Patent Description:
In order to protect an electric device such as for example an electric motor from the negative effects of an excess current such as overload and/or a short circuit occurring in the circuit comprising the electric device, a complete safety motor starter including a combination of a protective switching device acting as a power switch and one or more contactors are generally employed.

In the case of a short circuit, the protective switching device, which may be a circuit breaker or a motor protective switching device (MPSD), interrupts the supply of electric current to the motor in order to avoid permanent damages to the motor by opening a contact of the protective switching device. Said opening of a contact cannot be done by the contactor, if a short circuit occurs, since the response time of the contactor is too slow. While a response time of around <NUM> is needed in the case of a short circuit, the general response time of a contactor is around <NUM>.

Instead, if the safety motor starter detects an overload using its sensors and its evaluation electronics, the contactor is switched off, while a contact at the protective switching device remains closed. Typical reaction times needed in the case of an overload are tenths of seconds until several minutes, which the contactor can perfectly cope with. Later on, for example after a predetermined amount of time, the contactor may be switched on again remotely via an auto-reset.

However, it might occur that the main contacts of the contactor are welded as a result of the overload. Hence, the contactor does not switch off and there is still current flowing in the circuit comprising the safety motor starter and the motor.

In such a situation, in which the contactor fails, the protective switching device is used to open a contact and thus to interrupt the circuit. First, the excess current in the circuit causing the overload is transformed into a trip signal by sensors and evaluation electronics. Said trip signal then acts on a so called trip actuator, which subsequently trips a latch resulting in interrupting the previously closed circuit. Hence, the contact of the protective switching device is opened. Once an operator has solved the problem in the circuit, which had caused the excess current and thus the overload and/or the short circuit and/or has replaced the welded contactor by a new one, and/or has obtained information that the problem in the circuit does not exist anymore, he or she is enabled to reset the latch by manually moving a handle attached to the protective switching device. When the latch is manually reset by the operator into an initial latch state, the open contact of the protective switching device is closed again, so that the normal functioning of the electric device such as for example of the motor can be re-assumed.

However, the operator might erroneously regard the problem having caused the excess current and thus an overload and/or a short circuit as overcome and/or might have forgotten to replace the welded contactor. If the operator thus moves the handle to reset the latch, the resulting re-closure of the contact of the protective switching device might cause further damage to the electric device such as the motor, which is again exposed to an excess current.

Therefore, there is a need for a protective switching device and an operation method thereof, which inhibit manual re-closing of the contact of the protective switching device as long as a problem occurring in the circuit persists.

Hence, it is the object of the present invention to provide a protective switching device, as well as a safety motor starter comprising such a protective switching device, and an operating method thereof allowing safely re-closing an open contact.

<CIT> discloses an electronic circuit breaker. Said electronic circuit breaker has main electrical contacts configurable between an opened and a closed condition, a handle interfacing with a moveable contact arm coupled to at least one of the main electrical contacts and being moveable between at least an ON configuration and an OFF configuration, secondary electrical contacts configured to engage each other in the ON configuration, and a moveable stop operable to maintain separation of the main electrical contacts initially when moved towards the ON configuration, and operable to unlock and allow closing of the main electrical contacts upon successful completion of a self-test. Said moveable stop is hereby configured to interact with a locking member included in the moveable contact arm.

<CIT> discloses a circuit breaker having a movable contact arm for opening and closing the circuit which is controlled separately by a circuit breaker mechanism for circuit protection and by a switch lever mechanism which does not require actuation of the circuit breaker mechanism to function. The switch lever may be activated by a solenoid or other suitable means, and various interlocking mechanical states exist among the elements that provide added safety features.

It is the object of the present invention to provide a protective switching device and method of operation thereof, which is reset in an initial state in a safe and quick way.

In the following a summary is provided to introduce a selection of representative concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used in any way that would limit the scope of the appended claims.

Briefly, the subject matter of the present invention is directed towards a method for inhibiting manual re-closing of a contact of a protective switching device as long as an electrical reset has not yet occurred. In a first step of said method, a trigger mechanism is preloaded into a first, preloaded state by moving a handle from an off-position to an on-position, which results in a closed contact state of the protective switching device. If the trigger mechanism is tripped by a first event, the trigger mechanism transits from the first, preloaded state to a second, tripped state, what results in an open contact state of the protective switching device. Subsequently, a transition of the trigger mechanism from the second, tripped state to the first, preloaded state is inhibited despite moving the handle from a tripped position to the on-position, as long as a second event has not occurred. In response to the occurrence of the second event, the trigger mechanism is electrically reset, so that moving the handle from the tripped position to the on-position results in transitioning of the trigger mechanism from the second, tripped state to the first, preloaded state. Said transition of the trigger mechanism from the second, tripped state to the first, preloaded state further results in a re-closing of the contact of the protective switching device, so that the closed contact state of the protective switching device is achieved. Hereby, said first event is related to an excess current from an overload or a short circuit or another external trigger input, and the second event is related to an electrical reset signal indicating re-establishment of a safe condition.

Hence, it is an advantage of the present invention to prevent premature manual resetting of a trigger mechanism in a protective switching device, which would result in closing the contact of the protective switching device, although a failure resulting in an excess current still persists in the circuit. Instead, a manual reset of the trigger mechanism by moving a handle results only in closing of the contact of the protective switching device, after the trigger mechanism has been electrically reset by an electrical signal provided by a controlling instance. Therefore, based on the method for operating a protective switching device according to the present invention, an increased security is obtained against erroneously re-exposing an electric device to a damaging excess current by means of a too early re-closing of the contact of the protective switching device.

In the method according to the present invention, the trigger mechanism is achieved by a trip actuator and a lock containing a latch, a lever and a spring.

Hence, the step of preloading the trigger mechanism into the first, preloaded state comprises preloading the lock, wherein the spring is compressed and the lever engages with the latch being in an initial latch state.

Tripping the trigger mechanism by the occurrence of the first event includes the trip actuator interacting with the latch by moving from an initial state into a displaced state, so that the latch is shifted from the initial latch state into a blocked state.

Moreover, in the method of the present invention, the trigger mechanism is electrically reset by moving the trip actuator back to the initial state in response to the electrical reset signal, so that the latch is reset to move back from the blocked state to the initial latch state.

In an embodiment of the present invention, the trip actuator comprises a linearly movable plunger in an electromagnetic coil attached to a spring and surrounded by a permanent magnet. A magnetic field of the permanent magnet keeps the plunger in a first position against a force of the spring. In response to the excess current of the first event, the magnetic field of the permanent magnet, which acts on the plunger, is weakened, so that the force of the spring pushes the plunger and thus linearly displaces the trip actuator from the initial state into the displaced state.

Further, in the method of the present invention, the advantage of linearly displacing the trip actuator consists in tripping the latch and making the lock transit from the first, preloaded state into a relaxed state, so that the contact of the protective switching device is opened.

In a preferred embodiment of the present invention, electrically resetting the trigger mechanism is performed by applying a voltage of a changed polarity to the trip actuator. Hereby, the voltage, which needs to be applied for electrically resetting the trigger mechanism, is significantly higher than a voltage acting on the trip actuator when the trigger mechanism is tripped. Said high voltage signal provides further security against erroneously resetting the trigger mechanism, although the circuit is still plagued by a failure resulting in an excess current.

Applying the voltage signal of the changed polarity to the trip actuator results in again strengthening the magnetic field of the permanent magnet and thus moving the linearly movable plunger of the trip actuator back to an initial state. Hence, the latch is reset to move back from the blocked state to the initial latch state.

In an embodiment of the present invention, the electrical energy needed for applying the voltage of the changed polarity to the trip actuator is hereby taken from an externally charged energy storage.

In another embodiment of the present invention, electrically resetting the trigger mechanism is performed by a reset actuator. The reset actuator moves the linearly movable plunger of the trip actuator back to the initial state and thus resets the latch to move back from the blocked state to the initial latch state.

Alternatively, in an embodiment of the present invention, electrically resetting the trigger mechanism may be performed by employing an electric motor moving a spindle on a propeller shaft, wherein the spindle pushes the linearly movable plunger of the trip actuator back to the initial state and thus resets the latch to move back from the blocked state to the initial latch state.

In still a further embodiment of the present invention, tripping the trigger mechanism causes to release a small finger locking the lock and causing a blocked state of the latch. Electrically resetting the trigger mechanism subsequently comprises retracting said previously released small finger by applying an electric signal to an additional locking finger reset actuator, so that the latch is reset to move back from the blocked state to the initial latch state. In the method according to the present invention, the first event and the second event are monitored by a plurality of sensors.

Hence, electrically resetting the trigger mechanism is performed by a controller including evaluation electronics analyzing information from the plurality of sensors and subsequently providing an electrical signal.

In the method of the present invention, preloading the trigger mechanism into the first, preloaded state by moving the handle from the off-position to the on-position comprises inputting mechanical energy, which is being stored in the spring.

Further, in the method according to the present invention, tripping the trigger mechanism by the first event comprises using the stored mechanical energy of the spring for opening the contact of the protective switching device.

In the method of the present invention, inhibiting the transition of the trigger mechanism from the second, tripped state to the first, preloaded state despite moving the handle from the tripped position to the on-position as long as a second event has not occurred comprises the lever not engaging with the latch being in the blocked state.

Moreover, the present invention comprises a protective switching device, which inhibits manual re-closing of a contact as long as an electrical reset has not yet occurred. Said protective switching device comprises at least one trip actuator, a lock comprising a latch, a lever, a spring and an actuating part, a contact connected to the actuating part, a controller connected to a plurality of sensors and a movable handle. The lock of the protective switching device is configured to be preloaded into a first, preloaded state, in which the spring is compressed and the lever engages with the latch in an initial latch state, by moving the handle from an off-position to an on-position, which results in a closed contact state of the protective switching device. The latch is configured to be tripped by a first event moving the trip actuator from an initial state into a displaced state and thus shifting the latch from the initial latch state into a blocked state. Said first event is hereby related to an excess current from an overload or a short circuit or another external trigger input. In response to said first event, the spring is decompressed and the lock is thus configured to transit from the first, preloaded state to a relaxed state resulting in an open contact state of the protective switching device. The lock is further configured to be inhibited to transit from the second, tripped state to the first, preloaded state despite moving the handle from the tripped position to the on-position, since the lever does not engage with the latch being in the blocked state as long as a second event has not occurred on the trip actuator. The latch is finally configured to be electrically reset to move back from the blocked state to the initial latch state in response to the occurring of the second event. The second event is hereby performed by the controller analyzing information from the plurality of sensors and comprises an electrical reset signal indicating re-establishment of a safe condition and moving the trip actuator back to the initial state. Therefore, moving the handle from the tripped position to the on-position results in the lock transitioning from the relaxed state to the first, preloaded state, which further results in a re-closing of the contact of the protective switching device to achieve the closed contact state of the protective switching device.

Therefore, the present invention advantageously provides a protective switching device, which after opening a contact due to an excess current from an overload and/or a short current and/or another external trigger input cannot be reset into an initial, closed contact state without first obtaining an electrical reset signal indicating a normal, safe state of the circuit. Like this, possible damages to an electric device in the circuit caused by a too early re-closing of the contact of the protective switching device can be efficiently avoided.

In an embodiment of the present invention, the protective switching device comprises a trip actuator equipped with a linearly movable plunger in an electromagnetic coil, which is attached to a spring and surrounded by a permanent magnet. A magnetic field of the permanent magnet keeps the plunger in an initial state against a force of the spring. In response to the excess current of the first event, the magnetic field of the permanent magnet acting on the plunger is weakened, so that the force of the spring pushes the plunger, which results in a linear displacement of the trip actuator into a displaced state.

In an embodiment of the present invention, the latch of the protective switching device is configured to be electrically reset by applying a voltage of a changed polarity to the trip actuator.

In a specific embodiment of the present invention, the applied voltage for electrically resetting the latch of the protective switching device is significantly higher than a voltage acting on the trip actuator when the latch is tripped.

Further, applying the voltage signal of the changed polarity to the trip actuator of the protective switching device according to the present invention results in again strengthening the magnetic field of the permanent magnet and thus moving the linearly movable plunger of the trip actuator back to the initial state and thus resetting the latch to move back from the blocked state to the initial latch state.

In the protective switching device according to an embodiment of the present invention, the electrical energy needed for applying the voltage of the changed polarity to the trip actuator is taken from an externally charged energy storage.

In another embodiment of the present invention, the protective switching device further comprises a reset actuator. The reset actuator electrically resets the latch by moving the linearly movable plunger of the trip actuator back to the initial state and thus resetting the latch to move back from the blocked state to the initial latch state.

In a further embodiment of the present invention, the protective switching device comprises an electric motor including a spindle movable attached to a propeller shaft. The trigger then is configured to be electrically reset by the spindle pushing the linearly movable plunger of the trip actuator back to the initial state and thus resetting the latch to move back from the blocked state to the initial latch state.

In another alternative embodiment of the present invention, the protective switching device further comprises a small finger. Said small finger is blocked by the latch in a first, preloaded state of the lock of the protective switching device. When the latch is tripped by a first event, the finger is released and subsequently blocks the latch, so that the latch is kept in a blocked state and the lock of the trigger mechanism is locked. The trigger mechanism is then electrically reset by again retracting said previously released finger by applying an electric signal to an additional locking finger reset actuator. Hence, the latch is again reset to move back from the blocked state to the initial latch state.

Alternatively, the protective switching device of the present invention may further comprise a second trip actuator being a bimetal element, which is configured to be thermally expanded by the excess current of the first event. Hence, said second bimetal trip actuator may act as a temperature sensor and advantageously allow interrupting the controlled circuit if a temperature exceeds a certain limit.

The present invention further comprises a safety motor starter, which comprises a contactor and a protective switching device according to the present invention as described above, which allows manually switching the motor on and off and which is connected in series to the contactor. Further, the safety motor starter may be connected to an emergency stop switch, which is configured to open the contactor in response to being pressed by an operator.

While an overload detected in the circuit comprising the safety motor starter and the motor generally results in switching off the contactor and maintaining the contact of the protective switching device in a closed contact state, a main contact of the contactor may also be welded in response to an overload. Hence, the contactor does not open and the circuit is not interrupted. In said case, according to the present invention, the latch of the protective switching device is configured to be tripped and the lock thus is configured to transit from the first, preloaded state to a relaxed state, which results in an open contact state of the protective switching device.

As soon as the contactor comprising the welded main contact is replaced by a new contactor, the latch is configured to be electrically reset to move back from the blocked state to the initial latch state. Hereby, the controller recognizes the new contactor by detecting a changed state of an auxiliary contact of the contactor.

Generally, safety motor starters usually need to comprise at least two contactors in order to guarantee that a circuit remains interrupted when a first contactor is welded due to an excess current, what results in permanently closing a main contact. When however a protective switching device according to the present invention is used in the safety motor starter, there is no need any more for a second contactor for making sure that the circuit remains interrupted as long as the welded first contactor has not been replaced by a new contactor. Hence, it is another advantage of the present invention that at least one contactor can be saved in a safety motor starter compared to prior art systems.

Other advantages may become apparent from the following detailed description when taken in conjunction with the drawings.

<FIG> shows a cut view of a protective switching device <NUM> according to the present invention, which inhibits manual re-closure of a contact <NUM> as long as a failure in a circuit has not yet been resolved. Throughout the description, the term protective switching device comprises for example a circuit breaker or a motor protective switching device (MPSD).

On top of the external cover <NUM> of the protective switching device <NUM>, a manual handle <NUM> is attached, which can be moved from an off-position to an on-position in order to switch on a device comprised in the circuit controlled by the protective switching device <NUM>. Such a device generally is a motor, but it is not limited thereto, and may also be an electrical heating element etc. Further, said manual handle <NUM> also has to be moved by an operator in order to reset the protective switching device <NUM> into a closed contact state, after a trigger mechanism <NUM> of the protective switching device <NUM> has been tripped due to a first event related to an excess current caused by an overload detected automatically in the circuit controlled by the protective switching device <NUM>.

<FIG> further illustrates a trip actuator <NUM> forming part of the trigger mechanism <NUM>, which is displaced in response to a first event and hence causes the tripping of a latch (not shown in <FIG>), which is also included in the trigger mechanism <NUM> of the protective switching device <NUM>. Said trip actuator <NUM> may comprise a linearly movable plunger in an electromagnetic coil, which is attached to a spring and surrounded by a permanent magnet (also not shown in <FIG>). Alternatively, the trigger mechanism <NUM> of the protective switching device <NUM> may additionally include a bimetal element acting as a second trip actuator, which is bent due to heat produced by an excess current. Hence, said second trip actuator embodied as a bimetal element acts as a temperature sensor and interrupts the circuit containing the protective switching device <NUM> and the controlled device if temperatures exceed a certain limit.

The tripping of the latch results in opening the contact <NUM> of the protective switching device <NUM>. The tripped trigger mechanism <NUM> cannot be directly reset into a first, preloaded state, in which the contact <NUM> of the protective switching device <NUM> is closed, by merely manually moving the handle <NUM> from a tripped position to an on-position as long as it is not made sure that all components are correctly working again and free from any failures. Different embodiments of said inventive trigger mechanism <NUM> will be discussed with respect to <FIG>.

The description of further features of <FIG> is omitted for the sake of clarity.

<FIG> shows a lock <NUM>, which achieves the trigger mechanism <NUM> of the protective switching device <NUM> of <FIG> together with the trip actuator <NUM>. Said lock <NUM> comprises a latch <NUM>, a lever <NUM>, a spring <NUM>, an actuating part <NUM>, a movable connecting element <NUM> connecting the lock to the handle <NUM> and movable links <NUM>. Said movable links <NUM> are preferably made of metal and connect the connecting element <NUM> and thus the handle <NUM> to the lever <NUM> and the lever <NUM> to the actuating part <NUM>. The actuating part <NUM> is connected to a mounting structure <NUM> of the protective switching device <NUM> by means of the spring <NUM>. Said spring <NUM> allows together with the movable links <NUM> the preloading and subsequent decompressing of the lock <NUM>. Further, the actuating part <NUM> of the lock <NUM>, which is connected to the spring <NUM>, is responsible for opening and closing the contact <NUM> of the protective switching device <NUM>. The handle 130is connected to the lock <NUM> by means of the movable connecting element <NUM>, which can be displaced by moving the handle 130handle <NUM>, and thus allows interacting with the trigger mechanism <NUM> by means of the external handle <NUM>.

It is important to note that the shown lock <NUM> and latch <NUM> comprise only one of a plurality of different embodiments for realizing a similar trigger mechanism <NUM>, and that the present invention is not limited to the exact embodiment of the trigger mechanism <NUM> shown in <FIG>. Instead, the present invention comprises all kind of triggering mechanisms <NUM>, which provide a functioning similar to the one of the trigger mechanism <NUM> described with respect to <FIG>. Likewise, the movable handle <NUM> may also be implemented in the form of a push button, a toggle or a pivoting lever, which transits from an off-position to an on-position in response to an input of an operator and which adopts a tripped position in response to a triggering event.

<FIG> illustrates the latch <NUM> in an initial latch state and the lock <NUM> in a non-preloaded, relaxed initial state, before an action of preloading the lock <NUM> has occurred. When the latch <NUM> is in the initial latch state shown in <FIG>, it is possible to preload the lock <NUM> into a first, preloaded state, by manually turning the handle <NUM> from an off-position to an on-position.

The result of said transition of the lock <NUM> into a first, preloaded state is illustrated in <FIG>. As can be seen in <FIG>, the action of manually moving the handle <NUM> from an off-position to an on-position has caused the lever <NUM> to engage with the latch <NUM>, so that the spring <NUM> is compressed. Hence, the mechanical energy input by a user when moving the handle <NUM> is stored in the spring <NUM> of the lock <NUM>.

At the same time, by preloading the lock <NUM>, the actuating part <NUM> of the lock <NUM> working with the contact <NUM> has been moved up compared to <FIG> when compressing the spring <NUM>. Therefore, the previously open contact <NUM> of the protective switching device <NUM> has been closed (not shown in <FIG>), so that the protective switching device <NUM> has reached a closed contact state. The first, preloaded state of the lock <NUM> shown in <FIG> corresponds to the normal, closed contact state of the protective switching device <NUM> during correct and safe operation of a controlled device.

<FIG> illustrates the lock <NUM> being again in the same relaxed state of <FIG>, whereas the latch <NUM> of the triggering mechanism <NUM> is in a second, tripped state. The latch <NUM> has been shifted into said second, tripped state from the initial latch state by the trip actuator <NUM> (not shown in any of <FIG>, <FIG>, <FIG> and <FIG>, respectively) in response to a first event that has acted on the at least one trip actuator <NUM>. Said first event is related to an excess current caused by an overload or a short circuit or to another external trigger input, which has displaced the at least one trip actuator <NUM> from an initial state to a displaced state. Said another external trigger input may be an input via a network or an input originating from an additional shunt trip or an undervoltage trip accessory.

The second, tripped state of the latch <NUM> corresponds to a blocked state of the latch <NUM>, since the latch <NUM> cannot move back to its initial latch state as long as the trip actuator <NUM> remains into the displaced state.

The trip actuator <NUM> may be for example a trip actuator <NUM>, which comprises a linearly movable plunger in an electromagnetic coil surrounded by a permanent magnet, whose magnetic field keeps the plunger against the force of a spring in a first position. When the first event occurs, an excess current is detected by the sensors and the electronics. A processor subsequently decides whether the trip actuator <NUM> is tripped or not. If the processor decides that the trip actuator <NUM> should be tripped in response to the detected excess current, a magnetic field of the permanent magnet acting on the trip actuator <NUM> is weakened, for example by discharging a capacity. Hence, a magnetic force of the magnetic field holding the plunger in the initial state becomes weaker than the force of the spring, which results in the spring linearly pushing the plunger. This linear movement of the plunger causes a linear displacement of the whole trip actuator <NUM>. When the trip actuator <NUM> is linearly displaced and thus reaches a displaced state, the latch <NUM> is tripped and thus shifted into the blocked state, in which it remains as long as the trip actuator <NUM> is not moved back to its initial state. Tripping the latch <NUM> causes the lock <NUM> being relaxed and adopting the same non-preloaded, relaxed state shown in <FIG>.

Alternatively, the protective switching device <NUM> may include additionally a second trip actuator <NUM>, which is composed of a bimetal element. In response to the excess current of the first event, the bimetal element of the second trip actuator <NUM> is heated up. If the overcurrent supersedes the usual current by more than about <NUM>%, the bimetal element is thermally expanded and bends. Hence, said second trip actuator embodied as a bimetal element acts as a temperature sensor and opens the contact <NUM> of the protective switching device <NUM> if temperatures exceed a certain limit. Once the bimetal element cools down again, it bends back and thus again closes the open contact <NUM> of the protective switching device <NUM>.

Tripping the latch <NUM> due to the linear displacement of the trip actuator <NUM> in response to the occurrence of the first event results in relaxing the lock <NUM> and thus in decompressing the spring <NUM> and releasing the mechanical energy stored in the spring <NUM>. The mechanical energy previously stored in the spring <NUM> is subsequently used for opening the contact <NUM> of the protective switching device <NUM>. Hence, the protective switching device <NUM> reaches an open contact state free from damaging overcurrents. This can be seen in <FIG> by the actuating part <NUM>, which is responsible for opening and closing the contact <NUM> of the protective switching device <NUM>, being moved down again compared to <FIG>.

At the same time, tripping the latch <NUM> results in the latch <NUM> dis-engaging from the lever <NUM>, which causes the handle <NUM> to move automatically from the on-position to a tripped position.

<FIG> shows the latch <NUM> still in the second, tripped state, in which it is blocked by the displaced trip actuator <NUM> (not shown in <FIG>). However, compared to <FIG>, the lever <NUM> and the connecting element <NUM> between the handle <NUM> and the lock <NUM> are displaced. The lever <NUM> and the connecting element <NUM> between the handle <NUM> and the lock <NUM> have been moved by an external operator (not shown in <FIG>) by manually moving the handle <NUM> from the tripped position to the on-position in an attempt to reset the lock <NUM> from the relaxed state to the first, preloaded state. Said attempt has however been in vain, since manually moving the handle <NUM> from the tripped position to the on-position has not resulted in the lever <NUM> re-engaging with the latch <NUM> and thus in closing the open contact <NUM> of the protective switching device <NUM>. The moved handle <NUM> does not remain in the on-position, but automatically moves back to the tripped position. Hence, as can be seen in <FIG>, the latch <NUM> remains in the blocked state regardless of any movement of the movable handle <NUM> performed by an external operator.

In some embodiments of the present invention, it is not possible to move the handle <NUM> directly from the tripped position to the on-position. Instead, such a movement may only be performed via the off-position. However, the result remains the same, i.e. the handle <NUM> does not remain in the on-position, but automatically moves back to the tripped position.

Hence, once the latch <NUM> has been tripped and moved into the blocked state by a first event acting on the trip actuator <NUM>, which has caused the lock <NUM> to transit from the first, preloaded state of <FIG> into the relaxed state of <FIG>, the lock <NUM> is inhibited to be reset from the relaxed state back to the first, preloaded state by inputting mechanical energy by moving the handle <NUM>. As can be seen in <FIG>, the reason for inhibiting such a resetting of the lock <NUM> into the first, preloaded state, in which the contact <NUM> of the protective switching device <NUM> is closed, is the latch <NUM> being in the blocked state, in which it cannot be engaged with the lever <NUM> by merely moving the handle <NUM>.

What is thus needed for resetting the lock <NUM> into a first, preloaded state and thus the protective switching device <NUM> into a closed contact state, is an outside force acting on the trip actuator <NUM>. Such an outside force acting on the trip actuator <NUM> should then push the trip actuator <NUM> back into an initial position, which would result in resetting the latch <NUM>, so that it can move back from the blocked state to the initial latch state.

By rendering it impossible for an operator to manually reset the lock <NUM> into a first, preloaded state without the help of an additional outside force acting on the trip actuator <NUM>, it is successfully prevented that an operator manually resets the lock <NUM> into the first, preloaded state, which corresponds to a closed contact state of the protective switching device <NUM>, although failure conditions may not yet have been resolved in a controlled circuit.

In the present invention, such an outside force, which generally consists in inputting additional electrical energy into the protective switching device system <NUM>, is provided by an electrical reset signal. Such an electrical reset signal is merely provided if it is made sure that failure conditions do not exist anymore in a circuit, so that a normal operation of the circuit can be safely resumed. The information that a normal operation can be resumed in a controlled circuit is obtained from a controller device, which for example receives an external reset signal provided by an operator by pushing a button either directly at the protective switching device <NUM> or on a remote control.

The electrical reset signal provided by the controller subsequently performs a reset operation on the trip actuator <NUM> and thus on the latch <NUM>. In response to the electrical reset signal, the trip actuator <NUM> is moved back from the displaced state to the initial state. Removing the trip actuator <NUM> results in resetting the latch <NUM> to move back from the blocked state to the initial latch state. Hence, the latch <NUM> is again in the initial latch state shown in <FIG>, in which it is feasible to preload the lock <NUM> by manually moving the handle <NUM> from the tripped position, either directly or via the off-position, to the on-position.

By moving the handle <NUM> from the tripped position to the on-position, the lock <NUM> is again preloaded, which includes the lever <NUM> engaging with the latch <NUM> and the spring <NUM> being compressed. Hence, the actuating part <NUM> is moved up again, so that the contact <NUM> of the protective switching device <NUM> is automatically re-closed. Finally, the lock <NUM> reaches again the first, preloaded state illustrated in <FIG>.

The present invention comprises four different embodiments for performing the electrical reset operation of the latch <NUM> and thus of the whole trigger mechanism <NUM>. In what follows, said four embodiments will be discussed with respect to <FIG>.

<FIG> shows a top view <NUM> of the protective switching device <NUM> comprising the trigger mechanism <NUM>. In contrast to the side view of the trigger mechanism <NUM> displayed in <FIG>, the actual lock <NUM> is not clearly visible in <FIG>. However, the trip actuator <NUM>, the lever <NUM>, the latch <NUM> and the handle <NUM> are shown in <FIG>. Based on <FIG>, the first concept of the present invention for performing the electrical reset of the latch <NUM> and thus of the trigger mechanism <NUM> will be described.

In the concept of <FIG>, the latch <NUM> is reset electrically from its blocked state by applying a voltage signal with a changed polarity to the trip actuator <NUM>. The voltage signal of the changed polarity to the trip actuator <NUM> results in again charging the capacity and hence strengthening the magnetic field of the permanent magnet. Subsequently, the linearly movable plunger <NUM> of the trip actuator <NUM> is pushed back to an initial state against the force of the spring by means of the magnetic field of the permanent magnet. Hereby, the voltage signal of the changed polarity is provided by a controller device, when an external reset signal is provided by an operator by pushing a button directly at the protective switching device <NUM> or on a remote control or when the result of the analysis of information obtained from the plurality of sensors indicates that the controlled circuit may resume its normal operation.

Once the trip actuator <NUM> has been removed from its displaced state back to an initial state by the voltage signal of changed polarity, the latch <NUM> is reset. The latch <NUM> thus is enabled to move back from its blocked state into the initial latch state, in which the latch <NUM> can engage with the lever <NUM> when the handle <NUM> is manually moved from a tripped position, either directly or via the off-position, to the on-position. Hence, electrically resetting the trip actuator <NUM> into an initial state causes the latch <NUM> moving back from the blocked state to the initial latch state, in which a subsequent mechanical reset of the lock <NUM> into a first, preloaded state becomes feasible.

The voltage of the electric signal with changed polarity used for resetting the trip actuator <NUM> to an initial state is preferably chosen to be significantly higher than a voltage that typically acts on the trip actuator <NUM> in order to displace the trip actuator <NUM> to the displaced state, to trip the trigger mechanism <NUM> and thus to open the contact <NUM> of the protective switching device <NUM>. Generally, a voltage of around <NUM> V is already sufficient for displacing the trip actuator <NUM> and thus tripping the latch <NUM> and making the lock <NUM> transit from the first, preloaded state to the relaxed state, while a voltage of around <NUM> V is used in order to perform the reset operation on the trip actuator <NUM> and thus to reset the blocked latch <NUM>.

The reason for choosing to perform the electrical reset operation on the trip actuator <NUM> and thus on the latch <NUM> merely in response to such a high voltage signal is the increased security against erroneously resetting the trigger mechanism <NUM>. It might be possible that a small voltage signal of changed polarity occurs in the circuit, although the controller has not yet approved a secure state of the controlled circuit. By demanding a higher voltage signal for electrically resetting the trigger mechanism <NUM>, it is made sure that the protective switching device <NUM> is finally reset into a closed contact state only when the circuit is again in a safe state. The electrical reset signal may thus be a superposition of a first signal necessary for actually moving the trip actuator <NUM> back to its initial state and a second signal merely serving as an indicator that the reset operation may be safely performed.

However, alternatively, it is also possible to reset the trip actuator <NUM> to an initial state by applying an electric signal of a same or even smaller voltage compared to the voltage typically acting on the trip actuator <NUM> to displace the trip actuator <NUM> into the displaced state. Such a solution may be for example realized by implementing the trip actuator <NUM> as a bi-static actuator.

The electrical energy, which is needed for applying such a - generally rather high - voltage signal to the trip actuator <NUM>, is generally taken from an energy storage included in the protective switching device system <NUM>, which is charged by external sources, in order to be able to provide said large amount of electric energy. Alternatively, said energy storage can be avoided by directly providing a sufficient amount of electrical energy from an external source.

<FIG> displays another concept <NUM> of the present invention for performing the electrical reset operation of the trigger mechanism <NUM>. Compared to <FIG>, <FIG> additionally shows a second reset actuator <NUM>, which may be for example a linear motor. In response to receiving the electrical signal from the controller indicating that the trigger mechanism <NUM> may be safely reset, the second reset actuator <NUM> is switched on and moves the plunger <NUM> of the trip actuator <NUM> back to the initial state. Hence, the latch <NUM> is freed from its blocked state and moves back into the initial latch state, from where a mechanical reset of the lock <NUM> into the first, preloaded state becomes feasible by manually moving the handle <NUM> from the tripped position, either directly or via the off-position, back to the on-position.

Compared to the concept described with reference to <FIG>, a rather small amount of electric energy is sufficient for safely performing the electrical reset operation of the trigger mechanism <NUM> by resetting the trip actuator <NUM> back into an initial state, when a second reset actuator <NUM> is employed. A rather small electric signal is sufficient for switching on the second reset actuator <NUM>, and there is basically no risk that the second reset actuator <NUM> may be switched on erroneously by an electric signal occurring in the circuit. On the other hand, in the concept described with reference to <FIG>, it is necessary to additionally employ a second reset actuator <NUM> apart from the trip actuator <NUM>.

<FIG> shows an additional reset actuator motor <NUM>, which is used for resetting the trip actuator <NUM> back to an initial state. The small electric motor <NUM> shown in <FIG> moves a spindle <NUM>, which is attached on a propeller shaft <NUM>. Said spindle <NUM> is further configured to push the plunger <NUM> of the trip actuator <NUM> back to the initial state and thus to reset the latch <NUM> to move back from the blocked state to the initial latch state, if the controller has deemed the circuit to be in a safe state again and has provided an electric signal to the small electric motor <NUM> of <FIG>.

Hence, when using the motor <NUM> for resetting the displaced trip actuator <NUM>, the second reset actuator is realized by the spindle <NUM>, which is an economic and easy to manufacture embodiment of a reset actuator.

However, moving the trip actuator <NUM> back to the initial state with the help of the spindle <NUM> attached to the propeller shaft <NUM> of the small electric motor <NUM> of <FIG> takes around <NUM> seconds. During said rather large amount of time needed for resetting the trip actuator <NUM>, the trigger mechanism <NUM> of the protective switching device <NUM> cannot be tripped. It has been however found out that usually time intervals, during which the safety functioning of a protective switching device <NUM> is not available, should be smaller than <NUM> seconds.

Alternatively, it is also feasible to directly employ a larger and thus stronger motor <NUM>, which has faster reaction times of less than <NUM>. Such a fast reacting motor <NUM> may be also directly employed as the trip actuator <NUM>. Hence, said motor functions as bi-static actuator.

<FIG> relates to another alternative embodiment <NUM>, how manually resetting a trigger mechanism <NUM> and thus re-closing the contact <NUM> of a protective switching device <NUM> can be efficiently avoided as long as an electrical reset indicating a safe condition of the controlled circuit has not yet occurred.

<FIG> depicts a small finger <NUM>, which is blocked by the latch <NUM> in a first, preloaded state of the lock <NUM> of the protective switching device <NUM>. When the latch <NUM> is tripped by a first event causing an excess current in the controlled circuit, the small finger <NUM> is released and subsequently blocks the latch <NUM> itself. Said small finger <NUM> thus locks the lock <NUM> by keeping the latch <NUM> in a blocked state, in which the latch <NUM> is prevented from re-engaging with the lever <NUM>. Any manual resetting attempts of the triggering mechanism <NUM> performed by an operator by manually moving the handle <NUM> from a tripped position to an on-position are unsuccessful until the electric reset of the trigger mechanism <NUM> performed by the controller results in a small electric signal being applied to an additional locking finger reset actuator <NUM>. Said electric reset signal again retracts the previously released finger <NUM> and thus resets the trigger mechanism <NUM>. Hence, the blocked latch <NUM> is enabled to move back from the blocked state to the initial latch state. Subsequently, the lock <NUM> can be again reset into a first, preloaded state, in which the latch <NUM> engages with the lever <NUM> and the contact <NUM> of the protective switching device <NUM> is closed by manually moving the handle <NUM> from a tripped position, either directly or via an off-position, to an on-position.

Also in the embodiment described with reference to <FIG>, a rather small electric signal is sufficient for safely resetting the trigger mechanism <NUM>, once a controller has confirmed a safe state of the circuit.

<FIG> shows a block diagram of the safety motor starter <NUM> for a motor <NUM> according to an embodiment of the present invention. Said safety motor starter <NUM> comprises a protective switching device <NUM> equivalent to the one previously described with regard to <FIG> and <FIG>. Further, the safety motor starter <NUM> may comprise an emergency stop switch <NUM> for manually tripping the trigger mechanism <NUM> and thus switching the motor <NUM> off in case of an emergency event. The protective switching device <NUM> is further connected in series to a contactor <NUM>.

When an excess current caused by an overload is detected by the sensors and communicated to the evaluation electronics of the controller of the safety motor starter <NUM>, at first the contactor <NUM> is switched off, while a contact <NUM> of the protective switching device <NUM> still remains in a closed contact state. Typical reaction times for switching off the contactor <NUM> are tenths of seconds up to several minutes depending on the amount of the overload. However, if after switching off the contactor <NUM>, there still flows an electric current in the circuit, the contact <NUM> of the protective switching device <NUM> is additionally opened. Subsequently, for example after a predetermined amount of time and/or after an operator has controlled the safety motor starter <NUM> and resolved any failures in the circuit, the contactor <NUM> may be switched on again remotely via an auto-reset.

In case of the first event being related to an excess current caused by a short circuit, on the other hand, the contact <NUM> of the protective switching device <NUM> is directly opened, since the contactor <NUM> reacts too slowly. It is necessary to react in response to an excess current caused by a short circuit within around <NUM>, whereas a typical reaction time of the contactor <NUM> is around <NUM>. After the occurrence of a short circuit, an operator has to control the whole system and all of its components before resetting the safety motor starter <NUM>. Therefore, a safety handle inhibit according to the present invention cannot be used in the case of an excess current caused by a short circuit.

Coming back to the case of the first event being an excess current caused by overload, it might occur that the main contacts of the contactor <NUM> are welded as a result of the overload experienced. Hence, the contactor <NUM> does not switch off and there is still current flowing in the circuit comprising the safety motor starter <NUM> and the motor <NUM>.

Such a welded state of the contactor <NUM> is detectable by the evaluation electronics of the protective switching device <NUM>, since the auxiliary contacts of the contactor <NUM>, which act as sensors, have not changed their state (e.g. from closed to open) as they however are supposed to do in response to the opening of the main contacts of the contactor <NUM>. Hence, the auxiliary contacts still indicate the contactor <NUM> as switched on. Therefore, it is recognized by the evaluation electronics of the controller of the protective switching device <NUM> that the contactor <NUM> has not switched off the safety motor starter <NUM> in response to the overload.

In such a situation, in which the contactor <NUM> apparently fails, the protective switching device <NUM> is employed to open the contact <NUM> and thus to finally interrupt the circuit, as described in detail above with respect to <FIG>. Like this, it is guaranteed that the motor <NUM> is securely switched off.

In a next step, the welded contactor <NUM> has to be replaced with a new contactor <NUM> by an operator. Said replacement of the welded contactor <NUM> with a new contactor <NUM> is detected by the evaluation electronics of the controller of the protective switching device <NUM> due to the changed contact state of the auxiliary contacts of the new contactor <NUM>. Hence, the auxiliary contacts act again as sensors for the controller of the protective switching device <NUM>. Based on the feedback received from the auxiliary contacts, the controller of the protective switching device <NUM> provides an electric signal for performing the reset operation of the trigger mechanism <NUM> according to any one of the embodiments described with reference to <FIG>.

After the trip actuator <NUM> has been reset and thus enabled the latch <NUM> to move back to the initial latch state, the operator is finally enabled to reset the lock <NUM> of the trigger mechanism <NUM> into a preloaded state by manually moving the handle 130attached to the protective switching device <NUM>. Hence, the open contact <NUM> of the protective switching device <NUM> is closed again, so that the normal functioning of the electric device such as for example of the motor can be re-assumed.

Therefore, a safety motor starter <NUM> according to the present invention inhibits that the contact <NUM> of a protective switching device <NUM> may be re-closed and thus the motor <NUM> is switched on again, as long as the welded contactor <NUM> is not exchanged with a new contactor <NUM>.

Therefore, according to the present invention, a safety motor starter <NUM> does not need to comprise a second contactor <NUM>, which makes sure that the system is interrupted when a first contactor <NUM> is welded due to an excess current caused by an overload until the first contactor <NUM> is replaced by a new contactor <NUM>. Compared to safety motor starter systems <NUM> known in the prior art, one of two contactors <NUM> can be saved by coupling a contactor <NUM> in series with a protective switching device <NUM>, whose controller detects that the main contacts of the contactor <NUM> have not been opened and which further inhibits manual re-closing of a contact <NUM> according to the present invention as long as the welded contactor <NUM> has not been replaced.

Apart from by an overload, the contactor <NUM> may also be switched off and thus the circuit be interrupted by an operator pressing the emergency stop switch <NUM>. Again, it might occur that the contactor <NUM> does not open and thus interrupt the circuit of the safety motor starter <NUM> as foreseen in response to pressing the emergency stop switch <NUM>. In such a case, the protective switching device <NUM> takes over and opens the contact <NUM>.

Alternatively, the action of pressing the emergency stop switch <NUM> by an operator may also directly cause a mechanical displacement of the trip actuator <NUM>. Said displacement of the trip actuator <NUM> causes the latch <NUM> to be tripped and thus being shifted from the initial latch state into a blocked state. At the same time, the lock <NUM> transits from the preloaded state to a relaxed state and the contact <NUM> of the protective switching device <NUM> is finally opened.

<FIG>, <FIG> show an interconnected flow diagram describing the main steps of the method of the present invention for inhibiting manual re-closing of a contact <NUM> of a protective switching device <NUM> as long as an electrical reset has not yet occurred. Said method is generally characterized by an interplay of actions performed on a handle 130and/or on a trigger mechanism <NUM> of the protective switching device <NUM>, which then result in either opening or closing of the contact <NUM> of the protective switching device <NUM>. Therefore, <FIG>, <FIG> are structured into three columns comprising the actions performed on the handle 130handle <NUM>, the trigger mechanism <NUM> and the contact <NUM> of the protective switching device <NUM>, respectively.

The method begins in step <NUM> with a user manually moving a handle 130of the protective switching device <NUM> from an off-position to an on-position. By this movement of the handle 130handle <NUM>, mechanical energy is input into the trigger mechanism <NUM>, which is subsequently stored in a spring <NUM> forming part of the trigger mechanism <NUM>. Hence, the trigger mechanism <NUM> is manually preloaded <NUM> into a first, preloaded state. Preloading <NUM> the trigger mechanism <NUM> into said first, preloaded state results in closing <NUM> the contact <NUM> of the protective switching device <NUM>. Thus, the protective switching device <NUM> enters into a closed contact state.

When the trigger mechanism <NUM> is in a first, preloaded state and the protective switching device <NUM> in a closed contact state, a first event characterized by an excess current causing an overload or a short-circuit on the circuit controlled by the protective switching device <NUM> may safely occur <NUM>.

In response to such a first event, the trigger mechanism <NUM> of the protective switching device <NUM> is tripped, and the trigger mechanism transits <NUM> from the first, preloaded state to a second, tripped state. Transiting <NUM> from the first, preloaded state to the second, tripped state goes along with the contact <NUM> of the protective switching device <NUM> being opened <NUM> and thus interrupting the circuit in order to protect a controlled device. For opening <NUM> the contact <NUM> of the protective switching device <NUM>, which thus enters an open contact state, the mechanical energy previously stored in the spring <NUM> is used and the spring <NUM> is decompressed. At the same time, the handle <NUM> is automatically turned back <NUM> from the on-position to a tripped position, when the trigger mechanism <NUM> is tripped.

The following steps of the method according to the present invention are governed by whether or not a second event occurs <NUM>. <FIG> describes the proceeding of the method of the present invention in response to the occurrence of such a second event <NUM>, while <FIG> discloses how the method of the present invention continues in the case of absence of said second event <NUM>.

Referring now first to <FIG>, it is assumed that said second event occurs <NUM>. Said second event is related to an electrical reset signal indicating re-establishment of a safe condition of the circuit controlled by the protective switching device <NUM>. Said second event is performed by a controller, which generates said electrical reset signal in response to analyzing information about the state of the controlled circuit obtained from a plurality of sensors or based on receiving a signal from an operator pushing a button at the protective switching device <NUM> or on a remote control.

In response to the occurring of the second event <NUM>, the trigger mechanism <NUM> is electrically reset <NUM>. As a result of this electrical reset, manually moving the <NUM> handle <NUM> from the tripped position, either directly or via the off-position, to the on-position enables transitioning <NUM> of the trigger mechanism <NUM> from the second, tripped state to the first, preloaded state. When the trigger mechanism <NUM> is again reset into the first, preloaded state, the contact <NUM> of the protective switching device <NUM> is re-closed <NUM> and the closed contact state of the protective switching device <NUM> is again achieved. Hence, the protective switching device <NUM> is again set back into its initial state and ready to interrupt the electric circuit in order to protect a controlled device such as a motor from any potential damage caused by an excess current.

<FIG>, on the other hand, illustrates the process of the method of the present invention as long as the second event has not yet occurred <NUM> and the trigger mechanism <NUM> has thus not been electrically reset by means of an electric signal.

If the user in this situation manually moves <NUM> the handle <NUM> from the tripped position to the on-position, the transition of the trigger mechanism <NUM> from the second, tripped state to the first, preloaded state is inhibited <NUM>. Hence, despite manually moving <NUM> the handle <NUM>, the contact <NUM> of the protective switching device <NUM> remains <NUM> in the open contact state and the re-closing of the contact <NUM> of the protective switching device <NUM> is inhibited as long as the controlled device is still deemed to be in an unsafe state.

Claim 1:
A method for inhibiting manual re-closing of a contact (<NUM>) of a protective switching device (<NUM>) as long as an electrical reset has not yet occurred, comprising:
preloading a trigger mechanism (<NUM>) into a first, preloaded state by moving a handle (<NUM>) from an off-position to an on-position resulting in a closed contact state of the protective switching device (<NUM>);
tripping the trigger mechanism (<NUM>) by a first event, in response to which the trigger mechanism (<NUM>) transits from the first, preloaded state to a second, tripped state resulting in an open contact state of the protective switching device (<NUM>);
inhibiting transition of the trigger mechanism (<NUM>) from the second, tripped state to the first, preloaded state despite moving the handle (<NUM>) from a tripped position to the on-position as long as a second event has not occurred, wherein the first event and the second event are monitored by a plurality of sensors;
in response to the occurring of the second event, electrically resetting the trigger mechanism (<NUM>) by a controller including evaluation electronics analyzing information from the plurality of sensors, so that moving the handle (<NUM>) from the tripped position to the on-position results in transitioning of the trigger mechanism (<NUM>) from the second, tripped state to the first, preloaded state resulting in a re-closing of the contact (<NUM>) of the protective switching device (<NUM>) to achieve the closed contact state of the protective switching device (<NUM>), wherein
said first event is related to an excess current from an overload or a short circuit or another external trigger input and the second event is related to an electrical reset signal provided by the controller indicating re-establishment of a safe condition.