Often power sources for electrophysical methods of processing play a major role in achievement of the necessary result. The electrochemistry, control of gas-discharge and arc processes adds up to introduction of the electric power with certain parameters. These parameters play a role of limiters of the entered energy. Sometimes it is enough to limit a voltage level on loading, but more often should limit power to more flexible methods. For example, at manual arc welding use special transformers for the purpose of creation of the volt ampere characteristic (VAC) of a source, necessary for steady burning of an arch. In the course of work parameters VAC do not change. The dynamic balance between the power source and an arch is reached.   Though these methods are simple and reliable, now use pulse regulators with the negative feedback (NFB). However, the method founded on use VAC of a source did not lose the relevance and can be applied at the new level to a number of tasks. For example, at dimensional electrochemical processing at big capacities with closed gaps between electrodes is necessary fast restriction of a short-circuit current. During the work with gas plasma there are difficulties of control of process at pinching of current in a homogeneous field. Process of a pinching happens so quickly, what it is almost not possible to prevent it by means of NFB and the regulator. Reaction to perturbation of a source from set VAC goes with a speed comparable to an overstrain on the inductor coil in which disconnected current.   Research of the resonant semi-bridge converter showed, that in the certain frequency range he behaves as the effective power limiter VAC close to the welding transformer for manual arc welding, that is with a big internal resistance of a source. Unlike the welding transformer, such converter is executed on the same element base and in the same frequency range, as all modern converters. Efficiency of a source same, as at the converter with pulse-width modulation. Tests of the developed model showed:   1. The source has the maximum power on the loading coordinated with it which is rated for it. 2. If resistance of loading is less rated, the power consumption of a source in proportion falls to a quarter of rated power at a short circuit. 3. If resistance of loading is more rated, then voltage output grows up to the tension of no-load operation, and power consumption reduces practically to zero. 4. Changing frequency, it is possible to change approval of loading, at the same time, the relation of a short-circuit current to rated current for any set frequency and parameters of power part will be constant.   In the power limiting mode the source is ideally suited for a capacitor charge, electrochemistry, for any loading when using the rectifier with the capacity filter. On alternating current all properties remain for the active loadings and complex loadings consisting of the parallel capacity and resistance. Additional benefits of this source which are in a study stage are had.