LSSM = Low Speed Synchronous Motor Drive Operation

LSSM SAG Mill Motor
low speed synchronous motor drive in operation

In the world of mining and milling the “electrical term” LSSM stands for “Low Speed Synchronous Motor” and usually means a mill where the motor rated speed is in the range of 10 RPM, the same speed as the mill turns.  A high speed motor can run at 900 RPM and uses a gearbox to turn down the speed. A medium speed motor runs in the range of 100 RPM and uses the gear ratio of the pinion and mill ring-gear to step down the speed.

GMD Gearless mills are always variable speed. The incoming electrical supply voltage has a frequency of 50-60 Hz (3000 – 3600 RPM) that must be stepped down to control the input frequency of the low speed motor (10 RPM). The only way that is done on a modern mill is with a cycloconverter which is also a variable speed control mechanism.

A variable speed mill driven by a LSSM motor would have a cycloconverter (variable speed drive) ahead of it in the electrical network.

Also note that a motor with a reducer is much less efficient that the LSSM that is directly driving the mill.

Low Speed Synchronous Motor Drive Operation

The video below helps explain.

 

Overview on the grinding mills and their dual pinion mill drives