Brazil’s WEG installs SAG and ball mill slip ring motors at Polyus Gold’s Natalka mine in Russia’s Magadan region

Global mining drives major WEG via its Russian Commercial Operation WRU has completed a major project for customer PJSC Polyus Gold at its Natalka mine in the Magadan Region. The scope of supply included a pair of slip ring motors of 9,000 kW at 1,000 rpm and another two motors of 7,500 kW also at 1,000 rpm and fully designed to be interchangeable with the old existing motors providing a smooth drop-in replacement. The motors are being applied in pairs to SAG and ball mills that operate through dual pinion drives supplying power to each mill.

Historically, WEG says the customer was facing problems for a number of different reasons such as mechanical fits, overheating of antifriction bearings and electrical overload events. “The WEG team evaluated different options in order to offer the most reliable product. A robust design of slip ring rotor motors was recommended including reliable features such as fixed or liftable brushes, internal or external slip ring chamber and different series of sleeve bearings or antifriction bearing in oil bath. The final design was approved after customer inspection at WEG headquarters facilities in Brazil and a technical visit to a cooper mine in Chile where similar WEG motors are successfully operating. A key factor for this project was the local WEG specialists in the market providing fast response to the customer and listening carefully to the customer needs.”

The WEG Slip Ring Mining motors were designed in such a way to allow another technical key factor for this project where  they can operate both as a slip ring motor or as an induction motor fed by inverter when the temperature is very cold (-50°C) and the ore inside the mills gets frozen and then the mills speed can be automatically controlled. The electric motors were delivered in July 2020. Due to sanitary restrictions, the commissioning was postponed to December and work was carried out from November 15 to December 23, 2020.  The target for Natalka is 1,200 t of ore per hour and the average in 2019 was 1,400 t per hour – in the fourth quarter 2020, hourly productivity was usually exceeding 1,500 t.