US Patent 11277087 Thyristor starter

In a thyristor starter, an inverter converts DC power provided from a converter through a DC reactor into AC power having a variable frequency, and supplies the AC power to a synchronous machine. A controller controls the inverter based on a phase control angle. A voltage regulator regulates an induced voltage of the synchronous machine by supplying a field current to the synchronous machine. When a rotation speed of the synchronous machine exceeds a reference rotation speed during acceleration of the synchronous machine, the voltage regulator controls the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine. The controller decreases a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed.