AU2003283470A1

AU2003283470A1 - Electronic control device for motor

Info

Publication number: AU2003283470A1
Application number: AU2003283470A
Authority: AU
Inventors: Thierry Garcia; Jean-Yves Giroux; Alain Krzywdziak
Original assignee: Fillon Investissement SA
Current assignee: Fillon Investissement SA
Priority date: 2002-09-16
Filing date: 2003-09-16
Publication date: 2004-04-30
Anticipated expiration: 2023-09-16
Also published as: FR2844650B1; AU2003283470B2; FR2844650A1; WO2004025818A1; CN1682426A; CN1682426B; EP1540805A1; JP2005539472A

Description

PUBLISHED SPECIFICATION VERIFICATION OF TRANSLATION lI I, Joachim Buchner, of Spruson & Ferguson, 31 Market Street, Sydney, New South Wales, 2000, Australia declare as follows: 1. That I am well acquainted with both the English and French languages, and 2. That the attached document is a true and correct translation made by me to the best of my knowledge and belief of: (a) The specification of International Bureau pamphlet numbered WO 2004/025818 International Application No. PCT/FR2003/002723 (Date) (Signature of Translator) (No witness required) Electronic Control Device for Motor The present invention relates to a device for the electronic control of motors, preferably asynchronous, single-phase or three-phase motors, and comprises at least one electronic circuit board and a static relay to control the power supplied to the motor, with the circuit board and the relay being mounted preferably in the interior of a box. The control devices of the above-specified type can be very well adapted to standard environments or to environments involving the risk of explosions but they are used particularly in explosive atmospheres of all sorts, gas or coal dust, for electric explosion-proof motors of [the non limited] types like LEROY-SOMER, ELNOR or ATAV (registered trademarks). Such motors are particularly widely employed for the operation of mixers of paints or other products containing volatile components for which IIB T4 is the most widely encountered risk category. For a long time motor control devices have been based mainly on mechanical concepts as illustrated particularly by the patent EP-A-0.091.360. Similarly, the document US-A-6.150.792 describes a phase controller designated for a three phase asynchronous motor. In that document, it was provided to energize the motor exclusively with the aid of a current whose electrical parameters, frequency and voltage, are adapted to the proper functioning of the motor. In order to solve this technical problem, the means used require an electromagnetic relay associated with a power switch implying as well-known inconveniences: large energy requirements and large power as well as development of sparks in each switching operation. Thus, in phase control, a switch is closed to allow the power to be supplied to a first sensor which detects the voltage and frequency of the current and, if the conditions are favourable, supplies power to the motor by closing the electromagnetic relay and triggering the power switch; a second detector system of greater sensitivity than the first detector system and working with a delay relative to this first detector system detects again the frequency and the voltage of the current supplied. This second system is therefore capable of triggering the opening of the relay and of the power switch when the conditions for supplying current are unfavourable. The electromechanical relays of the aforementioned type have still many shortcomings in comparison with an electronic control system. Further, the document EP-A-1.079.509 describes a power supply unit in which three capacitors are arranged in series and form in this way a capacitive impedance supplied with power from the power net of the motor, with the capacitive impedance serving to reduce the supply voltage of the rest of the device. This capacitive impedance serves to supply power to a led [light-emitting IRN 710930 1 diode]. A photodetector sends to a microprocessor a signal depending on the state of the led, lighted or extinguished. When the led is lighted, the microprocessor, set off by the photodetector, provides for the bias voltage of the transistor which then becomes conductive and energises an electromagnetic relay, allowing in this way the motor to be supplied with power. When a fault occurs in the input current, the led is extinguished, the photodetector indicates quenching of the led to the microprocessor which then opens the electromagnetic relay, stopping the supply of power to the motor. The important shortcoming of such a device is once more related partly to the presence of an electromagnetic relay which necessarily implies delicate damageable contacts within equipment designated for environments with high risk of explosions. The use of at least three capacitors shows that the energy required for the control is large because of the kept type of the control elements. Thus, electronic controls have steadily appeared on the market in response to the technological developments of products. Several electronic control principles compete in the use of controls of standard motors or explosion-proof motors and are in this context distinguished by the nature of the electronic control with wired or programmed logic, the means used for switching the power of electromechanical relays with dry contacts or static relays with electronic thyristor contact, the on/off control elements, the protection and security modes required for ensuring that no electrical risks occur under all conditions and particularly the risk of explosions in explosive atmospheres in accordance with valid European directives and unified norms. The examples given below show embodiments based on the above-indicated criteria. A certain number of motor controls have been directly proposed by the manufacturers of motors, particularly in the USA, such as the FRANKLIN or RELIANCE motors. The electronic control with programmed logic is applied via an electrical connection cable to a plastic box which is compact and light. The connection cable is with its other end connected to the terminal box of the motor in which the power switching is effected, mainly by relays which can be of the electromechanical or static type. Start and stop of the motor are handled with a keyboard with flexible membranes for sensor buttons. The elements of electrical safety in an explosive atmosphere are ensured by combining the mode "d" of the flame-proof casing for the motor with the mode "i" of intrinsic safety for the electronic circuit board and its outside control elements. This control device has the disadvantage of being connected in an inseparable way with a motor type having the appropriate connection means. This proprietary "motor and electronic control" IRN 710930 2 assembly is not universal and can not be retained for an other outside motor unless it is provided for this design. Some other motor controls have been suggested by the manufacturers of electrical components such as LEGRAND ATX, TECHNOR or BARTEC. They do not have electronic control but are built only with standard electrical components such as power circuit breakers and motor protection relays capable of limiting very high currents, of the type of the TELEMECANIQUE components, assembled in an explosion-proof "d" casing and associated with pushbuttons with electrical contact for the start/stop command in a similar protection mode or in the increased safety mode "e" as described in Norm EN50019. The control board is connected to the motor by appropriate electrical cables. These electrical control devices listed in the catalogues of great manufacturers of electrical equipment for motors in explosive atmospheres have the shortcoming of a prohibitive cost despite of their providing only the basic functions of full or no operation, of large space requirements, and of excessive weight due to a very thick aluminium or plastics casing of the "d" type casing to satisfy the safety requirements. Consequently, these solutions are not economically satisfactory as they cannot be optimised because of the fact that the basic model has integrated secondary features to avoid investments for heavy tools required for making the boxes. Furthermore, any design approval is made out for a single given industrial application and cannot be generalised to an other application. This type of device, which in the catalogues of the distributors is built on demand is immediately available in the trade but it turns out that it has use with recall in the case of paint mixer machines for which the overall cost must always be reduced. This is the reason why recently, in the specific field of paint mixers, the companies FAS and FILLON-PICHON have developed their own more economical motor control solutions, which can be adapted to explosion-proof motors as well as to standard motors. Thus, two innovative versions of original electronic controls have seen the light of the day from 1995 on the world market of mixers of paint for the repair of car bodies. The electronic control version of FAS comprises a very compact electronic circuit board with wired circuitry on which the ensemble of control and power switching components in the form of an electromechanical relay is mounted. It can be integrated either in a standard plastics box or in an explosion-proof "d" casing of aluminium specifically for use in explosive atmospheres, in accordance with norm EN50018. Start and stop of the motor are effected by touch buttons on a flexible membrane keyboard. A protective element of the type of an ammeter provides for the safety of the IRN 710930 3 motor. An other alternative solution involves placing the electronic ensemble into the terminal box of the motor and to set outside only the contactors such as the pushbuttons with electrical contact, possible in protection mode "d" for explosive atmospheres. The electronic control version of FILLON-PICHON places in the interior of a box at least one electronic circuit board with a program and a power-switching component of the type of a static CELDUC relay for the supplying power to the motor. Start and stop of the motor are obtained by touch buttons on a keyboard with flexible membranes. The general rules described in European norm EM50014 are employed for protection in explosive atmospheres and particularly the norm "m" of encapsulation (norm EN50028) with a polyurethane or epoxy resin in combination with the intrinsic safety norm "i" (norm EN50020) is used. In these two versions, the electronic circuit board comprises at least one transformer to be soldered into an electronic circuit which is connected by the phase line of the a.c. net supplying the motor with mains power. This transformer has the objective of reducing the mains voltage for providing the energy required as supply of a regulator which restores the voltage in the form of a d.c. voltage of a few volts, used exclusively for the control logic. This transformer is protected on the input side by components of the type of fuses for overloads or of the type of varistors for overvoltages. These different customised control devices have various shortcomings. As a matter of fact, it is not possible to design a transformer of reduced space requirements which at the same time could sustain high maximum input voltages without the risk of heating and could cover a very extended range of line voltages. In regard to the first point, even in operation without a load, a transformer consumes energy and heats up. High voltages near or above 250 volts enhance the heating and cause irreversible damage of the component. As far as the second point is concerned, the design of a transformer itself implies dependence on a transformation ratio set to a constant value "rt" and corresponding to the relation between the number ni of turns on the primary winding and the number n 2 on the secondary side of the transformer such as: U2/U1 = 11/12 = n 2 /ni = rt where U 1 and I1 denote the voltage and the current, respectively, in the primary coil, and U 2 and I2 denote the voltage and the current, respectively, in the secondary coil. IRN 710930 4 Under these conditions, the search for an acceptable compromise implies overdimensioning of the transformer for the requirements of norm EN50028 relating to the protection mode "in" of encapsulation and the addition of a thermal fuse for temperature control. In all these designs, a special production must be undertaken at high cost. Furthermore, the available transformers with the best performance features obtained still have a very narrow operating range in regard to the requirements of net assemblies around the world with their large ranges. It is therefore necessary to have at least two types of transformers and to adapt each time the control device to the net of the country in which the control device is to be installed. Further, depending upon the importance of this voltage range, the voltage must be reduced to a value which can always be used for the regulating component which has to supply d.c. to the control components of the electronic circuit. Furthermore, the fact of having, on the one hand, a bulky transformer on an electronic circuit board with exceeding height on an aluminium plate and, on the other hand, having the ensemble which is independent of a static standard relay placed in the interior of a box on the aluminium plate for heat dissipation, creates a very extended ensemble with a relatively large volume. At the same time, this ensemble must be embedded inside a protective material such as a resin in order to insulate all electrical parts in a zone with an explosive atmosphere in order to conform to the design requirements of mode "in" encapsulation. An overlapping height of 3 mm is then imposed not only above the highest component but also around the electrical components. The bulkiness inevitably implies a large consumption of resin, with an extra cost of the control device being the consequence. Furthermore, the assembly of several independent electrical sub-ensembles by means of connection boxes with soldered or crimped wires, of directly applied weld seams or of added shunt resistors implies a significant preparation time and complicated production processes which are not easily mastered. The guarantee of a long life of the product is no longer ensured despite all the care in numerous quality controls in all stages of the industrial production. As a matter of fact, the risks of failure can appear after a period of transport or abnormal utilisation of the product in extreme environments. Finally, the use of control elements of the type consisting of a keyboard with membranes implies a certain number of breakdowns in the course of time, such as the rupture of the electrical connection layer during an excessive expansion of the resin or the blocking of the touch-buttons under the influence of an excessive ambient temperature. Such a system finally requires strict IRN 710930 5 selections of materials and a very extensive, appropriate industrial expertise which becomes very expensive to manage for an unsuitable or poorly prepared work. Apart from that, any electrical element such as a control keyboard must be placed outside the encapsulation zone, i.e., in a danger zone with the risk of explosions, and this means inserting a Zener barrier before the transformer. This component will limit the energy of external electrical components to prevent the development of sparks. This holds particularly for a fuse. Similarly, the electronic circuit board is made safe by means of elements of the type of fuses which prevent any bad tapping or any starting of the motor if the conditions required and necessary for proper functioning of the motor are not fulfilled. Nevertheless, since such elements as fuses are embedded in the resin, after their triggering the control device becomes unusable because it is not possible to reset it. It is therefore a goal of the present invention to provide a control device of a novel type the concept of which makes it possible to reduce the space requirements of the ensemble, to omit all types of components which are sources of failure under severe conditions, for instance transformers or key boards with flexible membranes, which nowadays imply a number of shortcomings, and to have efficient handling of electrical safety measures without need for incorporating elements with irreversible function such as fuses or varistors, in the insulation.. It is an other goal of the invention to provide a control device with continuous intelligent monitoring by means of a microcontroller which can block the start of the motor in the case of a minimum or maximum failure voltage involving the risk of destroying the electric motor. It is an other goal of the invention to provide a control device working reliably while reducing the electrical connections by omitting terminals on the electronic circuit board. It is another goal of the invention to provide a control device which can sustain increased temperatures of up to 50 "C under normal conditions of use at a relative humidity above 95%. It is an other goal of the present invention to provide a control device the concept of which allows operation with full safety in explosive atmospheres of the type gas "G" by using basically the protection mode "in" of encapsulation considered to be the simplest and most economical method, particularly because of the possible use of a standard plastic box in combination with the mode "i" of intrinsic safety, if necessary, for components outside the encapsulated region. Furthermore, full encapsulation of the electrical parts allows use in environments of the dust "D" type which are much more restrictive and prescribe a protection index at least equal to IP 65. IRN 710930 6 It is an other goal of the invention to standardise a unique motor control regardless of the asynchronous motor used, whether of standard type or type EX. It is an other goal of the present invention to provide a control device capable of working within extended voltage ranges to overcome the greatly differing problems of the highly heterogenous worldwide electrical power nets. To this end, the object of the invention is an electrical control device for motors, preferably asynchronous, single-phase or three-phase motors, comprising at least an electronic circuit board and a relay for controlling the supply of power to the motor, with the electronic circuit board comprising at least one microcontroller analysing the electrical parameters of the mains, such as frequency and voltage, to ensure that they are compatible with the proper running of the motor, to actuate the relay inserted in the power supply net of the motor, with the circuit board and the relay preferably mounted in the interior of a box, characterised in that the relay is a static relay and that the electronic circuit board further comprises: - a capacitive impedance supplied with power from the power supply net of the motor and serving to reduce the supply voltage of the reminder [other parts] of the device and - at least one switching component for starting and/or stopping the device, adapted to be actuated by means of a command component which, in turn, is actuated by a preferably manual movement command. Replacement of the transformer by capacitive supply means and the intelligent management realised with the microcontroller make it possible to obtain a control device of small space requirements and of perfectly safe functioning, which, in particular, is stable in time. According to a preferred embodiment of the invention, the ensemble of the electronic circuit board and the static relay is embedded in a block of an insulating material, such as a resin. According to an other preferred embodiment of the invention, the ensemble of electronic circuit board and static relay is housed in a type "d" jacket, such as an aluminium casing designed particularly for the terminal box of the motor. The switching element(s) is (are) formed by flexible-leaf switches which can be actuated preferably by intermediate magnets. The invention will be understood by reading the following description of embodiments with reference to the appended drawings in which IRN 710930 7 Figure 1 is a perspective view of a control device according to the invention, with the components in extended position and Figure 2 is a sectional view of a control device according to the invention. The device, which is the object of the invention, is to allow the electronic control of a motor, preferably an asynchronous, single-phase or three-phase motor, designated particularly for operation in explosive atmospheres. The device is housed preferably in the interior of a box 1, preferably of an insulating, anti static plastic material, and contains, in general, an electronic circuit board 2 and a static relay 3 for controlling the power supply of the motor and for switching on or off the same in dependence on the characteristic features of the main supply. In a manner characteristic of the invention, the electronic circuit board 2 bears a capacitive impedance 4, double-throw blade switches 5 actuated by magnets 6 and pushbuttons 12, and a microcontroller 7. The control device is supplied with power from the power net of the motor. It is connected to the line of the phase which in turn is connected to the mains. The voltage of that net can vary from 70 to 260 volts single-phase with possible tapping of a 400 v three-phase net with a frequency of 50 or 60 Hz. In order to allow the control device to supply power to the motor from this a.c. net, the voltage must be reduced and a low d.c. voltage must be obtained for supplying power to the circuitry of the electronic circuit board 2. Contrary to the state of the art in which a transformer is used to reduce the supply voltage, the solution adopted involves a capacitive impedance 4. This capacitive impedance is formed by two, preferably plastic, capacitors connected in series. For example, in the case of supplying power to a single-phase motor, the capacitive impedance 4 consists of two capacitors with a capacity of 1 pf, connected in series, type X2 275 VAC, with identical dimensions of 23 x 20 x 9 mm, which ensure operation without a temperature rise, and it handles higher voltages of the order of 260 volts. As a matter of fact, with a very low control current of less than 10 mA in our application, it becomes possible to use very small capacitors with very small space requirements in this technology for a minimum volume of resin. These capacitors can nevertheless function up to 2/3 of the maximum power of the components in accordance with the electrical safety requirements in Explosive Atmospheres, as defined by the valid norms, which impose a limit on the temperature increase at the maximum operating voltage. IRN 710930 8 Doubling the capacitance of a capacitor, which implies a greater current, results in an exponential increase in its volume. The lower current consumption advantageously leads to optimisation of the volume. The same reasoning can be used for an increase in the number of capacitors, which is caused by the requirement of greater energy. In the case of a single-phase motor, this capacitive impedance is connected to the cable of the motor's phase and makes it also possible to reduce the supply voltage of the device to a value below 25 volts. Between the impedance 4 and the neutral conductor there is inserted a rectifier diode bridge which limits the rectified voltage to the exact value of 5 volts. Other capacitors can be inserted in this circuit downstream from this bridge in order to ensure smoothing of the current and short-circuiting of all remaining a.c. voltage. The goal is to obtain by means of the plurality of these components a d.c. voltage of the order a few volts, with this voltage used specifically for supplying power to a microcontroller 7 of the type PIC 16C620. This microcontroller 7, which is mounted on the electronic circuit board 2, analyses the electrical parameters of the mains such as the frequency and the voltage in order to ensure that they are suitable for the proper functioning of the motor and to operate the static relay 3 inserted in the power net of the motor, particularly in the cable of the motor's phase. This static relay 3 functions to turn on or shut off the flow of current for powering a motor in dependence on the characteristics of the current supplied by the mains. The microcontroller 7 in certain instances also determines the time of motor operation. The microcontroller 7 plays a decisive r6le in the monitoring of the electrical quantities in the input of the electronic circuit board. As a matter of fact, it controls all the time the supply parameters for impeding the operation of the static relay or the triggering of electrical safety means before the equipment. The goal of the monitoring is to adjust the parameters of the threshold voltage for keeping the motor within the fixed safety limits (failure detection and recovery of information, relay delay time, ..) or other software functions. For this purpose there is used an input of the type "analog or comparator" of the microcontroller in order to analyse the parameters required for monitoring. The supply voltage is reduced with the aid of a capacitive impedance as a function of the frequency with the formula Iu = Ur/Zc with Zc = l/(Cq-2-if) IRN 710930 9 so that Ur = Iu/(Ceq-2-n-f). The voltage therefore differs as a function of the frequency. The monitoring of the frequency makes it possible to identify the voltage of the net (indirectly, by measuring the reduced voltage) and to set the minimum and maximum threshold voltages at which the microcontroller outputs the command to stop the motor. Switching on and switching off the device is effected by means of flexible-blade switches 5 which can be actuated by pushbuttons 12 and magnets 6. Pushbuttons 12 can be replaced by any other movement controlling means, preferably manual means, with the pushbutton solution being the preferred solution for the intended applications. In order to meet the safety norms in the case of explosive media, the assembly consisting of electronic circuit board 2 and static relay 3 is encapsulated, i.e., embedded in a block 8 of insulating material, such as a resin. The small volume of the capacitive impedance 4 and the placement of the static relay 3 in relation to the electronic circuit board makes it possible to obtain an ensemble of small size, limiting the amount of insulating material to be used. The definition of the encapsulation implies a method of applying a compound of the type of epoxy or polyurethane resin to enclose an electrical device or electrical devices by appropriate means such as embedding or potting. Thus, embedding involves a process of completely covering an electrical device or electrical devices by pouring on it in a mould a compound and by removing the embedded device from the mould after solidification of the compound. As far as potting is concerned, it is an embedding process in which the mould remains attached to the electrical device (devices) embedded. The encapsulation process is therefore an embedding process in which, in regard to pouring the insulating material, the mould remains attached to the embedded electrical device. It is therefore distinguished from the embedding technique in which, after discharge of an insulating material into a mould, the electrical devices are taken out of the mould. Therefore there is obtained a resin thickness of the order of 26 mm for a thickness of only 8 mm of the electronic circuit board and the static relay. In this configuration, the device has at least two flexible-blade switches 5 held by supports 11 in a manner such that they are close to the surface of the block 8 of insulating material in order to trigger their operation and to ensure remote or nearby switching without electrical contact, for example, by means of magnets 6. An equivalent version may imply omission of the insulating material and insertion of the ensemble in a jacket of type "d." IRN 710930 10 A possible version in which the technological option of an encapsulated electronic circuit board is not employed means to take out the control element, providing its protection by "m" encapsulation or by combination with an other form of intrinsic safety type "i" or an explosion-proof "d" jacket. One can also envisage a sensor placed outside the zone of encapsulation of the electronics, wherein the preferably encapsulated control element itself is actuated by manual or automatic commands for movement. The static relay 3 comprises by itself at least one thyristor 3A, preferably two thyristors in upside/downside position, soldered to a plate 10 of conductive material such as aluminium which serves as a heat sink adapted to the use and customised to ensure, in a volume reduced as much as possible, a heat exchange sufficient to avoid overheating. The support plate 10 has the form of a "U" for a thickness 1.5 mm in order to obtain the greatest possible heat dissipation surface. The ensemble is placed in a box 1 which comprises: a base plate 1A carrying the block 8 of insulating material in which the electronic circuit board 2, the static relay 3, and the heat sink element are embedded; and a cover 1B to be fixed on base plate 1A by locking without the aid of a tool. Placing a thyristor or thyristors on a plate 10 of conducting material makes it possible to set this plate first on the bottom of the box and to superimpose thereafter on the plate the electronic circuit board with the ensemble of the other above-listed elements, with the circuit board to be connected by soldering. Once the ensemble is in its position, the insulating material can be discharged into the interior of the box to encapsulate the various elements. As indicated above and in accordance with the norm EN 50028, when electrical equipment is encapsulated, the encapsulated section of the electrical equipment or the encapsulated Ex component has a protective cover of insulating material (potting); there is not set a minimum thickness of the layer between the protective jacket and any component or conductor if the thickness of the jacket is at least 1 mm. Thus, optimisation of the resin volume has been reached with a thickness of at least 1 mm of the jacket of the box. The heat sink is put into direct contact with the bottom of the box. For switching on and shutting off such a device, there are provided - as mentioned above magnets 6 acting on flexible-blade switches. Each of the magnets 6 is mounted on a pushbutton 12 subjected to the load of a spring 14 and incorporated in the cover 1B of the box 1. One of the pushbuttons 12 serves to switch on the device, whereas the other one stops the device. These switches with flexible blades make the microcontroller 7 operative. IRN 710930 11 As mentioned above, the electronic circuit board is supplied with power directly from the power net supplying power to the motor. To this end, the ensemble is connected to the line of the motor phase in the case of a single-phase motor. The control device can also be supplied with power from the supply net of the motor after reducing the supply voltage by means of the capacitive impedance. This capacitive impedance can handle voltages which can vary within a large range, namely from 70 to 260 volts with frequencies which can vary between 50 and 60 Hz. Once the voltage has been reduced to between 8 and 25 volts, the microcontroller 7 analyses the electrical parameters of the reduced voltage and the frequency and determines by extrapolation the input voltage in a way such that the actuation of the static relay is impeded when this voltage is outside a preset range in order to preclude any damage of the motor. The static relay is likewise inserted in the line of the motor phase in accordance with the electrical safety norms indicating interruption of all phases. In order to obtain an ensemble ready for mounting, the base plate 1A of the box has a compartment for the entry of the mains cables and for the exit of the motor cables, which is separated from the block 8 of insulating material by a partition 13. Near its upper edge, this partition has a number of notches to facilitate placing the cables. This box is likewise provided with packing seals through which the cables connected to the mains and those going to the motor are passed. In a version of greater complexity, it can be contemplated to move the connections to a terminal box outside the encapsulated region but remaining in the interior of the jacket to allow a possible wiring option not depending on the electronics box. For protection in Explosive Atmosphere, this terminal box must be protected in conformity with the increased safety norm "e." This implies particularly that the casing is sealed with a protection index equal at least to IP 54. For this purpose, the box has a groove on its circumference for accommodating sealing means such as a flexible packing which ensures the required degree of protection. Finally, in order to ensure continuous monitoring of the functioning of the device, the electronic circuit board 2 holds a two-color diode 15 which protrudes from the insulating block 8. This diode 15 is covered by a lightguide 16 connected to the cover lB of the box in a manner such that the light signal emitted from the diode 15 is visible from the outside of the box 1. Any failing therefore can be recognised in real time and all the time. The control of the static relay in real time and all the time precludes any passage of current to the motor when the current does not meet the characteristics which allow satisfactory functioning of the motor. IRN 710930 12 In order to facilitate the placement of the box 1 on some support, the base plate 1A of this box 1 can be provided with deformable elastic fastening means matching the support. The operation of such a control device is very simple. Once connection have been established to the motor on the one hand and to the mains on the other, the device can be switched on simply by actuating the pushbutton corresponding to starting the device. This actuation of the pushbutton allows the magnet of a pushbutton to attract a blade of the reed switch 5 such as a REED bulb in order to make contact. Then the microcontroller 7 can supply a small d.c. current through a bridge rectifier, ensuring the regulation of 5 volts at the capacitive impedance, and the electrical parameters of the mains can be analysed. When the voltage supplied is suitable for proper operation of the motor, the microcontroller 7 energises the static relay 3 and allows the same to pass current to the motor. The motor then can run during a preset time period corresponding to that programmed in the microcontroller 7. Once the preset time period has elapsed, the motor is automatically stopped. In the case of an emergency stop, the other pushbutton can be actuated to call for stopping the motor. In the case of a three-phase motor, each phase line of the motor has an inserted static relay 3. IRN 710930 13

Claims

1. Electrical control device for motors, preferably asynchronous, single-phase or three-phase motors, comprising at least an electronic circuit board (2) and a relay (3) for controlling the supply of power to the motor, with the electronic circuit board (2) carrying at least one microcontroller (7) analysing the electrical parameters of the mains, such as frequency and voltage, to ensure that they are compatible with the proper running of the motor, to actuate the relay (3) inserted in the power supply net of the motor, with the circuit board (2) and the relay (3) preferably mounted in the interior of a box (1), characterised in that the relay (3) is a static relay and that the electronic circuit board (2) composes: - a capacitive impedance (4) supplied with power from the power supply net of the motor and serving to reduce the supply voltage of the reminder [other parts] of the device and - at least one switching component (5) for starting and/or stopping the device, adapted to be actuated by means of a command component (6) which, in turn, is actuated by a preferably manual movement command.

2. The device according to Claim 1, characterised in that the ensemble of electronic circuit board (2) and static relay (3) is embedded in a block (8) of insulating material, such as resin.

3. The device according to Claim 1, characterised in that the ensemble of the electronic circuit board (2) and the static relay (3) is placed in a type "d" jacket such as an aluminium casing.

4. The device according to any one of Claims 1 to 3, characterised in that the switching components (5) are formed by two flexible blade switches (5) which are actuated preferably by means of magnets (6).

5. The device according to any one of Claims 2 and 4, characterised in that it comprises at least two flexible blade switches (5) each of which is held by supports (11) so that they are close to the surface of the block (8) of insulating material to facilitate their control by the magnets (6).

6. The device according to Claim 1, characterised in that the static relay (3) comprises at least one thyristor (3A) soldered to a plate (10) of conducting material, such as aluminium, serving as heat sink.

7. The device according to Claim 1, characterised in that the capacitive impedance (4) is formed by two capacitors, preferably plastic capacitors, connected in series.

8. The device according to Claim 1, characterised in that the box (1) comprises IRN 710930 14 - a base plate (1A) containing the block (8) of insulating material in which the electronic circuit board (2) and the static relay (3) are embedded, - and a cover (IB) to be fixed on the base plate (1A) by locking without the aid of a tool.

9. The device according to Claim 8, characterised in that the cover (1B) of the box (1) has two pushbuttons (12) each of them bearing a magnet (6) for controlling a flexible blade switch (5), one for starting the device, the other one for stopping it.

10. The device according to Claim 8, characterised in that the base plate (1A) of the box has a compartment for entry of the mains cables and the exit of the motor cables, with separation from the block (8) of insulating material by means of an internal partition (13).

11. The device according to Claim 8, characterised in that the electronic circuit board (2) carries a two-color diode (15) protruding from the insulating block (8), with this diode (15) covered by a lightguide (16) connected to the cover (1B) of the box in a manner such that the light signal emitted from the diode (15) is visible from the outside of the box (1).

12. The device according to any one of Claims I to 11, characterised in that the box (1) is made of anti-static plastic material. IRN 710930 15