Methods of Computing the Time Constant and Impedance of Magnets

For regulation and ripple studies of dc magnets, the essential parameters which must be known as a function of dc magnetization and/or frequency are the unit step time constant and impedance. An exact value for the unit steptime constant of a laminated or solid core magnet can only be obtained by measurement. It can, however, be estimated from the dc time constant which is easily computed from the magnet geometry, number of coil turns, and the coil resistance. Measured unit step time constants and computed dc time constants are given for a number of magnets. Formulas to compute the impedance of laminated core magnets are developed. An empirical formula for calculating the impedance of solid core magnets is deduced from test data.