(PACs) for the control of medium size pr

Application notes
Ascon Spa
Using the latest state-of-the-art Programmable Automation Controllers
(PACs) for the control of medium size processes and machines.
The demanding of the applications
Medium size processes and machines need, more and more, control systems with the
same level of sophistication of large plants. This is now possible without facing excessive
costs and without using cumbersome oversized equipment. Medium size control systems
need to be more user friendly than the large systems but need the same power, flexibility,
sophistication, modularity, fieldbus networking and enterprise data integration capability. In
other words medium size control systems need compact devices able to incorporate
sophisticated functions such as the advanced PID algorithm of a process controller, the
floating point processor, the powerful sequencing functions of a PLC and the flexibility of a
PC based system. This device is now available on the market and has been termed a
Programmable Automation Controller or PAC. The PAC has the broader capabilities
needed built into its design. The demanding of the applications of this type was the starting
point of the R&D department of Ascon Spa when it was decided to develop the
“microPAC”, a small but powerful programmable automation controller sized to cover the
most common applications for several industries such as food and beverage, plastic and
rubber, chemicals and pharmaceutics and the most common machines such as boilers,
furnaces, kilns, chillers etc. Since it was founded in 1969, Ascon Spa has always been on
the leading edge of trends in the automation market. Based in the northwest side of Milan
(Italy) the company offers decades of accumulated expertise in the controls industry. The
“microPAC” is the last borne product and it fully benefits of such expertise, its slogan is
“all in one” automation solution.
microPAC basic unit
The “microPAC”
With only the basic unit of the “microPAC” it is possible to control a process with eight
analogical variables measured by any type of transducer or sensor directly connected as
inputs; up to four analogical outputs are available to command final control elements such
as control valves or power controllers; eight digital inputs and eight digital outputs are
available to manage interlocks, sequences and commands to the plant machinery such as
pumps and shut-off valves. Expansion units for up to 32 DI + 32 DO are available for
applications requiring more sequencing functions of discrete signals. The OpenPCS
programming environment allows applications to be created in the 5 programming
languages that comply with the IEC 61131-3 international standard. The Ascon’s libraries
offering a large selection of function blocks aid the programming of the CPU. The
processor is 32 bit with ARM architecture, Flash Memory is 4Mbyte (2Mbyte for
programming), and the RAM is 16Mb, 128 Kb retentive. Connectivity is assured by one RS
232/485 port with Master/Slave Modbus RTU protocol or ASCII, one RS 485 port with
Master/Slave Modbus RTU protocol and one Ethernet port with Modbus TCP/IP protocol.
Advantages include being able to independently meet complex requirements that PLCs
require extra components to do, reduce panel dimensions due to the compact size, lower
the cost of the hardware of control system and reduce the work for the development and
integration.
Applying the “microPAC” to a modern application
A typical example of application is the control of a medium size boiler. The boiler process
is one of the more critical ones to be controlled. This is due to the fact that each variable of
the process influences all the other ones. Also, often, industrial boilers are subject to
frequent and quick load changes. Boiler controls include typically outlet main header
steam pressure or water temperature control (master), combustion control with air/fuel
ratio and trim adjustment, three elements drum level control, combustion chamber draft
control, burner management system and its interlocks, load distribution control if more than
one boiler is connected to the same header. A quantity of variables and status conditions
must be measured, detected and controlled in a fast and reliable way. This can be better
accomplished with the Ascon’s “microPAC” where the I/Os take care of operations such
as measurement linearization, data scaling, engineering units conversion and alarm
handling and the power of the CPU is dedicated to the realization of the function blocks
taking care of functions such as the master control with linkage-less parallel positioning,
the PID algorithms, the cross-limiting for the combustion, the boiler efficiency and fuel gas
mass flow computations and the lead led sequencing.
A modern condensing boiler under test
Many other machines can benefit of the features of the “microPAC”, this includes
autoclaves, heat treatment furnaces, plastic extruders, climatic rooms, floating cells, glass
annealing lehrs and many others.
When the “microPAC” is the solution
When evaluating automation controllers to meet the requirements of these applications the
machine manufacturer should check if the selected device needs additional processors,
network interfaces and/or middleware to get features similar to a PLC or a PC. In the
affirmative case the characteristics of the “microPAC” should be kept in consideration to
see if they more closely match the application demands.
EVERYTHING UNDER CONTROL
ASCON SpA
Via Falzarego, 9/11
20021 Bollate (Milan) Italy
Tel. +39-02-333371
Fax+39-02-3504243
E-mail [email protected]
www.ascon.it
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