Abstract: A variable speed drive arrangement including: a load; a gearbox to supply mechanical drive to the load; a converter electrically coupled with a power grid. Also a primary electrical machine to supply mechanical power to the gearbox and to receive electrical power; and a secondary electrical machine mechanically coupled to the gearbox and electrically coupled to the converter. An electrical circuit breaker to selectively electrically couple the primary electrical machine to the secondary electrical machine or to the power grid; wherein the secondary electrical machine is adapted to supply or extract mechanical energy from the gearbox and to receive or deliver electrical energy to the converter. Also a control method for the arrangement including a starting mode and a running mode.

Abstract: A method of controlling an inverter, in which the inverter includes a single-phase inverter arrangement comprising a complementary pair of power switches, comprises the steps of: controlling the complementary pair of power switches with a modulating signal to output an AC signal; judging which of the power switches in the complementary pair of power switches is at a higher temperature; determining the magnitude and sign of a DC offset signal to apply to the modulating signal to reduce the total current in the power switch judged to be at the higher temperature; and applying the DC offset signal to the modulating signal.

Abstract: A variable speed drive arrangement including: a load; a gearbox to supply mechanical drive to the load; a converter electrically coupled with a power grid. Also a primary electrical machine to supply mechanical power to the gearbox and to receive electrical power; and a secondary electrical machine mechanically coupled to the gearbox and electrically coupled to the converter. An electrical circuit breaker to selectively electrically couple the primary electrical machine to the secondary electrical machine or to the power grid; wherein the secondary electrical machine is adapted to supply or extract mechanical energy from the gearbox and to receive or deliver electrical energy to the converter. Also a control method for the arrangement including a starting mode and a running mode.