Development of high efficiency and crowbar switchless dc power supply for 1 MW CW CPD gyrotron

A high efficiency and high power de main power supply for the collector pot ential depression (CPD) gyrotron was developed and operated successfully wi th a real CPD gyrotron. The capacity of the power supply is 5 MW, 100 kV ou tput voltage and 50 A maximum current, adopting a de 100 kV IGBT switch for Fast switching and a pair of 3-phase ac thyristor switches for de output v oltage control. The IGBT switch consists of 100 insulated gate bipolar tran sistors (IGBTs) connected in series. The switch can protect the CPD gyrotro n by fast switching which achieves input energy below 10J and has first tur n-on performance within 10 mu s. The ac thyristor switch controls the outpu t voltage of the power supply using feedback control and feedforward contro l, so as to regulate the voltage in the case of load transition from no loa d to rated load at the IGBT switch turn-on timing. The combination of feedb ack and feedforward controls enables us to maintain the voltage stability o f the main power supply between -1.0% and +3%. As the power supply does not include any heavy dissipation element such as a series regulator, its effi ciency achieves more than 95%.