Device for adjusting the tripping threshold of a multipole circuit breaker

A device for adjusting a tripping threshold of a multipole circuit breaker including an insulating casing having a first orifice, said device comprising:

• a magnetic circuit including a fixed core and an excitation coil;
• a plunger spaced apart via an air-gap from said fixed core, the air-gap defining the tripping threshold of the circuit breaker;
• an operating component secured to the plunger to position the plunger with respect to the fixed core, said operating component including a ramp;
• return means for biasing the plunger to be separated from the fixed core;
• adjustment means for finely adjusting the air-gap between the plunger and the fixed core, including a rotary knob which drives a positioning stud along the ramp of the operating component to set the air-gap, said rotary knob extending through the first orifice in the insulating case;
• setting means for setting a maximum tripping threshold of the circuit breaker, including an annular ring having a central orifice in which said rotary knob is disposed, said annular ring including a protuberance which forms an end-of-travel stop to prevent rotational movement of the rotary knob;
• a top cover plate covering the insulating casing, the top cover plate including an opening over said rotary knob to allow access thereto;
• and
• preventative resetting means for preventing resetting of the maximum tripping threshold when said top cover plate is positioned on the insulating casing, wherein the opening of the top cover plate has a diameter less than a diameter of the annular ring.