WEG creates a new series of slip-ring motors

Jon Lawson

WEG has launched a new M (for mining) series of slip ring motors. Available in frame sizes IEC 355 to IEC 1000, the new motors cover the power range from 250 kW to 10 MW at 50 Hz or 60 Hz line frequency. These three-phase induction units have between 4 and 14 poles and are designed for voltages up to 13.8 kV. It is intended for dusty environments in the iron ore or cement sectors, like for mills, crushers, blowers, exhaust fans, conveyors and centrifuges.

Why do wound rotors allow such high starting torques?

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 that allow a variable resistance to be inserted in the rotor circuit. This has several major benefits for users including higher rotor circuit resistance which allows the motor's start-up characteristics to be improved. Further advantages include higher efficiency and simple installation.

The new motor series has a brush compartment with a completely new design and a transparent window for inspection and access. Commissioning is simplified by combining the motor with a fully integrated control panel as an option. 

Choice of two different brush systems

The motor series is available in two versions: either with a brush lifting device, or with brushes in constant contact. 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.

The 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.