Abstract:
The fundamental frequency power factor is improved and a practical reduction in significant harmonic current is made in electrical power systems where the power to the load is controlled by a non-linear device, such as a saturable reactor, by using series inductive-capacitive filters to filter the significant harmonic current to act as a shunt for harmonic current in conjunction with a supply line inductive reactance. The resonant frequency of each filter is less than the frequency of the harmonic current and the impedance of each said inductivecapacitive filter is a net inductive reactance. The capacitive element of the filter provides a leading power factor component to compensate for the lagging power factor component imposed on the supply system by the non-linear control device.
Abstract:
Incipient failure of a capacitor operating as a part of an induction furnace circuit is detected by monitoring the capacitor to determine the presence of high-frequency signals generated by the capacitor as its dielectric material deteriorates. The lower limit of the frequencies of such signals is in the range from 50 to 200 kHz. The sensing apparatus for a 3 kHz induction heating circuit includes detector means for converting the generated signals exceeding about 150 kHz into a control signal whose level exceeds a predetermined value when the generated signals are representative of incipient deterioration of the dielectric. Indicator means responsive to the control signal is operated when the latter signal exceeds said predetermined value, and may disconnect power from the capacitor.
Abstract:
THE ABILITY OF A CORELESS INDUCTION FURNACE TO MELT FINE PARTICLES IS ENHANCED BY PROVIDING A LOWER SINGEL PHASE COIL WHICH SUPPLIES MELTING CURRENTS AND AN UPPER POLYPHASE COIL WHICH STIRS THE MOLTEN METAL SO AS TO LIFT THE OUTER RIM OF MOLTEN METAL ADJACENT THE SURFACE.
Abstract:
Sections of an induction heating coil are connected in parallel with sections of a shunt coil so that the section to section impedance of the unit differs. Accordingly, the amount of heat power applied to sections of a metal object by the heating coil is varied according to a predetermined pattern. Electric power applied to the entire shunt coil and heating coil unit is lowered over a period of time to cool the metal object progressively along a geometrical axis.