  The minimal set of thermodynamic control parameters consists of a statistical
(thermal) and a mechanical one. These suffice to introduce all the pertinent
thermodynamic variables; thermodynamic processes can then be defined as paths
on this 2-dimensional control plane. Putting aside coherence we show that for a
large class of quantum objects with discrete spectra and for the cycles
considered the Carnot efficiency applies as a universal upper bound. In the
dynamic (finite time) regime renormalized thermodynamic variables allow to
include non-equilibrium phenomena in a systematic way. The machine function
ceases to exist in the large speed limit; the way, in which this limit is
reached, depends on the type of cycle considered.
