Circuit arrangement for operating electromagnetic drive systems

The present application is a U.S. National Phase of International Patent Application Serial No. PCT/EP2016/079706 entitled “CIRCUIT ARRANGEMENT FOR OPERATING ELECTROMAGNETIC DRIVE SYSTEMS,” filed on Dec. 5, 2016. International Patent Application Serial No. PCT/EP2016/079706 claims priority to German Patent Application No. 10 2015 015 580.6, filed on Dec. 4, 2015. The entire contents of each of the above-cited applications are hereby incorporated by reference in their entirety for all purposes.

The present invention relates to a circuit arrangement for actuating an electromagnetic drive system for electromechanical devices as well as a method for operating a circuit arrangement for actuating an electromagnetic drive system for electromechanical devices.

Electromagnetic drive systems are often used in electrical engineering to apply force on movable mechanical components. Such systems use for example pull magnets or other electromagnetically operative component assemblies. These drive systems are used inter alia in contactors, circuit breakers, relays, solenoid valves, etc. in various forms.

In the actuating of such drive systems, the magnetic system is usually directly energized by the control voltage source; an acceleration of mechanical components thereby occurs such as e.g. armature or lever systems. That causes, for example, the closing of switch contacts. However, the force curve and closing speed in this case depend on the amount of voltage applied.

Yet it is also known that the energy supply of drive systems is often controlled by electronic assemblies (ballasts) such that the displacement/time characteristic of the force curve optimally corresponds to the requirements of the mechanical system during actuation

Already known from DE 20 2011 051 972 U1 is a circuit arrangement for actuating a switching device which exhibits a first switch position and a second switch position and can be switched between the first switch position and the second switch position and comprises at least one electromagnetic actuating device for generating a actuating force for switching the switching device between the first switch position and the second switch position and a trigger circuit for actuating the electromagnetic actuating device.

The actuation of the aforementioned drive systems by directly loading the magnetic systems with the available control voltage has the disadvantage of the supplied control current and thus the magnetic force usually not being adapted to the existing force/displacement characteristic of the powered mechanical system.

The known electronic ballasts for operating magnetic drive systems directly clock the magnetic systems via one or more electronic switches. Thereby disadvantageous is that while the available control voltage can be reduced, it cannot be increased.

Yet it is advantageous in a number of applications of said drive systems to also be able to increase the actuation control voltage if needed. Otherwise in such applications—for example in undervoltage situations—safe actuation is not possible.

Furthermore, these ballasts preferably serve in the actuating of switching devices in the form of in contactors in which the power requirement is initially high but which then drops over time.

The direct clocking of the electrical drive system additionally results in an interference voltage spectrum which can negatively affect other electronic systems. The pulse gradient also causes an increased loading of the coil structure of the magnetic systems which are mostly designed for DC or low-frequency AC operation. The clocked mode of operation can thus cause damage to the winding of the magnetic system.

It is therefore the task of the present invention to further advantageously develop a circuit arrangement and a method for operating a circuit arrangement, in particular to the effect of ensuring reliable and less mechanically aggressive operation without substantial emitted interference across the entire input voltage and temperature range and enabling the actuating of such drive systems having a greatly increasing power requirement over time during actuation as well as a mechanically locked stable end position.

The invention solves this task by a circuit arrangement having the features of claim 1 . According thereto, a circuit arrangement is provided for the actuating of an electro-magnetic drive system for electromechanical devices, in particular comprising a mechanically locked end position, at least one control voltage source, at least one regulating and control circuit, at least one drive system, at least one transformer, at least one rectifier bridge, at least one smoothing capacitor, at least one main switching transistor, by means of which the drive system can be controlled in a characteristic pulse tracking system and wherein the main switching transistor is connected in series to a primary branch of the transformer, wherein the transformer is connected to the supply voltage and the secondary winding of the transformer supplies the rectifier bridge, the output DC voltage of which is smoothed by the smoothing capacitor and added to the voltage of the control voltage source so as to result in a DC voltage feed having a chronological supply progression.

The invention is based on the basic concept of a clocked transformational converter stage providing the electrical supply characteristic required for the specific operation of the electromagnetic drive system throughout the entire input voltage and temperature range without pulsed loading of the drive system coils by way of a control and regulating circuit. The disadvantages of the known control systems identified in the prior art are avoided and a circuit arrangement is provided which operates the magnetic system of said drive systems, in particular those with DC solenoid coils, such that reliable and less mechanically aggressive operation without substantial emitted interference is ensured throughout the entire input voltage and temperature range and also allows the actuating of such drive systems having a greatly increasing power requirement over time during actuation as well as a mechanically locked stable end position.

The operation of switching devices having electromagnetic drive systems, for example battery circuit breakers having drive system pull magnets and a mechanically locked end position, contactor and relay coils as well as solenoid valves with electromagnetic valve control, gives rise to limited operating voltage ranges and increased wear of the mechanically moved components due to the internal structure. Clocked voltage operation gives rise to emitted interference which can affect electronic circuits.

To avoid these disadvantages, a circuit arrangement is now inventively provided which supplies a regulated DC voltage having a beneficial supply progression for the drive system by means of a switching stage and transformer arrangement with a downstream rectifier and also enables the actuating voltage to be increased over the existing and possibly highly tolerance-dependent control voltage when needed. This thereby ensures their safe activation, as in the example case of a battery circuit breaker having drive system pull magnets and a battery-backed power supply system subject to a wide input voltage range. The circuit arrangement moreover enables a delicate and thus life-extending mode of operation for the mechanically moved components. Feeding DC voltage to the drive system largely prevents emitted interference, particularly in the case of longer wirings between the described circuit arrangement and the drive system.

An auxiliary diode connected to the transformer/main switching transistor node on the anode side and to the rectifier bridge cathodes node on the cathode side can be provided.

The rectifier bridge can be formed by a plurality of diodes. These diodes can, for example, be fast diodes for output rectification.

It can furthermore be provided for a second transistor to be furnished and for the switching arrangement to be switchable such that a hold circuit can be activated in the power circuit by means of a second transistor using the return magnetization energy of the transformer for the activation time via the processing of a gate voltage, whereby the second transistor is activated and is disabled after the activation time by the switching off of the main switching transistor and the ceasing of the return magnetization energy.

It is moreover possible for the control and regulating circuit to comprise a PWM circuit (PWM=pulse width modulation) with activation time limitation and for a pulse pattern corresponding to the specifics of the drive system able to be assigned to the respective application by an appropriate selection to be stored via the PWM circuit.

It can furthermore be provided for the circuit arrangement to comprise a microcontroller circuit and for the microcontroller circuit to be used for the coordinated control and pulse processing.

Additionally possible is for a thermal fuse, in particular a reversible thermal fuse, and a series resistor for the control current supply to be arranged such that in the event of failure in the main current path, the combination of thermal fuse and series resistor can be arranged and switched such that the main current path is interruptible via the thermal coupling of the thermal fuse and series resistor.

It can furthermore be provided for the circuit arrangement to further comprise a safety circuit having an optocoupler and a Z-diode which can be switched such that in the event the output load is interrupted, inadmissibly high output voltage can thereby be prevented by the safety circuit responding in the event of failure such that the optocoupler is activated by the excessive output voltage via the Z-diode and the output of the optocoupler thereby acts on the control and regulating circuit, with the activation period thus being reduced for the power transistor such that the output voltage remains restricted to a permissible level.

The present invention further relates to a method for operating a circuit arrangement.

In one method of operating a circuit arrangement for the actuating of an electromagnetic drive system for electromechanical devices, in particular comprising a mechanically locked end position, at least one control voltage source, at least one regulating and control circuit, at least one drive system, at least one transformer, at least one rectifier bridge, at least one smoothing capacitor, at least one main switching transistor, by means of which the drive system can be controlled in a characteristic pulse tracking system in at least one operating state and wherein the main switching transistor is connected in series to a primary branch of the transformer, the process is thereby for the transformer to be connected to the supply voltage and the secondary winding of the transformer to supply the rectifier bridge, the output DC voltage of which is smoothed by the smoothing capacitor and added to the voltage of the control voltage source so as to result in a DC voltage feed having a chronological supply progression.

It can furthermore be provided for a second transistor to be furnished and for the switching arrangement to be switched during operation such that a hold circuit can be activated in the power circuit by means of a second transistor using the return magnetization energy of the transformer for the activation time via the processing of a gate voltage, whereby a second transistor is activated and is disabled after the activation time by the switching off of the main switching transistor and the ceasing of the return magnetization energy.

It is moreover possible for the regulating and control circuit to comprise a PWM circuit with activation time limitation and for a pulse pattern corresponding to the specifics of the drive system able to be assigned to the respective application by an appropriate selection to be stored via the PWM circuit.

Additionally possible is for a thermal fuse, in particular a reversible thermal fuse, and a series resistor for the control current supply to be arranged such that in the event of failure in the main current path, the thermal fuse and series resistor combination can be switched such that the main current path is interrupted via the thermal coupling of the thermal fuse and series resistor.

It can additionally be provided for the circuit arrangement to further comprise a safety circuit having an optocoupler and a Z-diode which can be switched in the event of failure such that if the output load is interrupted, inadmissibly high output voltage can thereby be prevented by the safety circuit responding in the event of failure such that the optocoupler is activated by the excessive output voltage via the Z-diode and the output of the optocoupler thereby acts on the control and regulating circuit, with the activation period thus being reduced for the power transistor such that the output voltage remains restricted to a permissible level.

Further specifics and advantages of the invention will now be described in greater detail on the basis of an example embodiment depicted in the drawings.

Shown are:

FIG. 1 a schematic circuit diagram for one example embodiment of a circuit arrangement for actuating an electromagnetic drive system as well as a corresponding method thereto; and

FIG. 2 the quantitative progression of the force/displacement characteristic of the power mechanism of the switching arrangement according to FIG. 1 .

FIG. 1 shows a schematic circuit diagram of an example embodiment of a circuit arrangement, realized here as a battery circuit breaker having a pull magnet, its circuit and operating principle illustrated in FIG. 1 as well as described in greater detail below.

The circuit arrangement comprises a regulating and control circuit 1 which in detail comprises a stabilizer circuit for the internal control voltage U S with ZD 1 . 1 , a measured value detection 1 . 2 , a PWM circuit (pulse width modulation circuit) with activation time limitation t 1 . 3 as well as a driver circuit 1 . 4 for the power switch (VT 2 ).

In addition, the switching arrangement comprises an electromagnetic drive system 2 .

The switching arrangement is connected to a control voltage source with an operating voltage (U B ).

The MB reference symbol indicates the negative potential (main current).

The switching arrangement moreover comprises a power button S 1 , a series resistor R 1 for the current supply U S , a gate bleeder resistor R 2 for the switching transistor VT 1 , a discharge resistor R 3 in the snubber circuit for the power transistor for the self-holding circuit VT 2 , a gate bleeder resistor R 4 for the power transistor VT 2 as well as a standing resistor R 5 for detecting the main current for the generating of the control variable. Further provided are a current limiting resistor R 6 , an overvoltage protector R 7 , a low-inductance intermediate circuit capacitor C 1 , an intermediate circuit capacitor C 2 of higher storage capacity, a smoothing capacitor C 3 , a capacitor C 4 of the DRC snubber circuit for the power transistor VT 2 , and a smoothing capacitor C 5 for the output load. The switching arrangement VD 1 additionally comprises a reverse pole diode and freewheeling diode VD 1 , a fast diode VD 2 of the DRC circuit for the power transistor VT 2 , a gate voltage limitation VD 3 , a fast rectifier diode VD 4 for the processing of the gate voltage for the switching transistor VT 1 , fast diodes for output rectification VD 5 , VD 6 , VD 7 and VD 8 as well as a freewheeling diode VD 9 for the switching transistor VT 1 , an input choke L 1 (inrush current limitation), a thermal fuse F 1 as well as an overcurrent protector F 2 .

An auxiliary diode connected to the transformer T 1 /switching transistor VT 2 node on the anode side and to the node comprised of the cathodes VD 6 , VD 8 of the rectifier bridge, formed by diodes VD 5 , VD 6 , VD 7 , VD 8 , on the cathode side.

Furthermore provided are terminals 1 / 2 , representing the power button connections, one terminal 3 as supply input for the control current supply, one terminal 4 for the connection of the switching transistor VT 1 activation, one terminal 5 as negative potential of the control voltage level, terminals 6 / 7 as shunt voltage supply for the regulating circuit with measuring field detection 1 . 2 , and terminals 8 / 9 as connection for the output load 2 of the electromagnetic drive system 2 .

The t Ein reference symbol indicates the activation time and the t tot reference symbol indicates the dead time.

The functionality of the control arrangement and the inventive method will now be explained as below:

When activated, the battery circuit breaker reaches a mechanically locked stable end position. The function of safely energizing pull magnets and reliably achieving the mechanically fixed end position of the battery circuit breaker must be ensured in a voltage range of from 65V to 150V, whereby the rated control voltage amounts to 110V.

In this application, the proposed arrangement must ensure that despite greatly increasing power requirement—as opposed to the commonly known contactors—sufficient energy needs to be provided for the magnetic system at the end of the actuation period.

The activation process is started via the start button S 1 so that the transistor VT 1 in the off state is bridged and the regulating and control circuit activated via the series resistor R 1 ; the control voltage processing 1 . 1 is symbolized by ZD. To establish the pulse pattern, a pulse-width modulated signal at a constant base frequency of 40 kHz is generated.

The activation time t Ein is calculated such that the required pick-up time in consideration of the permissible pull magnet operating period is maintained under all environmental conditions, as depicted in FIG. 2 .

The pull magnets 2 are designed for short-term operation; inadmissibly long periods of operation lead to damage. Should the permissible operating period be exceeded in the event of a failure, the thermal fuse F 1 is activated due to the thermal coupling with resistor R 1 . Series resistor R 1 and the reversible thermal fuse have the same basic casing design (TO220) and are mechanically connected at the thermal contact surfaces of the casings so as to ensure safe and defined activation in the event of failure. The selecting of the resistor size results in approximately thermally equivalent behavior to the pull magnets 2 .

The transistor VT 2 is activated by the regulating and control circuit 1 within the time t Ein of 1.6 s of the PWM circuit, a voltage generated by the rectifier bridge of VD 5 to VD 8 and smoothed by C 5 corresponding to the transmission ratio of the transformer T 1 is thereby added to the control (input) voltage U B . This arrangement achieves the voltage at the pull magnets being able to be brought to a value both below and above the control voltage by varying the PWM duty cycle. Switch S 1 can be reopened after being closed; the self-holding circuit with VT 1 further powers the circuit by supplying the return magnetization voltage of T 1 via diode VD 4 , the current limiting resistor R 6 of the limiting and stabilizer circuit with VD 3 , R 2 and C 3 to the gate by VT 1 so that it is activated. As long as the stage is clocking with VT 2 , the power circuit remains activated via VT 1 . After time t Ein has elapsed, the stage with VT 2 is deactivated, the power circuit is interrupted. After a dead time t tot has elapsed, the switching operation can be restarted. The dead time t tot prevents the drive system coils from being overloaded due to improper use.

The internal control voltage processing 1 . 1 moreover ensures with its own time stage that stabilizer ZD is not overloaded due to improper actuation of power button S 1 (uninterrupted keying); in such a case, 1 . 1 is forcibly deactivated after a predefined period of time which is longer than the normal operating time of the device.

Capacitors C 1 and C 2 are provided to sufficiently decouple the inherent resistances of supply source U B , whereby low-inductance capacitor C 1 feed in the activation moment of VT 2 and moreover the AC portion of the intermediate circuit capacitor C 2 with the substantially higher capacity and higher internal resistance takes over.

The choke L 1 is provided for the inrush current limitation and the power discharge from switch S 1 .

The circuit is equipped with a current control; the main current is detected in the power circuit and fed to the measured value detection 1 . 2 via the shunt resistor R 5 . The measured value detection 1 . 2 provides the signals for the control and regulating circuit 1 . 3 which processes the pulse-width pattern according to the specific characteristic of the electromagnetic drive system 2 . A series of specific supply characteristics can be stored in the control and regulating circuit 1 . 3 which can be appropriately selected and thus correspond to the respective intended application.

If there should be no connection of the output terminals 8 , 9 to circuit breaker 2 due to an error during use, the output voltage is limited by the control and regulating circuit 1 . 3 .

As is evident from FIG. 2 , Lite force/displacement characteristic is such that upon the switching device 2 switching from a first switching position so corresponding to one of the open positions into a second switching position s End corresponding to the closed position over displacement path s, a comparatively low initial force F Anf is initially required which then increases to a maximum force F max as of a pressure point s 2 up to a maximum point S 2 and, subsequent the maximum point s 2 , drops to a final force F End until the second switching position s End . The actuating force F on the pull magnets ZM 1 , ZM 2 is generated according to the curve of this force/displacement characteristic so that the actuating force F of the force/displacement characteristic of the switching device 2 is adjusted.

Adapting the actuating force F to the force/displacement characteristic of the switching device 2 ensures a less mechanically aggressive operation of the switching device 2 . In particular, excessive actuating force F is prevented which could lead to wear or even damage of the switching device 2 upon striking mechanically actuated components.

In addition, adapting the actuating force F to the force/displacement characteristic of the switching device 2 ensures reliable switching of the switching device 2 independent of the specific control voltage U Dauer available. In particular, modifying the control voltage U Dauer in the intermediate circuit voltage U ZK and adapting the actuating force F to the force/displacement characteristic of the switching device 2 over the entire voltage range of the control voltage U Dauer ensures that there will be sufficient energy to switch the switching device 2 and moreover excludes a bouncing of mechanically actuated components of the switching device 2 .

1 —regulating and control circuit

1 . 1 —stabilizer circuit for internal control voltage U S with ZD

1 . 2 —measured value detection

1 . 3 —PWM circuit with activation time limitation t

1 . 4 —driver circuit for power switch (VT 2 )

2 —electromagnetic drive system

U B —operating voltage

MB—negative potential (main current)

S 1 —power button

R 1 —series resistor for control current supply U S

R 2 —gate bleeder resistor for VT 1

R 3 —discharge resistor in snubber circuit of VT 2

R 4 —gate bleeder resistor for VT 2

R 5 —shunt resistor for detecting the main current to generate the control variable

R 6 —current limiting resistor

R 7 —overvoltage protector

C 1 —low-inductance intermediate circuit capacitor

C 2 —intermediate circuit capacitor of higher storage capacity

C 3 —smoothing capacitor

C 4 —capacitor of DRC snubber circuit for VT 2

C 5 —smoothing capacitor for output load

VD 1 —reverse pole diode and freewheeling diode

VD 2 —fast diode of DRC circuit for VT 2

VD 3 —gate voltage limitation

VD 4 —fast rectifier diode for processing the gate voltage for VT 1

VD 5 to VD 8 —fast diodes for output rectification

VD 9 —freewheeling diode for T 1

VT 1 —switching transistor

VT 2 power transistor for self-holding circuit

L 1 —input choke (inrush current limitation)

F 1 —thermal fuse

F 2 —overcurrent protector

Terminals: 1 / 2 connections for power button

3 supply input for control current supply 4 connection for activating VT 1 5 negative potential (control voltage level) 6 / 7 shunt voltage supply for the regulating circuit with 1 . 2 8 / 9 connection for output load 2

t Ein activation time

t tot dead time

F actuating force

F Anf actuating force at moment of activation

F max actuating force at pressure point

F End actuating force at end of displacement path

s armature path of pull magnet

s 0 deactivation position

s 1 distance between deactivation position and pressure point

s 2 distance between deactivation position and required maximum force

s End distance between deactivation and final position