EP0190209A1

EP0190209A1 - Device for the control of an electromagnet coil and electric switching apparatus provided with such a device

Info

Publication number: EP0190209A1
Application number: EP19850903665
Authority: EP
Inventors: Jacques Arvisenet; Christian Bataille; Elie Belbel; Bernard Dumortier; Jean-Noel Gast; Michel Lauraire; Jean Marc Moulin
Original assignee: Telemecanique Electrique SA
Current assignee: Telemecanique SA
Priority date: 1984-08-03
Filing date: 1985-07-19
Publication date: 1986-08-13
Also published as: FR2568715B1; ES545867A0; BR8506862A; WO1986001332A1; ES8702730A1; JPS61502923A; FR2568715A1

Abstract

Dispositif de commande de la bobine d'électroaimant d'un appareil de communication, comprenant un commutateur à transistor MOS (12) en série avec la bobine (B), un redresseur double alternance (11) alimentant la bobine, un générateur de signal ayant un circuit d'asservissement (13) relié à un élément de lecture du courant dans la bobine et délivrant au commutateur un signal de commande ayant un niveau d'appel et un niveau de maintien, et un circuit abaisseur de tension (14) relié aux bornes continues de la bobine. Le circuit d'asservissement (13) est relié à la grille du transistor MOS et maintient le courant (IB) de la bobine à un niveau indepéndant de la tension de la source.Control device for the electromagnet coil of a communication device, comprising a MOS transistor switch (12) in series with the coil (B), a full-wave rectifier (11) supplying the coil, a signal generator having a servo circuit (13) connected to a current reading element in the coil and supplying the switch with a control signal having a call level and a hold level, and a step-down circuit (14) connected to the continuous coil terminals. The servo circuit (13) is connected to the gate of the MOS transistor and maintains the current (IB) of the coil at a level independent of the voltage of the source.

Description

DEVICE FOR CONTROLLING AN ELECTRO¬ MAGNET COIL AND ELECTRIC SWITCHING APPARATUS EQUIPPED WITH SUCH A DEVICE.

The present invention relates to an electronic device for controlling an electromagnet coil belonging to an electrical switching device. It also relates to the electrical device, such as a contactor, equipped with this electronic device and the electromagnet controlled by the latter.

To control a contactor electromagnet, it is sometimes desirable to have an electronic circuit provided with a switch in series with the coil of the electromagnet, this switch being controlled by the circuit so as to ensure successively, in the coil, a high level of so-called inrush current, then a little before bonding or as soon as the mobile armature of the electromagnet is bonded, a lower level of holding current in order to minimize current consumption and heat dissipation .

It is known to use, to control relay or solenoid valves, chopping devices which are associated with the switch and are implemented after a determined duration of application of the inrush current, in order to lower the current coil at its holding level. However, these devices are difficult to adapt to the control of contactors and they require the use of an interfacing relay between the electronic control circuit and the contactor.

In addition, known devices lack the flexibility sometimes required for the implementation of contactors; they are, in particular, unsuitable for operating indifferent to direct current or alternating current and, moreover, prohibit plugging in the contactor with which they are associated on an alternating network, either of 110 volts, or of 220 volts , for example, or on a bare voltage source, for example between 100 and 400 volts.

In particular, it is known from US Pat. No. 3,549,955 to use, for controlling an electromagnet coil, a switch constituted by a bipolar transistor, the base of which is controlled by a voltage comparator; this comparator compares a voltage, a function of the current flowing through the coil, with a reference voltage capable of taking two successive values. The inrush current in the coil is however obtained by means of a fixed voltage plateau, while the holding current is produced by the application of voltage slots of fixed value at the base of the transistor.

By the very fact of its constitution, this system is rigid and it cannot function satisfactorily with various supply voltages, except by the substitution of numerous components.

The object of the present invention is in particular to enable the control of an electromagnet of an electrical switching device, more specifically of a contactor, by means of a device authorizing the supply of the coil of the electromagnet with a inrush current then a lower holding current, from a DC voltage or alternative whose variation within a predetermined range has no effect on the constitution of the device.

It also aims to allow the current in the coil to be controlled by a high frequency cutting of the voltage applied to it using an electronic device with low current consumption and with reduced heat dissipation, this device can be controlled by an isolated signal of very low power.

Finally, it aims to combine, in the same electrical switching device, a cutting device with large power dynamics and low current consumption with a direct current electromagnet, simple and inexpensive, with reduced ampere-turns and with low temperature rise.

The invention relates to a control of a ¹ solenoid coil of the electronic device for switching electrical apparatus connected to a voltage source, comprising a static switch arranged in series with the coil of the electromagnet and a signal generator provided with a servo circuit connected to a reading element of the current flowing in the coil, the servo circuit delivering to a switch control electrode, in response to a switching command, a control signal having a level of call corresponding to a call phase, then after a delay at the hold level obtained by chopping and corresponding to a hold phase of the electromagnet.

According to the invention, the device comprises:

- a full wave rectifier, the alternating terminals of which are connected to the voltage source and the continuous terminals of which are connected to the coil,

- a step-down circuit connected to the continuous terminals of the rectifier and arranged to deliver to the assertion circuit- screwing a reduced direct voltage independent of the source voltage within a predetermined range of said source voltage,

- The servo circuit being connected to the switch control electrode and arranged to maintain both in the call phase and in the maintenance phase the current of the coil at a level independent of the voltage of the source.

As a result, the same electromagnet can be controlled by the same electronic device connected to a 24 or 48 volt, 110 or 220 volt alternating network, or 380 or 660 volts, or even to a continuous source of 100 to 400 volts, practically without any modification of the components of the control device.

The static switch can comprise at least a bipolar transis¬ tor or a Darlington circuit or, preferably, a MOS transistor.

The servo circuit can advantageously comprise a pulse modulator, for example with variable duty cycle and at fixed high frequency of the order of a few tens of KHz, receiving from a setpoint circuit with a contour generator a signal setpoint at two independent levels of the source voltage, and receiving from the current reading element, in particular constituted by a resistor or by a current mirror circuit, a signal representative of the effective current in the coil . It should be noted that such a control contributes to meeting the proposed goal since it determines in the coil a programmed current independent of the voltage of the source.

The contour generator of the servo circuit can comprise a means for developing the call level of the reference signal, a means for delaying the signal at its call level for a determined duration and a means for developing the level to maintain the setpoint signal. It is preferably possible to provide a setpoint circuit validation member, this member turning the setpoint circuit on and off in response to a low level signal delivered electrically or optically by a control system, in particular an output of 'programmable robot ; the validation member comprises an isolation element, for example a photocoupler, which makes it possible to isolate the low level signal driving the control device, so that disturbances of the latter do not affect the control system.

When the electronic control device associated with the contactor is of the voltage drop detection type, the setpoint circuit can advantageously include a comparator, a first input of which receives a fixed voltage signal delivered by the step-down circuit, and a second input of which receives a voltage signal appreciably independent of the nominal voltage of the source but sensitive to its fluctuations, the output of the comparator bringing the setpoint signal to its quiescent level when the voltage of the source drops to- below a predetermined threshold.

On the other hand, to insensitize the control device to micro-cuts in the source voltage, there may be provided a filter with asymmetrical time constants when the source voltage rises and falls, this filter being arranged between a continuous terminal of the full wave rectifier and the setpoint circuit. Finally, the setpoint circuit can be provided with a means for monitoring the reduced voltage delivered by the step-down circuit, this monitoring means bringing the setpoint signal to its rest level when the reduced voltage drops to- below a determined threshold.

The invention also relates to an electrical switching device capable of operating in direct current or in alternating current and equipped with the control circuit described. and of an electromagnet of the simplified direct current type, in particular by its magnetic circuit in thick sheet metal which is weak or not laminated and by the absence of phase shift ring, and using a reduced number of ampere-turns while having an important appeal division. The low level of inrush current required by 1 * electromagnet contributes to reducing the dimensioning and the cost of the electronic device previously described.

The description below of an embodiment, carried out by way of nonlimiting example with reference to the appended drawings, will better explain the advantages of the invention.

FIG. 1 represents the block diagram of a contactor control device according to the invention.

FIGS. 2A, 2B, 2C respectively show the signal delivered by the reference circuit, the signal delivered by the pulse duration modulator and the current flowing in the coil of the electromagnet when the contactor is actuated.

FIG. 3 is the block diagram of a variant of the control device.

The control device 10 illustrated in FIG. 1 is associated with the coil B of an electromagnet E belonging to an electrical switching device C which could be constituted by a relay but which is preferably a contactor. Contactor C is connected to a DC or AC voltage source S; the control device of 10 is arranged to operate even if the nature or the voltage of the source changes, this being the case if the contactor is connected to a network, for example from 24 to 48 volts, or from 110 to 220 volts or 380 to 660 volts in alternating current or 100 to 400 volts in direct current, and it includes, for this purpose, a double alternation rectifier 11. The control device 10 comprises a MOS transistor switch 12 whose drain-source circuit is in series with the coil B and whose gate G is connected to a servo circuit 13 delivering a low power signal cut at high frequency. The control device 10 aims to ensure the closing and opening of the contactor C in response to the on and off orders from an I / O output module of a programmable logic controller PC, by means of an electrical or optical link. , or coming from another control member associated with the contactor and capable of delivering a signal at very low level.

A voltage step-down circuit 14 is included in the control device 10 and it is connected to the DC voltage terminals V__ stabilized and insensitive to transients, for example of 12 or 14 volts.

A freewheeling diode 15 is arranged in parallel with the coil B.

The servo circuit 13 has a pulse width modulator 15 at a fixed frequency of a few tens of KHz, for example 20 KHz, and with a duty cycle which is continuously variable as a function of the error signal resulting from the comparison between a current setpoint signal delivered by a setpoint circuit 16 and an actual current signal produced by a measuring element 17 of the current flowing in the coil B. The modulator 15 can also be a pulse frequency modulator.

The measuring element 17 can be a resistor in series with the switching MOS transistor 12 or preferably a current mirror circuit which can be combined by integration with the MOS transistor.

The setpoint circuit 16 is a contour generator capable of delivering a setpoint signal I _c at two levels I _C1 , I _C2 (FIG. 2A) whose rise time at level _cl , the holding time at level I, and the descent time at level I _p - are respectively designated by tt ₂ and tg. These times, in particular t ^ _ and t ₂ r are predeter¬ mined and easily modifiable to take account of the characteristics of the electromagnet and of the contactor. The sum of the times t, and t- is preferably greater than the time necessary to obtain the bonding of the mobile part of the electromagnet E in response to the rise of the setpoint signal. It can, in certain cases, be lower than it to reduce the hammering of the contacts.

An input 16a of the reference circuit 16 is connected to the voltage step-down circuit 14 to receive the lowered voltage V _n _ so that the circuit 16 uses it after having checked it; on the other hand, an input 16b of circuit 16 is connected to a DC terminal of rectifier 11 in order to control the voltage level of the source, for example 110 or 220 volts, and an input 16c of circuit 16 is connected to a photocoupler 18 itself connected by electrical conductors 18a (FIG. 1) or by an optical fiber 18b (FIG. 3) to the card or to the I / O output module of the programmable automate PC. It goes without saying that the on / off control of the device 10 can be carried out either by means of an isolated signal at low level from a control system different from the represented automaton, or upstream of the rectifier 11 at by means of a suitable switch.

The low power signal S _G (FIG. 2B) leaving the PWM modulator to attack the gate of the MOS transistor is cut at a constant frequency of 20 kHz, therefore at constant period T, with a duty cycle modulated as indicated in FIG. 2B by the error signal resulting from the compa¬ reason between the setpoint contour I_ and the effective current signal I_ (Figure 2C) read by element 17, this error signal conventionally affecting a sawtooth signal or triangular. The high frequency of the PWM modulator makes it possible to obtain a very fine cutting of the current in the coil of the electro¬ magnet, the magnetic circuit of which can therefore be without drawback made of thick sheet metal and exclude the need for a turn of Frager.

It should be noted that the chopping at 20 kHz is effected both in the call phase t ,, t ₂ defined by the contour generator and in the hold phase. 0

The setpoint circuit 20 shown in FIG. 3 presents an input 20a for controlling the voltage V _DD delivered by the voltage step-down 14, an input 20b connected by a link 21 to one of the continuous terminals of the rectifier bridge

15 double alternation 11 and an input 20c connected to the photocou¬ pleur 18.

The link 21 includes two resistors in parallel R, and R ₂ , the resistor R ₂ being switched on or off by means

20 of a jumper 22. This brings the voltage at the input 20b of the reference circuit to a level substantially independent of the nominal level of the voltage of the source S, but varying with the fluctuations of this voltage. It follows that, when the coil B of the electromagnet must

25 be de-energized in the event of a drop in the voltage of the source below a determined fraction of its nominal voltage, the detection of the decrease in voltage by the setpoint circuit is ensured for example both at 110 and at 220 volts by simply moving the jumper

30 22.

In the embodiment of FIG. 3, the setpoint circuit 20 comprises a filter 20d, the time constants of which are asymmetrical when the rectified voltage transmitted to the input 20b rises and falls; this allows the control device not to react to the micro-cuts of the source S, without however delaying the implementation of the contactor for a fairly low source voltage. Moreover, there is provided in the setpoint circuit 20, a means 20e for monitoring the control voltage delivered by the step-down circuit 14, this means 20e causing the setpoint signal to zero when the control voltage drops below a predetermined threshold.

In the modulator 15 a comparator 23 has been shown, a first input 23a of which receives the signal I "from the reference circuit 20 and a second input 23b of which is connected to the element 17 to receive the signal I"; the resulting error signal is superimposed on a triangular or sawtooth signal to produce a series of pulses with continuously modulated duty cycle.

The electromagnet 30 of FIG. 1 is in the form of a pot of axis X-X comprising a fixed cylinder head 31 and a frame in the form of a movable cap 32; the coil B is housed in respective annular recesses 31a, 32a of the yoke 31 and of the movable frame 32. The yoke and the frame 31, 32 each have a flange 31b, 32b developed radially towards the outside in planes perpendicular to the axis XX, so as to form polar expansions which extend the polar surfaces of appeal. As a consequence of this arrangement, in a contactor of a given rating, the electromagnet 30 can be combined with the high frequency switching electronic control device described to operate with reduced ampere-turns and a relatively current consumption. weak, however providing the necessary flow.

The cylinder head and the pot frame may have a generally parallelepiped shape; they are however preferably machined in a part of general shape of revolution, substantially cylindrical, to best use the flux created by the reduced ampere-turns delivered by the MOS switch. In the variant of FIG. 3, the magnetic circuit of the electromagnet 40 comprises a yoke 41 in the form of an asymmetrical double T and an armature with a peripheral ring 42 movable along the axis XX and surrounding the upper T 43; the wings of the lower T 44 of the magnetic circuit terminate in an annular chamfer 45, while the ring 42 has, opposite this chamfer, a corresponding truncated front edge 46 so as to constitute a frustoconical annular air gap e. increasing the appeal section. A cylindrical annular air gap e ₂ is provided between the radially inner surface of the ring 42 and the radially outer face of the wings of the upper T 43. This electromagnet is more fully described in patent application No. 84 11704 of July 24, 1984 of the Applicant .

The choice of the electromagnet with large inrush areas of the type illustrated in FIGS. 1 and 3 correlatively allows the use of an electronic control device delivering a reduced inrush current, therefore of reduced power and of low cost.

A toric or annular elastic damping means not indicated may be provided between the fixed and movable parts of the electromagnet.

The magnetic circuits of the electromagnets illustrated in FIGS. 1 and 3 are made of thick sheet which is weakly leafed or not laminated; they do not have a phase shift ring and the large area polar surfaces are not ground.

Modifications can be made to the embodiment without departing from the scope of the invention. The MOS switch can be constituted by any static switch member with insulated gate.

Claims

Patent claims

1. Electronic device for controlling an electromagnet coil for an electrical switching device connected to a voltage source, comprising a static switch arranged in series with the electromagnet coil and a signal generator provided with a circuit 'servo connected to a reading element of the current flowing in the coil, the servo circuit delivering to a switch control electrode, in response to a switching command, a control signal having a call level corresponding to a call phase, then after a time delay a level of maintenance obtained by chopping and corresponding to a phase of maintenance of the electromagnet, characterized in that it comprises:

- a full-wave rectifier (11) whose alternating terminals are connected to the voltage source (S) and whose continuous terminals are connected to the coil (B),

- a step-down circuit (14) connected to the continuous terminals of the rectifier and arranged to deliver to the servo circuit (13) a DC voltage (V _n _) reduced and independent of the source voltage within a predetermined range of said source voltage,

- The servo circuit (13) being connected to the control electrode of the static switch and arranged to maintain, both in the call phase and in the maintenance phase, the current (I) from the coil to an independent level of the source voltage,

2. Control device according to claim 1, characterized in that the control circuit (13) comprises a pulse modulator (15) capable of delivering to the control electrode of the static switch, a control signal (S _G ) cut at high frequency both in the call phase and in the maintenance phase.

3. Control device according to claim 2, characterized in that the static switch is a MOS transistor commu¬ tor (12).

4. Control device according to claim 2, characterized in that the modulator (15) is a pulse width modulator (PWM) with fixed frequency and variable duty cycle.

5. Control device according to claim 1, characterized in that the servo circuit (13) comprises a setpoint circuit with contour generator (16) having a means for developing the call level (I _C τ) of the control signal (S _G ), a means for delaying the signal at its call level for a predetermined duration and a means for developing the maintenance level (I _C2 ) of the control signal.

6. Control device according to claim 5, characterized in that the setpoint circuit is connected to a first input (23a) of a comparator (23) associated with the pulse width modulator (15), while that the current reading element (17) is connected to a second input (23b) of the comparator, the error signal of the comparator adapting the modulation of the duty cycle so that the coil current (I _β ) is that fixed by the contour generator (16) of the reference circuit.

7. Control device according to claim 5, characterized in that a validation member is connected to the setpoint circuit for delivering to the latter a validation signal in response to an isolated low level control signal.

8. Control device according to claim 7, characterized in that the validation member comprises a photocoupler (18) electrically connected to an output module (I / O) of a programmable controller (PC).

9. Control device according to claim 7, characterized in that the validation member comprises a photocoupler (18) connected by optical fiber (18b) to an output module (I / O) of programmable logic controller (PC).

10. Control device according to claim 5, characterized in that the current measuring element (17) is a current mirror circuit.

11. Control device according to claim 5, of the voltage drop detection type, characterized in that the reference circuit comprises a comparator, a first input (20a) of which receives a reduced fixed voltage signal from the voltage step-down circuit ( 14) and of which a second input (20b) receives a voltage signal substantially independent of the nominal voltage of the source but sensitive to fluctuations of the latter, the output of the comparator bringing the setpoint signal to its quiescent level when the voltage of the source drops below a predetermined threshold.

12. Control device according to claim 5, characterized in that a filter (20d) with asymmetric time constants at the rise and fall of the source voltage (S) is arranged between a continuous terminal of the double rectifier alternation (11) and the setpoint circuit (20).

13. Control device according to claim 5, characterized in that the setpoint circuit (20) comprises a means for monitoring the reduced voltage delivered by the step-down circuit (14), this means of surveil¬ lance carrying the signal setpoint (I _r ) at its rest level when the reduced voltage drops below a threshold.

14. Electric switching device with electromagnet provided with the electronic control circuit according to claim 13, characterized in that the electromagnet (E) is of the direct current type and has a coil (B) at low amps. towers while being equipped with peripheral polar surfaces with large cross-section.

15. An electrical switching device according to claim 14, characterized in that the electromagnet (30) is pot-shaped and has a fixed yoke (31) and a hat-shaped frame (32), the yoke and the hat each comprising a collar (31b, 32b) developed radially outward to extend the polar contact surfaces.

16. An electrical switching device according to claim 14, characterized in that the electromagnet is of the armature type in the form of a movable ring (42) with a chamfered front edge (46) having a small frustoconical annular gap (e,), a small cylindrical annular air gap (e ₂ ) and a large frustoconical call section.