Abstract: A capacitor precharge circuit limits both peak DC link current and peak AC line current to any desired peak magnitude thereby providing for optimum precharge control and robust operation. The precharge circuit employs a microprocessor which implements a non-linear discontinuous current control scheme without the need for current sensors. The precharge circuit is well suited for use with an AC to DC converter having link inductor and a DC bus capacitor which requires precharging before full power is applied to the converter.

Abstract: A harmonic compensator comprises a transformer having low leakage reactance connected between a utility and a load and a signal generator which injects into the transformer a signal having a frequency which cancels undesirable higher order harmonics induced by the load. The low leakage reactance nature of the transformer permits injection of high frequency signals which restore the fundamental sine wave of the signal from the utility and thereby eliminates undesirable nonlinear harmonics which cause up-line disruptions. The low leakage reactance transformers may comprise a coaxial structure having a thin hollow tube as the primary coil, a coaxial structure having a single main coaxial cable distributed into several paralleled coaxial cables of smaller diameter, or a co-planar transformer structure having flat strip line conductors wrapped around a conventional core as the primary and secondary coils.