Defines efficiency classes for single-speed, three-phase, 50 Hz and 60 Hz, cage-induction motors that: - have a rated voltage UN up to 1000 V; - have a rated output PN between 0,75 kW and 375 kW; - have either 2, 4 or 6 poles; - are rated on the basis of either duty type S1 (continuous duty) or S3 (intermittent periodic duty) with a rated cyclic duration factor of 80% or higher; - are capable of operating direct on-line; - are rated for operating conditions in accordance with IEC 60034-1, Clause 6.