An apparatus for controlling a turbogenerator system when a power electronics circuit of the turbogenerator system is unable to provide a sufficient load on the turbogenerator to prevent the turbogenerator from accelerating uncontrollably is described. The apparatus comprises a monitor including a first sensing device operable to detect a condition of the turbogenerator, and a brake controller responsive to a turbogenerator detection output from the first sensing device to issue a first brake control signal for operating a brake circuit to prevent the turbogenerator from accelerating uncontrollably and a second brake control signal for operating the brake circuit to permit resumption of normal operation of the turbogenerator.