A New Energy Recovering DeQing for Line-Type Pulse Modulators

In a typical line-type modulator the amplitude of the pulse forming network (PFN) voltage is controlled by a deQing circuit (resistor or resistor and capacitor in parallel, and SCR), connected to the secondary of the charging choke. The energy stored in the charging choke at the moment of deQing is usually dissipated in the deQing resistor. For the SLAC modulator, for instance, the typical value of average power dissipated in this resistor is 5-10 kW. At the moment there is only the SLAC energy recovering deQing system, which is based on accumulation of the deQing energy into a capacitor bank, from where it is then transferred by inverter to the main ac line. This paper describes a new simple energy recovering deQing system. Other than the SLAC deQing system, the energy accumulated in the storage capacitor bank during a current PFN charging cycle is being transferred directly into the PFN capacitors, before the following charging cycle is started. The preliminary low-voltage model investigation shows that this scheme, besides reduction of the power consumption and elimination of the powerful deQing resistor along with it’s cooling system, allows to increase the level of deQing and insures a stable modulator output voltage over a wide range of the main ac voltage.