Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1988-01-19
1990-06-12
Hix, L. T.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361205, H01H 4728
Patent
active
049338064
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and device for controlling an electromagnet whose energization, by means of a monoarch periodic current such as a rectified half wave current, causes actuation of a mobile part.
It applies more particularly to the control of electromagnets used in electric contactors were closure is caused following energization of the coil of the electromagnet by a periodic current of said type, such energization causing the mobile contacts of the contactor to be applied to the fixed contacts. However, the invention is not limited to this type of application. It may, in fact, be suitable for numerous other devices actuated by an electromagnet such for example, an electromagnetic valves.
In devices of this kind, the mechanical energy communicated to the mobile parts of the electromagnet for actuating the mobile part is variable depending on the closure angle of the switch which usually controls the energization of the coil of the electromagnet, that is to say depending on the time marking the beginning of the energization, considered in the corresponding period of the periodic current.
It has been observed, in particular, that this energy is maximum when the closure angle is zero and that it decreases as this angle increases in the fraction of the period considered containing an arch. It then follows, in certain devices, that if the electromagnet is not dimensioned for certain unfavorable angles, the desired actuation, for example the closure of the contactor, will not occur or else the mobile assembly will be stopped before total crushing of the contacts.
The purpose of the invention is then more particularly to reduce the dimensioning of such an electromagnet and the drawbacks which result therefrom, particularly in so far as the cost, size and energy saving is concerned.
To reach this result, the invention provides more particularly a method for controlling an electromagnet including a coil to which may be applied a monoarch periodic current coming from a source following the emission of a control order, for causing a given actuation of a mobile part, this method being more particularly characterized in that it includes, from the time when said control order has been emitted:
detection of the zero cross-over times from the increasing and/or decreasing values of the voltage of the source; and
the application, at one of these times (or close thereto) of the periodic current to the coil of the electromagnet.
This method may be used by associating, with a controllable switch device in series with the coil of the electromagnet, a relatively simple electronic circuit comprising:
a member for determining the zero cross-over times from the positive and/or negative values of the voltage of the source; and
a switching device controlled by said determining member for delivering a closure signal to the switch device when a zero cross-over time is detected following the control order for energizing the coil.
It is then clear that, with this method and this device, whatever the time when the control order is emitted, the energy communicated to the mobile part of the electromagnet will be optimum. The result is a decrease in the size and cost of the electromagnet.
One embodiment of the invention will be described hereafter, by way of non limitative example, with reference to the accompanying drawings in which:
FIG. 1 is the general diagram of a control device in accordance with the invention; and
FIG. 2 is a diagram representative of the electric signals at different points of the circuit shown in FIG. 1.
Such as shown in FIG. 1, the control device for an electromagnet of which only the coil L has been shown comprises, in series in a circuit connecting the coil L to the terminals of an AC source (terminals B.sub.1, B.sub.2), a control switch I whose closure is caused by application of an order for energizing the coil, a diode D1 providing half-wave rectification of the AC current and a controllable switch device formed by a thyristor TH shunted, in a conventional way, by a resistor R.sub.1 in
REFERENCES:
patent: 3329837 (1967-07-01), Hewie
patent: 3668422 (1972-06-01), Pascente
Bataille Christian
Belbel Elie
Gast Jean-Noel
Lauraire Michel
Drucker William A.
Gray David M.
Hix L. T,.
La Telemecanique Electrique
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