Short Pulse Tranformers

These special transformers are integrated critical sub-systems of High Voltage pulsed power generators (modulators). They can supply different types of loads like Radio Frequency amplifiers (magnetrons, klystrons), electrostatic plates for pulsed electric field generators, etc. for the following applications:

  • Scientific applications (e.g. particle accelerators)
  • Medical applications: Radiotherapy machines
  • Industrial and military applications (e.g. radars, cargo X-ray scanners, sterilization machinery, food processing, water treatment, etc.)

In order to comply with required fast rise times (few microseconds) and required pulse flat top accuracy (better than 0.1%) and reproducibility, the design of these transformers requires in depth knowledge of magnetic materials, finite element analysis and optimization algorithms aimed at maximizing efficiency while reducing volume and cost. Furthermore, modelling of parasitic elements like stray inductance and stray capacitances is essential. From a construction point of view, mechanical stiffness due to high electrodynamic forces and vibrations developed as well as precision of winding constitute the main challenges.

Short pulse transformer 3D model
Short pulse transformer 3D model
Short pulse transformer 3D model
Plot of the output pulse voltage including a zoom of the time the pulse reaches 99% of its peak value. 0-99% rise time is then 2.1 µs¨, within 5% of the value from the equations (2.0 µs)
Transformer has outer dimensions 12.6x16.7x35.3 cm Parameter table: V2 = 50 kV I2 = 100 A Pulse rise time = 2 µs Pulse length = 10 µs PRR = 50 Hz S (number of subcores) = 6 Secondary windings: 2, connected in parallel Primary windings: 12, each connected to independent power supply N2 (turns per secondary winding) = 160 N1 (turns per primary winding) = 23
Magnetostatics, short circuit: Leakage inductance verified to be within 20% of estimated value.
Magnetostatics, open circuit: Magnetic peak flux density ~1.2 T in straight sections
Electrostatics: Peak electrostatic field around 9 kV/mm at anti-corona rings (5 mm diameter).
Electrostatic field distribution 1
HV Pulse Transformer Prototype
HV Pulse Transformer Prototype First pulse at voltage 12.5kV in air insulation medium
Ch1 (Yellow): Primary voltage
Ch2 (Blue): Load voltage