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DC current unbalance in the windings of a transformer may initiate a runaway process and ultimately drive the transformer into saturation. Such a situation could arise in a transformer coupled resonant converter that does not include a series capacitor. This issue was explored in this study theoretically, by simulation and experimentally. A method is proposed for automatically adjusting the transformer's DC current to zero by correcting the asymmetry of the drive. This balancing control is facilitated by a signal obtained from a DC/AC current sensor which senses the transformer's primary and secondary currents such that they cancel each other for the no DC case. The proposed method was tested on a self oscillating, parallel loaded DC-DC resonant converter of 12V input voltage 500V output voltage and 700W power level. The proposed approach allows the design of resonant converters without DC decoupling capacitors which could lead to a significant cost and size reduction.

The achievable gain in magnetic mirrors fusion machines is limited by particles and energy flux through the mirrors. The moving multiple mirrors (MMM) concept is based on many mirror coils at each end of the trap, synchronized in sequence to generate magnetic mirror that moves towards the centre of the trap. Particles escaping from the main cell are scattered out of the loss-cone in the MMM sections and propelled back inside by the magnetic wave. Analytical optimization of the MMM parameters for a conceptual fusion mirror machine, suggests that gain >>1 can be obtained with reasonable voltage, current and power dissipation in the MMM driving system. We present the design of an experimental system aiming to explore the MMM concept and demonstrate orders of magnitude reduction in axial plasma flux.

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