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Simulation of Ferroresonant Transformers

IP.com Disclosure Number: IPCOM000075204D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 4 page(s) / 102K

Publishing Venue

IBM

Related People

Hendrickson, KE: AUTHOR

Abstract

F1 and F2 in Fig. 1 are primary and secondary fluxes of the transformer and initially both are assumed to be zero. The steps shown in Fig. 1 are then carried out using physical dimensions, winding turns and resistance permeability curves for the lamination material, resonant and filter capacitor parameters and load. One of the steps includes computing loop fluxes F1 and F2 and feeding back these computed loop fluxes to again carry out the steps with the new flux values. By repetitively calculating the time rate change in flux and integrating, new flux values are generated for a period of time corresponding to the condition being simulated; i.e., transient conditions, steady state conditions, power line disturbance conditions, etc.

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Simulation of Ferroresonant Transformers

F1 and F2 in Fig. 1 are primary and secondary fluxes of the transformer and initially both are assumed to be zero. The steps shown in Fig. 1 are then carried out using physical dimensions, winding turns and resistance permeability curves for the lamination material, resonant and filter capacitor parameters and load. One of the steps includes computing loop fluxes F1 and F2 and feeding back these computed loop fluxes to again carry out the steps with the new flux values. By repetitively calculating the time rate change in flux and integrating, new flux values are generated for a period of time corresponding to the condition being simulated; i.e., transient conditions, steady state conditions, power line disturbance conditions, etc.

The reluctances are calculated for each time step using permeability curves and computed flux densities. These reluctances, the fluxes F1 and F2, and the secondary winding current IS, are used to calculate the currents IR and IP. The current IS is initially assumed to be zero. These currents, and the values of primary voltage and resonant capacitor voltage (obtained by integration of IR), are used to calculate the resonant and primary winding voltages.

These are equal to the rate of change of flux linkage in the coils which may be integrated to find the fluxes F1 and F2. Since the secondary windings and resonant windings are on the same structure, the voltage induced in the secondary windings is calculated knowing the resonant winding voltage and the turns ratio. The secondary current and rectified output voltage is calculated from the secondary winding voltage.

There is no limit on the number of output voltage windings because to simulate a multiple output ferro, there will be several terms in place of the NS.IS term in the calculation of IR. The calculation of secondary winding voltages and output voltages is done for each output just as it was for IS.

A lumped magnetic parameter model of the transformer is formed as in Fig.
2. The R's (R101, 102, etc.) are reluctances, the generators G1, G2, G3 are magnetomotive force sources which represent ampere turns in the transformer windings. F1 and F2 are the loop fluxes.

The reluctances of R101, R102, etc. correspond to the magnetic path branches L10l, L102, etc. of the transformer cross section in Fig. 3. Symmetry allows analyzing one-half of the transformer. Each reluctance is given by R = L over MU.W.T.SF where

L = Average path length in the branch

W = Width of the branch

T = Thickness of the branch

MU = Average permeability of the branch

SF = Stacking Factor.

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