batch - technical report
TRANSCRIPT
TEC 3601
April, 2011
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Statement of Authorship
I,________________________, hereby solemnly confirm that the work submitted
for assessment is my own and its contents are expressed in my own words. Any
uses of the works of any other author, in any form (ideas, equations, figures, texts,
tables, programs), are properly acknowledged at the point of use. A list of the
references used is included.
Table of Contents
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Statement of Authorship ii
List of Equations vi
List of Figures vi
List of Tables vii
List of Symbols viii
Executive Summary ix
Introduction 1
Purpose 1
Background 1
Scope 4
Sequence of Operation 5
PLC Program Long Comments 7
Memory Mapping 7
Troubleshooting Aid 8
Power-Up Delay 8
Scaling 8
Weight Comparators and Solenoid Valve Control 8
Cycle Control and Drum Counter 9
Conversion to Internals for Bit Offset 9
Masked Inputs 9
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Set Inputs of ICMP / Outputs of DRUM 10
Pulse Timer 10
Mixer Speed Control 1/2 10
Mixer Speed Control 2/2 11
Process E-Stops and Reset 11
Set Read from Drum Location Limit Switches 12
Detect Drum Locations 12
Sequencer Step Initiator 12
ICMP and Sequencer 12
PLC Card Health 1/2 13
PLC Card Health 2/2 13
Workstation and Schematic Diagrams 14
Actual PLC Rack and Workstation 14
Main Schematic Diagrams 15
PLC Input Cards 15
DAI 540 00 115V Discrete Input 15
ACI 030-00 4-20 Analog Input 15
PLC Output Cards 16
DRA 840-00 Relay Output Card 16
ACO 020-00 Analog Output Card 16
Traffic Cop 16
Interfacing with RSView32 17
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Using ANIMATE with RSView32 18
Interacting with ProWorx via KEPServer 19
The Graphical User Interface 20
The “Login” Screen 20
The “Process Display” Screen 21
The “Monitor” Screen 22
The “Alarms” Screen 23
The “PLC Card Health” Screen 24
Using the Altivar 31 Electronic Drive 25
Advantages of Using an Electronic Drive 26
Parameter Settings 28
Conclusion 31
Recommendations 32
References 33
Appendix A – Mixer Motor Speed Control 34
Appendix B – Batch Processing PLC Schematics 36
Appendix C – PLC Program 42
Appendix D – Omega DMD-466 Specifications 65
Appendix E – Altivar 31 Electronic Speed Drive Characteristics and Specifications 67
Appendix F – Parameter Settings for the Altivar 31 Electronic Drive 81
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List of Equations
EQUATION (1.1): THE ROTATIONAL SPEED OF A 3 PHASE MOTOR 25
EQUATION (1.2): THE INDUCTIVE REACTANCE IN A COIL 27
EQUATION (1.3): THE PHASE ANGLE OF THE STATOR AND ROTOR MAGNETIC
FLUX IN A 3 PHASE MOTOR 27
List of Figures
FIGURE 1: PLC WORKSTATION 14
FIGURE 2: ACTUAL PLC RACK 14
FIGURE 3: TRAFFIC COP IN PROWORX 17
FIGURE 4: THE ANIMATE SOFTWARE PROGRAM 19
FIGURE 5: KEPSERVER SOFTWARE 19
FIGURE 6: NAVIGATING MENUS IN THE RSVIEW32 GUI 20
FIGURE 7: THE LOGIN SCREEN 21
FIGURE 8: THE PROCESS DISPLAY SCREEN 22
FIGURE 9: THE MONITOR SCREEN 23
FIGURE 10: THE ALARM SCREEN 23
FIGURE 11: THE ALARM LOG VIEWER 24
FIGURE 12: THE PLC CARD HEALTH SCREEN 24
FIGURE 13: FLOWCHART LEGEND 34
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FIGURE 14: BATCH PROCESSING MIXER SPEED FLOWCHART 35
FIGURE 15: BATCH PROCESSING PLC SCHEMATIC DIAGRAM 1 OF 2 36
FIGURE 16: BATCH PROCESSING PLC SCHEMATIC DIAGRAM 2 OF 2 37
FIGURE 17: PLC 115V DISCRETE INPUT CARD SCHEMATIC 38
FIGURE 18: PLC ANALOG INPUT CARD SCHEMATIC 39
FIGURE 19: PLC RELAY OUT CARD SCHEMATIC 40
FIGURE 20: PLC ANALOG OUTPUT CARD SCHEMATIC 41
List of Tables
TABLE 1: PARAMETER SETTINGS FOR THE ALTIVAR31 28
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List of Symbols
CMD Command
CONT Contactor
M Contactor (except M4, which is a relay)
CV Conveyor
CYC Cycle
DDE Dynamic Data Exchange
E-Stop Emergency Stop
Freq. Drive Frequency Drive, otherwise known as Electronic Speed Drive
GUI Graphical User Interface
HMI Human-Machine Interaction
INI Initiate
ICMP Input Compare
INS/OUTS Inputs/Outputs
MX Interposing Relay
LM_SW Limit Switch
LS Limit Switch
MISCOMP=0 Returns the value 0 is there is no comparison
O/L Overload
POS Position
PWR Power
PLC Programmable Logic Controller
PWM Pulse Width Modulation
SV Solenoid Valve
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Executive Summary
IMPLEMENTING A PROGRAMMABLE LOGIC CONTROLLER SYSTEM
TO CONTROL AND MONITOR A BATCH PROCESS
As with all industrial processes, the costs of maintenance and
operations, along with production, are the leading factors in
determining profits. Mitigating lost production time as a result of
maintenance is, therefore, one of the highest priorities of
industries. Programmable Logic Controllers (PLC) offer the same
operational control of a process as your standard relays and “hard-
wired” control schemes, but they also allow for expansion in terms
of monitoring and control capabilities. This, in turn, lowers your
down time and increases production, which ultimately results in
increases in profit. Additionally, PLCs are a proven piece of
technology that have a much longer life than their electro-
mechanical counterparts (e.g.: relays), and can handle many more
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components at a time (adding or removing input/output cards
allow for total control over many things at once).
A batch fill and mix station, specifically, consists of continuously
adding ingredients together and mixing them, and follows a general
sequence that is repeated over and over. Furthermore, such a
process is not keen on manual intervention. A properly
programmed PLC is excellent at creating such a sequence, based on
the state and status of certain inputs/outputs, consequently
completely automating the process.
Using monitoring software in combination with the PLC makes the
most powerful combination. Every bit of information about the
ongoing process can be constantly monitored (by a user or a
computer) and programmed to alarm if something was to go
wrong, all without adding the slightest component. This seamless
interaction between the PLC and the monitoring software greatly
simplifies the whole troubleshooting experience, thus positively
affecting production, down time, and maybe even employee
morale (less pressure on the employees make it a less stressful
environment).
The mixing station of the batch process includes a mixer that
usually operates at different speeds – it ramps up and down. This
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ramping sequence allows for more even mixing and prevents the
ingredients from being spilt during the startup of the motor (less
initial “shock”). The best way to control and vary the speed of a
motor is with an electronic frequency drive. The latter allows for
complete speed control with maximum torque, and improves
motor efficiency. Moreover, it improves the power factor of the
motor, removing the need for extensive power factor correction,
which saves money and many foreseeable headaches.
Choosing to implement a PLC and its dedicated monitoring
software to control and monitor a batch fill and mix station will
improve the overall process, which include (but isn’t limited to)
total productions and better, more proficient maintenance
practices. In addition, it will allow for constant monitoring over the
entire process, including faults and alarms. These accrued benefits
will result in a higher return of investment, and make the batch fill
and mix station a very efficient, lucrative industrial process.
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Introduction
Purpose
This report details the process of implementing a Programmable Logic Controller
(PLC) to control, in its entirety, a batch process. The batch process in question is a
fill and mix station, where two ingredients are poured into a drum and mixed for
50 seconds. After 10 completed drums, the process stops.
It must be noted that there are theoretical limitations to this report. The entire
process was created and tested “theoretically” in the PLC lab class. This means
that the real inputs supposedly connected to the PLC discrete input cards are
simulated with switches. Furthermore, the analog-in signal is simulated with a
potentiometer, and the output of the analog out is simulated with an indicator (0
to 100%). With all of these simulations taken into consideration, and with my
knowledge of field processes, I believe this report is still a very accurate depiction
of an actual batch fill and mix station. I am confident that it would undoubtedly
work if it ever were to be implemented in the field.
This report also satisfies the academic requirements of the Electrical Engineering
Technology program at Cambrian College.
Background
Batch processes are found in a myriad of production plants. “Manufacturers, of
anything from cakes to computer chips, have numerous ways of organizing
production. One of these methods is called batch production. This is when,
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instead of manufacturing things singly, or by continuous production […], items are
manufactured in batches” (Ellis-Christensen, 2010). Batch processing is the engine
that drives the production of many different everyday goods, and in these
systems, total automation is paramount; manual intervention is greatly
undesirable, and can even become detrimental to the entire process. This is
where PLCs come into play.
Programmable Logic Controllers are the best method of controlling a process
automatically, with a user being capable of troubleshooting and making changes
to the system simply by interfacing with a computer. In this report, the
implementation of a PLC is done with the Modicon Quantum Series Automation
PLC system. The PLC rack consists of ten slots – six of which are filled with the
following cards: one CPS 114-20 power supply card, one CPU 454 12A controller
card, two DAI 540-00 discrete inputs cards, one ACI 030-00 analog input card, one
ACO 020-00 analog output card, and one DRA 840-00 relay output card. The
interface system used is the Microsoft Windows XP Service Pack 3 platform, and
all the programming is done on ProWorx NxT version 2.20 Special 8. The
communications between ProWorx and the PLC controller is achieved through
Modbus Plus.
Modbus “is a serial communications protocol published by Modicon in 1979 for
use with its programmable logic controllers (PLCs). Simple and robust, it has since
become one of the de facto standard communications protocols in the industry,
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and it is now amongst the most commonly available means of connecting
industrial electronic devices” (Drury, 2009). For the batch processing in this
report, Modbus Plus is used, which is essentially an extended version of Modbus,
with faster transmission speeds. The batch process also has a graphical user
interface (GUI), which visually depicts the process as it unfolds. The software
used to achieve this is RSView32, and communications from the PLC to RSView32
is done with the aid of KEPServerEx v4.0.
The advantages of using a PLC system to control an entire batch process are
numerous, ranging from saving loads of money by reducing down time for
troubleshooting, to having a constant visual indication of what is going on through
the process at all times. Additionally, as mentioned above, in batch processes
total automation is paramount, and a PLC is the best way to achieve this.
Disadvantages to using a PLC are the initial setup costs and the setup itself; firstly,
the schematic diagrams tend to be more complicated and don’t adequately
represent the process (you must refer to the PLC program to understand how the
process works). Secondly, the entire PLC program must be written beforehand
and thoroughly tested before it can be implemented, and lastly, the sum of the
costs with purchasing a PLC with all the required software may seem a bit
exuberant at first. However, by looking at the bigger picture, it is easily observed
that the advantages simply outweigh these mere initial inconveniences.
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Scope
The topics covered in the report are: the sequence of operation of the batch fill
and mix station, the long comments associated with all the networks of the PLC
program, a detailed analysis of the schematic diagrams, the explanation of the
Traffic Cop used for the PLC I/O cards, the interfacing with RSView32, using the
Altivar Electronic Drive to control the mixer motor, and finally, the conclusion and
recommendations.
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Sequence of Operation
The following paragraphs will detail the sequence of operation of the batch fill
and mix station. All steps will have a link to the corresponding network in the PLC
program where the action is being controlled. It is assumed that there are no
faults on the system, as most faults encountered1 turn off the process until it is
remedied. Refer to the PLC program in Appendix C for the networks.
1. Press “Cycle Start” pushbutton in the field or in the RSView32 GUI, and the
cycle on light comes on (network 6: Cycle Control and Drum Counter).
2. The Program detects where the drum is located with the help of the limit
switches (network 15: Detect Drum Locations). If LS1 is actuated (drum
ready), then the next step is step 3. If LS2 is actuated (drum in fill position),
then the next step is step 4. If LS3 is actuated (drum in mixing position),
then the next step is step 6 (all of the initial sequencing is controlled by
network 16: Sequencer Step Initiator).
3. The conveyor starts and runs until the drum arrives to the fill station [until
LS2 is actuated (network 17: ICMP and Sequencer)].
4. SV3 opens and chemical #1 is dispensed until the fill weight reaches 30 lbs
(transducer specs sheet in Appendix D). SV3 closes and SV4 opens,
dispensing chemical #2 until the fill weight reaches 60 lbs. SV4 is then
closed (network 5: Weight Comparators and Solenoid Valve Control).
1 Example: A PLC Card failure will not shut down the process, but will generate an alarm in RSView32 with high severity.
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5. The conveyor starts and runs until the drum arrives to the mix station
[until LS3 is actuated (network 17: ICMP and Sequencer)].
6. M2 energizes, making the mixer motor descend until LS4 (mixer in down
position) is actuated (network 17: ICMP and Sequencer).
7. M4 energizes sending a start command to the drive controlling the mixer
motor. The mixer motor has two speeds and is ramped up/ramped down,
and for the full speed control sequence refer to Figures 13 and 14 in
Appendix A [networks 10 thru 12: Pulse Timer (N:10), Mixer Speed Control
1/2 (N:11), and finally, Mixer Speed Control 2/2 (N:12)].
8. After the mixer motor is ramped down M3 energizes, making the mixer
motor ascend until LS5 (mixer in up position) is actuated (network 17:
ICMP and Sequencer).
9. The conveyor starts and runs until the drum arrives at its final destination
and the next drum arrives at the ready position. (network 17: ICMP and
Sequencer).
10. The count for the completed drums in the current cycle increments by
one. After 10 completed drums, the system shuts down (network 6: Cycle
Control and Drum Counter).
11. The total amount of drums in all cycles is stored in a separate register, and
then the process proceeds back to step 3 (network 6: Cycle Control and
Drum Counter).
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PLC Program Long Comments
Memory Mapping
PLC Coil Range Allocation
00001 – 00128 Real Discrete Outputs (Used to 00048)
00129 – 00149 Internal Coils (Used to 00142)
00150 – 00159 Sequencer Coils (Used to 00150)
00700 – 00800 MMI Control Coils (Used to 00702)
10001 – 10065 Real Discrete Inputs (Used to 10032)
PLC Register Assignments
30001 – 30032 Real Register Inputs (Used to 30009)
40001 – 40009 Real Register Outputs (Used to 40004)
40010 – 40399 Internal Registers (Used to 40354)
40400 – 40500 Internal Registers for Masking (Used to 40500)
40501 – 40699 Spare Registers (Not Used)
40700 – 40799 STAT Block / Card Health (Used to 40712)
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Troubleshooting Aid
This network visually displays the state of all the discrete inputs and outputs used
in the program in order to help with the troubleshooting of a fault. The top
portion consists of all the discrete inputs, and the bottom portion consists of the
discrete outputs
Power-Up Delay
This network sets up a delay on power-up for 5 seconds in order to let the
transmitters self-check and calibrate themselves and then energizes internal coil
00100.
Scaling
This network reads raw data (counts 0-4095) from a Load-cell transducer unit and
converts it to an engineering unit (0 – 150 lbs) and stores that data into register
40205.
Weight Comparators and Solenoid Valve Control
This first function of this network is to detect two different weight values inside
the drum when in the fill position. It detects when the weight reaches 30 lbs and
is held at or above that weight for at least two seconds (anti-glitch feature) by
energizing output coil 00005. It also does the same thing for 60 lbs, energizing
output coil 00006.
The other function of this network is to control and shutoff solenoid valves 3 and
4 when the weight reaches 30 lbs and 60 lbs respectively.
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Cycle Control and Drum Counter
The first function of this network is to control when the cycle is ON or OFF with
internal coil 00101. In order for the cycle to be started there must no stop
commands and no overloads (faults).
The second function of this network is to count the amount of drums per cycle,
and store it in register 40101. Once register 40101 reaches 10, it initiates a system
shut down via internal coil 00103.
The third function of this network is to add the amount of completed drums per
cycle to the total amount of drums completed and store it in register 40300.
Registers 40101 and 40300 are added together whenever the cycle is stopped or
completed.
Conversion to Internals for Bit Offset
This network converts output registers 00001 thru 00006 to internal coils. This
offset is to allow the ICMP to read the values of inputs and outputs
simultaneously.
Masked Inputs
This network copies the discrete inputs and real outputs, and applies a mask to
them so that they can be conditioned and then used by the ICMP.
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Set Inputs of ICMP / Outputs of DRUM
This network uses the masked inputs/outputs set up in network 8 and combines
them into one common register (40500). This conditioning allows the ICMP to
compare both the desired inputs and outputs simultaneously.
Pulse Timer
This network sets up a 1 second pulse timer that is used to ramp up/down and
control the mixer motor speed. The pulse timer is stopped when we have a speed
latch (at 50% speed and 100% speed) or when the mixer motor has finished
ramping down.
Mixer Speed Control 1/2
This network controls the ramping up and ramping down of the mixer motor. The
permissives for the mixer motor to run / change speeds are as follow:
1-The PLC must be sending a start command to the frequency drive (that means
the cycle is ON)
2-There must not be a speed latch engaged (at 50% or 100% speed) and the
motor cannot be fully ramped down
3-There must be a pulse from the pulse timer
If there isn’t a ramp down command (internal coil 00110 is not energized), the
mixer motor’s speed will be ramped up by 511 counts (or 12.5%) at every pulse
from the pulse timer. If there is a ramp down command (internal coil 00110 is
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energized), the mixer motor’s speed will be ramped down by 511 counts (12.5%)
until it reaches 0%.
Mixer Speed Control 2/2
This network is only in operation when the cycle is ON. It detects when the mixer
motor reaches 50% and 100% speeds and latches/un-latches the speed as
necessary. When the motor reaches 50% speed during ramp up, coil 00106 is
energized and it latches the mixer motor in at 50% speed for a total of 17 seconds.
After the 17s have elapsed, a “gear change” allows the motor to ramp up to 100%,
and then latches (coil 00108) the mixer motor at that speed for 26 seconds. After
the 26s have elapsed, coil 00110 is energized and initiates a ramp down
command.
Process E-Stops and Reset
This network deals with the emergency stops and the resets. When the cycle is
OFF, the mixer speed is reset to 0%, sequencer step is returned to 0, and the
outputs are reset. Input 10019 and MMI coil 00702 allow the total complete
drums register 40300 to be reset to 0.
The second function of this network is to detect if any of the motors have an
overload and engage internal coil 00112.
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Set Read from Drum Location Limit Switches
This network reads the limit switches that determine the drum location on the
conveyor (discrete inputs 10005 thru 10007). It then sets up a mask, and applies it
the aforementioned limit switches, and then stores it in register 40213.
Detect Drum Locations
This network uses the value in register 40213 to detect where the drum is located.
Additionally, it provides the program with the means to expand and work for
more than one drum at a time per cycle if it ever were required. When the drum
location is detected, the associated internal output is energized.
Sequencer Step Initiator
This network sets the correct step to the sequencer. When the cycle is switched
ON, the program allows the sequencer 1/10th of a second to set itself up. If the
drum is in the fill position, register 40140 (the current step register for the
sequencer/ICMP) is set to 3. If the drum is in the mix position, register 40140 is set
to 5. If the drum is neither in the fill or mix positions, register 40140 remains at 0.
ICMP and Sequencer
This network deals with the sequence of the cycle. When the cycle is switched on,
there is a 1/10th of a second delay to allow the initial step to be setup (network
16). This network has two SCIF blocks, one being a sequencer and the other an
ICMP.
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The ICMP compares the state of inputs/outputs conditioned in the previous
networks to the data of the current step. If there is a match, the ICMP energizes
internal coil 00150. This means that the step is complete.
When coil 00150 is energized it sends a pulse to the sequencer. This allows the
sequencer to change the current step and control certain outputs. When all the
steps are complete, the sequencer energizes internal coil 00102, which is the
“cycle complete” command. That coil then restarts the sequencer, which in turn
restarts the ICMP.
PLC Card Health 1/2
This network is the first of two that detects the health of the PLC cards. The STAT
block sets up register 40712 to be the word with the state of all the cards in the
PLC rack. Output 00137 is de-energized if the power supply card fails, output
00138 is de-energized if the analog input card fails, and finally, output 00139 is
de-energized if the analog output card fails.
PLC Card Health 2/2
This network is the second of two that detects the health of the PLC cards.
Output 00140 is de-energized if the first discrete input card fails, output 00141 is
de-energized if the second discrete input card fails, and finally, output 00142 is
de-energized if the relay output card fails.
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Workstation and Schematic Diagrams
Actual PLC Rack and Workstation
As mentioned in the Purpose section of the introduction, there are theoretical
limitations to the project. The entire the project is done in the PLC lab class at a
computer workstation (Figure 1).
Figure 1: PLC Workstation
Additionally, the discrete and analog inputs are simulated using switches and a
potentiometer respectively – they are mounted directly on the PLC rack (Figure 2).
The switches are on the input cards, and the potentiometer (and indicator, for the
analog output) is on the simulation card XSM 010 00.
Figure 2: Actual PLC Rack
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Main Schematic Diagrams
The main schematic diagram is found on Figures 15 and 16 in Appendix B. It
consists of 3 x 575V motors: the conveyor motor, the mixer up/down motor
(which operates in forward and reverse), and the mixer motor (which is controlled
by a frequency drive – the reasoning behind this will be explained in great detail
later in this report). The control circuit stems off of the conveyor motor power
circuit, and feeds all of the components/inputs/outputs required to control the
process. In essence, a single 575V, 3-phase supply is required for the entire
process (none of the motors are on at the same time).
PLC Input Cards
DAI 540 00 115V Discrete Input
The first set of schematics for the PLC input cards are the 115V discreet inputs,
which are found on Figure 17 in Appendix B. The use of two separate cards was to
facilitate the ICMP function in the PLC program, and I had two cards at my
disposal.
ACI 030-00 4-20 Analog Input
The second schematic for the PLC input cards is the analog input, which is found
on Figure 18 in Appendix B. A weight is received by the load cell sensor and
interpreted by the transducer, and then converted to a 4-20 mA signal. This
analog signal then goes to the analog input, where it is converted to counts (0-
4095) to be used by ProWorx.
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PLC Output Cards
DRA 840-00 Relay Output Card
The first schematic for the PLC output cards is the relay out, which is found on
Figure 19 in Appendix B. As its name implies, this card does not provide power to
its outputs, it is simply comprised of 16 normally opened contacts that are
controlled within the PLC program (like a relay).
ACO 020-00 Analog Output Card
The second schematic for the PLC output cards is the analog output, which is
found on Figure 20 in Appendix B. As previously mentioned (for the analog input),
ProWorx does not directly work with the 4-20 mA, it must first convert it to counts
(0-4095). The Analog output card acts as a transducer by converting the count
value back to a 4-20 mA signal. This signal is then sent to the frequency drive
analog input AI3 and used to control the mixer motor speed.
Traffic Cop
Traffic Cop is what ProWorx utilizes to determine which PLC cards are being used
and where they are physically located in the PLC rack. Additionally, it is used to
set up the addressing, and therefore generally sets up the memory mapping (refer
to the PLC Long Comments section of this report for a complete list of the
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memory mapping) to be used within the PLC program. Figure 3 visually displays
the Traffic Cop used for the Batch Fill and Mix Station.
Figure 3: Traffic Cop in ProWorx
A quick comparison between Figures 2 and 3 will show which cards are being used
in respect to what is actually in the PLC rack. The Traffic Copped PLC rack is
composed of the following cards (in order from left to right in Traffic Cop): one
CPS 114-20 power supply card, one CPU 454 12A controller card, one ACI 030-00
analog input card, one ACO 020-00 analog output card, two DAI 540-00 discrete
inputs cards, and one DRA 840-00 relay output card.
Interfacing with RSView32
RSView32 is an integrated human-machine interaction (HMI) software program
that enables us to obtain data from the field (in this case, acquired from the PLC)
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and display it in an easy to follow graphical interface. The program greatly
facilitates the troubleshooting of a fault, and keeps the user up to date on the
entire process at all times. A “mediator” program, known as KEPServer, does the
communications between the PLC and RSView32. In laymen’s terms, KEPServer
allows the data collected in ProWorx to be seamlessly shared with RSView32.
Another great feature of RSView32 is its versatility – it can be used in conjunction
with other programs (such as ANIMATE) to create animations without doing any
additional programming in ProWorx.
Using ANIMATE with RSView32
ANIMATE is a DDE (Dynamic Data Exchange) server that is used with RSView32 to
create animations. The advantage of using ANIMATE is that no additional
programming is required – it has values of constantly changing numbers (as seen
in Figure 4), which can be used to create rotations and other simple types of
animations without the slightest bit of change to the PLC program. This proves
itself as being advantageous because it keeps the PLC program de-cluttered,
simple, and easier to read. The only inconvenience of ANIMATE is that it must
constantly be operating in the background, and if it is closed, RSView32 will not
operate correctly.
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Figure 4: The ANIMATE Software Program
Interacting with ProWorx via KEPServer
As mentioned above, in order for the PLC and RSView32 to communicate and
exchange information, we need a “mediator”. KEPServer (Figure 5) sets up these
communications (in this case, in Modbus Plus) and interactions between the PLC
and RSView32. Like ANIMATE, it must be operating in the background at all times,
or else RSView32 will not be able to communicate with the PLC.
Figure 5: KEPServer Software
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The Graphical User Interface
The RSView32 GUI (Graphical User Interface) for the Batch Fill and Mix Station is
composed of 5 screens: the Login screen, The Process Display screen, the Monitor
Screen, the Alarms Screen, and finally, the PLC Card Health Screen. The navigation
between menus (see Figure 6) is achieved with the “Navigation” button (1), which
opens up a submenu (2), allowing the user to navigate through the menus without
interfering with any pertinent visual aspects of the process.
Figure 6: Navigating Menus in the RSView32 GUI
The “Login” Screen
The Login screen (Figure 7) does exactly what it implies: it allows the user to
“login” to the GUI, and provides the security to prevent unauthorized access. The
correct password must be entered before the rest of the buttons become visible.
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Figure 7: The Login Screen
The “Process Display” Screen
The Process Display (Figure 8) screen gives the user a visual representation of
what is happening in the field. It displays whether the cycle is on or off, the drum’s
location on the conveyor, the limit switches (along with their current state), the
SVs and the fill weight of the drum, the position of the mixer motor along with its
current speed, the amount of drums completed, and finally, the most recent
alarm encountered. The Progress Display screen also allows the user to start and
stop the current cycle, and even reset the count of total completed drums with
the software pushbuttons incorporated in the top left portion of the screen.
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Figure 8: The Process Display Screen
The “Monitor” Screen
The Monitor screen (Figure 9) is very similar, yet different to the Process Display
screen. It differs by showing the actual state of every input and output connected
to the PLC in an easy to read, structured setting. In addition, it provides the user
with the information on the current step being performed. It also displays (as text)
the position of the drum and mixer. Just like the Process Display screen, The
Monitor screen displays the most recent alarm encountered.
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Figure 9: The Monitor Screen
The “Alarms” Screen
The Alarms screen (Figure 10) is a popup window that displays the alarms
received, at what time the event occurred, the severity of the alarm (1 being the
most severe), and the time the alarm was acknowledged.
Figure 10: The Alarm Screen
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The alarm screen also allows the user open the alarm log viewer (Figure 11),
which is the log of all the alarms that occurred, with all the same information
provided on the alarm screen.
Figure 11: The Alarm Log Viewer
The “PLC Card Health” Screen
The PLC Card Health screen (Figure 12) is a popup window that displays the health
of each individual PLC card Traffic Copped in ProWorx.
Figure 12: The PLC Card Health Screen
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Using the Altivar 31 Electronic Drive
Electronic drives, or frequency drives, are becoming increasingly popular in
modern processes due to their versatility and ease of use. The drives offer
optimal control of motor speeds without the need of additional components in
the motor circuit, like extra contactors, timers, resistors or autotransformers. The
Altivar 31 electronic drive used in this project uses pulse width modulation (PWM)
to control the output voltage and output frequency going to the motor. It
essentially receives a sinusoidal 3-phase 575V input, rectifies it into a DC voltage,
and then inverts it back into a square wave pulsating AC voltage. The pulses of
the AC voltage are then varied according to the desired speed of the motor, and
this results in a change of output frequency to the motor (which is where the
name “frequency drive” is derived from). This method of speed control is
mathematically proven by (1.1), where RPM is the actual motor speed in rotations
per minute, Hz is the frequency applied to the motor, and #poles (constant) is the
amount of poles the motor has (typically 4).
RPM=120×Hz¿ poles (1.1)
To get a list of all the specifications/characteristics of the Altivar 31 electronic
drive, please refer to Appendix E.
The Altivar 31 must first be setup properly in order to control the speed of the
mixer motor – consulting the manufacturer’s manual is always a good idea before
the first power up. As mentioned previously, the drive receives a 4-20 mA input in
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its analog input AI3 and uses that as a reference, where 4 mA is minimum speed
(0% or 0Hz), and 20 mA is maximum speed (100% or 60Hz). However, without a
start command, the drive will not operate – this is where logic input LI1 comes
into play. When +24 Vdc is applied and held to LI1, the drive receives a start
command, and the speed of the mixer motor is now controlled depending on the
amount of current applied to AI3 (refer to Figure 20 and Figure 16 in Appendix B
for a visual representation of terminals AI3 and LI1 respectively). Getting the drive
to operate this way is very simple, and is set with the aid of parameter settings,
which will be discussed shortly. Before talking about the settings of the drive, I
will begin by explaining the advantages of using an electronic drive to control the
mixer motor.
Advantages of Using an Electronic Drive
The first advantage of using the Altivar 31 is the torque-speed characteristics it
brings to the mixer motor; other “across the line” methods of speed control
(generally varying the voltage to the motor) for motors offer low torque at lower
speeds. With the electronic drive, nearly 100% torque is maintained at all speeds.
This is due to varying the frequency instead of the voltage applied to the motor,
thus positively affecting the interaction of the stator and rotor magnetic fields. By
lowering the output frequency to the motor, the inductive reactance (which is a
type of resistance obtained in magnetism) in the motor coils is also lowered,
which is proved by (1.2), where XL is the inductive reactance (in ohms), F is the
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frequency (Hz), and L is the inductance of the coil (stays constant, and is
expressed in Henries).
X L=2π FL (1.2)
This will, in turn, cause a smaller difference between the phase angle in the stator
and rotor magnetic flux, as proved by (1.3), where Tan is the phase angle in the
stator or rotor, XL is the inductive reactance (in ohms), and R is the actual
resistance in the coil (is constant, and expressed in ohms).
tanφ=X LR (1.3)
This causes increased torque at lower speeds, increased efficiency, and improves
the power factor of the motor. All these advantages will result in a longer motor
life and improved performance.
Another advantage of using the Altivar 31 is that we no longer need thermal or
magnetic overloads to monitor the mixer motor for thermal damage. The drive
can be programmed to monitor the temperature of the mixer motor and engage a
contact if an overload condition exists.
This brings me to the next advantage: the drive constantly monitors the mixer
motor for over current, incorrect voltages, and other faults. Additionally, it also
filters and snubs transients, and has a plethora of different settings that can be
used to control the motor.
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Parameter Settings
Most of the advantages listed above cannot come to fruition without the proper
programming of the parameter settings to the drive. Consult Appendix F for all
the available parameter settings – only the prominent settings are programmed to
the drive. The following table lists the parameter settings used, the setting at
which they are set, and the reason for that particular setting.
Settings Menu (SEt)
Parameter Setting What is does
LSP 0 HzThis setting sets the low speed of the motor. When the speed reference is at its minimum value, the motor will operate at a speed of 0 Hz.
HSP 60 HzThis setting sets the high speed of the motor. When the speed reference is at its maximum value, the motor will operate at a speed of 60 Hz.
ttd 115%
This setting sets the motor thermal state threshold, above which the relay contact (R1) will change state. It is used to set the overload, in this case set at 115%; the motor will have an overload if its temperature reaches 115% its rated temperature.
Drive Control Menu (drC)
Parameter Setting What is does
bFr 60 Hz This setting is the motor frequency
UnS 575 VThis setting is the nominal motor voltage (as indicated on the motor nameplate)
FrS 60 HzThis setting is the nominal motor frequency (as indicated on the motor nameplate)
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nCr variesThis setting is the nominal motor current (as indicated on the motor nameplate)
nSP variesThis setting is the nominal motor speed (as indicated on the motor nameplate)
COS variesThis setting is the motor power factor (as indicated on the nameplate)
I/O Menu (I-O)
Parameter Setting What is does
tCC 2CThis setting is to set the type of control, in this case set to 2-wire control
tCt trnThis setting is to set the type of 2-wire control. It is set so that a transition from low to high on the logic input must occur before a start command is received.
CrL3 4 mAThis setting sets the minimum reference value for AI3. When this value is reached, the motor will go at its lowest speed (LSP)
CrH3 20 mAThis setting sets the maximum reference value for AI3. When this value is reached, the motor will go at its highest speed (HSP)
r1 tSAThis sets what relay R1 will engage to. In this case it is set to motor thermal threshold reached - when the setting (ttd) is reached, the R1 contacts will change state.
Control Menu (Ctl)
Parameter Setting What is does
Fr1 AI3This setting configures the speed reference, in this case set to AI3, which is the 0 - 20 mA current input.
rFC Fr1 This setting assures that the reference set cannot change from Fr1.
rOT dFrThis setting sets the direction of rotation of the motor, in this case, forward.
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Application Functions Menu (FUn)
Parameter Setting What is does
Stt rNPThis setting sets the normal stop type of the motor. When the run command disappears from the logic input the motor will follow the ramp to stop.
Fault Menu (FLt)
Parameter Setting What is does
OPL YESThis setting assures that the drive will trigger an OPF fault if there is a motor phase loss.
IPL YESThis setting assures that the drive will trigger a fault if there is a line phase loss.
OHL YESThis setting allows the motor to come to a freewheel stop in the event of a drive overheating fault.
OLLYES
This setting allows the motor to come to a freewheel stop in the event of a motor overload fault.
LFLYES
This setting allows the motor to come to a freewheel stop in the event of a loss of the 4 - 20 mA current signal.
Table 1: Parameter Settings for the Altivar31
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Conclusion
In conclusion, the implementation of a PLC system to control and monitor a batch
fill and mix station was successful. A programmable logic controller is the best
option for total automation of a process, and with the integration of RSView32 as
an HMI, the process is not only visually displayed at all times, it also logs any fault
that occurs at any given time. This greatly enhances the troubleshooting efficiency
and results in a proactive reduction of down time. By looking at the big picture, I
strongly believe that the overall process improvements (with regards to time for
troubleshooting, constantly monitoring, etcetera) attained by using a PLC to
control a batch fill and mix station make it the most viable option for total costs.
The upsides of using the PLC will result in quickly repaying the large initial costs of
the system. To sum it all up, the powerful combination of ProWorx, RSView32
(and its associated programs: KEPServer and ANIMATE), Modbus Plus, the
Modicon Quantum Series Automation PLC, a personal computer (with Windows
XP), and a knowledgeable user make a great team for any industrial process.
The use of an electronic drive to control the speed of the mixer motor was also a
key point in this report: the drive provides the motor with more torque at all
speeds, better speed control, better power factor (and efficiency), and more
monitoring capabilities.
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Recommendations
The only good recommendation I can make is to have the project tested in the
field prior to the first startup. Although I am confident of its functionality, testing
is always the safest option – the theoretical limitations of the project limit my
testing capabilities.
Another recommendation (not as feasible as the first) would be to upgrade the
outdated ProWorx NxT to ProWorx 32. This newer version of ProWorx can import
programs from its older NxT counterpart and convert it to a 32-bit format
(currently at 16-bit) without changing the initial program, and this would result in
the PLC program being useable on newer operating systems. All communications
(through Modbus Plus) would remain the same, and RSView32 would still work
the same way. With the constant innovations in computer technology, older
software programs (like ProWorx NxT) tend to become obsolete faster, and
keeping the PLC program up to date could help solve compatibility issues down
the road. This would be particularly advantageous on a new installation.
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References
Drury, B. (2009). Control Techniques Drives and Controls Handbook (Second ed.).
London, England: Institution of Engineering and Technology.
Ellis-Christensen, T. (2010, March 30). What is Batch Production? Retrieved April
5, 2011, from WiseGeek: http://www.wisegeek.com/what-is-batch-
production.htm
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Appendix A – Mixer Motor Speed Control
The following flowcharts describe the decision tree process used for the speed
control of the mixer motor.
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Figure 13: Flowchart Legend
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Figure 14: Batch Processing Mixer Speed Flowchart
Appendix B – Batch Processing PLC Schematics
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Figure 15: Batch Processing PLC Schematic Diagram 1 of 2
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Figure 16: Batch Processing PLC Schematic Diagram 2 of 2
BATC
H PRO
CESS
ING PR
OGRA
MMAB
LE LO
GICCO
NTRO
LLER C
ARD S
CHEM
ATICS
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Figure 17: PLC 115V Discrete Input Card Schematic
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Figure 18: PLC Analog Input Card Schematic
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Figure 19: PLC Relay Out Card Schematic
BATCH
PROC
ESSING
PROG
RAMM
ABLE
LOGIC
CONTR
OLLER
CARD
SCHE
MATIC
S
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Figure 20: PLC Analog Output Card Schematic
Appendix C – PLC Program
The following pages include the entire PLC Program as printed from ProWorx. It
contains the ladder logic, short comments, long comments, and all component
addresses.
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Appendix D – Omega DMD-466 Specifications
The following pages contain the specifications sheet for the load cell transducer
used in this process: the Omega DMD-466.
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Appendix E – Altivar 31 Electronic Speed Drive Characteristics
and Specifications
The following pages include the characteristics of the Altivar 31 Electronic Speed
Drive. It also consists of the applications of the drive, as well as the electrical
specifications.
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Appendix F – Parameter Settings for the Altivar 31 Electronic
Drive
The following pages include the parameter settings used for the drive to optimally
control the mixer motor. The pages were taken from the drive’s programming
manual, which is copyrighted by Schneider Electric.