The electric circuit for electroerosion machining comprises erosif discharge delivery means (1) and pre-ignition means (6-12). The pre-ignition means, provided with a transformer (6) and a Zener diode (3), comprise a clipper branch (11, 12) also with a Zener diode. In addition, power regulating means (14, 15, 22, 23, 24) are connected to limit the pre-ignition pulse current as a functionof the clipper current, measured by the voltage drop at the terminals of a resistance (12) in series with the clipper Zener diode (11). The arrangement of the pre-ignition means relates mainly to the control of electric and geometric parameters related to the pre-ignition and to the general operation of the machining unit.