Abstract: Method to control the power supply for electric arc furnaces, whether they be fed with AC or DC, the furnaces including a melting cycle which includes the loading of the scrap carried out at time T.sub.0, an initial step of pre-melting the scrap with low and average power with a duration of (T.sub.1 -T.sub.0), a step of melting at maximum power with a duration of (T.sub.2 -T.sub.1) and a refining step with a duration of (T.sub.3 -T.sub.2), the method including the dynamic identification of the approximate moment when situations of risk inside the furnace cease, with a consequent permission to start delivery of maximum power, the dynamic identification being governed by the control and analysis of the electrical quantities, tension and current, fed to the furnace.

Abstract: A device for controlling the level in a container of a liquid which will emit infra-red rays and particularly molten metal is described. The device comprises a housing, at least one longitudinal window at one end of the housing and arranged so that when in use it will overlook an edge of a container containing the liquid, the level of which is to be controlled; and at least one photo-element for sending out an electrical signal through said window to said liquid; at least one second window which is substantially punctiform and which overlooks a substantially constant portion of the liquid in the container and within the vertical field of adjustment; and a second photo-element in cooperation with the second window for sending out a pilot signal, and circuitry to correct the signal indicating the liquid level of the container by means of the pilot signal and for amplifying and comparing the signal coming from the correction circuit.