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• Eight devices with an onboard Industrial Ethernet
interface in a space-saving design (4 MW)
• Crystal-clear display with six lines and three
selectable background colors
• Optional LOGO! CMR2020 and CMR2040
communication module
• Integrated web server for hassle-free programming
via remote control, IWLAN, or the Internet
Source: Siemens.com
High performance at a low price
Compared with its predecessor, LOGO! 0BA7, the innovated
LOGO! 8 logic module offers more functionality in its spacesaving
design of only 4 MW, at lower costs. Eight basic devices
with and without display and for different voltage
ranges have the same range of functions, which makes it very
easy to choose the required version. Externally, the crystalclear,
perfectly readable display, which now features six lines
with 16 characters each, catches the eye. The user now benefits
from twice as many characters per notification than
before, as well as three interchangeable background colors.
For greater visualization demands, another text display can
be connected to the integrated Industrial Ethernet interface.
The module is programmed via Industrial Ethernet, eliminating
the need for a special programming cable.
An outstanding feature of the new LOGO! is the integrated web server,
which can be configured with no special programming skills
and enables hassle-free and inexpensive remote control and
monitoring via IWLAN or the Internet.
The LOGO! Soft Comfort V8 software has been completely redesigned.
Communications via Industrial Ethernet are now
configured automatically in the network view. Linking of
function blocks and transfers between the various programs
are easily performed with drag and drop. Existing programs
from older versions can be carried over directly, making it significantly
simpler to migrate to LOGO! 8.
Siemens micro automation offers targeted and cost-effective solutions for minor
automation tasks. The new LOGO! 8 logic module provides tailored, expandable solutions
and enables communication via web server without HTML programming skills.
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Android App is available for Siemens Logo! Download here!
The new Simatic ET 200SP CPU Distributed Controller is a
modular distributed controller that is compact and flexible.
Thanks to its compact design, it requires little space in the
control cabinet. Because it has the same storage systems,
volumes, and features as the Simatic S7-1511 and S7-1513
CPUs, customer programs with varying design types can be
used. Three Industrial Ethernet ports with variable bus
adapters (RJ45, FC, SCRJ) have been integrated for flexible
bus connection. Option handling in the central configuration
also makes it possible to flexibly retrofit options without engineering
effort.
Source from: siemens.com
The distributed controller series is rounded off with the first
1510SP F CPU and 1512SP F CPU for modular and failsafe
automation. This makes it possible to implement standard
and failsafe applications using one controller in the ET 200SP.
Another benefit is its high investment protection, because
once a user program has been developed, TIA Portal makes
it possible to easily port the program to both Simatic S7-1200
and Simatic S7-1500 controllers.
The compact Simatic ET 200SP Open Controller is another
addition to the modular distributed controller series and is
particularly suited for series machine manufacturing. It is the
first controller of this type to combine the functions of a
PC-based Software Controller with visualization, Windows
applications, and centralized I/Os in a single compact device.
This means that users need to stock fewer spare parts, and
evaluation and maintenance efforts are also significantly reduced.
The Open Controller can be flexibly expanded with
standard ET 200SP modules and can be optimized for series
machines and machines with a distributed structure. Because
it has a compact design, it requires little space in the
control cabinet. It is also fully compatible with ET 200SP CPU
projects, so various performance requirements can be met
without additional effort.
siemens.com/distributed-controller
siemens.com/open-controller.
New Feature
• ET 200SP Open Controller: powerful all-in-one
device with small footprint on the DIN rail
• Very compact system with minimum space
requirements in the control cabinet
• Modular expansion of functions with all
ET 200SP modules
• Complete engineering in TIA Portal for increased
productivity with reduced engineering effort
“PLC” means “Programmable Logic Controller”, that’s clear. The word “Programmable” differentiates it from the conventional hard-wired relay logic. It can be easily programmed or changed as per the application’s requirement. The PLC also surpassed the hazard of changing the wiring.
The PLC as a unit consists of a processor to execute the control action on the field data provided by input and output modules. In a programming device, the PLC control logic is first developed and then transferred to the PLC.
So, what can a PLC actually do?
It can perform relay-switching tasks.
It can conduct counting, calculation and comparison of analog process values.
It offers flexibility to modify the control logic, whenever required, in the shortest time.
It responds to the changes in process parameters within fractions of seconds.
It improves the overall control system reliability.
It is cost effective for controlling complex systems.
It trouble-shoots more simply and more quickly
It can be worked with the help of the HMI (Human-Machine Interface) computer
There are many other things this little ‘mean’ thing can do, but one thing I’m sure – that PLCs are irreplaceable in many industry applications and control projects.
Here is an example of wired ABB’s AC500 programmable logic controllers.
Figure 1 shows the basic block diagram of a common PLC system.
Figure 2 – Block diagram of a PLC
As shown in the above figure, the heart of the “PLC” in the center, i.e., the Processor or CPU (Central Processing Unit).
The CPU regulates the PLC program, data storage, and data exchange with I//O modules.
Input and output modules are the media for data exchange between field devices and CPU. It tells CPU the exact status of field devices and also acts as a tool to control them.
A programming device is a computer loaded with programming software, which allows a user to create, transfer and make changes in the PLC software.
Memory provides the storage media for the PLC program as well as for different data.
Size of the PLC system
Usually they are classified on the basis of their size:
A small system is one with less than 500 analog and digital I/Os.
A medium system has I/Os ranging from 500 to 5,000.
A system with over 5,000 I/Os are considered large.
Components of the PLC system
CPU or processor: The main processor (Central Processing Unit or CPU) is a microprocessor-based system that executes the control program after reading the status of field inputs and then sends commands to field outputs.
I/O section: I/O modules act as “Real Data Interface” between field and CPU. The PLC knows the real status of field devices, and controls the field devices by means of the relevant I/O cards.
Programming device: A CPU card can be connected with a programming device through a communication link via a programming port on the CPU.
Operating station: An operating station is commonly used to provide an “Operating Window” to the process. It is usually a separate device (generally a PC), loaded with HMI (Human Machine Software).
PLC Configurations
There are two basic configurations that commercial manufacturers offer:
1. Fixed Configuration
Fixed PLC configuration
2. Modular Configuration
Modular type PLC ‘SLC 500’ (photo credit: ab.rockwellautomation.com)
A soft starter is, as you would expect, a device which ensures a soft starting of a motor.
A soft starter has different characteristics to the other starting methods. It has thyristors in the main circuit, and the motor voltage is regulated with a printed circuit board. The soft starter makes use of the fact that when the motor voltage is low during start, the starting current and starting torque is also low.
Motor soft starter
Advantages //
Soft starters are based on semiconductors. Via a power circuit and a control circuit, these semi-conductors reduce the initial motor voltage.
This results in lower motor torque.
During the starting process, the soft starter gradually increases the motor voltage, thereby allowing the motor to accelerate the load to rated speed without causing high torque or current peaks.
Soft-starting curve – Synchronous speed – Full load torque (left) and Full load current (right)
Soft starters can also be used to control how processes are stopped. Soft starters are less expensive than frequency converters.
Another feature of the soft starter is the soft stop function, which is very useful when stopping pumps where the problem is water hammering in the pipe system at direct stop as for star-delta starter and direct-on-line starter.
Drawbacks //
They do, however, share the same problem as frequency converters: they may inject harmonic currents into the system, and this can disrupt other processes.
Voltage ramp for soft starter. Run-up time is around 1 sec.
The starting method also supplies a reduced voltage to the motor during start-up.
The soft starter starts up the motor at reduced voltage, and the voltage is then ramped up to its full value. The voltage is reduced in the soft starter via phase angle. In connection with this starting method current pulses will not occur. Run-up time and locked-rotor current (starting current) can be set.
Electric Motor Soft Start 60HP (VIDEO)
Part 1
Part 2
Frequency converter starting
Frequency converters are designed for continuous feeding of motors, but they can also be used for start-up only.
The frequency converter is sometimes also called VSD (Variable Speed Drive), VFD (Variable Frequency Drive) or simply Drives, which is probably the most common name.
The drive consists primarily of two parts, one which converts AC (50 or 60 Hz) to DC and the second part which converts the DC back to AC, but now with a variable frequency of 0-250 Hz. As the speed of the motor depends on the frequency this makes it possible to control the speed of the motor by changing the output frequency from the drive and this is a big advantage if there is a need for speed regulation during a continuous run.
As stated above, in many applications a drive is still only used for starting and stopping the motor, despite the fact that there is no need for speed regulation during a normal run. Of course this will create a need for much more expensive starting equipment than necessary.
By controlling the frequency, the rated motor torque is available at a low speed and the starting current is low, between 0.5 and 1.0 times the rated motor current, maximum 1.5 x In.
Another available feature is softstop, which is very useful, for example when stopping pumps where the problem is water hammering in the pipe systems at direct stop. The softstop function is also useful when stopping conveyor belts from transporting fragile material that can be damaged when the belts stop too quickly.
It is very common to install a filter together with the drive in order to reduce the levels of emission and harmonics generated.
Frequency converter and its line diagram
Advantages //
The frequency converter makes it possible to use low starting current because the motor can produce rated torque at rated current from zero to full speed. Frequency converters are becoming cheaper all the time.
As a result, they are increasingly being used in applications where soft starters would previously have been used.
Frequency converter curve – Synchronous speed – Full load torque (left) and Full load current (right)
Drawbacks //
Even so, frequency converters are still more expensive than soft starters in most cases; and like soft starters, they also inject harmonic currents into the network.
Figure 1 illustrates a hardwired forward/reverse motor circuit with electrical and push buttoninterlockings. Figure 2 shows the simplified wiring diagram for this motor. The PLC implementation of this circuit should include the use of the overload contacts to monitor the occurrence of an overload condition.
The auxiliary starter contacts (M1 and M2) are not required in the PLC program because the sealing circuits can be programmed using the internal contacts from the motor outputs.
Figure 1 – Hardwired forward/reverse motor circuit
Low-voltage protection can be implemented using the overload contact input so that, if an overload occurs, the motor circuit will turn off. However, after the overload condition passes, the operator must push the forward or reverse push button again to restart the motor.
Figure 2 – Forward/reverse motor wiring diagram
For simplicity, the PLC implementation of the circuit in Figure 1 includes all of the elements in the hardwired diagram, even though the additional starter contacts (normally closed R and F in the hardwired circuit) are not required, since the push button interlocking accomplishes the same task.
In the hardwired circuit, this redundant interlock is performed as a backup interlocking procedure.
Figure 3 – Real inputs and outputs to the PLC
Figure 3 shows the field devices that will be connected to the PLC. The stop push button has address 000, while the normally open sides of the forward and reverse push buttons have addresses 001 and 002, respectively. The overload contacts are connected to the input module at address 003.
The output devices – the forward and reverse starters and their respective interlocking auxiliary contacts – have addresses 030 and 032. The forward and reverse pilot light indicators have address 031 and 033, respectively.
Additionally, the overload light indicators have addresses 034 and 035, indicating that the overload condition occurred during either forward or reverse motor operation. The addresses for the auxiliary contact interlocking using the R and F contacts are the output addresses of the forward and reverse starters (030 and 032). The ladder circuit that latches the overload condition (forward or reverse) must be programmed before the circuits that drive the forward and reverse starters as we will explain shortly. Otherwise, the PLC program will never recognize the overload signal because the starter will be turned off in the circuit during the same scan when the overload occurs.
If the latching circuit is after the motor starter circuit, the latch will never occurbecause the starter contacts will be open and continuity will not exist.
Table 1 shows the real I/O address assignment for this circuit. Figure 4 shows the PLC implementation, which follows the same logic as the hardwired circuit and adds additional overload contact interlockings.
Table 1 – I/O address assignment
I/O Address
Module Type
Rack
Group
Terminal
Description
Input
0
0
0
Stop PB (wired NC)
0
0
1
Fowrward PB (wired NO)
0
0
2
Reverse PB (wired NO)
0
0
3
Overload contacts
Input
0
0
4
Acknowledge OL/Reset PB
–
–
–
–
–
–
–
–
–
Output
0
3
0
Motor starter M1 (FWD)
0
3
1
Forward PL1
0
3
2
Motor starter M2 (REV)
0
3
3
Reverse PL2
Output
0
3
4
Overload condition FWD
0
3
5
Overload condition REV
0
3
6
–
0
3
7
–
Note that the motor circuit also uses the overload input, which will shut down the motor. The normally closed overload contacts are programmed as normally open in the logic driving the motor starter outputs. The forward and reverse motor commands will operate normally if no overload condition exists because the overload contacts will provide continuity.
However, if an overload occurs, the contacts in the PLC program will open and the motor circuit will turn OFF. The overload indicator pilot lights (OL Fault Fwd and OL Fault Rev) use latch/unlatch instructions to latch whether the overload occurred in the forward or reverse operation.
Figure 4 – PLC implementation of the circuit in Figure 1
Again, the latching occurs before the forward and reverse motor starter circuits, which will turn off due to the overload. An additional normally open acknowledge overload reset push button, which is connected to the input module, allows the operator to reset the overload indicators. Thus, the overload indicators will remain latched, even if the physical overloads cool off and return to their normally closed states, until the operator acknowledges the condition and resets it.
Figure 5 illustrates the motor wiring diagram of the forward/reverse motor circuit and the output connections from the PLC. Note that the auxiliary contacts M1 and M2 are not connected.
Figure 5 – Forward/reverse motor wiring diagram
In this wiring diagram, both the forward and reverse coils have their returns connected to L2 and not to the overload contacts. The overload contacts are connected to L1 on one side and to the PLC’s input module on the other (input 003). In the event of an overload, both motor starter output coils will be dropped from the circuit because the PLC’s output to both starters will be OFF.
Control circuit for forward and reverse motor (VIDEO)
Cant see this video? Click here to watch it on Youtube.
