FR2631510A1 - DEVICE FOR COOLING ELECTRICAL DISTRIBUTION CABINETS - Google Patents

Abstract

In this device 10 comprising an evaporator 12, a compressor 13 and a condenser 14, traversed by a cooling fluid according to a closed circuit 11 and among which the evaporator 12 is connected to the interior space of the cabinet and the air ambient is sent to the condenser 14 by means of an air filter 24, and comprising a first temperature sensor 16 placed at the outlet of the coolant from the condenser and a second temperature sensor 17, the latter is arranged in the zone d 'suction 26 of the ambient air sent to the condenser 14 and the value tc of the temperature of the condenser delivered by the sensor 16 and the value tu of the ambient temperature delivered by the sensor 17 are processed together with a value or a quantity ts of cabinet temperature. This device makes it possible to indicate the need for a replacement of the filter 24 in the event that its maximum permissible soiling is reached. Application in particular to electrical cabinets.

Description

The present invention relates to a device for cooling cabinets

  electrical distribution system, comprising an evaporator, a compressor and a condenser, which are traversed, in a closed circuit, by a cooling fluid and from which the evaporator is connected to the internal space of the distribution cabinet and the ambient air is sent to the condenser via an air filter, and having a

  first temperature sensor placed at the outlet of the flui-

  condenser cooling and a second sensor

temperature.

  In such devices, the cooling fluid

  It is usually vaporized during the cycle at a low pressure level at a temperature determined temperature dependent in the distribution cabinet, in which case heat is removed from the distribution cabinet to be cooled. After a compression performed in the compressor, this withdrawn energy is delivered to the ambient air, even when the ambient temperature is higher than said temperature, at which the evaporation takes place. The heating power that can be transmitted depends on the compressor power of the type and quantity of the cooling fluid, the process control and, in particular, the heat exchangers used. Since the condenser is cooled by ambient air, it is necessary to filter the ambient air before it reaches the condenser, in order to avoid a soiling of the condenser. The absorption of dirt by the filter during operation reduces the volume flow of the circulating ambient air, which leads to a reduction in power of the refrigerating machine. Therefore, after a certain period of operation, it is necessary to replace the filter. A corresponding operating state, during which it is necessary to replace the filter, should be indicated. A corresponding device, in which a dirtying of the air filter is indicated, is known for example from DE-CE 33 26 977. The condensation temperature tc is measured by the first temperature sensor and the temperature ts of the air. in the distribution cabinet is measured by the second temperature sensor. However, to these two sensors is associated, and this in a manner substantially independent between the two, a determined maximum temperature value, which is equal for example to 700 or 50 C so that, for the respective maximum admissible temperature, a anomaly transmitter, connected to the temperature sensor considered, indicates this operating state and / or disconnects the device. In this known device, it is assumed that in order to control the porosity of the air filter, it is possible to use the condensation temperature tc of the cooling fluid, since the latter is in direct connection with the volume flow rate of the necessary air. to cool the condenser, and with the temperature of this air. However, this relationship is not clear since the coolant outlet temperature at the condenser or compressor is not a reliable signal for dirtying the air filter. For a predetermined inlet temperature you have air in the condenser or in the compressor, a determined condensation temperature tc is established, in which case, when the volume flow rate of air decreases, the condensation temperature tc increases. despite a constant temperature you enter the air. In the diagram shown in FIG. 3A appended to the present application, it is possible to see the influence of the ambient temperature T0 and the temperature ts of the switching cabinet on the condensation temperature tc. The

  line with dashes for tc = 70 C represents the time

  boiling temperature of the coolant for

  a value of 18.105 Pa, for which the device

  naked is stopped in all cases. Using three examples

  ples a, b, c, it is shown in this figure that the ac-

  temperature increase is possible in the case of dirtying of the air filter, when, as mentioned, the threshold value for the air filter dirt is set at 70 ° C. In example a, for a room temperature t = 42 C and a temperature ts = C of the distribution cabinet, a possible increase of a value a = 4.5 K of the condensing temperature in the case of dirtying of the air filter . In example b, an even greater increase in temperature, corresponding to b = 2.5 K, is obtained for the operating state tu = 40 C and tus = 20 -C. In the case of the operating state c corresponding to tu = 41 ° C and ts = 50 ° C, a temperature increase of c = 2 K is obtained. Since the increase in temperature must be considered as the measure of degree of soiling, however, it results that, depending on the operating state, in an extreme case, a case of disturbance is displayed even in the case of an air filter 9, while in the other case, no disturbance of this kind is displayed, even in the case of a

  significant dirtying of the air filter.

  Therefore, the object of the present invention is to provide a device for cooling electrical distribution cabinets of the type indicated above, and by means of which a dirt of the air filter is definitely detected, which does not guarantee plus one

  perfect functioning, already at this stage.

  This problem is solved in a device

  to cool electrical distribution cabinets of the type indicated above, thanks to the fact that the second temperature sensor is disposed in the suction zone of the ambient air sent to the condenser, and that the value of the condenser temperature, delivered by the first temperature sensor, and the value of the ambient temperature delivered by the second temperature sensor are processed together with a value of the temperature of the cabinet or a size of the

temperature of the cabinet.

  In the cooling device according to the invention, provided for electrical distribution cabinets, the condensation temperature tc is therefore directly associated with both the ambient temperature and the temperature ts of the distribution cabinet. which ensures that a maximum permissible dirtiness of the air filter is detected

  and that a signal is delivered during such detection.

  Thanks to the combination of the three temperature values, it is possible to calculate the condensing temperature tc, which is established by means of the predetermined temperature ts of the distribution cabinet and the ambient temperature t o. If the flow rate of the cooling air decreases due to dirtying of the filter, it is established for the same values of the air temperature ts of the distribution cabinet and the ambient temperature of air, a condensation temperature tcv greater than the value, ctc proportional to the degree of soiling. By means of an electronic processing of the three temperatures as input variables as well as the control value tc, an output quantity can be obtained which indicates the need for filter replacement, in the case where the maximum permissible dirt of the air filter is reached. According to an exemplary embodiment of the present invention, according to which the temperature of the cabinet is measured by means of a third temperature sensor, this measurement can be carried out such that

  so that, so to speak, a three-dimensional dependency

  of the different temperatures and therefore the calculated process value is set, which leads to a possibility of very precise indication of the moment when the maximum permissible filter dirt has been reached.

to air is reached.

  In accordance with an exemplary embodiment

  of the present invention, according to which the temperature of the cabinet, which must be taken into account, is predetermined as a parameter value, a simple device is obtained from the point of view of the

  regulation technique, making it possible to achieve this ob-

  objective, which only requires the treatment of two

  temperatures, ie the temperature of the ambient air and

  the condensation temperature tc.

  In the case where in the device, the parameter magnitude of the cabinet temperature, which must be taken into account, is obtained from a temperature range, which lies between the characteristic curves for upper limit values. and lower constant temperature of the cabinet, it is advantageous to select a limited temperature range for the temperature of a cabinet, which must be taken into account. This is possible since the dependence of the condensation temperature on

  the temperature of the cabinet is not very pronounced.

  For example, in this range it is possible to select an average temperature of the cabinet according to the full range of the condensation temperature and the ambient temperature and then to select the combination of the temperature.

  condensation and ambient temperature.

  According to an embodiment of the present invention, according to which the magnitude of the temperature ts of the cabinet, which is to be considered, is determined by a control characteristic curve, which extends from a point of intersection corresponding to a minimum condensing temperature tc and at ambient temperature T0, for a maximum permissible temperature ts of the cabinet, up to a point of intersection corresponding to a maximum temperature

  permissible condensation rate tc and at a temperature of

  you, for a minimum temperature ts of the cabinet, is determined by tc - a. tu - b = 0, which however advantageously allows to obtain that, on the basis of the considered position of the control characteristic curve, weaker filings of the filter are allowed for higher temperatures of the cabinet since the cooling device works less in this range, whereas, for a lower temperature of the cabinet, more dirtying of the filter at

air can be allowed.

  According to another characteristic of the invention,

  according to which the parameters of the characteristic curve

  than the control curve are formed from the average control characteristic curve of all the control characteristic curves, determined for different cooling devices, including a permissible temperature overflow, which makes it possible to adjust the cooling devices in the same way having different powers, so that identical control systems can be used.

  Another provision aimed at increasing the

  in such cooling devices is obtained by virtue of the fact that the permissible

  temperature is lower in the vicinity of a

  ambient temperature and in the vicinity of a

  lower ambient temperature, since then

  only a smaller increase in the

  condensing temperature is allowed in the range of

  higher temperatures of the distribution cabinet.

  Other features and benefits of the

  present invention will emerge from the description given

  hereinafter referenced to the accompanying drawings, in which:

  FIG. 1 shows a diagrammatic representation

  tick of a device for cooling electrical distribution cabinets; FIG. 2 represents a diagram in the space of dependencies of the condensation temperature with respect to the ambient temperature and the temperature of the cabinet, making it possible to represent the mode of action of a device of FIG. cooling according to a first embodiment of the present invention;

  FIGS. 3A and 3B show diagrams

  grams showing the dependence of the condensation temperature with respect to the ambient temperature for constant temperatures different from the distribution cabinet as a parameter, to represent the mode of action of a known cooling device and to represent the mode of action of a cooling device according to a second embodiment of the present invention; and Figure 4 shows in more detail, but schematically, the control circuit of Figure 1 of the type used in the cooling device according to the second embodiment of the present invention. The device according to the invention 10 for cooling an electrical distribution cabinet (not shown) is in the form of a compression refrigeration machine and has, in a closed circuit 11 traversed by a cooling fluid, an evaporator 12, a compressor 13, a condenser 14 and an expansion valve 15. The compressor 13 disposed between the evaporator 12 and the condenser 14, and the expansion valve 15 is disposed between the capacitor 14 and the evaporator 12. A first sensor temperature 16 is disposed at the outlet 21 of the cooling fluid leaving the condenser 14 and is connected, via a line 22, to a regulator 23, the output of which can be connected to a display device of FIG. anomaly or the like. This first temperature sensor 16 indicates the condensation temperature tc of the cooling fluid. A second temperature sensor 17 is disposed in the air intake zone 26, equipped with a filter 24, of the compressor 13, whose heat exchanger or not shown are traversed, wrapped or other, as is indicated by the arrow A, by the ambient air having a temperature you determined. In all cases, the capacitor 14 delivers heat to the ambient air. The second temperature sensor 17 serves to

  measure the ambient temperature you (air).

  These two temperature sensors 16 and 17 are provided in the two embodiments of the present invention, described below. In a first exemplary embodiment, which will be described, of the present invention is further provided a third temperature sensor 18 located in an air suction zone 27 of the evaporator 12, the exchanger or exchangers no heat are shown or wrapped or the like, as indicated by the arrow B, the air inside the distribution cabinet. In any case, the evaporator 12 draws heat from the inside air of the cabinet so as to reduce the temperature ts (of the indoor air :) of the cabinet or maintain it at a determined value. This third temperature sensor 18 therefore serves to measure the temperature ts (of the indoor air) of the cabinet. As the second temperature sensor 17, which is connected by a line 27 to the regulator 23, in the case of the first embodiment, the third temperature sensor 18 is connected via the line 29 to the regulator 23, as is represented by a

line in dashed line.

  On the other hand, in both forms of

  a fourth temperature sensor is provided.

  19, which measures the temperature to cooling fluid at the outlet 31 of the evaporator 12 and is connected via a line 32 to the valve

Expansion 15.

  Figure 2 represents a diagram in the

  the temperature of the three temperatures measured using the three temperature sensors 16,17,18 according to a first embodiment of the present invention, namely the condensation temperature tc, the temperature ts of the cabinet and the ambient temperature you. In this spatial coordinate system, there is shown a characteristic panel 36, which is characteristic of a specific cooling device 10 placed in a specific distribution cabinet, in the case of the use of a new air filter 24 . From this feature panel 36, the reciprocal dependence of the three temperatures tc, ts, tu can be determined by calculation by means of establishing a mathematical relationship. From such a mathematical relation, it is possible to calculate the temperature of condensation tc which is established, in the case where the temperature ts of the cabinet and the ambient temperature you are predetermined. If the volume flow rate of the cooling air or of the ambient air varies due to a dirtying of the air filter 24 placed in the path of the cooling ambient air, we obtain, for the same values of ts and you, a condensation temperature tcv, which is greater than the value tc proportional to the degree of soiling, to the temperature tc corresponding to the characteristic diagram 36. With the aid of the electronic regulator 23, which processes by calculation the temperatures ts , you and tc as well as the permissible control value tc, constituting input quantities, there is obtained as an output value at the output 25 of the controller 23 a signal which indicates the need for replacement of the filter. While the set of features 36 shown in FIG. 2 is the same as that measured in the case of a new, ie unsalted, filter 24, a corresponding set of characteristics obtained with an air filter. .24 having a maximum permissible soiling, would be shifted substantially parallel, of a valueAtc, relative

  to the set of features 36.

  According to the second embodiment of the present invention, shown in FIG. 3B, a simplification of the regulator 23 and also of the cooling device 10 is obtained by measuring only the condensation temperature tc and the ambient temperature t 0, while the temperature ts of the cabinet is predetermined as a parameter. In FIG. 3B, there is shown the dependence of. the condensation temperature tc with respect to the ambient temperature T0 in the case of a given cooling device 10, both for a maximum permissible temperature ts1 of the cabinet, equal for example to 50.degree. minimum temperature of the cabinet ts2 equal for example to 20 C. This representation can be drawn from the spatial representation of FIG. 2, for the temperature of the cabinet

  to be considered respectively as isothermal.

  For example the points characterized by "1" and "2" are

  comparable in Figures 2 and 3B.

  It should be mentioned here that the representation of FIG. 3A also represents, but on a slightly different scale, the dependence of the condensation temperature tc with respect to the ambient temperature T0 for three isotherms ts, this representation showing the disadvantages according to the state of the art, according to which the temperature ts of the cabinet is measured outside the condensation temperature tc, in which case there is no corresponding combination and only limit values are

  predetermined for each temperature.

  According to the second embodiment of the present invention, within this range between the two isotherms as limit values for the temperature of the cabinet, a characteristic curve 37 is selected as a function representing the dependence of the condensation temperature tc with respect to the ambient temperature T0, which is a straight line G and whose relation is represented by a straight line G and takes into account the temperature ts of the cabinet in the form of a factor a and a number added b. The characteristic curve 37, which represents an approximation of the different temperatures ts of the cabinet, to be taken into account, starts from a point of intersection "1", which represents the point of intersection between the maximum temperature tsl of the cabinet and the minimum temperature of condensation and the minimum ambient temperature tcl or tul, to reach a point "2", which represents the point of intersection between the minimum temperature ts2 of the cabinet and the maximum condensation temperature tc2 and room temperature tu2. From there, a certain security is obtained insofar as a weaker dirt of the filter and consequently a

  lower increase in condensing temperature

  It is permissible for a higher temperature tul of the cabinet, since in this range the cooling device 10 works less. On the other hand, at the other point of intersection, that is to say for a low temperature ts of the cabinet, a greater dirt of the filter and consequently a greater increase in temperature of the cabinet.

compensation are allowed.

  The characteristic curve 37 represented by a straight line in FIG. 3B is a curve forming part of a multiplicity of correspondingly chosen characteristic curves of cooling devices 10, which are mounted in distribution cabinets of the same type. and have different powers, and is arranged in such a way that it can be considered here as being a characteristic characteristic curve of the other characteristic curves 37 ', 37 ", etc. represented by straight lines formed by dashes. 37 corresponds, like the characteristic curves 37 ', 37 ", to the following relation: tc - a tu-b = 0,

  the factor a and the element b to be added being respectively

  different for these characteristic curves. As already mentioned with reference to the embodiment of FIG. 2, these characteristic curves 37 ', 37 ", etc. and consequently the selected average characteristic curve 37 are valid - for cooling devices 10, mounted in switching cabinets and having a new filter 24, that is to say, not soiled, Because of a dirt of the filter 24, the characteristic curve 37 can be moved in parallel, by a distance ttc proportional to the degree of a temperature corresponding to the permissible increase in the condensation temperature, in accordance with the selected control characteristic curve 38, represented by a dotted line in FIG. , in addition to the parallel offset, an inclination towards the higher values of the condensation temperature and the ambient temperature, so that the parameters or factors and

  terms to add a and b vary correspondingly.

  In the case of the exemplary embodiment shown, the following is therefore obtained as a condition for the maximum permissible increase of the condensation temperature:

Atc> tc - a. you - b.

  As a result, the permitted increase in condensation temperature is lower in the higher condensation temperature range and higher ambient temperatures than in the lower condensation and temperature range.

  lower ambient temperatures.

  FIG. 4 represents, for the second exemplary embodiment of the present invention, an embodiment of the regulator 23. The two temperature sensors 16, 17, which are connected to a supply voltage by one of their inputs and to the mass by their other input, are connected by their outputs 41,41 ',

  to respective operational amplifiers 42,43.

  While the operational amplifier 42 carries out a determined amplification, for example of factor ten, of the voltage signal Utc, the operational amplifier 43 comprises, on its input side, a voltage divider 44, so that the input signal Utu is amplified by a factor other than that amplifying the signal Utc delivered by the first temperature sensor 16. In addition, the inputs of the operational amplifier 43 are exchanged with respect to those of the operational amplifier 42 so that the output signal U'tu of the operational amplifier 43 is inverted. In the summation line 46, therefore, a sum signal or a sum voltage, which corresponds to the temperature difference (tc - a.tu): 2, is obtained. This difference signal is sent via another amplifier

  47, to a fourth operational amplifier

  48, at the inverting input of which is furthermore

  yea, by a voltage divider circuit 49, a

  fixed voltage value, which is proportional to the

  number or number to be added, selected (b + Àtc): 2. The

  formation of the difference in the fourth ampli-

  operational indicator 48 results in the issuance

  of output 51 of this amplifier, of a signal Q satisfying the following relation:

Q. = tc - a. you - b - tc.

  If this signal is less than zero, the maximum permissible dirt of the air filter is not yet determined, but if this signal is greater than zero, there is obtained on the output 51 of the regulator 23 a signal indicating that the filter air 24 is unacceptably high so that it must be

replace or clean it.

Claims (7)

  1. Device for cooling electrical distribution cabinets, comprising an evaporator, a   compressor (13) and a condenser (14), which are   rus, according to a closed circuit (11), by a cooling fluid and among which the evaporator (12) is connected to the interior space of the distribution cabinet   and the ambient air is sent to the condenser (14) by the   an air filter (24), and having a first   first temperature sensor (16) placed at the exit of the   coolant of the condenser and a second cap-   temperature sensor (17), characterized in that the second temperature sensor (17) is arranged in the suction zone (26) of the ambient air sent to the condenser   (14), and that the value (tc) of the condensing temperature   the first temperature sensor (16), and the value (tu) of the ambient temperature delivered by the second temperature sensor (17) are processed together with a value of the cabinet temperature or a magnitude ( ts) of the temperature of the cabinet.   2. Device according to claim 1, characterized   characterized in that the temperature (ts) of the cabinet is measured using a third temperature sensor (18).   3. Device according to claim 1, characterized   controlled in that the temperature (ts) of the cabinet; which must be considered, is predetermined as parameter size.   4. Device according to claim 3, characterized   in that the parameter magnitude of the time   temperature (ts) of the cabinet, which must be taken into   te, is obtained from a range of temperatures, which lies between the characteristic curves tc = f (tu) for upper and lower limit values   constant temperature (ts) of the cabinet.   -5. Device according to claim 4, characterized   characterized in that the magnitude of the temperature (ts) of the cabinet, which is to be considered, is determined by a control characteristic curve (38), which extends from a point of intersection (1) corresponding to a minimum condensation temperature (tc) and ambient temperature (tu), for a maximum permissible temperature (ts) of the cabinet, up to a point   intersection (2) corresponding to a temperature of   maximum permissible amount of condensation (tc) and at a   room temperature (tu), for a minimum temperature (ts) of the cabinet, is determined by tc - a. you - b = 0.   6. Device according to claim 5, characterized   characterized in that the parameters (a, b) of the control characteristic curve (38) are formed from the average control characteristic curve (37) of all the control characteristic curves (37 ', 37 "... ), determined for different cooling devices (10), including an allowable exceedance temperature (4tc).   7. Device according to claim 7, characterized   in that the permissible temperature rise (ttc) is lower in the vicinity of a higher ambient temperature (t o) and in the vicinity of a   lower ambient temperature (μ).