Abstract: Induction heating apparatus, typically for metal melting, with multiple zone temperature control has an induction coil (10) divided into individual sections (10a, b, c) associated with respective zones and powered in parallel under regulation from controller (20) as shown in FIG. 1. To give precise and efficient automatic regulation of the zone temperatures the power supply is provided by a resonant invertor (14) as a medium frequency pulsed output and at an instantaneously selected level which is the sum of the power requirements of all the zones at any instant, and the average power applied in each zone is controlled by pulse width modulation with switching to high power for a proportion, determined by demand in that zone, of each of successive standard time periods.

Abstract: Induction heating apparatus, e.g. for melting, has induction coil sections, each associated with a respective zone of the melt or other work load, the power applied to each section from a supply being controlled individually through a saturable reactor respective to each section and each operable to shunt a proportion of power applicable in that section in response to regulation of excitation of the respective reactor related to a demand signal derived from the operation of the respective zone, so that the temperature in each zone is regulated independently of the regulation of the other zone(s).

Abstract: An induction melting apparatus including a vessel for holding a melt of molten metal, an induction coil operatively associated with the vessel, and a power supply for providing power input to the induction coil. The power input has a melting component at a first preselected frequency for operatively holding the melt at a preselected temperature by induction heating and an agitation component at a second preselected and different frequency for agitation of the melt by inducing turbulence therein. The power supply comprises an agitation power supply circuit operatively supplying current to the coil at the second frequency, and a melting power supply circuit including a series resonant circuit through which the melting component is operatively applied to the coil at the first frequency at the same time as the agitation component is applied to the coil.

Abstract: Method of and apparatus for providing agitation of the melt in the induction melting of metals. A medium frequency melting power supply (12) of an induction furnace or crucible (10) acts in conjunction with a modulating circuit incorporating a wave form generator (14) whereby modulation at predetermined amplitude and frequency is applied to the furnace power frequency during at least part of the melt processing cycle to cause agitation of the melt to a predetermined extent independently of the selected overall power input.

Abstract: Method of and apparatus for providing agitation of the melt in the induction melting of metals. A medium frequency melting power supply (12) of an induction furnace or crucible (10) acts in conjunction with a modulating circuit incorporating a wave form generator (14) whereby modulation at a predetermined amplitude and frequency is applied to the furnace power frequency during at least part of the melt processing cycle to cause agitation of the melt to a predetermined extent independently of the selected overall power input.