DE19507342C2 - Circuit arrangement for controlling the electrical consumer in a hoist or a travel drive therefor - Google Patents

Description

The invention relates to a circuit arrangement to control a consumer.

To power the electric drives from Controlling hoists and trolleys is safe For reasons of safety, heavy current relays or contactors have so far been used turns. These electromechanical devices are ver relatively robust and are therefore considered a comparison wise sure, but have the disadvantage of being quite a lot Need space. Thyristors or triacs with the same Current carrying capacity and switch-off capability are compared with such power relays, much smaller. Everything However, such electronic components are made from ver various reasons as not sufficiently reliable seen. It is feared that due to overvoltage electronic component is damaged in the network and becomes permanently conductive due to the damage.

In addition, you fear an accidental scarf ten of the electronic components because of the control tion in the sense of switching on the components control energy is extremely low and such components  even if the voltage rise is too steep, for example due to spikes, at least for one Half wave can be switched on. The switching energy for heavy current relays and contactors compared to many orders of magnitude larger, which is why so far electromechanical devices with safety-relevant connections controls have been brought forward.

In addition, from the magazine "Maschinen markt "Born 1973, page 2034, under the heading "How important is pulse control for the forklift lerbetrieb? "a circuit arrangement known that Makes use of the contactors for directional control switch in the de-energized state if possible. To are microswitches on the pedals of the forklift to operate the directional contactors. This Directional contactors are in the power supply to the motors and serve on the one hand as a main switch and on the other hand have the function of reversing the direction of rotation to effect. There is also a potentiometer with the pedals coupled to the pulse modulated signal for the triac control the speed control also in the engine power supply line.

This type of control is for the shooter it is a so-called path control, the purpose of which is the triac or thyristor in the de-energized state too bring before the contactors are actuated.

Proceeding from this, it is an object of the invention to Circuitry specifying the same security offers, like a contactor or heavy current relay control, but compared to that, it occupies considerably less space claimed.

This object is achieved by the scarf solved with the features of claim 1.  

With the help of thyristors and triacs can be large electrical powers are switched while others hand these electronic components also in connection take up very little space with the heat sink. The One reason for this is that with thyristors and triacs no moving parts occur that correspond need space, and also no mechanical Precautions are included to turn off extinguish any sparks that may occur. The isolation resistance of such electronic components normally high enough and prevents residual currents, which undesirably set the consumer in motion could. Thus, the electronic switch can be in shape of the thyristor or triac as a circuit breaker be used when switching off the consumer large currents and voltages occurring safely can switch.

To ensure the safety of the route, uses a comparatively small relay as a disconnector, which is controlled by an actuator that a change in the switching state on its contacts only occurs when the electronic component itself is in the locked state.

The relay no longer needs to be dimensioned in this way to be able to handle the maximum occurring To be able to safely switch off the operating current without to be damaged here. The contact set that is in series with the electronic component, just has to the current carrying capacity can no longer be dimensioned according to the switching ability. Precautionary measures that the Suppress the occurrence of switching arcs that burn for longer, can be saved, which is why the contact set together can be miniaturized very strongly with the magnetic coil. Even if the electronic component should fail, can at least once more with this miniaturized Contact set of electricity to be interrupted. It doesn't play  Role, if the contact set so far failed that he could not reconnect in can create the circuit.

With the new circuit arrangement is in hoists to control every electrical consumer, for example as the chassis motor, the hoist motor or assigned brake magnets. The motors can use universal mo toren or AC motors, being in the case of multi-phase AC motors simply more thyristors and contact sets are used.

For the rest, further developments of the invention are against stood by subclaims.

In the drawing are exemplary embodiments of the counter state of the invention. Show it:

Fig. 1 arrangement, a block diagram of the new circuit,

Fig. 2 shows an embodiment which is constructed in wesentli Chen exclusively with discrete components and

Fig. 3 shows an embodiment of the new circuit arrangement in connection with a microprocessor control.

Fig. 1 shows the basic principle for a miniaturized circuit for safely controlling a consumer 1 , which takes several kW of electrical power in operation. For the purpose of explaining the essential features of the new circuit, it is first assumed that the consumer 1 is a single-phase motor, for example a universal motor, or an AC motor with auxiliary starting winding. The engine 1 has two terminals 2 and 3, wherein the on connecting terminal 2 immediately with a phase line L2 of a power supply system not shown is connected. The other connection 3 of the motor 1 is connected to an electrode 4 of a triac 5 , the other main electrode 6 of which is connected to an electromechanical contact set 7 with contacts 8 and 9 . The contact 8 is a fixed mechanical contact and with this fixed contact 8 the movable mechanical contact 9 works together, which is connected via a corresponding connecting line to another phase line L1 of said network.

In order to control both the triac 5 and the mechanical contact set 7 into the current-carrying state, an actuating device 10 is provided which essentially contains two timing elements 11 and 12 . Both timers 11 and 12 of the actuating device 10 are optionally connected to a control or auxiliary voltage U via a manually operated push button 13 when the motor 1 is to be started. In particular, the manual button 13 is connected to an input 14 of the timing element 11 , which operates with a delayed fall. Its output 15 actuates the mechanical contact set 7 , as is illustrated schematically by a dashed line 16 .

The timing element is provided on the hand switch 13 also to its input 17 connected to 12, which acts on delay and its output 18 is at a control electrode 19 of the triac. 5

This circuit arrangement works as follows:

If the user wants to start the motor 1 , he actuates the manual button 13 , whereby the two inputs 14 and 17 of the timers 11 and 12 receive a corresponding control voltage. Due to this voltage fed into the input 14 , the timing element 11 actuates the contact set 7 in a substantial manner without delay, whereby its contacts 8 and 9 are brought into an electrically conductive contact with one another.

The switching of the contact set 7 takes place at a time when the triac 5 is still in the blocking state because it does not receive any trigger pulses. The timer 12 received a voltage signal at the same time as the timer 11 at its input 17 , but only after a delay passed the first trigger pulse for the triac 5 at its output 18 . The delay time between the arrival of the signal at the input 17 and the output of the trigger pulses at the output 18 for the gate 19 is such that this signal can only switch the triac 5 into the conductive state when the contact set has already been set with certainty 7 is in the conductive state.

Both the contact set 7 and the triac 5 now remain in the current-carrying state for as long as the user keeps the hand switch 13 closed. The current flow from L1 to L2 through motor 1 is switched on for this time.

When the user wants to stop the motor 1 , he releases the hand switch 13 . As a result, the control signal at inputs 14 and 17 disappears immediately. This change in state at the inputs 14 and 17 has the consequence that the timer 12 no longer issues trigger pulses at its output 18 without delay, so that the triac 5 at the next zero crossing of the AC current flowing through it can pass into the locked state and locked from now on remains.

The timer 11 , on the other hand, operates with a time delay with regard to switching off. It actuates the contact set 7 due to the time delay in the sense of opening the two contacts 8 and 9 with a delay that is large enough so that the triac 5 has certainly already interrupted the current when the two contacts 8 and 9 are apart become.

Because of this by the timers 11 and 12 he forced temporal order for actuating the triac 5 and the contact set 7 ensures that the contact set 7 never switches under load. Its contacts 8 and 9 can be miniaturized. It suffices to dimension the contacts 8 and 9 so that they are only able to carry the maximum flowing operating current. They do not need to be dimensioned taking into account opening sparks. There is also no contact erosion at contacts 8 and 9 because they only switch when de-energized, which is why the low contact resistance is maintained over almost any period of time. The service life of contacts 8 and 9 is practically no longer limited.

The triac 5, on the other hand, takes over the shutdown, with no wear occurring on it. The arrangement of contact set 7 and triac 5 can therefore be significantly reduced compared to a contactor control and may even be used in the conventional control bulbs or control switch housings for the control of hoists.

Possibly vaguely interfering radiation, which could possibly ignite the triac 5 , because it only requires extremely small control powers at its gate 19 , cannot trigger faults in the sense of an accidental starting of the motor 1 , because when the triac 5 is locked, the contact set 7 is also in the state the power cut is located.

Should the triac 5 fail or the timer 12 no longer work in the desired chronological order, a current interruption would still be possible via the contact set 7 . If this contact set 7 burns very soon because of the opening spark, the entire device fails on the safe side, because at some point the time has come when the contact has burned so far that the contacts 8 and 9 no longer make contact.

FIG. 2 shows a more detailed circuit diagram for the basic principle shown in FIG. 1. As far as components appear in the circuit according to FIG. 2 which have already been described in connection with FIG. 1, the same reference number is used for this. The rest of the structure is as follows:

The hand switch 13 is designed with two poles and has a first contact set 21 and a second contact set 22 mechanically coupled therewith. The contact set 21 connects the control voltage U with a series resistor 23 , via which a storage capacitor 24 is charged when the contact set 21 is closed. The storage capacitor 24 leads from the resistor 23 to a common circuit ground 25 . Parallel to the storage capacitor 24 is a relay winding 26 of a relay with two Ar beitskontaktsätze, namely the normally open contact set 7 and a normally open contact set 27th The normally open contact set 27 is in a series circuit which, in addition to itself, includes a resistor 28 and a further storage capacitor 29 and is connected in parallel with the relay winding 26 to the circuit mass 25 . At the connection point between the resistor 28 and the storage capacitor 29 there is at one end another relay winding 31 of a relay with a make contact set 32 . At the other end, the relay winding 31 is connected to the circuit ground via the working contact set 22 .

The normally open contact set 32 connects the control voltage U to an input of a triac ignition circuit 33 which is connected on the output side to the gate 19 .

Finally, a discharge resistor 34 is seen before, which is parallel to the capacitor 29 .

The relay with the relay winding 26 together with the capacitor 24 and the series resistor 23 be the time element 11 already explained in connection with FIG. 1, while the guide element 12, the relay with the relay winding 31 , the resistor 28 , the capacitor 29 and includes the contact set 22 .

The circuit explained so far works as follows measure:

If the manual button 13 is not actuated, its two working contact sets 21 and 22 are open, so that after a corresponding time neither the relay winding 26 nor the relay winding 31 can have current. The result of this is that the contact sets 7 and 27 are in their open rest position, as well as the working contact set 32nd Thus, the triac ignition circuit 33 receives no current and the triac 5 remains locked. In this switching state, the circuit to the motor 1 contains at least two power interruptions, namely one in the form of the contact set 7 opened and the other in the form of the non-ignited triac 5th

If the user wants to start the motor 1 , he actuates the manual button 13 , whereupon both Ar beitskontaktsätze 21 and 22 are closed. Because of the closing of the contact set 21 , the capacitor 24 can aufla via the resistor 23 to the control voltage U. In the course of this charging process, a voltage threshold is exceeded, from which the relay winding 26 is able to actuate the two working contact sets 7 and 27 in the sense of closing.

Only when the contact set 27 is closed, the storage capacitor 29 also comes through the series resistor 28 current from the control voltage U and can gradually charge. During this charging process of the storage capacitor 29 , a further switching threshold is exceeded, above which the relay winding 31 actuates the make contact set 32 . As soon as the normally open contact set 32 is actuated, it applies the control voltage U to the input of the triac ignition circuit 33 , which then emits ignition pulses to the triac 5 . The triac 5 is accordingly switched periodically to the conductive state, but not before the normally open contact set 7 has been closed. Thus, in the circuit according to FIG. 2, the contact set 7 switches from one operating state to the other operating state only in the de-energized state. The time delay with which the triac 5 becomes conductive for the first time depends on the interaction of the storage capacitor 29 with the relay winding 31 .

To stop the motor 1 , the user releases the manual button 13 , whereupon the current through the relay winding 31 is interrupted as a result of the contact set 22 which opens. The relay thus falling off immediately breaks the connection between the control voltage and the triac ignition circuit 33 , which stops continuing to deliver ignition pulses to the triac 5 . At the next current zero crossing, the triac 5 changes into the blocking state and subsequently becomes no longer conductive because the ignition pulses at its gate 19 are absent. Thus the circuit from L1 to L2 via the motor 1 is already interrupted while the contact set 7 is still closed at the moment.

Since the user has released the hand switch 13 , there is no recharging of the storage capacitor 24 from the control voltage U, which can consequently be discharged via the relay winding 26 . As soon as the discharge of the storage capacitor 24 has progressed far enough, the current is no longer sufficient for the relay winding 26 to continue to keep the two contact sets 7 and 27 closed, which then open. Thus, the contact set 7 in the circuit to the motor 1 switches from the closed switching state to the open switching state in the de-energized state.

Simultaneously with the discharge of the capacitor 24 via the relay winding 27 , the capacitor 29 is gradually discharged via the discharge resistor 34 , so that after a relatively short time both capacitors 24 and 29 are de-energized again. When the hand button 13 is pressed again, the game described above would be repeated.

By further contacts, which are actuated by the relay winding 26 , an even faster unloading of the capacitor 29 could be forced simply by short-circuiting it via this further set of contacts, which is not shown.

FIG. 3 shows a circuit arrangement derived from the basic principle of FIG. 1, which is used to selectively start the universal motor with different directions of rotation via a microprocessor control. Insofar as components are used in the circuit according to FIG. 3 which have already been explained in connection with FIGS. 1 and 2, the same reference symbol is used for these components. The structure of the circuit according to FIG. 3 looks as follows:

The engine 1 of FIG. 3 is a universal motor, comprising an armature 36 and a field winding 37.. In order to be able to change the direction of rotation of this motor 1 , there is a two-pole switch 39 in the connecting line between the phase lines L1, L2 and the armature 36 , which is to be actuated via a relay winding 41 . This switch 39 serves to change the polarity of the armature 36 with respect to the field winding 37 in a known manner.

The core of the circuit arrangement according to FIG. 3 is a microprocessor 42 which is connected with a connection 43 to the auxiliary or control voltage U.

The aforementioned relay winding 41 is also connected to this control voltage U with one connection, while its other connection is connected to an output 44 of the microprocessor. Another output 45 of the microprocessor supplies trigger pulses for the triac 5 , for which purpose the output 45 is connected to the gate 19 via the line 46 .

Because, as mentioned, the direction of rotation of the motor 1 can be arbitrarily determined by the user, two push buttons 13 a and 13 b with two contact sets 21 a and 21 b are provided in the circuit device according to FIG. 3. Both sets of contacts 21 a and 21 b are at one end at the control voltage U, while at the other end they are connected to an associated input 46 a and 46 b of the microprocessor 42 .

From each of the two sets of contacts 21 a and 21 b, a diode 47 and 48 leads to the resistor 23 , via which the storage capacitor 24 can be charged. The two diodes 47 and 48 are connected to the resistor 23 at the corresponding polarity of the control voltage U with the cathode.

In order to de-energize the relay winding 26 , which controls the contact set 7 as in the previous examples, the transistor 49 is provided, which is in series with the relay winding 26 and together with the relay winding 26 results in a series circuit which is parallel to that Storage capacitor 24 is connected. Overvoltages gene when switching off the transistor 49 are suppressed by an RC element consisting of the capacitor 51 and the opposing 52 . For this purpose, this RC element lies parallel to the relay winding 26 . However, the additional control by transistor 49 is not absolutely necessary.

The transistor 49 is finally controlled via an output 53 of the microprocessor 42 .

The operation of the circuit according to FIG. 3 looks essentially the same as has already been explained in connection with the previous exemplary embodiments:

For the stationary motor 1 , both push buttons 13 a and 13 b are released, so that the microprocessor 42 receives no voltage at its inputs 46 b and 46 a. He then also generates no ignition pulses for the triac 5 at its output 45 . At the same time, the relay winding 26 , because de-energized, does not attract the contact set 7 , which is consequently open (instead of a single-pole shutdown by only one contact set 7 , an all-pole shutdown can also be used, as is readily apparent).

In order to start the motor 1 with one or the other direction of rotation, the user operates either the hand switch 13 a or the hand switch 13 b, whereby the control voltage U is applied either to the input 46 a or to the input 46 b. Corresponding to the live input 46 a or 46 b, the microprocessor 42 switches the changeover switch 39 via the relay winding 41 into the position shown or the position not shown. Simultaneously with the generation of this direction of rotation signal at the inputs 46 a and 46 b, the control voltage U passes through one of the two diodes 47 or 48 to the opponent 23 and subsequently also to the capacitor 24 , which is then charged to the control voltage U. .

Feeding the control signal into one of the two inputs 46 a and 46 b has caused the microprocessor 42 to emit a signal at its output 53 which switches the transistor 49 into the conductive state. In combination with the charging voltage of the capacitor 24 which is increased to the corresponding voltage, the relay winding 26 receives current and when it reaches a corresponding voltage threshold it transfers the contact set 7 from the rest position into the working position in which the two contacts 8 and 9 are closed. Thus, the current connection from L1 via the changeover switch 39 , the motor 1 and the contact set 7 to the phase line L2 is prepared and the microprocessor 42 can trigger the triac 5 by emitting trigger pulses at its output 45 .

In the microprocessor solution, there is also the possibility of controlling the phase angle for the triac 5 with the aid of the microprocessor 42 in order to set the speed of the motor 1 .

If the user wants to stop the motor 1 again, he lets go of the previously operated manual button 13 a or 13 b, whereby the control voltage at the inputs 46 a and 46 b immediately disappears. With the disappearance of the control voltage at these inputs 46 a and 46 b, the microprocessor 42 switches off the trigger pulses for the triac 5 , whereby the power connection via the motor is de-energized. After a corresponding safety time, which is preferably at least as long as a mains oscillation plus a certain safety break, the microprocessor 42 also switches off the output 53 , as a result of which the transistor 49 changes into the blocking state. The current through the relay winding 26 is switched off and the resulting overvoltage pulse in the RC combination of the capacitor 51 and the resistor 52 is limited to values that are harmless to the transistor 49 . Switching off the transistor 49 has the result that the relay winding 26 no longer actuates the contact set 7 , which can return to its open position.

As in the previous examples, the capacitor 24 has the task of storing sufficient energy so that the relay with the relay winding 26 remains energized long enough to give the triac 5 the ability to safely interrupt the flow of current to the motor 1 . Otherwise, an undesired opening spark could arise on the contact set 7 , which, however, should be prevented with the help of the triac 5 .

The timers 11 and 12 are implemented in the microprocessor 42 as program parts.

The circuit arrangement described allows the flow of electricity to a powerful consumer Switch using an electronic semiconductor, wuh rend on the other hand with the help of a miniaturized Kon clock rate an increased security against failure of the electronic switch or against incorrect control of the same ben is reached.

Claims (13)

1. Circuit arrangement for controlling a consumer ( 1 ) in an electrically operated hoist or electrically operated travel drive for a hoist,
with at least one electronic switch ( 5 ) which is connected in series with the consumer ( 1 ) and via which, if it is controlled in a conductive manner, the current flows from a voltage source (L1, L2) to the consumer ( 1 ),
with at least one to the series circuit of the consumer ( 1 ) and the electronic switch ( 5 ) in series lying mechanical contact set ( 7 ), which has two states, wherein in one state a current flow through the contact set ( 7 ) is possible and in the other the current flow is interrupted,
with an actuating device ( 10 ), which is controlled by at least one button ( 13 ), which acts over a time link ( 11 ) on the mechanical contact set ( 7 ) and over a second timer ( 12 ) on the electronic switch ( 5 ) , so that when the button ( 13 ) is pressed, the switching on of the electronic switch ( 5 ) compared to the switching on of the mechanical contact set ( 7 ) and the switching off of the mechanical contact set ( 7 ) compared to the switching off of the electronic switch ( 5 ) is delayed, so that the mechanical contact set ( 7 ) only switches from one state to the other state when the electronic switch ( 5 ) is in its locked state. 2. Circuit arrangement according to claim 1, characterized in that the consumer is an electric motor ( 1 ). 3. Circuit arrangement according to claim 2, characterized in that the electric motor ( 1 ) is a universal motor. 4. Circuit arrangement according to claim 2, characterized in that the electric motor ( 1 ) is an AC motor. 5. Circuit arrangement according to claim 2, characterized in that the electric motor ( 1 ) is a multi-phase alternating current motor and that a contact set ( 7 ) and an electronic switch ( 5 ) is provided for each phase. 6. Circuit arrangement according to one of claims 1 to 5, characterized in that the electric motor ( 1 ) is a driving motor. 7. Circuit arrangement according to one of claims 1 to 5, characterized in that the electric motor ( 1 ) is a lifting factory motor. 8. Circuit arrangement according to claim 1, characterized indicates that the consumer is a brake release magnet. 9. Circuit arrangement according to claim 1, characterized in that the electronic switch ( 5 ) has a triac or at least one thyristor. 10. Circuit arrangement according to claim 1, characterized in that the electronic switch ( 5 ) is provided for phase control of the consumer ( 1 ). 11. Circuit arrangement according to claim 1, characterized in that the contact set ( 7 ) is a miniaturized contact set, which is undersized so that it can only carry the current flowing during operation of the consumer ( 1 ), but is not able, to switch the current through the consumer ( 1 ) on and / or off without it being damaged itself. 12. Circuit arrangement according to claim 1, characterized in that the actuating device ( 10 ) has at least one electromagnet ( 26 , 31 ) which forms a relay together with the contact set ( 7 ). 13. Circuit arrangement according to claim 1, characterized in that the timing elements ( 11 , 12 ) are at least partially realized in a microprocessor ( 42 ).