Power Electronics Controlled DC Drive for Geophysical Earth Magnet Field Reversal Simulation

A power electronics fed DC motor is controlled on a given constant speed and drives a generator with both series and auxiliary external excitation. The induced voltage at generator yields a DC current caused by load resistor. That current also is the main source for generator excitation holding the generator in stable steady state operation in connection with hysteresis in magnetic circuit. If we apply a small current in the auxiliary external excitation of generator we produce either a filed-increasing or a field-decrceasing component in magnetic field. A constant small counter-excitation will reduce the field until it gets zero. If this small counter-excitation is present for all the time we will reverse the field and finally establish a field in counter direction. At opposite polarity of current and field we reach again a condition stabilized by magnetic saturation at the generator. The established system is small-scale model of earth magnetic field described by geodynamic generator. This implies the existence of enormous currents in the core of the earth which cause the magnetic field in the range of about 1 milliTesla on earth surface. The small external current in the model has its, equivalent in the stream of charged particles emitted by the sun. The effect of magnetic field reversal in the 1 kW - model can be viewed by several display units over some seconds rather than millions years in reality.