DE1954063A1 - Circuit arrangement for switching on and off, and for monitoring positively commutated converters - Google Patents

Description

Circuit arrangement for switching on and off and for monitoring of forcibly commutated converters Forced commutated converters, in particular Inverters are widely used to supply drive motors.

Since they can be blocked very quickly (free time approx.

10 ... 100 µs), they are well suited as actuators. Such converter circuits because the construction packs used are practically free of wear and tear and are maintenance-free, Work trouble-free for an extraordinarily long time. The so-called "Periphery" devices that do not belong directly to the converter, but with it work together, mostly not up. There is therefore the task of failure of such a device and the associated consequences, such as a power failure, the converter or

Protect inverter.

To ensure safe and trouble-free operation with forcibly commutated circuits, especially with inverters with a direct current intermediate circuit, a number of conditions must be met, compliance with them by Monitoring devices must be constantly recorded.

If these requirements are not met, protective functions to be triggered.

The decisive operating parameters and their significance for the converter with its control and regulation devices as well as those required in this context Protective measures are to be explained in more detail below.

1. Voltage monitoring.

a) Instantaneous value of the voltage of the commutation capacitor.

b) Instantaneous value of the intermediate circuit voltage.

Crucial for perfect commutation in a given Switching is the instantaneous amount of the commutation capacitor voltage and the instantaneous value of the stream. The capacitor voltage must therefore be monitored. Because of Cost savings in multi-pulse circuits can, depending on the circuit) also the DC link voltage can be used for monitoring.

2. Current monitoring.

a) Instantaneous value of the current.

b) Average value of the current.

The instantaneous value of the current to be commutated and the commutation voltage determine the commutation limits in a given circuit. The current mean value monitoring in connection with timers, the expiry of which begins when a certain average current value is exceeded, enables the initiation more effectively and the Load condition of appropriate protective measures to relieve the converter by acting on the selected control variables (e.g. resetting the setpoint current, voltage, speed, etc.) as well as by actuating actuators, which on the peripheral devices, i.e. on the devices that are not directly connected to the converter include performing technological interventions (e.g. resetting slides, Valves etc.

to relieve the work machines). This allows the plant to can be exploited to the limit of therulic resilience.

Control voltage monitoring.

The control and regulating device for the converter is made of one power supply unit provided for this purpose.

When connecting or disconnecting the supply voltage, the there are no defective pulses, e.g. undefined pulses Triggering ignition pulses or malfunctions that lead to faults in the converter could. Several individual measures are therefore required: Maintaining the DC voltage on the power supply units when the supply voltage is lost.

b) Electronic pulse lock.

c) Static (mechanical) pulse lock.

If the existing supply or control voltage falls below the pending value, is due to storage capacity ensured, that the control and regulating device is still working normally until the The converter is protected and the electronic or static pulse block effects from malfunctions within the control and regulation device to the converter prevented.

The electronic and static pulse period of the grid pulse output stage, which controls the grid sections of the converter, consists of a combination of one electronic switch and a relay with mechanical contact that is in the idle state prevents pulses from being formed in the grid pulse output stage; be so daf? the Grid sections of the converter are not ignited. When the minimum control voltage is reached After switching on, the static impulse block is first activated by pressing the mechanical contact (opening or closing, depending on the circuit) is canceled, then the electronic impulse lock is delayed. Will turn off or if the supply voltage fails, the control voltage falls below the minimum, First of all, the electronic impulse blocker, which works much faster and without bouncing, takes effect one that also suffers from undesirable transient transition states when the Control voltage can be influenced. Only then does the transient come into play Processes unresponsive mechanical contact to effect. Di c storage capacitors must be maintained by maintaining the control voltage until the switching process is complete the static pulse lock a safe working of the electronic Pulse lock and ensure the control and regulation device.

The release or intervention of the electronic pulse lock can be made dependent on additional conditions.

In addition to the monitoring of voltage, current and Control voltage values can also be used to monitor technology-related variables, such as.

the slide zero position of working machines, the zero position of Speed setpoint potentiometers and the like. Be provided.

In order to provide extensive protection for a forced commutated converter, in particular to enable an inverter feeding asynchronous motors Monitoring devices in connection with digital linking elements according to According to the "switching algebra" used. In switching algebra, the states become two or more binary signals ("L" or "O") according to the rules of Boolean Algebra derived a new binary signal, which can also only be "L" or "O" can. Switching algebra knows three basic connections that make up all others let build: the "NOT", the "AND" and the "OR" link.

The invention now relates to a circuit arrangement for input and output control as well as for monitoring a forced commutated 15 converter, in particular an inverter, which is characterized in that of the Electrical parameters to be monitored, such as voltage, current and technological Variables (pressure, temperature and the like) derived signals of an "AND", "OR" or "NOT" link having linkage are supplied via a further Logic in which signals of other variables (maximum current, controlled variables) are linked, supplies an ignition or extinguishing signal to the converter via the grid pulse output stage, and that the output signal of the link delayed an Ilpulssperre for the Grid pulse output stage controls so that after normal deletion by means of the logic of the pulse flow for the converter is blocked when the links an impermissible value is supplied. This is particularly important with inverters the monitoring of the switch-on processes, the intermediate circuit voltage and the control voltage, as well as the thermal limit load. In the arrangement according to the invention can both voltages can be switched on independently of each other at any time. If inadmissible values occur, the current limit is reduced ;, the converter locked without the fuses responding or faults occurring in the converter and / or technological processes are influenced, e.g. the speed of the supplied Drive motor reduced; or the work machine is relieved. When switching Missing pulses (undefined ignition pulses) can occur, their access to the grid of the inverter must be prevented. The aforementioned static is used for this Impulse block with the mechanical contact. The pulse lock that, As already stated, it is advisable to use an electronic and a static one (mechanical) lock is formed, prevents malfunctions due to transient processes in the switching logic when building up or collapsing the control voltage, so that no Faults in the converter can be caused. To the effectiveness of the pulse lock The control voltage is not endangered even if the supply voltage fails Maintained for a short time by additional storage capacities.

The idea on which the invention is based is intended to be based on the figure will be explained in more detail using an exemplary embodiment.

t'5t 1 is a measurement trigger that has the task of measuring the intermediate circuit voltage UGist to monitor. If the voltage is greater than the specified, adjustable minimum value UGmin, the measuring trigger 1 gives the release signal. (A measurement trigger form @ input signals Any curve shape when exceeding or falling below certain values in the output signals L or O um).

The measuring trigger @ monitors the control voltage in the same way Ust is for the control and control device. As soon as U @@ is bigger than that Minimum control voltage Ust min, an enable signal appears in the output of trigger 2.

The output signals of the measurement triggers 1 and 2 and possibly via Line 20 upcoming technologically related variables (e.g. @@@@ llwert potentiometers) @@@ l @ n fed to an "AND" element 3, which only has an output signal gives up, if all inputs have an enable signal. The output signal of the "AND" stage 3 then arrives at a time-delaying stage 4, which increases the input signal by one certain amount, e.g. if 100 ms, delayed. If the input signal disappears, so the output signal follows immediately. This signal serves as an input signal for stage 5, which also delays switching on. The stage output signal 5 causes the converter 23 to be blocked by means of a clear signal in the event of a fault, which is based on the logic 21, which the grid pulse output stage 22 follows.

This stage 22 raises the low-power signal level of the pre-stages to a value which is sufficient to ignite the grid sections of the converter 23. It also creates a potential separation between the low-voltage part of the controller and the high-voltage part of the converter? 3. In the event of a fault, all groups of an inverter brought into extinguishing position. Load current no longer flows. The output signal of time stage 4 continues to be a relatively low one Switch-off delay (about 1 ms) having timer stage c supplied. This stage 6 behaves like a drop-out delayed timing relay. The output of stage 6 can The grid pulse output stage 22 for the converter via a G'tterimpulssperre 7 block or unblock immediately. The measuring trigger 2 also switches a relay 8, its normally closed contact to the output de3 level 7, which with level 6 the combination of a electronic and static impulse lock is connected in parallel.

For recording the maximum permissible instantaneous value of the unsmoothed The measurement trigger 9 is used for the current iist. As soon as the adjustable maximum value Îmax is exceeded is, a signal appears in the asgang of the measurement trigger 9, which the logic 21 blocks. A cancellation signal is generated. Level 10 smooths the motor current, so that with level 11 a predetermined mean value can be detected a mean. Exceeds the current the adjustable maximum mean value mean max, then the integrator 12 begins to work. The integrator 12 serves as a timing element, the downstream measurement trigger 13 and 14 have different response levels and switch at different times. The measuring trigger 13, whose response time @it is set by the setpoint adjuster 24 (tsollw.1) can be caused, if the current values are too high via line 28, technological Interventions to relieve the converter, e.g.

Relief of the drive motor of a work machine through relief this machine, speed reduction by lowering the frequency and the like .. These interventions take place after a time of approx. 1 to 10 seconds, depending on the working condition @@ der System. Stage 14 switches the system via the line leading to the main switch 26 as soon as the thermal limit load is reached. The response time can be be several minutes long. The line going from the measuring trigger 14 to the "AND element 3" 27 carries an "L" signal in normal operation. As soon as a fault occurs, the the thermal limit load is exceeded, appears in the output of the measurement trigger 14 and on line 27 an "O" signal, so that also in the output of the "AND" element "O"- Signal occurs even when all other input lines of the "AND" gate carry an "L" signal. This additional measure ensures that it is deleted immediately so that the converter is not endangered.

10 pages of description, 7 claims and 1 sheet of drawings with a figure

Claims (7)

P a t e n t a n s p r ü c h e Circuit arrangement for switching on and off as well as for monitoring a forced commutated converter, in particular one Inverter, characterized in that of the electrical to be monitored Quantities such as voltage, current, as well as technological quantities (pressure, temperature and The like.) derived signals of an "AND", "OR" or "NOT" element having Link (3) are supplied via a further logic (21) in the signals other variables (maximum current, controlled variables) are linked, an ignition or extinguishing signal via the grid pulse output stage (22) to the converter (23), and that the output signal the link (3) delayed a pulse lock (7) for the grid pulse output stage (22) controls in such a way that after normal deletion by means of logic (21) the Pulse flow for the converter (23) is blocked if the links (3 or 21) an inadmissible value is assigned. 2. Circuit arrangement according to claim 1, characterized in that the link (3) is designed as an "AND" element that the input of the link (3) the intermediate circuit voltage, the control voltage, the mean value of the load current and, if necessary, signals derived from technological variables are fed in and that if a permissible value is exceeded or not reached, the @ to be monitored Sizes @@ output of the link (3) a signal occurs, which is another logic (21), in the output of which a clear signal is generated, and a pulse lock (7) for the grid pulse output stage (22) is supplied. 3. Circuit arrangement according to claim 1, characterized in that the grid impulse barrier from the combination of an electronic (7) and a static one (8) Block exists and that when the minimum control voltage is reached, the static Pulse lock (8) and then, with a time delay, the electronic pulse lock (7) is repealed. 4. Circuit arrangement according to claims 1 and 3, characterized in that that first the electrical @ pulse lock (7) responds, if when switching off or If the control supply voltage fails, the control voltage falls below the control voltage and that the control voltage circuit has storage capacities @ geord @ et @ind, even if the supply voltage fails, the control voltage for the supply of the control and rule a direction until the completion of the switching process of the static pulse lock (8) maintained. 5. Circuit arrangement according to claim 1, characterized in that a flow trigger (9) is used to monitor the instantaneous value of the load current, which causes a blocking of the logic (21) when responding, which in turn via the Grid pulse output stage (22) a deletion of the still ignited inverter groups caused. 6. Circuit arrangement according to claim 1, characterized in that the mean value smoothed in step (10); of the load current to the input of the Measurement trigger (11) is performed and that in the output circuit of the Neßtrigger (11) Integrator (12) is connected, which serves as a timing element and initially one earlier responsive measurement trigger (13) controls the technological interventions for relief of the converter, and another measuring trigger (14) that responds later controls, which switches off the system when the thermal limit load is reached. 7. chl processing arrangement according to claim 1, characterized in that to record the impermissible values of the DC link and the Control voltage by comparing an adjustable minimum target voltage and the actual voltage controlled measurement trigger (1 or 2) are used.