CHAPTER 10. LEACHING OF MINERAL AND GLASS SURFACES DURING DISSOLUTION

A control system suitable for rendering an inverter circuit nonoperative in response to an undesirable load condition. In an SCR inverter circuit during the portion of the anode voltage cycle, when the SCR is normally nonconductive, the magnitudes of a first portion and a second portion of the voltage waveform appearing at the SCR are sensed. In response to the magnitude of the first portion being substantially equal to or greater than a predetermined percentage of the magnitude of the second portion of the waveform, a sense circuit enables a disabling circuit which renders the gating circuit nonoperative, whereby the SCR is not turned on. A timing circuit, responsive to the disabling circuit, deactivates the disabling circuit after a predetermined interval for enabling the gating circuit so that the load condition can be sampled. If the magnitude of the first portion of the sampled waveform remains greater than the magnitude of the second portion, the disabling circuit is once again enabled. The described testing cycle is repeated until such time as the magnitude of the first portion of the sample voltage waveform decreases below a predetermined percentage of the magnitude of the second portion of the waveform and the disabling circuit is inactivated, thereby rendering the gating circuit operative once more. Thus, the inverter circuit is returned to normal operation. A lock-out circuit, responsive only to the magnitude of the second portion of the voltage waveform appearing at the SCR increasing beyond a predetermined limit, is disclosed for also rendering the inverter circuit nonoperative.