A thyristor starter for starting a synchronous machine, comprising: a converter that converts AC power into DC power; a DC reactor that smoothes the DC power; and an inverter that converts the DC power applied from the converter through the DC reactor into AC power with a variable frequency and supplies the AC power to the synchronous machine, wherein the thyristor starter is configured to accelerate the synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode and a second mode, the first mode performing commutation of the inverter by intermittently setting DC output current of the converter to zero, the second mode performing commutation of the inverter by induced voltage of the synchronous machine, characterized in that the thyristor starter is further configured to change a switching rotation speed for switching from the first mode to the second mode in accordance with an inductance of the synchronous machine, wherein the inductance is an inductance of each of the armature windings of the synchronous machine, wherein in a first case in which a first synchronous machine having a first inductance is the synchronous machine, the thyristor starter is configured to set the switching rotation speed to a first rotation speed, wherein the first inductance is an inductance of each of the armature windings of the first synchronous machine, whereas in a second case in which a second synchronous machine having a second inductance larger than the first inductance is the synchronous machine, the thyristor starter is configured to set the switching rotation speed to a second rotation speed lower than the first rotation speed, wherein the second inductance is an inductance of each of the armature windings of the second synchronous machine. a converter that converts AC power into DC power; a DC reactor that smoothes the DC power; and an inverter that converts the DC power applied from the converter through the DC reactor into AC power with a variable frequency and supplies the AC power to the synchronous machine, wherein the thyristor starter is configured to accelerate the synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode and a second mode, the first mode performing commutation of the inverter by intermittently setting DC output current of the converter to zero, the second mode performing commutation of the inverter by induced voltage of the synchronous machine, characterized in that the thyristor starter is further configured to change a switching rotation speed for switching from the first mode to the second mode in accordance with an inductance of the synchronous machine, wherein the inductance is an inductance of each of the armature windings of the synchronous machine, wherein in a first case in which a first synchronous machine having a first inductance is the synchronous machine, the thyristor starter is configured to set the switching rotation speed to a first rotation speed, wherein the first inductance is an inductance of each of the armature windings of the first synchronous machine, whereas in a second case in which a second synchronous machine having a second inductance larger than the first inductance is the synchronous machine, the thyristor starter is configured to set the switching rotation speed to a second rotation speed lower than the first rotation speed, wherein the second inductance is an inductance of each of the armature windings of the second synchronous machine.