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To miniaturize a very low level dc current amplifier and to improve its output response speed, the switched capacitor negative feedback circuit (SCNF), instead of the conventionally used high-ohmage resistor, is presented in this paper. In our system, a switched capacitor filter (SCF) and an offset controller are also used to decrease vibrations and offset voltage at the output of the amplifier using SCNF. The theoretical output voltage of the very low level dc current amplifier using SCNF is obtained. The experimental results show that the unnecessary components of the amplifier’s output are much decreased, and that the response speed of the amplifier with both the SCNF and SCF is faster than that using high-ohmage resistor.
A novel high-power-factor Buck type converter with
average current control based on UC 3854 is proposed. The input current is
directly controlled by average current control scheme to deliver sinusoidal
input current and to gain a high power factor. The practical results, which
illustrate the proposed control philosophy, were obtained from a 120 W AC/DC
Buck type converter. The power factor can reach 0.97.
Transformer winding deformation？is
one of the main types of transformer faults.
To check if a power transformer is being under winding deformation, the
transformer can be connected in a current transformer during its testing. A
transformer winding simulating model is set up under this connecting manner.
Then the simulation has been performed with？current source which is
the frequency sweep power. The simulation results show that the winding
deformation can be reflected effectively with current
method lays the foundation for the realization of on-line monitoring and
diagnosis of the transformer
neutral directly grounded side winding.