Synchronous.

Basic synchros and servomechanisms Valkenburgh, Van 1978 Constant-voltage transmission Dwight, Herbert Bristol 1915 Permanent magnet synchronous and brushless DC motor drives Krishnan, R. 2010 Power system dynamics and stability Sauer, Peter W. 2018 Reluctance Synchronous Machines and Drives Boldea, I. 1996 Synchronous machines and D. C. Motors Murthy, A. S. Aravinda 2011 The performance and design of alternating current machines Say, M. G. 1958 The performance and design of alternating current machines; transformers, three-phase induction motors and synchronous machines Say, M. G. 1958