Relay Module

Abstract

The relay module (100) comprises a control input (102) for jointly controlling and supplying power to the relay module (100) using an alternating voltage. A fixed voltage regulator (114) of the relay module (100) generates a fixed voltage (116) after rectifying the alternating voltage or a portion of the alternating voltage. A comparator (120) is operated by the fixed voltage (116) and derives a reference voltage (118) from the fixed voltage (116). The comparator (120) compares the rectified and smoothed portion of the alternating voltage with the reference voltage (118). A switching stage (124) of the relay module (100) operates a relay unit (126) based on the comparison of the comparator (120), the relay unit (126) being connected to the switching stage (124) on the input side and to a switch connection of the relay module (100) on the output side.

Description

Technical Field

[0001] The present invention relates to a relay module. In particular, but not exclusively, the present invention relates to an alternating current-fed relay module having an adjustable switching threshold with low hysteresis. Background Art

[0002] Relay modules already on the market include a low-pass filter, such as an RC link, on the input side. Because such relay modules are directly fed with the alternating voltage (AC) of the control signal, a low-pass filter specifically for interference signals from the AC power grid is used on the control side. However, such relay modules have a relatively wide operating voltage and return voltage range based on the physical properties of the relay coil, such as the ferromagnetic state of the core of the relay coil. In this case, the advantage of the relay module's lower current consumption compared to conventional contactors can also have a negative impact. For example, at an AC rated control voltage of 230V, the operating voltage and return voltage range can be located between an operating voltage of 170V and an AC return voltage of 40V depending on the relay coil. In this article, the voltage and current description data for the alternating current refer to the corresponding effective value or mean square value.

[0003] When other motors and contactors are switched on, high interference voltages and high interference currents usually occur, which can be coupled into the control lines of the relay modules even in a separate AC network due to the long line lengths.

[0004] Interference voltages and interference currents in the control lines can lead to unintentional switching on of the relay coil or to delayed release. In addition, the status display can illuminate, especially the light-emitting diodes that activate even at low currents, even though the relay coil has not yet caused the switching process. Such displays and switching behaviors are misleading and therefore undesirable.

[0005] In order to limit the unintended properties of conventional relay modules, filters, such as RC links, are usually connected in parallel with the input. The filter should compensate for interference and ensure that the relay module is safely switched on or off. In some installations, especially in power plant engineering, such filters are not sufficient, so that erroneous behaviors of the relay module still occur. Summary of the invention

[0006] The object of the present invention is to propose a remedy. In particular, the present invention is based on the object of providing a relay module having an adjustable and / or low-hysteresis switching threshold.

[0007] This object is achieved according to the invention by means of the features of the independent claim. Suitable embodiments and advantageous developments of the invention are described in the dependent claims.

[0008] Other features and advantages of the invention are described below, in part with reference to the accompanying drawings.

[0009] According to one aspect of the present invention, the relay module includes a control input, wherein the control input is loaded with an AC voltage or can be loaded with an AC voltage so as to jointly control and power the relay module. The relay module also includes a fixed voltage regulator, which is configured to generate a fixed voltage after rectifying the AC voltage or a portion of the AC voltage. The relay module also includes a comparator, which is configured to operate with a fixed voltage and compare a reference voltage derived from the fixed voltage with a portion of the rectified and smoothed AC voltage. The relay module also includes a switching stage, which is configured to operate a relay unit based on a comparison of the comparator. The relay module also includes a relay unit that is connected to the switching stage on the input side and to the switch connection of the relay module on the output side.

[0010] Embodiments of the relay module can explicitly control whether the switching stage operates the relay unit based on the comparison in the comparator. Since the reference voltage is derived from the fixed voltage for the comparison, the switching threshold at the control input can be state-independent and / or low-hysteresis. Since the comparator is operated by the fixed voltage, the same or other embodiments of the relay module can be operated without a separate or permanent voltage supply.

[0011] The AC voltage may be a grid voltage. The AC voltage may be 110V AC to 230V AC. Alternatively or in combination, the fixed voltage may be 5V DC to 12V DC.

[0012] The derived reference voltage may be a fixed portion of the fixed voltage. The relay module, in particular the comparator, may include a voltage divider which is designed to derive the reference voltage as a fixed portion from the fixed voltage.

[0013] The relay module may further comprise a rectifier connected upstream of the fixed voltage regulator. The rectifier may comprise a bridge rectifier for rectifying the alternating voltage or a portion of the alternating voltage.

[0014] The switching stage can switch a coil loop of a relay unit fed by the rectifier. The switching stage can be designed to selectively connect the negative pole of the rectifier to the relay unit in an electrically conductive manner and disconnect it from the relay unit as a function of the comparison. A status indicator can be connected in the coil loop, preferably in series with the relay unit.

[0015] A reactance, preferably a capacitive reactance, which generates a portion of the AC voltage for rectification can be arranged between the control input and the rectifier (connected upstream of the fixed voltage regulator). A large portion of the AC voltage, preferably more than half or 75%, can be dropped at the reactance.

[0016] The comparator can include an operational amplifier for carrying out the comparison. The rectified and smoothed portion of the AC voltage and the reference voltage can be applied to the input of the operational amplifier. The control voltage for controlling the switching stage can be generated by the operational amplifier.

[0017] The comparator can also be configured to generate a rectified and smoothed portion of the AC voltage for comparison with a reference voltage independently of a rectifier connected upstream of the fixed voltage regulator. For example, the comparator can include a half-wave rectifier having a filter capacitor. The AC voltage or a portion of the AC voltage can be applied to the half-wave rectifier as an input voltage. The half-wave rectifier can be configured to generate a smoothed DC voltage for the rectified and smoothed portion of the AC voltage in the comparator.

[0018] The comparator may also include a voltage divider. The smoothed DC voltage of the half-wave rectifier may be applied to the voltage divider of the comparator. The voltage divider of the comparator may be configured to generate a smoothed DC voltage component as a rectified and smoothed component of the AC voltage in the comparator.

[0019] The voltage divider can be controllable, for example, by means of a potentiometer. As a result, the rectified and smoothed portion of the AC voltage used for the comparison can be controlled. In particular, the switching threshold at the control input can be controlled thereby. For example, the switching threshold can be manually adjustable at the relay module.

[0020] The input voltage of the comparator can be tapped between the control input and the rectifier (connected upstream of the fixed voltage regulator). The comparator can tap the input voltage before the reactance (e.g. via a megohm resistor in the comparator) or after the reactance (e.g. using a correspondingly smaller series resistor in the comparator).

[0021] The relay module can be arranged in a closed housing. The housing can be closed due to the low power loss of the relay module, for example because the circuit elements of the relay module are only energized during operation of the relay unit and / or the reactance reduces the voltage level of the AC voltage almost without loss.

[0022] The housing may be provided with externally accessible terminals of the switch connection. The housing may be designed for fastening to a support rail, in particular a top-hat rail. The control input may also be wired via externally accessible terminals on the housing. Alternatively or additionally, the control input and / or the switch connection may have plug-in contacts on the housing, which are arranged for contacting a busbar extending parallel to the support rail.

[0023] The housing can have a slot accessible from the outside for the exchangeable mechanical and electrical connection of a relay unit. This allows the relay module to be adapted to different switching powers, switching voltages, switching currents and / or relay functions by inserting or replacing a relay unit. For example, a relay unit for a pulse relay and / or for more than two states can be inserted. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Next, the present invention will be further described according to preferred embodiments with reference to the accompanying drawings.

[0025] Figure 1 A schematic diagram showing a block diagram of a relay module according to a first embodiment of the present invention;

[0026] Figure 2 An exemplary diagram showing the switching behavior of a relay module according to a second embodiment of the present invention;

[0027] Figure 3 A schematic circuit diagram showing a relay module according to a third embodiment of the present invention; and

[0028] Figure 4 An exemplary perspective view showing a relay module according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0029] Figure 1 A schematic diagram of a block diagram of a first exemplary embodiment of a relay module, generally designated by reference numeral 100 , is shown.

[0030] The relay module 100 comprises a control input 102 which is loaded or can be loaded with an alternating voltage (AC) in order to jointly control and supply power to the relay module 100. A fixed voltage regulator 114 of the relay module 100 generates a fixed voltage 116 after rectifying the alternating voltage or a portion of the alternating voltage. A comparator 120 of the relay module 100 is operated by the fixed voltage 116 as a supply voltage. The comparator 120 compares a reference voltage 118 derived from the fixed voltage 116 with the rectified and smoothed portion of the alternating voltage applied to the control input 102. A switching stage 124 of the relay module 100 operates a relay unit 126 of the relay module 100 as a function of the comparison of the comparator 120. The relay unit 126 is connected to the switching stage 124 on the input side and to a switch connection of the relay module 100 on the output side.

[0031] The first embodiment of the relay module 100 includes an AC control input 102, a fixed voltage regulator 114, a comparator 120, a switching stage 124, and a relay unit 126. The relay unit 126 may also be simply referred to as a relay.

[0032] The relay unit 126 may include a mechanical relay. The switching stage 124 operates the electromagnet of the relay unit 126 according to the comparator 120. The current switched on by the switching stage 124 flows in the excitation coil of the electromagnet of the relay unit 126 and generates a magnetic flux through the ferromagnetic core of the electromagnet. In a variant of the first embodiment, a movably mounted (e.g., also ferromagnetic) armature opens and / or closes the switch connection of the relay module 100 in the switching position. In the absence of current in the excitation coil, the armature returns to the starting position from the switching position by the spring force.

[0033] The voltage threshold and / or current threshold of the current in the field coil may be significantly different for closing and releasing the armature, for example due to the ferromagnetic core, and the switching stage 124 is designed to control the relay unit 126 to either close the armature or release the armature as a function of the comparator 130. As a result, a deviation or hysteresis between the closing voltage and the release voltage at the AC control input 102 can be reduced or at least substantially avoided.

[0034] Preferably, the first embodiment of the relay module 100 further comprises a rectifier 110 between the AC control input 102 and the fixed voltage regulator 114 for rectifying the AC voltage or a portion of the AC voltage applied to the AC control input 102. The DC voltage 112 of the rectifier 110 (e.g., the portion of the AC voltage rectified by the rectifier 110) feeds the fixed voltage regulator 114. Alternatively or additionally, the switching stage 124 switches the DC voltage 112 generated by the rectifier on the basis of the comparator 120 to operate the relay unit 126. For this purpose, the control voltage 122 output by the comparator 120 to the switching stage 124 corresponds to the comparison result of the comparator 120.

[0035] Optionally, the first embodiment of the relay module 100 also includes a capacitive reactance 108 between the AC control input 102 and the rectifier 110. The capacitive reactance 108 is designed to adapt the voltage level of the AC voltage to the voltage level of the rectifier 110 or the fixed voltage regulator 114. For this purpose, the majority of the voltage level of the AC voltage drops at the capacitive reactance 108. Due to the dominant reactive power, the voltage drops at the capacitive reactance 108 substantially without heat loss.

[0036] Less or substantially no heat loss improves the energy efficiency of the relay module 100 and / or enables a compact design, for example with a narrow housing and / or a housing without ventilation openings. In the case of a housing for mounting on a support rail, such as a top hat rail, a smaller width of the housing of the relay module 100 is particularly advantageous. For example, due to the smaller width, more modules can be mounted on the same support rail.

[0037] An input voltage 106 corresponding to or derived from the AC voltage present at AC control input 102 is present at comparator 120. From input voltage 106, the comparator generates a rectified and smoothed portion of the AC voltage present at AC control input 102 for comparison with reference voltage 118.

[0038] Because the reference voltage 118 is determined by the fixed voltage regulator 114 (i.e., is derived from the fixed voltage 116) and the input voltage 106 is not determined by the fixed voltage regulator 114 (e.g., is linearly dependent on the AC voltage applied to the AC control input terminal 102), the comparison of the comparator 120 can therefore detect the absolute change of the AC voltage applied to the AC control input terminal 102.

[0039] The input voltage 106 may be tapped directly at the AC control input 102 or between the AC control input 102 and the capacitive reactance 108 .

[0040] Optionally, the first embodiment of the relay module 100 comprises an RC filter 104 between the AC control input 102 and the capacitive reactance 108. The RC filter can filter out voltage fluctuations which are preferably shorter in time than the application-dependent switching rhythm of the relay module 100, for example, even when the voltage fluctuations exceed or fall below a uniform switching threshold of the relay module.

[0041] The input voltage 106 is preferably tapped after the RC filter 104 and before the rectifier 110 , for example before the capacitive reactance 108 .

[0042] Figure 2 An exemplary diagram showing the switching behavior of a relay module 100 according to a second embodiment of the present invention. The second embodiment can be implemented using the features of the independent claims and / or the first embodiment. Features that are consistent with or interchangeable with those in the first embodiment are described in the second embodiment with the same reference numerals.

[0043] This diagram 200 shows by way of example how small the hysteresis can be due to the second embodiment of the relay module 100, for example due to the fixed voltage regulator 114 in combination with the comparator 120 (also referred to as comparator circuit) for controlling the switching stage 124. In this case, the hysteresis relates to the difference between the switch-on voltage and the release voltage (i.e. the voltage threshold for switching on or releasing the relay unit 126) at the AC control input 102. The hysteresis is small in the sense that the difference is smaller than the switch-on voltage, for example less than 10% or 1%.

[0044] The diagram 200 shows the course of change over time (with a time scale on the horizontal axis). The voltage is plotted vertically. The alternating voltage at the AC control voltage input 102 is plotted on the right vertical axis. The input and output direct voltages for comparison in the comparator 120 are plotted on the left vertical axis and are indicated in the diagram 200 as V IN and V OUT .

[0045] Input DC voltage V IN 2 is an example of a rectified and smoothed portion 204 of an AC voltage 202 when compared with a reference voltage 118 in a comparator 120. For example, this input DC voltage 204 is linearly related to the AC voltage 202 present at the AC control input 102, so that the input DC voltage 204 for the comparison in the comparator 120 corresponds on the left scale in the diagram 200 to the corresponding value of the AC voltage 202 at the AC control input 102 on the right scale in the diagram 200.

[0046] The comparator 120 compares the input DC voltage 204 with the reference voltage 118. The result is an output DC voltage (V OUT ), the output DC voltage is an example for the control voltage 122. The control voltage 122 is a logic level that clearly sets: the connection of the relay unit 126 (i.e., the operating state) and the release of the relay unit 126 (i.e., the no-current state).

[0047] The difference between reference voltage 118 for switching on (i.e., reference voltage based on the currentless state) and reference voltage 118′ for enabling (i.e., reference voltage based on the operating state) is smaller than reference voltage 118. For example, in the case of a reference voltage 118 of 3.9 V, this difference is 0.2 V or 5% of reference voltage 118. Due to the linear relationship between AC voltage 202 and rectified and smoothed portion 204 of AC voltage 202, the hysteresis at AC control input 102 is likewise only 5%.

[0048] Figure 3 A schematic circuit diagram of a relay module 100 according to a third embodiment of the present invention is shown. The third embodiment can be implemented using the independent claims, the first embodiment and / or each or all of the features of the first embodiment. Features that are consistent with or interchangeable with those in the first or second embodiment are described in the third embodiment with the same reference numerals.

[0049] In order to selectively control the relay module 100, an alternating voltage 202 (e.g. 230 V AC) is applied to the AC control input 102 as a control voltage 202 at the connection 302 of the control input (with contacts A1 and A2). A varistor 306 in the AC control input 102 connected in parallel with the connection 302 serves as overvoltage protection. The capacitive reactance 108 serves to reduce the voltage.

[0050] The reduced AC voltage, that is to say the portion of the AC voltage 202 that is present downstream of the capacitive reactor 108 , is rectified by a rectifier 110 . The rectifier 110 comprises a bridge rectifier 308 having a smoothing capacitor 310 .

[0051] The fixed voltage regulator 114 comprises a voltage regulator 312 (e.g. a low-dropout voltage regulator), upstream of which a normally conducting (i.e. self-conducting) field effect transistor 314 (e.g. a depletion MOSFET) is connected. The voltage regulator 312 generates a fixed voltage 116, which is used as a supply voltage and, moreover, as a reference voltage 118 for a comparator 120 in a proportional manner. The comparator 120 can also be referred to as a regulation stage.

[0052] A high input voltage range (eg 110 V DC) is achieved via self-conducting MOSFET 314 in combination with low-dropout voltage regulator 312. Since the current required for driving comparator 120 and switching stage 124 (eg 1 mA) is still very small, only very low power losses occur there.

[0053] The comparator 120 compares the reference voltage 118 with a rectified and smoothed portion 204 of the AC voltage (i.e., the input DC voltage) determined by the input voltage 106 (e.g., before or after the RC filter 104). The input voltage 106 is rectified by means of a half-wave rectifier 316 and filtered by means of a further filter capacitor 318. The rectified and smoothed portion 204 of the AC voltage 202 can be adjusted via a voltage divider 320. Since the rectified and smoothed portion 204 is the input DC voltage for comparison with the reference voltage 118, a (substantially uniform) threshold value (also: switching threshold) of the AC voltage 202 for switching on and off the relay unit 126 can be adjusted by means of the adjustable voltage divider 320.

[0054] If reference voltage 118 is exceeded, comparator 120 switches on switching stage 124 and thus operates relay unit 126. The switching threshold can be determined (eg according to a specification) by varying voltage divider 320 (eg by adjusting potentiometer 322).

[0055] This ensures that the relay has fixedly defined (ie essentially uniform) switch-on and switch-off thresholds. In addition, the status display 125 (eg a light-emitting diode, LED) only illuminates when the relay unit 126 is switched on.

[0056] Unintentional switching on of relays, delayed opening of relays and / or erroneous status indications are thus prevented. Furthermore, no additional (in particular separate, uninterrupted) supply voltage is required for the relay module 100 .

[0057] exist Figure 3 The voltages and currents depicted in the circuit diagram are exemplary. For example, in the case of a 230V AC alternating voltage 202 at the AC control input 102, a corresponding input voltage 106 is applied. The current distribution can be composed as follows. A current of about 6 mA flows in the RC link 104. In the excitation coil (i.e. in the relay coil), a current of about 4 mA flows in the switched-on state. The other circuit parts require a current of about 2 mA. Therefore, the current consumption is small.

[0058] Due to the low current consumption of the reactor 108 and other circuit parts (especially the comparator 120 ), the power loss is very small.

[0059] Figure 4 An exemplary perspective view of a relay module according to a fourth embodiment of the present invention is shown. The fourth embodiment can be implemented using the features or all features of the independent claims, the first embodiment, the second embodiment and / or the third embodiment. Features that are consistent with or interchangeable with those in other embodiments are described in the fourth embodiment with the same reference numerals.

[0060] Due to the capacitive reactance 108 in the input and the low current consumption of the comparator 120, only very small power losses occur in the closed housing 400. The housing 400 can be, for example, preferably with a width of 14 mm (for example according to Figure 4 ) relay module.

[0061] The fourth exemplary embodiment can therefore correspond to existing physical conditions, in particular existing physical conditions in a relay module, without an additional external supply voltage (i.e., without additional connection points). Each of the exemplary embodiments can realize a low-cost, low-power-loss and space-saving relay module 100 with a uniform (low-hysteresis) and / or adjustable switching threshold.

[0062] Alternatively or additionally, the housing 400 may have a slot 402 for receiving the relay unit 126 in a replaceable manner. The relay unit 126 may be flush with the housing in the inserted state. A prestressed and longitudinally movable slide may fix the relay unit 126 in the slot 402.

[0063] Reference numerals list

[0064] Relay module 100

[0065] Control input terminal 102

[0066] RC filter 104

[0067] Input voltage 106

[0068] Capacitive reactance 108

[0069] Rectifier 110

[0070] DC voltage 112

[0071] Fixed voltage regulator 114

[0072] Fixed voltage 116

[0073] Reference voltage 118

[0074] Comparator 120

[0075] Control voltage 122

[0076] Switching level 124

[0077] Status display 125

[0078] Relay unit 126

[0079] Chart 200

[0080] AC voltage 202 at the control input

[0081] Rectified and smoothed portion 204 of the AC voltage

[0082] Control input terminal connection terminal 302

[0083] Switch connection terminal 304

[0084] Rheostat 306

[0085] Bridge rectifier 308

[0086] Filter capacitor 310

[0087] Voltage Regulator 312

[0088] Self-conducting field effect transistor 314

[0089] Half-wave rectifier 316

[0090] Additional filter capacitor 318

[0091] Voltage Divider 320

[0092] Potentiometer 322

[0093] Housing 400

[0094] Slot 402.

Claims

1. A relay module (100), comprising: a control input (102) which receives or is designed to receive an AC voltage (202) for jointly controlling and supplying power to the relay module (100); a fixed voltage regulator (114) which is designed to generate a fixed voltage (116) after rectifying the alternating voltage (202) or a portion of the alternating voltage (202); a comparator (120) which is driven by the fixed voltage (116) and is designed to compare a reference voltage (118) derived from the fixed voltage (116) with an RC-filtered, rectified and smoothed portion (204) of the AC voltage (202), wherein the comparator is adapted to switch the relay unit between an on state and an off state based on a comparison with a substantially uniform on and off threshold value; and a switching stage (124) which is designed to operate a relay unit (126) as a function of the comparison of the comparator (120); and a relay unit (126) which is connected on the input side to the switching stage (124) and on the output side to a switching connection (304) of the relay module (100), The switching threshold at the control input (102) is state-independent and / or exhibits low hysteresis.

2. The relay module (100) according to claim 1, wherein the derived reference voltage (118) is a fixed portion of the fixed voltage (116).

3. The relay module (100) according to claim 1 or 2, further comprising: A rectifier (110) is connected upstream of the fixed voltage regulator (114) and has a bridge rectifier (308) for rectifying the AC voltage (202) or a portion of the AC voltage (202).

4. The relay module (100) according to claim 3, wherein the switching stage (124) switches a coil loop of the relay unit (126) fed by the rectifier (110).

5. The relay module (100) according to claim 4, wherein a status display (125) is connected in series with the relay unit (126) in the coil loop.

6. The relay module (100) according to claim 3, wherein a capacitive reactance (108) is arranged between the control input (102) and the rectifier (110), which produces a portion of the AC voltage (202) for rectification.

7. The relay module (100) of claim 6, wherein a majority of the AC voltage (202) drops at the capacitive reactance (108).

8. The relay module (100) of claim 7, wherein more than half of the AC voltage (202) drops at the capacitive reactance (108).

9. The relay module (100) of claim 7, wherein more than 75% of the AC voltage (202) drops at the capacitive reactance (108).

10. The relay module (100) according to claim 3, wherein the comparator (120) is designed to generate a rectified and smoothed portion (204) of the AC voltage (202) for comparison with the reference voltage independently of a rectifier (110) connected upstream of the fixed voltage regulator (114).

11. The relay module (100) according to claim 1, wherein the comparator (120) comprises a half-wave rectifier (316), the half-wave rectifier having a smoothing capacitor (318), the AC voltage (202) or a portion of the AC voltage (202) being applied to the half-wave rectifier as an input voltage (106), and the half-wave rectifier (316) being configured to generate a smoothed DC voltage for the rectified and smoothed portion (204) of the AC voltage (202) in the comparator (120).

12. The relay module (100) according to claim 6, wherein the comparator (120) comprises a half-wave rectifier (316) having a smoothing capacitor (318), the AC voltage (202) or a portion of the AC voltage (202) being applied to the half-wave rectifier as an input voltage (106), and the half-wave rectifier (316) being configured to generate a smoothed DC voltage for the rectified and smoothed portion (204) of the AC voltage (202) in the comparator (120).

13. The relay module (100) according to claim 11, wherein the comparator (120) further comprises a voltage divider (320), to which the smoothed DC voltage of the half-wave rectifier (316) is applied, and the voltage divider is configured to generate a portion of the smoothed DC voltage as a rectified and smoothed portion (204) of the AC voltage (202) in the comparator (120).

14. The relay module (100) according to claim 13, wherein the voltage divider (320) is controllable by means of a potentiometer (322).

15. The relay module (100) according to claim 12, wherein the input voltage (106) of the comparator (120) is tapped between the control input (102) and the rectifier (110), wherein the rectifier is connected upstream of the fixed voltage regulator (114).

16. The relay module (100) of claim 15, wherein the input voltage (106) of the comparator (120) is tapped before the capacitive reactance (108).

17. The relay module (100) according to claim 1 or 2, wherein the relay module (100) is arranged in a closed housing (400).

18. The relay module (100) according to claim 17, wherein externally accessible connections of the switch connections (304) are arranged on the housing (400), and the housing (400) is designed for fastening to a supporting rail.

19. The relay module (100) according to claim 18, wherein the housing (400) is configured to be fixed to a top hat rail.

20. The relay module (100) according to claim 17, wherein the housing (400) has a slot (402) accessible from the outside for replaceably mechanically and electrically connecting the relay unit (126) to the relay module (100).

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