Apparatus and method for controlling power supply to an inductive load, such as a furnace.

摘要

An apparatus for controlling the power supplied to an inductive load, such as an induction furnace, by an inverter power supply having switch means for generating an alternating polarity voltage across a load comprises means (120) for monitoring the current (100) in the load and generating a signal (102) representative of zero crossings of the load current, and means for controlling the operation of the power supply switch means in response to said signal. The control system preferably includes automatic control with a manual override for emergency situations. The system in one embodiment includes means for monitoring the power delivered to the load and means for varying the power delivered to the induction load by controlling the phase difference between voltage and current delivered to the load. Feedback means automatically control the phase difference between voltage and current in response to the measured power delivered to the load. Means are further provided for introducing an external signal into the feedback means, whereby the external signal supersedes the automatic control of the power delivered to the load. <IMAGE>