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Presentation About Company

Address:
JSC “Pluton”
5 Novostroyek st.
Zaporozhye
69076 Ukraine

Tel:
+38 061 220 4811
+38 061 220 4813

Fax:
+38 061 220 4812


APCS and OSC “Zaporozhstal” rolling table electric drive frequency converters

(Joint work of German company “transresch Antriebssysteme Berlin GmbH” and Zaporozhye JSC “Pluton”)


Authors – Ignatenko V.N., Kupetz I., Mischenko A.V., Ovsyaniker D.E., Tzimbal P.P.
Telephones: (061) 220-48-11, 220-48-40, 220-48-27. E-mail: deo@pluton.zp.ua

Published:
journal Ukraine Metall and Moulding. - 2003. - ¹9-10. - P.29-34
journal Industrial ACS and controllers. – 2004. - ¹1. – P.10-15

The article is devoted to creation of DC automatic electric drive and hot rolling light sheet continuous rolling mill collecting roller table ACS at OSC “Zaporozhstal”.
Rolling table electric drive frequency converters and automatic rolling strip transportation process control system is described.

Introduction

In the course of the common upgrade of ÍÒËÑ 1680 – hot rolling light sheet continuous rolling mill, one of the main OSC “Zaporozhstal” rolling mills, there was brought up a question on collecting roller table electric drives upgrade and automatic rolling strip transportation process control system from the last finishing mill to coiling machines, folding machines or flying shears creation. 

Structurally rolling table consists of 6 groups, in each of which from 28 to 36 rollers devided into odd and even subgroups. Further, after mechanical equipment replacement it is planned to install from 48 to 50 rollers in each group.  

According to control six rolling table groups are combined into two sections: the first is from the first to the second group, the second - from the third to the sixth group. 

Each roller is equipped with drive induction motor with short-circuited rotor, power 2,5 kW. The rollers from the first to the fifth group are connected to motors via reducer with reduction ratio 1,4; rollers of the sixth group – directly. Motors of several types are different according to their features, with rated value spread up to 10 %, except rated rotational speed, which is 635 revolutions per minute at synchronous speed 750 revolutions per minute. 

Previously rolling table motor feeding was done via individual automatic switches from rotating converters (two for each group), which changed motors rotation frequency and correspondingly strip transportation speed by changing output voltage and frequency.

Rotating converters operation mode and condition of automatic switches was controlled visually by machine hall on-duty with the help of panel indicating instruments; rolling table operation was controlled by operator direct observation of the strip movement and rollers rotation. Strip transportation speed was set manually, separately for each section, actual transportation speed was not controlled.

Such a control as a rule led to folds appearance on the strip during transportation, especially during several automatic switches switching off in one rolling table group. Moreover, rotating converters endurance was over long time ago and generators often failed, therefore there came out downtime and big expenses on equipment repairs.

Necessity of rolling table electric drives upgrading using frequency converters (FC) and creation of automatic control system was evident.

 

Aim of upgrading

Aim of upgrading was to

  • make rolling table electric drives control process at most automatic;
  • exclude appearance of rolled metal defects because of transportations;
  • provide automatic and manual rolling table control modes, joint and separate control of rolling table groups and sections;
  • provide automatic and manual strip transportation speed setting mode, possibility to set individual speed for each group;
  • provide possibility to control rolling table drive and control three operators’ stations, possibility to control equipment operation modes by machine hall on-duties;
  • considerably improve electric drive operation dynamic, aiming to increase productivity and decrease downtime;
  • provide overall automatic operational control of all APCS units and electric drive with data visualization and deflections in operation archiving;
  • provide rolling table control system integration into rolling mill automatic control system;
  • decrease power consumption and feeding transformer peak current loads in dynamic operation modes;
  • exclude consumption of reactive power by rolling table drive.

Such a task workers of German company “transresch Antriebssysteme Berlin GmbH” and Zaporozhye JSC “Pluton” had to solve within a short period of time on operating mill.

Electric drive

For control of rolling table motors German company “transresch Antriebssysteme Berlin GmbH” manufactured and delivered frequency converters, which had all the features of the most up-to-date converter units:

  • cabinet execution, ready to be connected, with in-built power fuses, disconnector, input reactor, noise filter, output sinusoidal filter; 
  • with possibility to implement single-engine and multi-engine induction motor drives;
  • providing stable without breakdown motor and generator operation modes, braking with recuperation to feeding network
  • having sinusoidal input current with possibility to regulate power coefficient from minus 0,8 to + 0,8;
  • with control and information interchange with the help of serial interface Profibus DP; 
  • with high dynamic, moment reverse less then 2 ms beforehand, with complete provision of all drive features in 4 quadrants; 
  • with complete diagnostics of all systems, with storage of worst-case situations, emergency trace, with all the needed protections for converter and motor. 

 

Frequency converters are executed as two cabinets with one-side servicing. Power part and control system have modular design, what is very convenient during adjustment, servicing, repairs, troubleshooting. Network and mechanical converters are executed on IGBT-modules, each one is provided with its own ÌÏÑÓ having similar layout and design, and different software. IGBT-modules control circuits are executed of fiber-optic cable due to which high noise immunity and control reliability is reached.  

Three frequency converters are provided for each group of rolling table motors control: two in operation for odd and even subgroup and one stand-by. Stand-by converter is constantly connected to the system and can be put into operation by simple switching of power output circuits.

Rolling table automatic control system

Functions 

The main designation of the developed system was generation and distribution of speed task (correction) signals between frequency converters of each collecting rolling table group, control of rolling table sections during strip transportation in different modes and signaling about equipment condition.

According to the put task control system has to provide:

  • constant data exchange between CS PLC; 
  • rolling table and CS condition data collection, processing and analysis;
  • generation of controlling impacts;
  • transfer of controlling impacts (signals, commands) for execution;
  • supervision of controlling impacts execution;
  • technological signaling;
  • displaying of the needed parameters and coefficients;
  • operational input and changing of speed parameters;
  • operational changing of system setting parameters;
  • control of keeping to technology by CS operators with necessary interlockings and limitations;
  • protection from some actions of personnel, leading to rolling table and CS emergency condition;
  • protection from random changes and damage of information and programs, and also from unauthorized interference;
  • CS setting without technological process interrupting, protection from accidental or error changes;
  • control algorithms in different operation modes, including algorithms of «speedup», «stop», «speed jam», «slow down»;
  • diagnostics with indication of place, kind and reason for irregular functioning of rolling table and CS;
  • acknowledgment of warning and alarm messages;
  • system operation logging;
  • registration and storage of information concerning pre-emergency status of CS and FC in operation («emergency trace»);
  • protection from errors during input and processing of information, providing set quality of CS functions execution
  • complete execution of functions under necessary data for it (absence of separate data doesn’t influence execution of those functions, which realization doesn’t use that data);
  • intuitive graphic interface;
  • upkeep of universal time in all the system.

System structure and hardware

Drives control is provided by control system and frequency converters controller parts (CS PLC and FC). Rolling table groups drives control is parallel and independent, i.e. CS PLC simultaneously works out control signals and interacts with all FC ÐLÑ, which take part in operation. CS PLC is designed on the basis of B&R SYSTEM 2003 and 2005 controllers. CS PLC include two control cabinets (CC), one of them is stand-by, three control panels (CP) and six cabinets with controllers for collection of information concerning condition of remote inputs (PLC RIO). 

 

 

 

Each CC is complete with Programmable Logic Controller (PLC) and controller with display panel (DP PLC). Stand-by CC is in hot standby, automatically it switches over to the main CC operation mode and any moment can start operation instead of it without any additional settings. 

Three operator’s control panels (CP) are distributed along rolling mill. CP are located at control stations. Distance between control stations is from 100 to 200 m. Each of 3 CP is equipped with DP PLC, what allows to fulfill full-function control from any of control stations.

Six PLC RIO are located along rolling table, straight near the cabinets with rolling table group motors automatic switches. Distance between PLC RIO is from 100 to 200 m. One of the six PLC RIO is MASTER and five are SLAVE. All the 6 PLC RIO are connected between each other with the help of CAN network.
Controlling PLC, located in CC (one of which is «MASTER» of the network), with the help of industrial network Profibus DP are connected with FC PLC Ï×, which are «SLAVE» (total 18 (12+6) «SLAVE», but it can be increased to 32). Controlling CC PLC are connected with three DP PLC of control stations via CAN network. Remote inputs level PLC RIO MASTER is also connected to network CAN. Moreover, each controlling CC PLC ØÓ is connected via separate CAN with its DP PLC. So each controlling CC PLC enters network Profibus DP and two networks CAN. Connection of controlling PLC with system of rolling mill ACS level with the help of Modbus network is also provided.

All in all CS PLC includes 26 full-function PLC and 5 PLC for data collection from remote inputs. Such connection structure allows to increase reactivity of the system, i.e. to minimize time for input parameters sampling and control impact delivery. In spite of such a number of PLC and not an simple network structure, all the complex operates as single mechanism and reliably fulfills its tasks.

On control station and in control cabinet DP PLC are installed. It allowed to provide reliable system control and gave a number of service possibilities appropriate to the systems, which use PC-compatible industrial computers.

For example, not stopping technological process (ÒP), being present near any unit of the system, its possible to supervise TP, and also make diagnostics of equipment, network operation, change different coefficients (having corresponding access level), work with different archives.

Thanks to DP PLC at control station there is a possibility to display all the needed for technological process parameters for operating personnel. It is possible to make speed task input both with the help of switches «more/less», or with the help of keyboard buttons. In case of non-correct actions, pre-emergency and emergency situations not only corresponding signal lamp lights, but also immediately the reasons of technological alarm are explained in text form. All the progress of work is recorded and archived. 

Or, for example, when one of the motors failures (or shutdowns because of the other reason of automatic circuit breaker), that very moment signaling appears. Explanatory text appears on the display panel and with the help of corresponding window the number and location of the failed motor is directly defined.

Controllers of three control panels interact with CC controllers, at this the main CC receives information, processes it and forwards control and other response commands. Stand-by CC works for reception, displaying and storage of the incoming data; it doesn’t transfer control and response commands via network. In case of necessity the main and stand-by CC interchange functions: the main one becomes stand-by, the stand-by one becomes the main. Stand-by CC can be put out of operation without any complications for repairs, updating, checking, etc., whereupon again put into operation. 

Necessity to carry out rolling table control with the help of one of three operator’s stations is solved by installation at these stations (one for each station) three similar control panels having its controller, display, signaling and control facilities. One of three CP is in operation, two others are in standby state for displaying and storage of data. All adjustments and control is done from the operating panel, at this all adjustments are stored in CC and during transfer of control to another CP they remain. Features and limits of different adjustments, which are done from CP, are preset in CC. Complete information concerning the whole complex operation any moment can be transferred on any CP by operator’s request. Any violations in operation, attempt of wrong acts or personnel mistakes are immediately displayed and stored on three CP and two CC with time fixation.

CAN three CP, two CC and one PLC RIO «MASTER» are connected with interface network and located on the territory of 0,04 square km., total length of network is more then 800 m.

Programming tools

B&R Automation Studio 2.10 (AS) was used for development of software (SW). AS allows developing of intellectual systems for data collection and processing.

AS is an integrated development environment, which allows programming of PLC on any of six languages: Basic, C, Instruction list, Ladder Diagramm, Sequential function chart, Structed text. The package puts powerful means for programs writing and debugging (detection, localization and errors recovery) at disposal of a developer. AS allows loading and checking of programs piecemeal and allows changing of some programs without correction of others.

For control system development language “C” is used (everyone knows its power and laconism)..

For controlling PLC integration to network Profibus DP B&R Fieldbus Configurator is used..

System implementation was carried out on constantly operating structure – rolling table was given for adjustment 15 – 20 minutes 1 – 2 times a day.

That’s why special requirement was made to quality of the written code.

In some cases for especially complicated algorithms patterns with Borland C++Builder 5 package were developed. Debugging of especially complicated algorithms from the beginning was done on PC without usage of B&R equipment, then after on JSC “Pluton” test benches and combined test benches.

Software

SW provides fulfillment of all the functions given by control system and has means for organization of all required processes.

SW allows to fulfill all automated functions in all system functioning regulated modes in real time scale.

The following principles were observed while SW formation:  

  • functional completeness; 
  • reliability and validity (correspondence to the given operation algorithm, control and filtering of incoming data, absence of false actions); 
  • construction modularity and encapsulation (SW is divided into tasks, each task functions only with its data);
  • multitasking (simultaneous fulfillment of several programs);
  • hierarchy (different programs priorities);
  • adaptability and flexibility (possibility of fast configuration and possibility of fast control algorithms rearrangement); 
  • modifiability (possibilities in modification and extension, updating, development and growth); 
  • serviceability and maintainability. 

SW structure and specific features

All CS PLC (only its controller part) is possible to divide into structure with the following levels:

  • controlling PLC level: control of eighteen FC PLÑ according to commands received from CP PLC, blocking of unauthorized switching, data transfer to CP, the system includes two master controllers, any of them can work both as the main and stand-by controller;
  • CP level: the whole rolling table centralized control can be fulfilled from one of the three existing CP;
  • human-machine interface (HMI) level. It has two DP PLC. Each DP PLC is connected with one master PLC;
  • remote logons level.

CS includes 26 full-scale PLC. Not all PLC must be switched on for valid operation of the system. Not at the moment operating in TP equipment can easily be switched off, e.g. for preventive maintenance, and then after again switched on. The system will just record this fact, without stopping its operation.

Total amount of system signals was 696 (sampling resolution 100 ms). I.e. sampled inputs – 473, sampled outputs – 83, analog inputs – 3, analog outputs – 3, digital inputs – 79, digital outputs - 55.

Optimally distributed functions between CS PLC at design stage, we were able to program all application SW in 4 AS projects. E.g. in spite of some differences in control functions and mapping windows, the same program is loaded in each of 3 PLC, DP level. When started, application program tunes for operation in definite CS place itself. 

Each project is divided into tasks. It increased modularity and made project maintenance easier.

Execution clock time is optimally selected for all the tasks. E.g. all control system algorithms operate with 100 ms time, and some visualization tasks with 500 ms time.  

Especially we want to point out a number of system help functions for the system equipment condition diagnostics. Servicing personnel has already fully estimated these possibilities. 
Except detailed diagnostics and detailed visualization SW considers human factor of operating personnel controlling the rolling table. E.g. it’s possible to change quickly rolling table speed both with the help of switches (traditionally), and key-board..

Due to a big number of settings, updating of which can be done by servicing personnel with the help of display panel, the system is easily reset, but the changes can be made only by the users knowing the password.

During tasks performance in PLC, application programs are controlled by operating system (ÎS).

ÎS of this PLC family is well adapted for usage in the sphere of control automation and is a deterministic multitasking system, which allows to work on strict real time basis.

It’s difficult to describe all the features of developed application programs within this article. We only want to mention the fact that during application programs development we used advantages of multitask system, i.e.:

  • deterministic multitasking;
  • different classes of tasks;
  • adjusted cycle time for each class of tasks;
  • optimal processor loading;
  • priority of tasks class;
  • flexible system upgrading;
  • error logging file;
  • checking of separate tasks.

The main results

Complex of FC and ACS of collecting roller table electric drive was put into operation starting Ocrober 1, 2002. 

Putting of FC and ACS into operation showed rightness of technical solutions made during system development. Already short experience of operation showed that ACS fulfills reliable control and has simple and convenient interface. Allows operating and servicing personnel to have complete information about rolling table condition, efficiently fulfill the needed switching and preventive maintenance of the system. 

Implementation of the described FC and ACS for collecting roller table electric drive allowed to decrease costs on electric drive servicing, increase reliability and safety of its operation, highly improve operability and flexibility of control.

Within 7 months of operation there were no downtimes, defects or other worst-case situations caused by FC and ACS RTD. Power consumption by rolling table drive decreased in 30% (approximately in 50000 kW h/month) and peak loads on feeding network four times decreased. Reactive component in consumed power of CRT ED is completely eliminated and reactive component of other consumers is partially compensated. CRT ED operation dynamics 2,5 times improved, what gives a possibility to considerably reduce or eliminate downtimes in worst-case situations.  

Conclusion

The results of fulfilled work showed that combining of efforts, experience and technical possibilities of German company “transresch Antriebssysteme Berlin GmbH” and Zaporozhye JSC “Pluton” allow to create automated electric drives and APCS of any complexity within a shortest period and on a high technical level.

List of abbreviations

  1. PLC – programmable logic controller
  2. HMI (IGI) – human-machine interface (intuitive graphic interface)
  3. FC – frequency converters
  4. PC – personal computer
  5. SW – software
  6. ÑS – control system
  7. PLC ÑS – controller as a part of control system
  8. CC – control cabinet
  9. PLC RIO – cabinet with controller for collection of remote inputs condition
  10. CP – control panel
  11. PLC DP - programmable logic controller with display panel
  12. TP – technological process
  13. FAS – factory automation system
  14. AS - B&R Automation Studio
  15. PC – personal computer
  16. ED – electric drive
  17. CRT – collecting rolling table
  18. RTD – rolling table drive
  19. ACS – automatic control system
  20. OS – operating system
  21. APCS – automatic process control system

Published:
journal Ukraine Metall and Moulding. - 2003. - ¹9-10. - P.29-34
journal Industrial ACS and controllers. – 2004. - ¹1. – P.10-15

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