FI81925B - DIGITALT STYRD KONTAKTOR OCH FOERFARANDE FOER REGLERING AV KONTAKTOR. - Google Patents

Abstract

The invention concerns a contactor 2 for connecting and separating installations and loads and a method for regulation of a contactor. The contactor comprises a contactor body 8, a magnetic circuit 5 attached to the contactor body 8 and divided into at least two, a coil 3 connected to the magnetic circuit 5 by which the magnetic circuit 5 can be connected to an undivided circuit, coil connectors 4 arranged on the body 8 for supplying electrical current to the coil 3, load contacts 7 arranged on the body 8 for connection to the installations or loads, and a connection bridge 6 connected to the magnetic circuit 5 for connecting the load circuits 7 in the required way. According to the invention a digital control device is arranged inside the body 8 or in a separate box which is attached to the body 8 which obtains its working voltage from the coil connectors 4 and which comprises a measuring unit 30 for the control voltage for measuring the voltage between the coil connectors 4, a modulator unit 31 for modulating the current of the coil 3 based on the measurement values from the voltage measuring unit 30, an I/O unit which controls and monitors the function of the control device and communicates with the outside world and a time setting unit 32 for creating the time settings which are required by the measuring unit 30 for the control voltage, the modulator unit 31 and the I/O unit 33. <IMAGE>

Description

81 925

The present invention relates to a 'smart' contactor according to claim 1 for connecting and separating installations and loads.

The invention also relates to a method for adjusting a contactor.

In current contactors, the coil circuit is dimensioned to operate in a very narrow voltage range and coils of different sizes are required for DC and AC operation. More than a hundred different coil options are needed for one contactor model.

In addition, auxiliary contacts and an external series resistor are used in connection with the DC coils of larger contactors to reduce the current flowing through the coil during the holding phase and thus reduce the heating of the coil.

The magnetic surfaces of the unadjusted contactor are subjected to unnecessarily high stress, because during the drawing cycle the power of the coil is constant, so the final speed of the contact bridge before the closing of the magnetic circuit becomes quite high. Since the power required in the drawing phase is higher than the power required to keep the magnetic circuit closed, the coil current has to be oversized by a factor of up to ten times, depending on the contactor design. As a result of oversizing, both electricity consumption and coil heat increase.

·. : To eliminate the above-mentioned problems, there are separate control units based on analog technology, which • · control the current in the coil circuit. The voltage range of the existing control devices is considerably narrower than that of the device disclosed herein, because it has not been possible with analog technology to achieve a sufficiently large control range. In addition, they are expensive and large in size, and implementation technology limits the increase in their functionality.

The object of the present invention is to obviate the disadvantages of the existing technology and to provide a completely new type of contactor and a method for adjusting the contactor.

For the purposes of this document, a control circuit is a device packaged in a single monolithic or hybrid circuit or on a single circuit board and which performs the necessary control and adjustment operations on the contactor coil circuit.

The invention is based on a control unit based on pulse width modulation connected to the coil circuit of a contactor, implemented by digital technology, in connection with which the power of the coil is controlled by a power section built in connection with it. The modulation instruction is generated by measuring the control voltage using the obtained voltage information.

The coil voltage is rectified and lightly filtered before modulation, so the device can be used in both DC and AC controls with a DC-designed magnetic circuit that does not require separate short-circuit rings to equalize the magnetic field.

More specifically, the characteristic features of the contactor according to the invention are set out in the characterizing part of claim 1.

The characteristic features of the method according to the invention are set out in the characterizing part of claim 8.

The invention provides considerable technical and economic advantages over current technology.

3,81925

With the solution according to the invention, the contactor can always be precisely adjusted according to the conditions. The magnetic surfaces are not stressed by too much tensile force and the thermal loads are reduced due to the limitation of the holding power. Thanks to the digital implementation, it is easy to integrate additional functions into the control circuit, which are described below.

The invention will now be examined in more detail with the aid of application examples according to the accompanying drawings.

Figure 1 shows a partially sectioned side view of a contactor according to the invention.

Figure 2 shows graphically the power required by the contactor coil as a function of time at different stages of contactor closing.

Figure 3 shows as a block diagram one alternative according to the invention to the operating level of the control circuit.

Figure 4 shows a block diagram of one voltage measuring unit according to the invention.

Figure 5 is a block diagram of one pulse width modulator unit and power section according to the invention.

• - Figure 6 shows graphically the fit of the traction force of the contactor coil to the contact and counter spring loads as a function of the force and the opening interval of the magnetic circuit.

The digital regulation and control circuit 1 is connected according to FIG. between the coil circuit 3 of the contactor 2 and the control network 4. The main function of the control circuit is to adjust the current flowing through the coil 3 of the contactor 2 at different stages of the contactor closing (Fig. 2) so that the coil 3 does not heat up unnecessarily, but the magnetic circuit 5 remains stuck even in difficult environmental conditions, e.g. strong vibration.

4,81925

When the magnetic circuit 5 closes, the bridge 6 closes and the contactor 2 short-circuits the poles 7. The position of the bridge 6 is monitored by a sensor 9. The voltage of the control network 4 may vary freely between 24-120V or 120-450V and may be direct current or alternating current. The control circuit 1 obtains the information it needs for current control from the voltage of the control network 4 and the contactor information wired to the control circuit 1. In order to diversify the possibilities of use, the circuit has a special (not shown) I / O unit, through which the control circuit communicates with the outside world. The I / O unit will be described in more detail later.

In the design of the control circuit 1, special attention has been paid to the operating conditions of the contactors. It has to operate well in varying temperatures, strong vibrations and strong magnetic fields. To eliminate magnetic and electrical interference, the control circuit is equipped with a number of monitoring and resetting structures to minimize possible fault-to-operation time. Due to the susceptibility to interference, the control circuit does not use a microcontroller, but only scatter logic, which is divided into independent function blocks, which are reset at regular intervals by a reset pulse from the timing unit. With the block structure and forced reset, the recovery time of the control circuit is considerably shorter than with the microcontroller implementation, and in the best case, the malfunction is limited to only one block, in which case it does not necessarily affect the operation of the whole.

According to Figure 2, three different current levels are required in the start-up situation:

At the beginning of the drawing phase a, so much power is applied to the coil 3 that the contacts close, but the magnetic circuit does not yet close completely. At this point, power is only needed. to overcome the return spring load.

5,81925

In the second part b of the drawing phase, the energy of the coil 3 is increased so large that the magnetic circuit 5 closes under all possible environmental conditions.

The third cycle, hold phase c, lasts until the next control cut-off. In the holding phase, the current of the coil 3 is limited so that the magnetic circuit remains closed, but the coil does not heat up.

Minimizing the difference between tensile and counterforce forces as shown in Figure 2 during the start-up phase reduces the acceleration of the contact bridge and thus reduces the mechanical stress caused by the start-up. The current technique attempts to fit the traction curve to the counterforce curve (Figure 6) with different lever structures. With the solution according to the invention, the adjustment of the traction curve is done electronically, in which case no mechanical damping structures are required.

The operation of the control circuit 1 has taken into account some fault situations, the resolution of which with an ordinary contactor requires the use of additional components. One of the most used is quick reconnection after a short power failure. The control circuit l remembers its state for about one second after the coil voltage is interrupted. If contactor 2 had pulled the coil voltage off, ·, ·. circuit 1 starts the start sequence if the voltage 1! the volume is restored within the memory time. After a long break, the control circuit locks in the open state and all control signals must be switched off briefly before the next closed control. The quick reconnection can be switched off, in which case even a momentary disconnection of the coil voltage causes the control circuit to be reset, and the contactor does not pull until the next close control command. Implementing a quick reconnection. * does not require external RC circuits, as in current systems. .. · systems.

.. · To prevent welding of the contacts, control circuit 1 has: \: a control command delay built in, which prevents the next 6 81925 closed control for so long that the contact bridge reaches the upper position after the previous open control. The delay is different for different sized contactors, but is typically less than 200 ms. The next control command is accepted, but the start sequence does not start until the delay time has elapsed. This feature also applies to quick reconnection. Currently, the delay is implemented by auxiliary contactors.

According to the standard for contactors, in the event of an undervoltage, the contactor must open 20-75% of the rated voltage with AC control and 10-75% of the rated voltage with direct current. Undervoltage monitoring is built into the voltage measuring unit 30, which gives the modulator unit a run signal if the coil voltage is within the allowable limits. The undervoltage limit is set to the range required by the standard based on the coil voltage measured during the start-up phase.

In the event of an overvoltage, the control is switched off when the voltage rises 15% above the upper limit of the voltage range of the control circuit (138 V in the voltage range 24 to 120 V and 517 V in the voltage range 120 to 450 V). For overvoltage monitoring, two separate systems have been built into the voltage measuring unit, one of which detects rapid voltage changes and the other measures the change in the average voltage over a longer period of time. Both undervoltage and overvoltage disconnection reset the control circuit, and the return of voltages to the allowable range does not cause the contactor to be pulled without a new control command.

The ASIC circuit containing the intelligence of the control system is divided into four functional blocks according to Fig. 3. All information transfer between blocks is asynchronous to eliminate • interference. The interfaces and signals to be given outside the blocks are defined in more detail later.

The functional blocks of the control circuit are: 7 81925 - voltage measuring unit 30 - modulator 31 - timing unit 32 - I / O unit 33

As shown in Figure 4, the measurement of the operating voltage is performed by an A / D converter 40 based on Sigma-Delta modulation connected downstream of the voltage divider circuit 46, followed by an averaging digital low pass filter 41. An alternative to the averaging filter is an integrating filter that requires more efficient significantly more silicon area and the mean is a sufficiently accurate approximation considering the environmental conditions. With sufficient oversampling, the S / D modulator of the A / D converter 40 (not shown) filters high and medium frequency interference from the signal to be measured, and the measurement result is a 7-bit binary number that the digital low-pass filter 41. . then reports the average of the measured voltages. Voltage; the information is provided to the coding logic at appropriate intervals to set a new modulation instruction. Overvoltage and undervoltage monitoring takes place in the detector 42 after filtering, so that any interference peaks in the supply network do not cause an overvoltage cut-off. Due to the slowness of A / D conversion and filtering, the system has a separate analog overvoltage monitoring implemented by voltage reference 47 and comparator 43. To eliminate interference spikes, the output of the comparator is connected to a delay line 44 to prevent overvoltage tripping caused by fast transients (e.g. 1-2). The delay line only sets the overvoltage signal to the detector unit when the output of the comparator has been mid / ·: uninterrupted for the time determined by the delay (approx. 1-2 ms).

The detector unit cuts off the run signal when it receives an overvoltage signal 45 from the delay line, despite the fact that the average β 81925 average measurement would indicate that the voltage is within the allowable range. The overvoltage limit is set to the maximum peak voltage of the control circuit Ueffmax * 1.42 so that the cut-out does not occur within an acceptable voltage range.

When the control circuit is connected to the coil voltage, the voltage measuring unit first measures the voltage of the coil circuit via the measuring input 37 for about 20 ms to calculate a proper voltage average, after which it sets the undervoltage limit and gives the modulator 31 a Run signal. If the coil voltage (contactor control circuit voltage) is lower than the fixed lower limit or higher than the overvoltage breaker, no Run signal is given.

According to Figure 5, the modulator unit includes two main parts: a non-feedback digital pulse width modulator (NFBDPWM) 50 and a ROM 51 in which modulation instructions for different contactor types and voltages are stored, and memory address coding logic. PROM, EPROM, EEPROM, Flash or other structure utilizing memory technology can also be used as an external or built-in block.

The pulse width modulator unit 31 is independent internally: a synchronized unit whose only control information is the voltage information from the voltage measuring unit 30 and the Run signal on the basis of which the modulator unit sets its operating state. The pulse width modulator 50 modulates the signal to the power switch control unit 52 into the memory 51 based on the pre-calculated pulse ratio information. This structure eliminates the instability typical of analog pulse width modulators and the control errors caused by feedback. The modulator 50 resets it itself after each pulse and reads a new modulation instruction from its latch circuit. The latch circuit has a one-sided design of 9,81925, which allows it to be set and read asynchronously. The modulator unit 31 is able to control the pulse ratio with an accuracy of 0.4% in the range of 0.4..98.4%. There is a small break between each pulse, during which a new modulation instruction is read and the modulator is reset, so full 100% modulation cannot be used. Compared to similar analog solutions, NFBDPWM offers a remarkably wide pulse ratio range.

The memory 51 is programmed with test-calculated hold power pulse ratios, which are retrieved from the voltage and contactor information at the address to be coded and placed in the modulator latch. Coils of different voltage ranges are dimensioned so that they do not require separate memory blocks. The powers of the start-up phase are obtained by adding to the value contained in the memory a constant value selected on the basis of the contactor type. The memory can be organized, e.g., into eight rows, which are assigned by 3-bit contactor information 56, and 128 into columns, which are assigned by 7-bit voltage information 57. Each memory element contains an 8-bit modulation program. . j een.

The actuator of the control system is a switch regulator implemented with a power fetet, the inductance of which is a contact coil. The fett is controlled by the non-feedback pulse width modulator (NFBDPWM) described above based on the voltage information from the voltage measuring unit 30 according to the selected contactor-specific modulation instruction. The frequency of the switch is more than 20 kHz, so it does not cause audio frequency oscillations in the magnetic circuit 5 of the contactor 3.

The fet control circuit 52 is not included in the modulator unit 31 because it cannot be integrated with the control logic on the same silicon piece due to different operating voltage ranges. An SA circuit 54 is connected in parallel with the fet "," the function of which is to filter the switching spikes formed over the fet 53 and reduce the switching losses of the fet. 101. The protection diode 55 connected in parallel with the coil 3 attenuates the coil's own voltage spikes. the current carrying capacity of the CMOS circuits is rather low and the 5 V supply voltage of the control logic is not sufficient to control the fet 53, which normally has a normal gate voltage of more than 10 V. To achieve a proper control level and protect the control logic, a controller / separator block is built between the control circuit.

Figure 3 shows a timing unit 32, from which all the timings required by the control circuit 1 are obtained. The clock generator of the timing unit 32 is a free-oscillating 5 MHz ring oscillator, the frequency of which is used as the fundamental frequency of the modulator. Other timing signals are obtained by dividing the fundamental frequency and forming different sequences therefrom. Different frequencies are needed e.g. for the voltage measuring unit 30 and the I / O unit 33. The timing unit 32 also generates the reset signals required in the start-up phase for the different blocks in the correct order. The unit also includes a passive timer for delaying control commands and a short start delay for starting the clock generator.

The I / O unit 33 controls the operation of the control unit 31 (pulse width modulator with peripheral blocks Fig. 5) and acts as an outward communication interface for the entire system. Thanks to the digital implementation of the i / O unit, it is possible to integrate functions that can only be implemented with stand-alone devices with current technology.

All the contactor control is centralized in the I / O unit 33; functions related to communication, control and internal diagnostics. The unit contains e.g. three different types of logic control interfaces, interface for serial bus control, adjustable timer for setting traction and emission deceleration, start logic that gives other units 83225 commands in start order and error message logic that collects all reported faults, etc.) and indicate them with a signal LED and an optically separated open collector output. All I / O unit Communication to other circuit units takes place via a separate control bus 36. The number of messages to be transmitted has been minimized by designing the units as independent as possible, including internal diagnostics. The only external connections that do not pass through the I / O unit are the measuring input of the voltage measuring unit and the outputs of the pulse width modulator (2 pcs.). The connections of the I / O unit are described below by reference numerals 33a to 33h.

An opto-isolated (4 kV isolation) connection 33a is intended for logic level (5..24 V DC / AC) control. The contactor pulls the external signal at the rising edge and releases at the falling edge. If the control signal is high when the coil circuit is turned on, the contactor will not pull until the control signal goes down. Automatic quick reconnection after a short power failure remembers the status of the contactor before the power failure and operates when the control signal is high.

.; / The closing contact terminal 33b has the same function as the PLC terminal 3 3a, but operates with closing contacts instead of voltage control. This connection can be controlled by a relay, switch or open collector output logic. The shut-off contact control is parallel to the other controls so if one of the controls is on, the contactor pulls.

The pulse control interface 33c is intended for motor controls and other applications where a push button is used as the start switch. The contactor pulls with a short pulse, after which *: **: it retains its state for the next control voltage interruption or ·· * 'reset pulse, which is given by switching off the PTC control at the moment.

12 81 925 The I / O unit has two resistance measuring circuits 33d to which PTC resistors used for temperature monitoring of motor windings and bearings can be connected. When the external resistance increases above the set limit, the control circuit is reset and does not restart until the resistance has fallen below the limit value and all controls are momentarily switched off. The thermal cut-out is indicated via a 1/0 unit with a specific signal. the error message remains in the memory until the next coil voltage failure.

The I / O unit has a separate direct connection for the electronic thermal relay 33e. The connection works on the principle of a closing contact and prevents the contactor from being pulled as long as the contacts of the thermal relay are open. By means of the connection, the information of the thermal relay can be obtained directly to the contactor and the tripping of the thermal relay can be notified to the control automation via the error notification interface of the contactor. The thermal relay connection can be switched off.

The control circuit I / O unit includes an interface 33f for optical read forks that monitor the position and position of the contact bridge. Alternatively, e.g. magnetic sensors or microswitches can be used as sensors. Position monitoring ensures that the contacts close properly and that any welding of the contacts is detected during the release phase.

Leaving the normal state with the bridge up, the circuit executes a start sequence. If the contact bridge is not in the down position at the end of the sequence, the circuit will cut off the control *. its, wait for the bridge to return to the up position and repeat the same two more times. If the third attempt fails, the • I / O unit sets a fault flag and issues an alarm signal. The fault flag prevents the control circuit from operating before the control voltage is switched off. If the bridge is not properly up when starting, the fault flag is set immediately and the start sequence is not started.

i3 81 925 A timer is built inside the I / O unit to delay traction after close control. The traction deceleration time can be set to 0.1..18 s or 1..180 s (± 20%). The emission deceleration has its own separately adjustable timer with a time range of 0.1..18 s. The emission deceleration only works with external controls.

Ltd.

The control circuit 1 includes an operation by which the windings of motors in humid conditions can be heated to prevent water condensation, the control circuit continues to modulate after open control, but the output of the modulator is controlled to a separate output terminal to which a separate power fet with control circuits is connected. The input heating power is calculated in advance, coded according to the contactor type and stored in the modulator's memory.

Internal diagnostics monitors the operation of all internal blocks in the control circuit and seeks to correct individual malfunctions. The diagnostics also monitors the condition of the power components and the control circuit si- in case of failure of the power switch. . contains an electronic fuse which, in the event of a fault, breaks the coil circuit.

»* • * ·

Claims (12)

A contactor (2) for connecting and separating installations and loads, the contactor (2) comprising - a contactor body (8), - a at least two-part magnetic circuit (5) attached to the contactor body (8), - a coil (3) connected to the magnetic circuit (5) , by means of which the magnetic circuit (5) can be closed integrally, - coil terminals (4) arranged in the body (8), from which electric current can be supplied to the coil (3), - load contacts (7) arranged in the body (8) to which plants or loads can be connected, and - the coupling bridge (6) connected to the magnetic circuit (5), the load contacts (7) being connectable in a desired manner, characterized in that - a digital coil control device (1) is arranged inside the body (8) or in a separate housing to be attached to the body (8), which derives its operating voltage from the coil terminals (4) and which comprises - a control voltage measuring unit (30) with which the voltage between the coil terminals (4) can be measured, ·. - a modulator unit (31) with which the current of the coil (3) can be modulated on the basis of the values measured by the voltage measuring unit (30), - an I / O unit which controls and monitors the operation of the control device and communicates with the external environment, and a timing unit (32) for generating the timings required by the control voltage measuring unit (30), the modulator unit (31) and the I / O unit (33). A contactor (2) according to claim 1, characterized in that the voltage measuring unit (30) comprises a voltage divider (46), an A / D converter (40) and a low-pass filter (41) in the signal path. Contactor (2) according to Claim 1 or 2, characterized in that the voltage measuring unit (30) comprises a voltage distribution circuit (46) on the signal path. . an A / D converter (40) based on Sigma-Delta modulation connected thereafter and a digital low-pass filter (41) subsequently connected on the signal path. Contactor (2) according to claim 1, 2 or 3, characterized in that the modulator unit (31) comprises a non-feedback digital pulse width modulator (50) and a memory (51) in which a modulation instruction for different contactor types and different voltages is stored . Contactor (2) according to one of the preceding claims, characterized in that the I / O unit (33) comprises connections for logic-level control (33a), for closing contact control (33b), for pulse control (33c), for resistance measurement connections. (33d) for measuring the temperature, for the electronic thermal relay of the connection (33e), for monitoring the position of the contact bridge (6) of the connection ie 81925, a memory output (33g) of a memory register storing information on how many times the contactor has pulled, indicating -Tactor (2) and to the serial bus protocol unit outside the interface (33h). Contactor (2) according to one of the preceding claims, characterized in that the modulator unit (31) has a separate output to which a heating current can be applied to the winding of the loaded motor to prevent the formation of condensation water when the motor contactor is open. mode. Contactor (2) according to one of the preceding claims, characterized in that the position monitoring logic of the contact bridge (6) is integrated in the control device (1) and obtains its information from sensors (9) arranged in the contactor body (8). A method for adjusting a contactor (2) comprising a contactor body (8), a magnetic circuit (5) at least two parts attached to the contactor body (8), a coil (3) connected to the magnetic circuit (5) for connecting a magnetic circuit to the body (8) coil connectors (4), load contacts (7) arranged in the body (8) for connecting plants and loads, and a connecting bridge (6) connected to the magnetic circuit (5) for connecting the load contacts (7), in which method - the coil voltage is measured and; - the current supplied to the coil (3) is controlled by the current supplied by the modulating rod, characterized in that the i7 81 925 - voltage is measured by an analog-to-digital converter and filter and detector units (Fig. 4), and - the current of the coil (3) is 50), which in turn is controlled by the data stored in the memory (51) so that each voltage value and contactor type corresponds to a predetermined pulse width information. A method according to claim 8, characterized in that a digital control system based on IC technology is connected to the coil, which performs a control function according to claim 8 and which further - filters out interference from the measurement signal as a digital filter, - monitors its own operation by means of internal diagnostics mm. by calculating the contactor operation times and! by monitoring the condition of the power section, and ··; * - includes an I / O unit that centralizes all external communication and controls the operation of the measuring and control units. Method according to Claim 8 or 9, characterized in that the operation of the control device is controlled and monitored by an I / O unit (33) integrated in the device, which processes the external control signals, handles errors centrally; create internal start-up delays and synchronize. : operation of other control unit units on the control bus • * | (36) through. Method according to one of the preceding claims, characterized in that the control circuit (1) monitors the position of the contact bridge (6) by means of sensors. 18 81 925 Method according to one of the preceding method claims, characterized in that the contactors supply a small heating current from a separate power control output to the motor windings when the motor is not running to prevent the formation of condensation in electric motors operating in humid conditions. II i9 81 925