FR2617634A1 - CONTACTOR CONTROL AND MONITORING DEVICE, AND CORRESPONDING MONITORING METHOD - Google Patents

Abstract

A contactor provided for the alternative is supplied with direct or rectified alternating, coil 1 being in series with a transistor 5 operating as a chopper, a resistor 7 and a light-emitting diode 11. The transistor control circuit 6 comprises a photo-transistor. 12 constituting with the diode 11 an opto-coupler 13 for measuring the current in the coil.

Description

261 763 4

  Contactor command and control device. and

corresponding control procedure.

  The invention relates to a command and control device for a contactor, and more particularly to a device for controlling an electromechanical contactor designed to be supplied with alternating current, and for controlling the position of the movable armature of this contactor, as well as the- process of

corresponding control.

  AC contactors are generally smaller, at equal power, than DC contactors. So they are more

  practical, they consume less and they heat less.

  But they have a drawback: they tend to open during the zero crossing of the value of

running, and they make noise.

  One of the aims of the invention is to propose a control circuit making it possible to use a contactor constructed to be supplied with alternating current, with a supply of direct current or of current.

  rectified AC, the control circuit assembly-

  contactor presenting the advantages of the contactor in

  alternative without having the disadvantages.

  Another object of the invention is to propose a method and a circuit for command and control of a contactor proceeding by measuring the intensity in the

  coil to check if the reinforcement is glued or not.

  The subject of the invention is a device for

  command and control of an electro-contactor

  mechanical with movable armature, designed to be supplied with alternating current, characterized in that it comprises: - a source of supply of direct current, or rectified alternating current, to supply the coil of the contactor, - a transistor operating as a chopper , with its control circuit, - a resistor mounted in series with the coil of the contactor and the transistor between the terminals of the power source, the resistor being mounted near the negative terminal, - and an optocoupler composed of a diode electro-luminescent crossed by a current as a function of the current in the coil, and of a photo-transistor connected to the control circuit of the transistor, - so that the illumination received from the diode by the photo-transistor is representative of the current intensity in the contactor coil,

  that is, the state of the contactor.

  According to other characteristics of the invention: the average operating frequency of the transistor chopper is low and of the order of 30 Hz, the transistor control circuit measures the intensity of the current in the coil during each cut of the chopper, via the opto-coupler, - the cut-off time of the chopper is constant, - in the event of rectified AC supply, the frequency of the chopper is synchronized to the network, - two thresholds are provided operation at 70% and 20% of the nominal voltage to restore the usual operating conditions of the alternating contactors, - the transistor control circuit comprises: a clock a freewheel time-out circuit, a transistor control stage, a circuit delay switch, a contactor control circuit, a regulation circuit, a position detection circuit of the contactor armature, and a short-circuit detection circuit in the coil of the contactor, - the start delay circuit defines three blocking periods for the chopper, one for the phase of attraction of the movable armature, the other for the phase of maintenance, the third, more

261T634

  long, to follow up on the detection of a short-

circuit in the coil.

  The invention also relates to a method for controlling an electromechanical contactor intended to be supplied with alternating current, and supplies with rectified direct or alternating current, by means of a chopper, of the type in which the inductance of the coil is a function of the position of the movable armature, characterized in that, to 1o check whether the movable armature is actually glued, an indirect measurement of the current intensity in the coil at

by means of an opto-coupler.

  By way of example, the drawing shows: FIG. 1: a block diagram of a contactor command and control device according to the invention; Figure 2: an embodiment of a contactor command and control device

according to the invention.

  Referring to Figure 1, we see a contactor symbolized by its coil 1, carrying in parallel a freewheeling diode 2. This contactor is of the alternating type, but it is supplied continuously, or alternatively rectifies, between terminals 3 and 4 of a power source. Between the coil 1 and the negative terminal 4 of the power source, are -provided in series: a transistor 5 operating as a chopper, and a

resistance 7.

  Between the coil 1 of the contactor and the positive terminal 3 of the power source, two diodes 8 and 9 are arranged in series. In parallel on these two diodes 8 and 9, a safety resistor 10 and an electroluminescent diode 11 are provided in series.

  light-emitting diode 11 is coupled to a photo-

  transistor 12 to form an opto-coupler 13. The photo-transistor 12 is connected to the control circuit 6

of transistor 5.

26 17634

  Thus, during the conduction periods of the transistor 5, the supply current passes through the coil 1, essentially via the diodes 8 and 9. A small part of the current in the coil 1 passes through the shunt consisting of the resistor 10 and the light-emitting diode 11, and causes this diode 11 to ignite. The illumination received by the photo-transistor -12 is a function of the current in the coil 1, which allows an indirect measurement of the current in the coil 1, that is to say an indirect measurement of the inductance of the coil 1. As this inductance varies according to the position, stuck or distant, of the movable armature of the contactor, the electrical signal provided by the photo-transistor 12 to the control circuit 6 makes it possible to control the position

of the movable frame.

  The transistor 5 operates as a variable frequency chopper but with constant blocking time. The resistance 7 is crossed by the current of the coil 1 only 'during the conduction periods of the transistor 5. When the transistor 5 is blocked, the diode 2 fulfills its role of freewheeling diode. In this way, an average, substantially constant current is maintained in the coil 1, which always flows in the same direction. The value of this current is high during the call duration of the movable armature of the contactor and low during the hold time of

the glued frame.

  The control circuit 6 defines a reference value for the current. During the conduction periods of the transistor 5, the current in the coil 1 rises to this reference value. When the current reaches the reference value, the transistor 5 blocks for a period of constant duration during which the current in the coil decreases slowly, so that the average current in the coil is relatively close to the reference current and is sufficient to provide illumination by diode 11,

  likely to be perceived by the photo-transistor 12.

  If the current in the coil becomes too low, the light emitted by the diode 11 becomes insufficient to ensure the conduction of the phototransistor 12. The photo-transistor therefore ensures the detection of the presence of current in the coil, with a threshold

  minimum non-zero detection thanks to opto-

  coupler 13, the control circuit 6 of the transistor 5 permanently observes the current in the coil 1 of the contactor. The operation of the device is analyzed as follows, assuming that the contactor is open at the start. When the order to close the contactor arrives, the control circuit 6 imposes a high value of the reference current during the call duration corresponding to the time necessary for the attraction of the movable armature of the contactor increases by a certain safety margin. At the end of this call duration, the reference current is reduced to maintain the armature. Throughout the duration of the maintenance of the movable armature, the optocoupler ensures the monitoring of the presence of a sufficient current in the coil of the contactor, this presence signifying that

  the contactor armature is well bonded.

  The average operating frequency of the chopper must be defined outside the audible spectrum due to the amount of noise that can be generated in a contactor. If one chooses a high average operating frequency, for example greater than 15 K Hz, one is confronted with several disadvantages. First of all, the control of the transistor, for relatively high intensities and a high frequency, requires a high power. Then, the transient state in the transistor causes a harmful heating. In addition, the line inductance becomes troublesome, especially if the power is supplied from a transformer. Finally, the noise phenomena are harmful, for the materials and for the personnel, especially if there are several contactors which operate simultaneously and

cause beating.

  To avoid these drawbacks, the operating frequency of the chopper is chosen below the audible spectrum, and for example at around 30 Hz. In the case of a full alternating rectified alternating current supply, the network must be charged in a balanced manner, especially if there are many contactors operating simultaneously. Thus, it is preferable to ensure the current rises in the coil alternately on the positive alternation and

  on the adjusted negative alternation.

  With a pause time (blocking of transistor 5) of approximately 25 ms, and a current rise time of approximately 5 ms, the rise in current occurs

all three alternations.

  It is then desirable to conduct the supply voltage in the rising period, so that the current reaches the reference value during this period: after a limited number of chopping phases, we observe

  automatic synchronization on the network.

  FIG. 2 represents a completed diagram of an exemplary embodiment of a contactor command and control device according to the invention. This figure shows the coil 1 of the contactor with its freewheeling diode 2, the opto-coupler 13, the transistor 5, the resistor 7 and the entire circuit

  control. The nomenclature, at the end of the description,

explains the symbols used.

  The overall supply is made either continuously or in alternating rectified full-wave alternation via a bridge 14. The circuit comprises a supply 15 supplying two continuous polarizations (+5 and +12 V); a clock 16; a freewheel timing circuit 1 ?; a stage 18 for controlling the transistor 5; a start delay circuit 19; a contactor control circuit; a regulation circuit 21; a circuit 22 for detecting a short circuit in the coil 1; a circuit 23 for detecting the position of the armature; a circuit 24 for discriminating the supply current, direct (DC) or alternating (AC); a circuit 25 for adjusting the nominal value of the supply voltage; circuits (26 to 29) for defining reference voltages; level detection circuits 30, 31; an OR gate 32; and a general protection diode 33, of the Transil type. The characteristics of these different circuits are

detailed below.

  Freewheel time delay (17) This is the function which gives the top for turning on the 5 MOS transistor and which generates the so-called freewheeling times. Two types of operation must be considered: - Starting: The magnetic circuit of the contactor is open. When the closing order occurs, an average current level equal to the contactor starting current must be imposed in the coil. This order arrives via the D / X bit, which goes to the state indicating start. To impose a sufficient current level, the solution chosen consists in chopping at a relatively high frequency (for example 1 to 5 K Hz. That is to say that, in the start-up phase, the wheel time free is reduced to a very small value. This option presents

two advantages.

  The value of the inductance being smaller when the magnetic circuit is open, it is necessary to plan a shorter freewheeling time, for

  ensure continuous conduction in the chopper.

  In addition, the difference between the regulation threshold and the average value of the current actually present in the coil is very small. Therefore, the level of regulation current gives a correct picture of the starting current. It is easier, under these conditions, to use the measurements made on these current levels. We can consider, without significant risk of error, that the regulatory threshold

  corresponds to the value of the coil current.

  When the D / M bit goes to the state indicating start-up, the FMOS signal to turn on the transistor is generated. The current increases in the

  coil, until reaching the regulation threshold Id.

  This information is received via the RTEMP bit which gives the order to open the transistor and which initializes the time delay. After a fixed duration, corresponding to the freewheeling time, an FMOS signal is generated. This cycle lasts until the D / M bit

goes to the maintenance state.

  - Maintenance: The operating principle is similar, but we return to the normal operating conditions of the chopper. The freewheeling time then takes a higher value. He's more

  as long as in the start-up phase.

  Control stage (18) of the MOS transistor (5) It has three main functions: - Extension of the control voltage: The FMOS signal will be an OV / 5V logic signal. The first function of the control stage is therefore to adapt the closing signal of the transistor to the control of the

grid (> 5V and 12 V).

  - Blocking of the power transistor: The switch opening order comes via the RMOS bit. The control stage must validate this order and maintain the transistor in the blocked state, until an FMOS signal is generated (end of the freewheeling time). In addition to the control function, we therefore

  appear the notion of memorizing information.

  - Management of switching speeds: This stage must impose a very low switching time, at the opening of the transistor, to facilitate management

  short circuits on the contactor coil.

  Detection of regulation levels (21) This is, in fact, only part of the regulation chain. It has received this designation insofar as its main function is to generate the blocking signal of the MOS transistor, 5, when the current in the measurement resistor, that is to say in the

  transistor, reaches the regulation threshold.

  It is the same stage which performs this function during the maintenance and start-up phases. The reference level of the control current is simply switched via the D / M bit, already

  used in the freewheel time stage.

  Detection of the short circuit on the coil (22) This stage must generate, in the event of a short circuit on the coil of the contactor, a DC signal allowing the

blocking of the MOS transistor, 5.

  The functional representation shows

  the principle used for short circuit detection.

  This consists of detecting a maximum current level. beyond which, it can be considered that the contactor coil is short-circuited. This principle has been retained, insofar as the purpose of this

  function is, to protect the power transistor.

  Or -a passing state, if there is destruction of the transistor, it will intervene by an excess of current.

Start delay (19).

  From the short circuit information (CC) and the closing or opening order (start / stop), this block generates the D / M bit (start / hold). This function can be broken down into two parts: - Generation of the start-up time: The function to be performed is to set, via the bit

  D / M, the TDEN duration of the start-up phase, i.e.

  say, the time during which the chopper will operate at a high frequency with current regulation

contactor call.

  We chose, according to the closing time measurements, to use a standard starting time for all of the contactors. This has been set to 100.ms, which allows, for currents below

  3A, to control any contactor.

  - Short circuit break: When a short-

  circuit on the contactor coil is detected, the MOS transistor is blocked and the contactor opens. If the short circuit disappears and the start order is maintained, the contactor closes. Must therefore,

  periodically perform start-up tests.

  The time interval between two tests (short-circuit pause) is set by the start delay block. This period has been estimated at 200 ms, to allow suitable power dissipation, at

MOS transistor level.

  At the time of the short circuit, the system receives

  CC information and generates an INV bit for 200 ms.

  This signal invalidates the FXOS bit and the transistor remains blocked. Beyond this period, the INV bit changes state and D / M switches the entire system to

Beginning phase.

  Current detection and position detection (13, 23).

  The purpose of these two functions is to generate a bit O / F- giving the position of the moving part of the magnetic circuit of the contactor. This function will only be validated during the regulation phase on the holding current. It will therefore be inhibited by the D / M bit. - Principle: To detect unwanted openings of the magnetic circuit, it is possible to use the existing choke variation, between a

  contactor closed and one contactor open.

  1i When the system operates in the so-called holding phase, the regulation current and the freewheeling time are such that, taking into account the inductance presented by the coil and the closed magnetic core, the current never vanishes. The chopper operates in continuous conduction. If the magnetic core opens, the choke decreases very strongly and the operation of the chopper is not

  more suitable for ensuring continuous conduction.

  Therefore, in the holding phase, it suffices to detect the presence or absence of the coil current to know the exact state of the contactor. This function is performed by the current detection block. The DIL result is only validated during the

hold (bit D / X).

  CC / CA discrimination and level detection (24, 30, 31).

  These two functions cannot be separated.

  They allow you to know the state of the network at any time. The CC / AC information gives the nature of the supply voltage (AC or DC). It is transferred to the two level detection stages. Thus, these detections are carried out either with respect to the nominal value of the DC voltage, or with respect to the effective nominal value of the

AC voltage.

  DO.2 DO.7 Network status (/ at nominal value)

<- UALIX <20%

> <20% <UALIM <70%

-> UALIM> 70%

  The measurement of these two parameters is continuous.

  It recreates the usual operating conditions for alternating contactors which have two operating thresholds: for a voltage below 70% of the nominal voltage, they cannot attract their armature, - for a voltage below 20% of the rated voltage they cannot keep

  their frame glued and they open.

  In the case of a rectified continuous or alternating supply, the contactor could operate beyond these thresholds. However, they are artificially recreated in order to remain in the usual operating conditions of alternating contactors.

Contactor control.

  This function is the central organ of the control system. The decision to give the closing or opening order (start / stop) is taken according to

two types of information.

  - External controls: The two bits X and Y select the operating modes (autonomous,

  remotely controlled or locally controlled).

  The ON / OFF information corresponds to the order received

  via remote control.

  The Reset signal is only valid during the local operating mode. It allows reset

of the whole map.

  - Control bits (BCS): there are four. They specify the actual state of the contactor (cc

  and o / f) and network (DO.7 and DO.2).

  The output information in two possible states: - START order to close the contactor,

  - STOP: order to open the contactor.

  The operating principle of the control unit can be summarized by the following table: on / off reset operation DO.2 DO.7 O / F CC autonomous control - stop> <F no start O - stop - yes stop> start command off to stop at on - <- stop distance> F no start O - stop - yes stop> <- start command off - - - - stop locally on - <- stop non stop

yes (see remote control).

  (- means that in this configuration, the state of the

  corresponding bit is indifferent).

  The advantages of the monitoring and control device according to the invention are, in particular, the following. Due to the fact that a contactor of the AC type is used, there is a gain in space, weight and consumption. Due to the fact that this contactor is supplied continuously or alternately rectified by means of a chopper, the current in the coil is always in the same direction and the problems associated with zero crossing are avoided.

  of the current, that is to say the detachment of the armature.

  In the usual contactors, the coils are calculated for a given supply voltage, and the coil must be changed if the supply voltage varies by around 10%. According to the invention, it is possible to accept, for the same coil, ranges of

  voltage varying in the ratio of 1 to 10.

  Because the resistor 7 is placed in the immediate vicinity of the negative supply terminal 4, it is traversed by the current only during the opening periods of the chopper, which

avoid heating.

  To maintain a practically constant current in the contactor coil during each of the stages of operation (call of the armature, and maintenance of the armature), a chopper at low frequency (30 Hz) is used, which makes it possible to control the noise associated with the operation of the

chopper.

List of symbols.

  UA / C: AC or DC supply voltage.

S DRL: freewheeling diode.

  LCONT .: contactor coil or choke value

of this coil.

  DIL bit indicating the presence or absence of

current in the coil.

H (t): clock signal.

  D / M: bit defining the function to be performed on

  the contactor (start / hold).

  FMOS top for switching on the MOS transistor.

INV: in validation of the FMOS signal.

  RTEMP. freewheel time delay reset.

  RLOS: opening top of the MOS transistor.

  CC / CA bit indicating the nature of the network.

  DO.7 and: status bits of the supply voltage.

DO.2

  O / F: bit specifying the state of the contactor.

  (opened closed). Reg regulation signal in operation

normal.

  CC: bit indicating presence or absence

a short circuit on the coil.

VREF: reference voltage.

  X and Y: bits defining the operating mode

of the whole system.

  start / stop Order to close or open the contactor.

  reset: system initialization bit.

  BCS: 4 bits of system control (returned

on control system).

Claims (9)

Claims   1. A command and control device for an electromechanical contactor with a movable armature, designed to be supplied with alternating current, characterized in that it comprises: - a supply source (3, 4) of direct current or current rectified AC, to supply the coil (1) of the contactor, - a transistor (5) operating as a chopper, with its control circuit (6), - a resistor (7) connected in series with the coil (1) of the contactor and the transistor (5) between the terminals of the * power source, the resistor (7) being mounted near the negative terminal (4), - and an opto-coupler (13) composed of a light-emitting diode ( 11i) crossed by a current   function of the current in the coil (1), and of a photo-   transistor (12 ') connects to the control circuit (6) of the transistor (5), - so that the illumination received from the diode (11) by the phototransistor (12) is representative of the intensity of the current in the coil (1) of the contactor, i.e. of the state of the contactor. 2. Device according to claim 1, characterized in that the average operating frequency of the transistor chopper (5) is low and around 30Hz.   3. Device according to claim 1, characterized in that the control circuit (6) of the transistor (5) measures the intensity of the current in the coil (1) during each cut of the   chopper, via the opto-coupler (13).   4. Device according to claim 1, characterized in that the cutting time of the chopper is constant. 2 6 1 7 6 3 4   5. Device according to claim 1, characterized in that in the case of an alternating supply rectifies, the frequency of the chopper is synchronized to the network.   6. Device according to claim 1, characterized in that two operating thresholds are provided at 70% and 20% of the nominal voltage to restore the usual operating conditions of the alternative contactors.   7. Device according to claim 1, characterized in that the control circuit (6) of the transistor comprises: a clock (16) a circuit (17) of freewheel timing, a stage (18) of control of the transistor (5 ), a start delay circuit (19), a circuit (20) for controlling the contactor, a regulation circuit (21), a circuit (23) for detecting the position of the armature of the   contactor, and a short-circuit detection circuit (22)   circuit in the contactor coil.   8. Device according to claim 7, characterized in that the start delay circuit (19) defines three blocking periods for the chopper, one for the phase of attraction of the movable armature, the other for the maintenance phase, the third, longer, to follow up on the   detection of a short circuit in the coil.   9. Method for controlling an electromechanical contactor intended to be supplied with alternating current, and supplied with rectified or alternating current, by means of a chopper, of the type in which the inductance of the coil is a function of the position of the movable armature, characterized in that, to check whether the movable armature is actually glued, an indirect measurement of the intensity is carried out at each cut of the chopper   current in the coil by means of an opto-coupler.