Protected thyristor circuit for electromagnetic vibrator - monitors voltage across anti-parasitic coil to determine state of thyristor and vibrator

摘要

The thyristor circuit has parasitics eliminated by an anti-parasitic coil (2) and a capacitor (3) receiving a preliminary charge from an RC circuit (4,5). The voltage drop across the anit-parasitic coil ( 2) is used as a measure of the operating state of the thyristor (1) and the electromagnetic vibrator (6) supplied with a chopped DC current by the latter. Pref. this voltage drop is measured during the zero transitions of the current during each negative half cycle. Pref. also a capacitor (10) is charged via a transistor (9) and controls a second switching transistor (12) via a resistor (11), the output of the second transistor controlling a signalling or release element. The circuit protection has good reliability and is unaffected by external influences.