Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Polarity-responsive
Patent
1991-03-04
1994-07-05
Donovan, Lincoln
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Polarity-responsive
335230, 335 18, H01H 5122
Patent
active
053271122
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an electromagnetic actuator of the type of a relay having a yoke polarized by a permanent magnet and a movable armature which is attracted by said yoke against a spring means, said actuator being controlled by an electric current sensor comprising a toroidal transformer wherethrough at least one electric conductor is passed.
The field of application of this invention is particularly, but not exclusively, related to electric guarding apparatus from differential currents, and reference will be made throughout the following description to just that field of application for convenience of illustration.
BACKGROUND ART
Known are, in this specific field of application, protection apparatus which are intended for installation at consumer's outlets of single-phase or three-phase power supplies of the civil or industrial kinds.
Such prior apparatus include a protective automatic breaker, usually of the magnetothermic type, whose break mechanism is driven by a solenoid.
Also provided is a differential current sensor which comprises a toroidal transformer encircling the power supply line and being adapted to warn of the appearance of such currents, also referred to as leakage currents, by sensing any unbalance in the currents flowing through the line conductors.
The sensor is connected to the solenoid coil so as to trip off the breaker mechanism on a predetermined differential current value being exceeded.
High performance (type "A") protection apparatus, such as those designed to become operative on unidirectional or pulsed currents being sensed, include an electronic circuit connected between the sensor and the solenoid. This circuit is generally made up of series and/or cascade connected capacitors.
While being in many ways advantageous and substantially up to their intended function, such apparatus still have several drawbacks, as pointed out herein below.
The current-detection and break mechanism trip-off steps involve a sequel of energy conversions from electric into electromagnetic, and vice versa, and ultimately into mechanical, which unavoidably brings about losses and restricts the apparatus response.
The provision of an electronic circuit including capacitors is both cost-, space-, and power-intensive.
The solenoid and the toroidal transformer which forms the current sensor, by their very presence restrict the possibility of making such protection apparatus more compact.
Patent Application GB-A-2074380 discloses an electromagnetic breaker having a yoke polarized by a permanent magnet and a movable element which is attracted by the yoke against spring; electric conductors are passed through a hole in the yoke so that the magnetic flux induced by conductors through the yoke interferes with the permanent magnetic flux from the permanent magnet.
The technical problem that underlies this invention is to provide an electromagnetic actuator of the type of a relay, which has such structural and performance characteristics as to overcome the above-noted drawbacks.
DISCLOSURE OF INVENTION
The solutive idea on which this invention is based is to provide an electromagnetic actuator which also combines the structure and function of the differential current sensor.
The technical problem is solved by an actuator as indicated being characterized in that said transformer is incorporated to the actuator such that the magnetic flux induced therethrough by the conductor will interfere with the permanent magnetic flux from said magnet.
The features and advantages of an actuator according to the invention will be apparent from the following detailed description of an embodiment thereof, given by way of illustration and not of limitation with reference to the accompanying drawing.
BRIEF DESCRIPTION OF DRAWINGS
In the drawings:
FIG. 1 shows, in elevation and in section, the electromagnetic actuator of this invention;
FIG. 2 is a view from above of the actuator shown in FIG. 1; and
FIG. 3 is a view showing in diagramatic form an equivalent electromagnetic circuit of the actuator o
REFERENCES:
patent: 3914723 (1975-10-01), Goodbar
patent: 4385280 (1983-05-01), Reisem
patent: 5010310 (1991-04-01), Frielinghaus
Bticino S.P.A.
Donovan Lincoln
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