 MW at 50 Hz or 60 Hz line frequency. These three-phase induction motors are between four and 14 poles and designed for voltages up to 13.8 kV, making them a reliable choice for mills, crushers, blowers, exhaust fans, conveyors, centrifuges, and other applications in the mining and cement industries, it said.
Andreas Schulte Mesum, Director European High Voltage Solutions, based at WEG Germany GmbH, said: “Their performance and robustness make the new M Mining series of motors, with their high IP rating, steel casing and two different brush systems, an excellent choice for applications in the mining and cement industries. The design is based on specific electromechanical properties that offer long life and high stability.”
The wound rotors of slip ring motors allow them to achieve high starting torques along with low start-up current. In contrast to squirrel-cage motors, the windings are connected to three slip rings to allow a variable resistance to be inserted in the rotor circuit. This has several major benefits for users including higher rotor circuit resistance to improve the motor’s start-up characteristics; the motor starting current and rated current are close to the same; and loads with high starting torque can be driven, as well as loads with high inertia. Further advantages include higher efficiency and simple installation, WEG said.
The new motor series has a brush compartment with a new design and transparent window for inspection and access. Commissioning is aided by combining the motor with a fully integrated control panel as an option, according to the company. At the same time, operating and maintenance costs are reduced and plant availability is increased.
The motor series is available in two versions: either with a brush lifting device, or with brushes in constant contact. “The lifting mechanism of the brush lifting device has been redesigned to make it even easier to maintain,” WEG said. “Compared to the version with fixed brushes, the brush lifting system requires less maintenance. In addition, brush wear is reduced by fitted pressure springs. An integrated control system is also available as an option for the brush lifting device.”
With its innovative design and new insulation arrangement, the system offers other advantages.
“For example, the cooling system of the brush compartment is independent of the motor cooling system, further boosting the efficiency,” WEG said. “The extended lifetime of the brushes is one of the main advantages, but user access to the brush compartment is also significantly easier with this version. The brush compartment achieves an IP rating of up to IP66.”
The M Mining motors are available with protection ratings from IP55 to IP66. They are also protected by WEG paint systems that enable operation in abrasive and humid environments with atmospheric sulphur dioxide.