WO2000002298A2 - Electromagnetic relay - Google Patents

Abstract

The invention relates to an electromagnetic relay with an exciter coil (2) that can be controlled by means of an input signal and at least one set of contacts (1) consisting of movable and fixed contact elements. The movable contact elements are mechanically coupled to an armature. A magnetic flux that is proportional to the load current (I1) is converted into an electrical measurement signal by a magnetic field sensor (4). The magnetic field sensor (4) is also coupled to a comparator (7) that compares the signals that are generated by a reference signal source (6) and the magnetic field sensor (4) and provides an output signal. A monitoring unit (8) has a first low pass (TP1) that is controlled by the control input signal, a second low pass (TP2) that is controlled by the output signal of the comparator, an initialization unit (IE) and a switching unit (SE) that controls the electrical connection between the control input contact elements (S1, S2) and the connecting elements of the winding (W1, W2). The mode of the switching unit (SE) can be changed by means of a switching mode memory unit (9).

Description

description

Electromagnetic relay

The invention relates to an electromagnetic relay with at least one contact set, contact connection elements, an excitation coil, winding connection elements, a core, an armature, one of a load current conductor, a magnetic field sensor, a reference signal source, a Ko parator, a monitoring unit and a switching state storage unit.

From US 4,456,943 an electromagnetic relay with a load current sensor is known. The load current sensor is integrated in a common circuit together with an output switching unit of the relay. By integrating the load current sensor and the output circuit, additional external components and interconnections can be omitted. In order to achieve a sufficient measuring sensitivity, the load current sensor is implemented by a Hall element, which enables an appropriate amplification of the measuring signals.

To date, however, only thermal fuse elements have been used for overcurrent protection, especially in motor vehicle electrical systems, which are destroyed in the event of an overload and then have to be replaced.

The invention has for its object to provide an inexpensive version of an electromagnetic relay, which is controlled by an electronic circuit and has an integrated load current sensor, which allows a Ku zschlußStrom- and overload monitoring, so that in the event of a short circuit or overload, both the relay and the load can also be protected against destruction by opening the relay switch contacts. In particular, the electromagnetic relay should be characterized by a differentiated response with regard to conducted interference peaks and _S chaltstromspitzen distinguished with inductive loads, so that Fehlausschaltvorgänge can be excluded.

According to the invention, this object is achieved by an electromagnetic relay

- two control input connection elements,

- winding connection elements,

an excitation coil which can be controlled via a control input signal and in which a core is arranged axially, at least one contact set which has fixed and movable contact elements,

- connecting elements for the movable and fixed contact elements,

an anchor mechanically coupled to the movable contact elements,

- a load current conductor,

a magnetic field sensor which converts a magnetic flux proportional to a load current into an electrical measurement signal, a magnetic flux guiding element which surrounds the load current conductor and which is coupled to the magnetic field sensor,

- a reference signal source,

a comparator, which is coupled to the magnetic field sensor and to the reference signal source and generates a comparator output signal,

- A monitoring unit which has a first low-pass filter controlled by the control input signal, a second low-pass filter controlled by the comparator output signal, an initialization unit and a switching unit, the initialization unit having means for controlling the two low-pass filters and the switching unit and the switching unit having at least one switching element which controls the electrical connection between the control input connection elements and the winding connection elements, and - A switching state storage unit with means for tilting the state of the switching unit belonging to the monitoring unit.

In the relay according to the invention, the two low-pass filters take on the function of time delay elements. This makes it possible to implement a relay switch-on delay, which is necessary in order to prevent the relay contacts from sticking, caused by an arc, in the event of an overload. In this way, a delayed reactivation of the relay is possible even in the event of a short circuit, as a result of which the contact sets can cool down. The purpose of delaying the comparator output signal is that the switching state memory unit or the switching unit is only addressed via the second low-pass filter when there is a short-circuit or overload situation. Brief inrush current peaks, for example when switching on inductive loads, would not be rated as a short-circuit or overload condition in this case. This means that such briefly occurring disturbance variables, which are not caused by a critical operating state, do not trigger the monitoring and protection elements. Furthermore, the time delay resulting from the low-pass filter is used to delay the relay from being switched off. This also contributes to a reduction in wear on the contact sets. The function of the initialization unit essentially consists in activating or deactivating the two low-pass filters depending on the operating state.

The switching state memory unit is preferably coupled both to the first low pass and to the second low pass, since statements about the operating state of the relay can be derived from the activation or deactivation of the low pass. In order to enable the measurement signal obtained by the magnetic field sensor to be processed, the magnetic field sensor should be coupled to the comparator via a measurement signal amplifier with an adjustable amplification ratio. To- In addition, the comparator can have means for adjusting the measurement signal amplifier drift, which can be supplemented by additional means for adjusting the magnetic field sensor drift.

The magnetic field sensor is preferably implemented by a Hall element with a negative temperature coefficient. The positive measuring output of the Hall sensor is supported by a first impedance converter, at the output of which the reference signal is present at the same time. The reference signal source is thus implemented by the first impedance converter. Furthermore, the negative measuring output of the Hall element is connected to a non-inverting input of the measuring signal amplifier. While a positive power supply connection of the Hall element is coupled to a first control input connection element via a second impedance converter, the negative power supply connection of the Hall element has an electrical connection to the second control input connection element. The output of the measurement signal amplifier is preferably connected to a first comparator input, the output of the first impedance converter and the inverting input of the measurement signal amplifier being combined at a second comparator input.

Furthermore, the measurement signal amplifier preferably has an operational amplifier. The amplification ratio of the measuring signal amplifier can be set via two resistors, a first resistor being connected between the inverting input of the operational amplifier belonging to the measuring signal amplifier and the output of the operational amplifier, while the second resistor is arranged between the inverting input of the operational amplifier and the second comparator input .

The second impedance converter is preferably formed by an operational amplifier, the output of which is connected to the positive power supply connection of the Hall element. At the same time, the output of the corresponding operational amplifier is fed back to the inverting amplifier input, the non-inverting amplifier input being connected to the first control input connection element. The cathode of a zener diode whose anode is electrically coupled to the second control input connection element is connected to the non-inverting amplifier input of the operational amplifier belonging to the second impedance converter. The non-inverting input of the operational amplifier belonging to the second impedance converter can be connected to the first control input connection element via an additional series resistor.

The comparator preferably has an operational amplifier, a switching element connected on the output side to the operational amplifier and means for setting the comparator threshold value, a non-inverting input of the operational amplifier forming the first comparator input. In a preferred embodiment, the means for comparing the magnetic field sensor and measurement signal amplifier drift into the

Integrated means for setting the comparator threshold. The means for setting the comparator threshold value can be implemented in a particularly simple manner by means of a voltage divider. A first resistor of the voltage divider is arranged between the second comparator input and the inverting input of the operational amplifier belonging to the comparator. A second resistor of the voltage divider, on the other hand, represents an electrical connection between the inverting input of the operational amplifier and the second control input connection element. The switching element belonging to the comparator is preferably implemented by a bipolar transistor, the base of which is connected via an additional series resistor to the output of the operational amplifier belonging to the comparator .

In a preferred embodiment, both the first low pass and the second low pass are each by an RC element realized. The first low-pass filter is always connected to the two control input connection elements via the initialization unit. The second low-pass filter, on the other hand, is only connected to the two control input connection elements via the initialization unit if the comparator output signal does not vanish. The function of the initialization unit is, in particular, to discharge the capacitors of the RC elements and thus to set initial conditions for the two low-pass filters.

Furthermore, both the switching unit and the switching state storage unit can each have a threshold-dependent connecting element. These threshold-value-dependent connecting elements are preferably implemented by Zener diodes. The anode of the zener diode belonging to the switching unit is connected between the resistor and the capacitor of the first low-pass filter at the second connection of the initialization unit, while the anode of the zener diode belonging to the switching state storage unit is connected between the resistor and the capacitor of the second low-pass filter at the fourth connection of the initialization unit.

The switching unit preferably has a bipolar transistor as the switching element, whose emitter is connected to the first control input connection element. This bipolar transistor is connected to a first winding connection element with its collector, while its base is connected to the second connection of the initialization unit via the zener diode of the switching unit. Instead of using a bipolar transistor as a switching element, it is also possible to use two bipolar transistors, which form a Darlington circuit, to implement the switching element of the switching unit.

In addition, the switching state memory unit preferably has a bipolar transistor whose emitter is coupled to the first control input connection element. The collector this bipolar transistor is connected between the resistor and the capacitor of the first low-pass filter to the second terminal of the initialization unit, while the base is connected via a zener diode of the switching state memory unit between the resistor and the capacitor of the second low-pass filter to the fourth terminal of the initialization unit.

In a preferred embodiment, the initialization unit has a first diode which is connected with its anode to the first control input connection element. With its cathode, this diode is connected to the third connection of the initialization unit. In addition, the initialization unit has a second diode which is connected with its anode to the first control input connection element and with its cathode to the first connection of the initialization unit. Furthermore, the initialization unit has a first bipolar transistor which is connected to the third terminal of the initialization unit with its collector and to the fourth terminal of the initialization unit with its emitter. A second bipolar transistor of the initialization unit is connected with its collector to the first connection of the initialization unit and with its emitter to the second connection of the initialization unit. In addition, the initialization unit has a third diode which is connected with its anode to the first control input connection element and with its cathode both to the base of the first bipolar transistor belonging to the initialization unit and to the base of the second bipolar transistor belonging to the initialization unit. Furthermore, the cathode of the third diode is electrically connected to the second control input connection element via a resistor.

In a preferred embodiment, the relay according to the invention also has a status display unit, which is provided by an input resistor, an operational amplifier and a zener diode is formed. The non-inverting input of this operational amplifier is connected to the output of the reference signal source. The inverting input of the operational amplifier of the status display unit is electrically connected to the second control input connection element via the input resistor. Furthermore, the zener diode of the status display unit is connected with its cathode to the inverting input of the operational amplifier and with its anode to the second control input connection element. In addition, a status signal can be tapped at the output of the operational amplifier belonging to the status display unit. It is also possible to arrange an additional shunt resistor in parallel to the excitation winding, which is connected to the two winding connection elements.

The invention is explained in more detail below using exemplary embodiments with reference to the drawing. It shows

1 shows a schematic representation of a relay according to the invention and FIG. 2 shows a relay according to the invention according to FIG. 1 with a preferred embodiment of a monitoring unit.

The relay shown in Figure 1 has a contact set 1 with a fixed and a movable contact element. The movable and fixed contact elements are also equipped with connection elements, a first load connection element L1 representing the connection element assigned to the movable contact element, while a second load connection element L2 represents the connection element assigned to the fixed contact element. An armature, which is not explicitly shown, forms part of the magnet system of the relay and is mechanically coupled to the movable contact elements. A load current Iτ_ flows through an electrical conductor 3. The magnetic field produced by the load current I] _ is detected by a magnetic field sensor 4. The coupling of the magnetic flux caused by the load current I] _ into the magnetic field sensor 4 takes place via a Load current conductor 3 surrounding flux ring 4a, which is shown in dashed lines in Figure 1. The magnetic field sensor 4 can convert a magnetic flux proportional to the load current I] _ into an electrical measurement signal.

The magnetic field sensor 4 is preferably a Hall element. A positive power supply connection I _p is supported by a DC voltage source U _s , while the negative power supply connection I _{n of} the Hall element 4 is electrically connected to a reference potential GND. A positive measurement output M _{p of} the Hall element 4 is connected to a first input Q1 of a reference signal source 6. The reference signal source 6 is implemented by a first impedance converter N4, the output Q3 of the first impedance converter N4 to the inverting input Q2 of the associated one

Operational amplifier is fed back and provides the reference signal. A negative measuring output M _{n of} the Hall element 4 is connected to a non-inverting input Ml of an optional measuring signal amplifier 5. The reference signal at the output Q3 of the reference signal source 6 is fed to an inverting input M2 of the measurement signal amplifier 5. The output M3 of the measurement signal amplifier 5 is connected to a first input Kl of a comparator 7.

The output Q3 of the reference signal source 6 is connected to a second comparator input K2. In a particularly simple embodiment, the comparator 7 has an operational amplifier N3, which has the function of a threshold switch, and a voltage divider formed by two resistors R4 and R5. A non-inverting input of the operational amplifier N3 simultaneously forms the first comparator input Kl. A first resistor R5 of the voltage divider is arranged between the inverting input of the operational amplifier N3 and the reference potential GND. The second resistor R4 of the voltage divider is arranged between the second comparator input K2 and the inverting input of the amplifier N3. Through the loading measurement of the resistors R4 and R5, it is possible to adapt the comparator threshold value as desired. If the amplified measurement signal falls below a certain threshold value, the output K3 of the comparator 7 supplies a non-zero comparator output signal which logically corresponds to a positive state of the comparator 7.

Furthermore, the relay according to FIG. 1 has a monitoring unit 8, which contains a first low-pass filter TP1, a second low-pass filter TP2, an initialization unit IE and a switching unit SE. While the first low-pass filter TP1 is controlled by a control input signal present between two control input connection elements S1 and S2, the second low-pass filter TP2 is activated by the comparator output signal. The second control input connection element S2 is electrically connected to the reference potential GND. The initialization unit IE is coupled both to the first low-pass filter TP1 and to the second low-pass filter TP2 and is used to establish initial conditions for the two low-pass filters TP1 and TP2. Furthermore, the initialization unit IE is coupled to the switching unit SE, which controls the electrical connection between the first input connection element S1 and a first winding connection element W1 of the excitation coil 2. The second winding connection element W2, like the second control input connection element S2, is connected to the reference potential GND. The two low-pass filters TP1 and TP2 are also coupled to a switching state memory unit 9, which checks the two low-pass filters TP1 and TP2 for activation or deactivation and derives the operating state of the relay therefrom. The switching state storage unit 9 is equipped with means for tilting the state of the switching unit SE and consequently also has a connection to the switching unit SE. The first low-pass filter TP1 is also coupled to the switching unit SE of the monitoring unit 8, as a result of which a relay switch-on delay is implemented. The second low-pass filter TP2 is used for the differentiated response of the monitoring unit 8 with regard to brief switch-on Current peaks, especially with inductive loads or short-circuit or overload conditions of the relay.

FIG. 2 shows a preferred embodiment of a relay according to FIG. 1, the structural structure of the relay according to FIG. 2 being largely identical to that of the relay according to FIG. 1. The differences between the relay according to FIG. 1 and the relay according to FIG. 2 essentially relate to a specific embodiment of the monitoring unit 8, the switching state storage unit 9, a second impedance converter 10 and an additional status display unit 11. Further differences arise in the configuration of the measurement signal amplifier 5 and the comparator 7.

The measuring signal amplifier 5 has two resistors R2 and R3, with which the amplification ratio of the measuring signal amplifier 5 can be adjusted. A first resistor R2 of the measurement signal amplifier 5 is arranged between the output Q3 of the reference signal source 6 and an inverting input of the operational amplifier N2 belonging to the measurement signal amplifier 5. Another resistor R3 is arranged between the output M3 and the inverting input M2 of the operational amplifier M2.

The comparator 7 according to FIG. 2 additionally has a bipolar transistor V4 as an additional switching element, the base of which is connected via a resistor R6 to the output of the operational amplifier N3 belonging to the comparator 7. The emitter of the bipolar transistor V4 is electrically connected to the reference potential GND, while the collector of the bipolar transistor V4 represents the output terminal K3 of the comparator 7.

In the relay according to FIG. 2, the positive power supply connection I _p is connected to the first control input connection element S1 via the second impedance converter 10. At the output T3 of the second impedance converter 10 there is one of the oscillators of the control input signal decoupled DC voltage U _Ξ . The second impedance converter 10 is formed by an operational amplifier Nl, the output T3 of which is fed back to the inverting input T2. The non-inverting input T1 of the amplifier NI is connected to the first control input connection element via a resistor R1. In addition, the non-inverting input T1 of the amplifier N1 is connected to a zener diode VI, the cathode of which is connected to the non-inverting input T1 of the amplifier N1, while its anode is electrically connected to the reference potential GND. The Zener diode VI serves to limit the voltage at the input of the second impedance converter 10 and to filter out fluctuations in the control input signal which is present between the control input connection elements S1 and S2.

Both the first low-pass filter TP1 and the second low-pass filter TP2 are formed by RC elements. The capacitor C1 of the first low-pass filter TP1 is connected between a first connection AI and a second connection A2 of the initialization unit IE, while the associated resistor RIO represents an electrical connection between the second connection A2 of the initialization unit and the reference potential GND. The capacitor C2 and the resistor R7 of the second low-pass filter TP2 are arranged analogously to this. While the resistor R7 of the second low-pass filter TP2 represents an electrical connection between a fourth connection A4 of the initialization unit IE and the output K3 of the comparator 7, the capacitor C2 is arranged between a third connection A3 of the initialization unit IE and the fourth connection A4.

Both the first connection AI and the third connection A3 of the initialization unit IE are decoupled from the first control input connection element S1 via the diodes V6 and V5. The anodes of the two diodes V5 and V6 are connected to the first control input connection element S1. Furthermore the initialization unit IE has two bipolar transistors V7 and V8, which serve to short-circuit the capacitors C1 and C2 of the low-pass filters TP1 and TP2. This discharges the capacitors and creates the appropriate initial conditions. A first bipolar transistor V7 of the initialization unit IE is connected with its emitter to the first connection AI of the initialization unit IE, while its collector forms the second connection A2 of the initialization unit IE. In a corresponding manner, the bipolar transistor V8 of the initialization unit IE is connected between the third connection A3 and the fourth connection A4 of the initialization unit IE. The base connections of the bipolar transistors V7 and V8 are connected to one another and decoupled from the first control input connection element S1 via a third diode V0 of the initialization unit IE. Here too, the third diode V0 of the initialization unit IE is connected with its anode to the control input connection element S1. In addition, an additional resistor R8 is arranged between the base connections of the two bipolar transistors V7 and V8 and the reference potential GND.

The switching unit SE has a bipolar transistor V9 and a zener diode V10. The emitter of the bipolar transistor V9 is electrically connected to the first control input connection element S1, while its collector is connected to the first winding connection element Wl. The base of the bipolar transistor V9 belonging to the switching unit SE is connected to the second terminal A2 of the initialization unit IE via the Zener diode V10. The cathode of the Zener diode V10 is connected directly to the base of the bipolar transistor V9.

The switching state storage unit 9 with means for tilting the state of the switching unit SE belonging to the monitoring unit 8 has a structure similar to that of the switching unit SE. A bipolar transistor V2 of the switching state memory unit 9 has its emitter connected to the first control unit. gangsanschlußelement S1 connected and its base is connected via a Zener diode V3 to the fourth terminal A4 of the initialization unit IE. In an analogous manner, the cathode of the Zener diode V3 is connected directly to the base of the bipolar transistor V2. The collector of the bipolar transistor V2 belonging to the switching state storage unit 9 is connected to the second connection A2 of the initialization unit IE.

In addition, the relay according to FIG. 2 has a shunt resistor R12 connected in parallel with the excitation winding 2, which is arranged between the winding connection elements W1 and W2, and a resistor R9, which is arranged between the second winding connection element W2 and the comparator output K3.

The Hall sensor 4, which is fed by the second impedance converter 10 and thus temperature-compensated, generates a measurement signal proportional to the load current. The voltage at the output Q3 of the reference signal source 6 forms a comparison variable for an overcurrent threshold, which can additionally be set via the division ratio of the resistors R4 and R5. The amplified measurement signal at the output M3 of the measurement signal amplifier 5 can therefore be compared with the overcurrent threshold value set on the comparator 7. The result of this analog measured value comparison is converted into a logic signal which can be tapped at the output K3 of the comparator 7. Since the Hall element 4 used has a negative temperature coefficient, while the Zener diode VI has a positive temperature coefficient at the input of the second impedance converter, temperature compensation takes place. The supply voltage U _s for the Hall element is namely increased with increasing temperatures and reduced with decreasing temperatures in accordance with the Zener diode temperature coefficient. The use of a reference signal source formed by a first impedance converter as an input variable for the comparator K7 offers the advantage that the reference signal source Limit signal source set overcurrent threshold is independent of the fluctuations in the control input signal between the control input terminals S1 and S2.

By varying the value for resistor R4, not only is the overcurrent threshold set, but drift compensation is also carried out for the Hall sensor and the measurement signal amplifier. The compensation of the drift of the magnetic field sensor 4 and of the measurement signal amplifier 5 and the setting of the overcurrent threshold value can thus be implemented in a single production step, whereby a considerable reduction in production costs is possible.

If a control voltage is present between the control input connection elements S1 and S2, the transistor V9 turns on after a time delay which is caused by the low-pass filter TP1. This switch-on delay is necessary in order to prevent the relay contacts from sticking due to arcing in the event of overload. The relay contacts are switched on again with a delay in order to allow the contacts to cool, particularly in the event of a short circuit. When switched on, the transistor V9 simultaneously blocks the transistor V2 of the switching state memory unit 9, since the potential at the base connection of the bipolar transistor V2 is raised approximately to the value of the control voltage.

If the amplified measurement signal at the output M3 of the measurement signal amplifier 5 falls below the set overcurrent threshold value, the bipolar transistor V4 of the comparator 7 is switched through via the operational amplifier N3, whereby the second low-pass filter TP2 is activated. If the blocking voltage of the Zener diode V3 and the transistor V2 is exceeded, the transistor V2 switches through and thereby raises the potential at the base connection of the transistor V9 to the value of the control voltage, as a result of which the latter is blocked. The second low pass TP2 is not only used for blanking inrush current peaks, but also as a switch-off delay for the relay.

If the bipolar transistor V2 of the switching state memory unit 9 is switched on due to a short-circuit current or an overload current, the transistor V9 of the switching unit SE remains switched off permanently. This stable switching state is maintained until the control voltage between the control input connection elements S1 and S2 is switched off and the capacitors C1 and C2 of the low-pass filters TP1 and TP2 are discharged via the transistors V7 and V8 of the initialization unit IE. The function of the diodes V0, V5 and V6 of the initialization unit can be seen in the fact that the emitter potential of the transistors V7 and V8 is decoupled from the control input connection element S1, which enables a defined and rapid discharge of the capacitors Cl and C2. The discharge of the capacitors C1 and C2 is also ensured if the control voltage source is isolated from the control input connection elements S1 and S2 in a potential-free manner. If a control voltage is present between the control input connection elements S1 and S2, the transistors V7 and V8 always remain blocked because their bases are coupled directly to the first control input connection element S1 via the diodes V0, V5 and V6.

The Zener diodes V3 and VI0 belonging to the switching unit SE or to the switching state storage unit 9, in addition to their actual switching function, also offer overvoltage and reverse polarity protection for the capacitors C1 and C2. Furthermore, the relay according to FIG. 2 has a status display unit 11, which is formed by an operational amplifier N5, an input resistor Rll and a zener diode Vll. The output signal of the reference signal source 6 is present at the non-inverting input of the operational amplifier N5. The inverting input of the operational amplifier N5 is electrically connected to the first winding connection element W1 via the input resistor R11. The cathode of the zener diode Vll is also connected to the inverting input of operational amplifier N5, while its anode is electrically connected to second control input connection element S2. The status signal can be tapped at the output ST of the operational amplifier N5 belonging to the status display unit 11. The function of the components Rll and Vll can be seen in the specification of the voltage threshold for determining the relay switching state and in the protection of the amplifier inputs of the operational amplifier N5 against possible overvoltages.

Claims

claims 1. Electromagnetic relay with - two control input connection elements (S1, S2), - winding connection elements (Wl, W2), an excitation coil (2) which can be controlled via a control input signal and in which a core is arranged axially, - at least one contact set (1) which has fixed and movable contact elements, - connecting elements for the movable and fixed contact elements, an anchor mechanically coupled to the movable contact elements, - a load current conductor (3), - a magnetic field sensor (4) which converts a magnetic flux proportional to a load current (Ii) into an electrical measurement signal, - a magnetic flux guiding element surrounding the load current conductor (3), which is coupled to the magnetic field sensor (4), - a reference signal source (6), a comparator (7), which is coupled to the magnetic field sensor (4) and to the reference signal source (6) and generates a comparator output signal, - A monitoring unit (8), which has a first low-pass filter (TP1) controlled by the control input signal, a second low-pass filter (TP2) controlled by the comparator output signal, an initialization unit (IE) and a switching unit (SE), the initialization unit (IE) having means for controlling the two low-pass filters (TP1, TP2) and the switching unit (SE) and the switching unit (SE) has at least one switching element which controls the electrical connection between the control input connection elements (S1, S2) and the winding connection elements (Wl, W2), and - a switching state storage unit (9) with means for Tilting of the state of the switching unit (SE) belonging to the monitoring unit (8). 2. Relay according to claim 1, so that the switching state memory unit (9) is coupled to both the first low-pass filter (TPl) and the second low-pass filter (TP2). 3. Relay according to one of claims 1 or 2, so that the magnetic field sensor (4) is coupled to the comparator (7) via a measuring signal amplifier (5) with an adjustable amplification ratio. 4. Relay according to claim 3, d a d u r c h g e k e n n z e i c h n e t that the comparator (7) has means for compensating the measurement signal amplifier drift. 5. Relay according to one of claims 1 to 4, that the comparator (7) has means for adjusting the magnetic field sensor drift. 6. Relay according to one of claims 1 to 5, characterized in that the magnetic field sensor (4) is realized by a Hall element with a negative temperature coefficient, the positive measuring output (M _p ) is supported by a first impedance converter (N4), wherein the output (Q3) of the first impedance converter (N4) supplies the reference signal and thus the reference signal source (6) is realized by the first impedance converter (N4) that the negative measuring output (M _n ) of the Hall element with a non-inverting input (Ml) the measuring signal amplifier (5) is connected that a positive power supply connection (I _p ) of the Hall element is connected via a second impedance converter (10) to a first control input connection element (Sl) and that the negative power supply connection (I _n ) of the Hall element is electrical is connected to the second control input connection element (S2). 7. Relay according to claim 6, characterized in that the output (M3) of the measuring signal amplifier (5) is connected to a first comparator input (Kl) and that the output (Q3) of the first impedance converter (N4) and the inverting input (M2 ) of the measuring signal amplifier (5) are connected to a second comparator input (K2). 8. Relay according to claim 7, characterized in that the measuring signal amplifier (5) has an operational amplifier (N2), that the amplification ratio of the measuring signal amplifier (5) can be set via two resistors (R2, R3), a first resistor (R3) is connected between the inverting input (M2) of the operational amplifier (N2) belonging to the measurement signal amplifier (5) and the output (M3) of the operational amplifier (N2), while the second resistor (R2) is connected between the inverting input (Ml) of the operational amplifier (N2) and the second comparator input (K2) is arranged. 9. Relay according to one of claims 6 to 8, characterized in that the second impedance converter (10) is formed by an operational amplifier (Nl), the output (T3) of which is connected to the positive power supply connection (I _p ) of the Hall element and is coupled back to the inverting amplifier input (T2), the non-inverting amplifier input (Tl) being connected to the first control input connection element (S1) and connected to the cathode of a zener diode (VI), the anode of which is electrically connected to the second control input connection element (S2). 10. Relay according to claim 9, characterized in that the non-inverting input (Tl) of the second impedance converter (10) associated operational amplifier (Nl) is connected to the first control input connection element (Sl) via a protective resistor (Rl). 11. Relay according to one of claims 1 to 10, characterized in that the comparator (7) has an operational amplifier (N3), a switching element connected on the output side to the operational amplifier (N3) and means for adjusting the comparator threshold value and that a non-inverting input of the comparator (7) belonging operational amplifier (N3) forms the first comparator input (Kl). 12. Relay according to claim 11, so that the means for comparing the magnetic field sensor and measurement signal amplifier drift are integrated in the means for setting the comparator threshold value. 13. Relay according to one of claims 11 or 12, characterized in that the means for setting the comparator threshold are realized by a voltage divider, that a first resistor (R4) of the voltage divider between the second comparator input (K2) and the inverting input of the comparator ( 7) associated operational amplifier (N3) is arranged, while a second resistor (R5) of the voltage divider constitutes an electrical connection between the inverting input of the operational amplifier (N3) belonging to the comparator and the second control input connection element (S2). 14. Relay according to one of claims 11 to 13, characterized in that the switching element belonging to the comparator (7) is realized by a bipolar transistor (V4), the base of which is connected via a series resistor (R6) to the output of the comparator (7). associated operational amplifier (N3) is connected. 15. Relay according to one of claims 1 to 14, characterized in that both the first low pass (TPl) and the second low pass (TP2) are each realized by an RC element (RIO, Cl; R7, C2), the first Low-pass filter (TP1) is always connected to the two control input connection elements (S1, S2) via the initialization unit (IE), while the second low-pass filter (TP2) is only connected to the two control input connection elements (S1, S2) if the comparator output signal does not disappear via the initialization unit (IE) ) connected. 16. Relay according to claim 15, characterized in that the initialization unit (IE) has means for discharging the capacitors (Cl, C2) belonging to the two RC elements (RIO, Cl; R7, C2), the capacitor (Cl ) of the first low-pass filter (TP1) between a first connection (AI) and a second connection (A2) of the initialization unit (IE), while the capacitor (C2) of the second low-pass filter (TP2) between a third connection (A3) and one fourth connection (A4) of the initialization unit (IE) is connected. 17. Relay according to one of claims 15 or 16, so that both the switching unit (SE) and the switching state storage unit (9) each have a threshold-dependent connecting element. 18. Relay according to claim 17, characterized in that the threshold-dependent connecting elements are realized by Zener diodes (V3, V10), the anode of the switching unit (SE) belonging to the Zener diode (V10) between the resistor (RIO) and the capacitor (Cl ) of the first low-pass filter (TPl) connected to the second connection (A2) of the initialization unit (IE) while the anode of the zener diode (V3) belonging to the switching state storage unit (9) is connected between the resistor (R7) and the capacitor (C2) of the second low-pass filter (TP2) at the fourth connection of the initialization unit (IE). 19. Relay according to claim 18, characterized in that the switching unit (SE) has a bipolar transistor (V9) as a switching element, the bipolar transistor (V9) with its emitter to the first control input connection element (Sl), with its collector to a first winding connection element (Wl ) and its base is connected to the second terminal (A2) of the initialization unit (IE) via the Zener diode (V10) of the switching unit (SE). 20. Relay according to claim 18, so that the switching unit (SE) has two bipolar transistors as switching elements, a first bipolar transistor with its emitter to the first control input connection element (S1), with its The collector is connected to a first winding connection element (W1) and its base is connected to the emitter of the second bipolar transistor, while the base of the second bipolar transistor is connected to the second terminal (A2) of the initialization unit (IE) via the zener diode (V10) of the switching unit (SE). , The collector of the second bipolar transistor is electrically connected via a resistor both to the second control input connection element (S2) and to the second winding connection element (W2) and the emitter of the second bipolar transistor is connected to the first control input connection element (S1). 21. Relay according to one of claims 18 to 20, characterized in that the switching state memory unit (9) has a bipolar transistor (V2) which with its emitter to the first control input connection element (Sl), with its collector between the Resistor (RIO) and the capacitor (Cl) of the first low-pass filter (TPl) to the second terminal (A2) of the initialization unit (IE) and with its base via the zener diode (V3) of the switching state memory unit (9) between the resistor (R7) and the capacitor (C2) of the second low-pass filter (TP2) is connected to the fourth terminal (A4) of the initialization unit (IE). 22. Relay according to one of claims 16 to 21, characterized in that the initialization unit (IE) has a first diode (V5) which with its anode on the first control input connection element (S1) and with its cathode on the third connection (A3) of the initialization unit ( IE) is connected that the initialization unit (IE) has a second diode (V6) which is connected with its anode to the first control input connection element (S1) and with its cathode to the first connection (AI) of the initialization unit, that the initialization unit ( IE) has a first bipolar transistor (V8), which is connected with its collector to the third terminal (A3) of the initialization unit (IE) and its emitter to the fourth terminal (A4) of the initialization unit (IE) such that the initialization unit (IE ) has a second bipolar transistor (V7) which with its collector at the first terminal (AI) of the initialization unit (IE) and with its emitter is connected to the second terminal (A2) of the initialization unit (IE), that the initialization unit (IE) has a third diode (V0), which has anode at the first control input connection element (S1) and with its cathode both at the base of the first the bipolar transistor (V8) belonging to the initialization unit (IE) and to the base of the second bipolar transistor (V7) belonging to the initialization unit and that the cathode of the third diode (V0) of the initialization unit (IE) is electrically connected to the via a resistor (R8) second control input connection element (S2) is connected. 23. Relay according to one of claims 1 to 22, characterized in that a status display unit (11) has an operational amplifier (N5), an input resistor (Rll) and a Zener diode (Vll) in that the non-inverting input of the operational amplifier (N5) of the status display unit ( 11) is connected to the output of the reference signal source (6), that the inverting input of the operational amplifier (N5) of the status display unit (11) is electrically connected via the input resistor (Rll) to the first winding connection element (Wl), that the Zener diode (Vll) the status display unit (11) is connected with its cathode to the inverting input of the operational amplifier (N5) of the status display unit (11) and with its anode to the second control input connection element (S2) and that at the output (ST) of the operational amplifier (N5 ) a status signal can be tapped. 24. Relay according to one of claims 1 to 23, so that a shunt resistor (R12) is connected in parallel with the excitation winding and is connected to the winding connection elements (Wl, W2). 25. Relay according to one of claims 1 to 24, d a d u r c h g e k e n n z e i c h n e t that the Load current conductor (3) surrounding magnetic flux guide element is realized by a ring made of magnetically conductive material, which has an air gap in which the magnetic field sensor (4) is arranged.