Field Control Type Current Regulator for Electromagnets

A system is described for regulating current in electromagnets of more than 1 H inductance and requiring more than 50 kW of power. Current stability of better than 1 part in 50,000 has been realized using this system with the main magnet coils of the Argonne 60-inch cyclotron. Design is based on the classical approach in which current through the generator load is controlled by the current through its field rather than the presently popular use of series transistor design.It incorporates advantages of developments in the fields of feedback control and solid state devices to provide a simple, reliable and flexible system. During startup, to minimize overshoot and consequent hysteresis effects, a voltage loop is used for control. For precise, long term regulation, a current loop is added in which the current through the magnet is controlled by a pre-set current reference signal or a magnetic field reference signal obtained from a nuclear magnetic resonance probe.