Downhole torque generator

摘要

A torque-generating apparatus includes a first assembly ( 10, 25 ) including a generally cylindrical member of magnetically soft material and having a longitudinal axis and a second assembly ( 2 ) arranged coaxially within the first assembly and including an electromagnetic winding ( 4 ). The first assembly ( 10, 25 ) and the second assembly ( 2 ) are rotatable relative to each other about the axis. Relative rotation between the first ( 10, 25 ) and second ( 2 ) assemblies induces a magnetic field which generates rotational torque between the first and second assemblies.