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Pulse Charging Transformers

In a repetitive power conditioning system it is often necessary to transfer energy from one capacitor to another at a different voltage level. This resonant energy transfer can be accomplished using a pulse transformer. The unit shown is used to transfer the energy from a 3 µF capacitor at 112.5 kV to a 13 nF capacitor at 1.5 MV. The pulse repetition rate is 0.2 Hz; much higher repetition rates are possible. The smaller transformer is a 175 kV trigger transformer with a 120 nsec rise time.

This transformer is used in the doubling project (SLED) at Stanford Linear Accelerator Center (SLAC). The unit is rated at 270 Kilovolts, 75 megawatts, for a 7 microsecond pulse. By using precision winding and construction techniques it was possible to limit the rise time to 0.5 microseconds (10-90), while maintaining less than 0.15% p-p flat top ripple. The tapered (constant gradient) secondary windings limit the leakage inductance to almost half of what it would be with the conventional construction. This also helps reduce the pulse rise time. The overall size of the unit is minimized and the efficiency is improved by DC resetting of the core. The bifilar secondary winding feeds heater power to the klystron.

Klystron/Gun Pulse Transformers

This unit supplies beam power to a klystron tube and pulse voltage to an electron gun. It is rated at 100 kilovolts, 6 megawatts, for an 8 microsecond pulse, 1000 pulses per second. The transformer is designed for immersion in transformer oil in the customer’s tank. The gun voltage of 70 kilovolts is provided by a tap in the secondary winding. This method of tapping the transformer is considerably less expensive than suppling pulse voltage to the electron gun by the use of a separate gun pulse transformer. In addition, the rise time of the gun voltage is decreased by the relatively lower impedance klystron, rather than by an energy-consuming dummy load across the gun.

Magnetron/Gun Pulse Transformer Assemblies

We have developed design techniques for magnetron pulse transformers which drastically reduce the ripple on the current pulse. The tanked pulse transformer shown here is used to supply beam power to a magnetron and pulse voltage to an electron gun. The unit is rated at 45 kilovolts, 4.5 megawatts, for a 3.5 microsecond pulse. The secondary winding is quadrufilar, and feeds heater power to both the magnetron and the gun. Included in the tank is a magnetron current monitor and bypass capacitors. The unit may be rotated and operated in any position.

Tanked Pulse Transformer Assemblies

This unit consists of a pulse transformer, heater   transformer, bypass capacitors, de-spiking network, current monitor, voltage monitor, klystron socket, and water cooling system. All components are mounted in a two-compartment oil tank. The tank has provisions for mounting of the klystron and the solenoid, and may be rotated and operated in any position. The pulse transformer is rated at 125 kilovolts, 11 megawatts, for a 6 microsecond pulse. The 250 watt klystron heater power is fed through the bifilar secondary winding.

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