Abstract: The trip device with an electronic processing unit which gives a tripping order in terms of the rms value of the current measured by current transformers and of the threshold and time delay setpoints. The non-linearity of response of the current transformers is corrected by a device which modifies the current, threshold, or time delay values. These corrected values enable precise trippings to be achieved in compliance with the values of the current flowing in the circuit breaker. The type of correction is adapted to the circuit breaker rating by parameters obtained by tests and previously stored in a device.

Abstract: The interface card fixedly secured to the circuit breaker supplies information representative of the circuit breaker type and rating to a standard removable trip device. It comprises for example resistances designed to be connected in parallel to a resistance of a divider bridge defining in the trip device the instantaneous tripping threshold, modifying this threshold automatically according to the circuit breaker type and rating. The interface card can also supply the trip device with information representative of the rated current flowing in the primary winding of the current transformers fixedly secured to the circuit breaker.

Abstract: The passive components of the analog channel of the trip device are achieved by serigraphy on a thick layered hybrid circuit. Adjustment, by laser, of the value of an offset voltage compensating resistance and of a measuring resistance enables the offset voltage and gain of the channel to be adjusted with precision.

Abstract: The front panel of the trip device is formed by a flat screen display, for example liquid crystal, controlled by the trip device microprocessor. The display provides a permanent display of the information relating to the type of trip device, the tripping parameters and measured values, from data entered in the trip device memory. Display is in alphanumeric and/or graphic form.

Abstract: The short time delay circuit comprises a counter which is zero reset when the signal representative of the current is greater than or equal to a threshold, and controls count-down of an up-down counter, when the content of the counter reaches a preset value. A clock circuit controls the count-up and count-down frequency of the counter and up-down counter.

Abstract: The solid-state trip device of a protective circuit breaker of a three-phase mains system comprises a fault type detection circuit comparing the currents flowing in the mains system conductors with a first threshold and a second threshold, higher than the first one. It supplies a signal representative of a certain type of fault, single-phase or two series pole, when a first number of currents are lower than the first threshold and a second number of currents are higher than the second threshold.

Abstract: The measuring device of the rms value of a signal comprises, in series, a full-wave rectifier, a low-pass filter, for example of the RC type, and a peak detector. The output signal of the device is representative of the rms value of the input signal, the cut-off frequency of the filter corresponding to an angular frequency comprised between 4.pi.f/6 and 4.pi.f/5.33, f being the fundamental frequency of the input signal of the device.

Abstract: A test circuit simulates the operation of a multipole electrical circuit breaker, and includes a pair of auxiliary terminals connected by a connection circuit to the input terminals of a bridge rectifier cell whose output is connected in parallel with the respective outputs to two other rectifier cells associated with current transformers. A first resistor delivers a first signal proportional to the maximum intensity of the mains currents. Diodes cooperate with a second measuring resistor of a residual earth leakage current discriminator. Reversing the direction of the test current flow in the test circuit is performed by simply changing the polarity of the test terminals, and enables overcurrent protection and earth leakage protection of the electronic trip device to be checked separately.

Abstract: An electric current-limiting circuit breaker comprises a pair of separable contacts and a selective solid state trip unit including an actuator cooperating with a latch mechanism for actuating the contacts to a positive open position upon occurrence of an overcurrent condition. The movable contact may also be moved by electrodynamic repulsion towards the open position when the fault current exceeds a predetermined threshold to effect current limiting. A tripping control device has an electronic counter which counts successive opening and closing cycles of the contacts so as to trip mechanism after a given number of cycles. The trip unit further comprises a first time delay tripping circuit, and a second instantaneous tripping circuit which cooperates with the cycle counter so as to ensure either instantaneous tripping or tripping by counting up to a number of cycles preselected on a setting selector.