Siemens SIPART DR20 Technical manual

s
Compact Controller
SIPART DR20
Project Planning Manual 02.05
Order No. 6ZB5600-0AAO2-0BA0

Project Planning Manual SIPART DR20
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SIPART DR20 Project Planning Manual
SIPART DR20
Project Planning Manual
This edition 1990 of the Project Planning Manual describes the SIPART DR20 compact
controller in the design with software version A09 (see page 91). This device can be used
to implement all functions which have already been described in earlier documents. A
number of function extensions have been made compared to earlier devices; these are
especially identified.
Notice
The controller SIPART DR20 is powered by electricity. Certain components within electrical
instruments are by necessity subject to very high voltages. Serious physical injury or damage to
property / equipment may ensue if the hints in this manual are ignored. Only suitable qualified
personnel should use this controller. The trouble-free and safe operation depends on proper
transport, professional storage, as well as careful operation and maintenance.
Subject to change
SIPART, TELEPERM, SIMATIC and COROS are registered trade marks
of the Siemens Aktiengesellschaft
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Project Planning Manual SIPART DR20
Contents Page
1. Fundamental Control Technology Terms 5
1.1 Control Loop 5
1.2 Sensors and Transmitters 5
1.3 Final Control Elements and Actuators 5
1.4 Controllers 6
2. The SIPART DR20 Controller 10
2.1 Application 10
2.2 Operation and Display Functions 11
3. Technical Description 13
3.1 Hardware 13
3.1.1 Front Module 14
3.1.2 Basic Circuit Board 15
3.1.3 Additional Modules (Options) 16
3.2 Software 18
3.2.1 Input Signal Processing 22
3.2.2 Input Signal Processing and Switchover 25
3.2.3 Control Algorithm 43
3.2.4 Output Signal Processing and Switchover 46
3.2.5 Restart Conditions 58
3.2.6 Optical Signalling of Functions and Operating State 58
3.2.7 Bus Interface 60
4. Technical Data 62
5. Mounting 70
5.1 Mechanical Installation 70
5.2 Electric Connection 70
5.2.1 Wiring 71
5.2.2 Serial Interface and Bus Driver 71
6. Adjustments and Operation 87
6.1 Process Operation 87
6.2 Parameterization 88
6.3 Configuring 89
6.4 Lamp Test 91
6.5 Display of Software Version 91
6.6 Further Information 91
6.7 Standard Measuring Ranges for Temperature 93
Measurements Using Thermocouples
7. Commissioning 95
7.1 Matching to Direction of Action 95
7.2 Matching of Step Controllers to Final Control Elements 96
7.3 Optimization Guidelines 97
8. Abbreviations 100
9. Ordering Data 101
10. SIPART Controllers in Systems 102
11. Representation of Various Setpoints 103
12. Planning Examples 108
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SIPART DR20 Project Planning Manual
1. Fundamental Control Technology Terms
1.1 Control Loop
An automatic control system has the function of bringing the output variable x of a controlled
system to a predetermined value and to maintain this value against the influence of disturbances z.
With digital controller, the controlled variable x is measured cyclically and compared with the
command variable w. The resulting negative deviation xd = w - x is processed in the controller to
form the manipulated variable y which acts on the controlled system.
w2
1
xy
z1
-xd
z2z3
wCommand variable
x Controlled variable
xd Negative deviation
y Manipulated variable
z Disturbance variables
1 Controlled system
2 Controlling means
Fig.1/1 Block diagram of a control loop
1.2 Sensors and Transmitters
The controlled variable may be any physical quantity. Frequently encountered variables in process
engineering are e.g. pressure, temperature, level and flow.
Certain sensors such as resistance thermometers, resistance transmitters and thermocouples can
be directly connected to the controller. Otherwise, transmitters supplying an electric output variable
must be connected between the sensor and the controller. Our controllers are designed for
transmitters with standardized signal outputs (0 to 10 V, 0 to 20 mA or 4 to 20 mA).
1.3 Final Control Elements and Actuators
In most cases in heating and process engineering, the manipulated variable y acts through a valve,
a damper or another mechanical positioning device on the controlled system. Three types of
actuators are possible to actuate such final control elements:
• Electric actuators, consisting of electric motor and gear unit. They have an integral action
and are driven by three-position step controllers. There are also electric actuators with
integrated (series-connected) positioners which then have a proportional action and are
driven by continuous controllers.
• Pneumatic actuators with compressed air as the supply and with electropneumatic positioner
or converter. These have a proportional action and are driven by continuous controllers.
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Project Planning Manual SIPART DR20
• Hydraulic actuators with electrically driven oil pump and electrohydraulic positioner. These
have a proportional action and are also driven by continuous controllers.
Electric actuators with single-phase or three-phase motors are robust, economical and require
practically no maintenance.
Pneumatic actuators are faster than electric actuators and are also explosion-proof. However, they
are not particularly suitable for large positioning forces.
Hydraulic actuators are fast and can also be used for large positioning forces, but they are more
expensive than electric or pneumatic actuators.
xd
t
step function
control action step response
P
y
t
Kp ∗xd
y0
PD
y
t
Kp ∗xd
Tv
Vv
Kp ∗Vv ∗xd
y0=0
PI
y
t
Kp ∗xd
Tn
PID
y
t
Kp ∗xd
Tn
Tv
Vv
1.4 Controllers
In the input circuit, the
controlled variable x is
compared with the
command variable W and
the negative deviation xd
is determined. This is
processed with or without
a time response into the
output signal. The output
signal of the amplifier can
represent the manipulated
variable w directly, e.g. if it
controls final control ele-
ments or actuators with a
proportional action. With
electric actuators, the
mani- pulated variable y
only appears after the
actuator. The positioning
increments required are
obtained as a PDM signal
from the con- troller output
by conversion.
Depending on the con-
struction of this circuit, the
controller has a
proportional (P),
proportional-differential
action (PD), proportional-
integral action (PI) or
proportional-integraI-diffe-
rential action (PID).
Fig. 1/2
Step responses with different control actions
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SIPART DR20 Project Planning Manual
If a step function is applied to the controller input, then step responses corresponding to Fig. 1/2
are produced.
Characteristic values of the P controller are the proportional gain Kp and the working point yo. The
working point is defined as the value of the output signal at which the negative deviation becomes
zero.
In contrast to the P controller, a permanent deviation is avoided in the PI controller, irrespective of
the working point, the setting of the command variable and the variation in the disturbance
variables, by means of an integrating component. The characteristic value of the integrating
component is the reset time Tn.
The PID controller achieves an improvement of the dynamic control performance by the addition of
a D component. The D component is determined by the derivative action gain Vv and the
derivative action time Tv.
The controller output signals must be matched to the actuators. Two types of controllers are
common for the most important kinds of actuator:
Æthree-position step controllers for electric actuators and
Æcontinuous controllers for pneumatic and hydraulic actuators
The three-position step controller switches the electric motor of the actuator to clockwise rotation,
stop or counterclockwise rotation by means of relays or semiconductor switches and can affect the
positioning speed of the final control element by means of different on/off ratios.
w
52
x-
+xd
3
1
y
x
4
M
L1
N
6
w Command
variable
x Controlled
variable
xd Negative
deviation
y Manipulated
variable
1 Transmitter
2 Setpoint adjuster
3 Three-point
switch
4 Feedback with
time response
5 Control amplifier
6 Final control
element
Fig 1/3 Three-position step controller, functional diagram
The switching performance of the three-point amplifier is reproduced in Fig 1/4 as a pulse diagram.
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Project Planning Manual SIPART DR20
y
∆y
t
t
Kp ∗xd
Tn
Kp Proportional gain
Tn Reset time
xd Negative deviation
∆y Manipulated variable
(controller)
y Manipulated variable
(motor)
Fig. 1/4 Three-position step controller,
transient function and parameters
The transient function produced at the final control element by these pulses resembles that of a
continuous PI controller. Therefore the parameters Kp and Tn are also applied to the description of
the transient function of three-position step controllers. This is referred to as quasi-continuous
control (see Fig. 1/4).
The response threshold A is adjustable in our controllers. Thus, for example, noise suppression
and a stabilizing effect can be achieved.
The main field of application of continuous controllers is in installations with pneumatic
actuators. The controller output signal of 0 to 20 mA or 4 to 20 mA acts continuously on the final
control element through an electropneumatic signal converter.
w
32
x-
+xd 4
1
y
0.2 ... 1.0 bar
y
x
5
0 ... 20 mA
(4 ... 20 mA)
w Command variable
x Controlled variable
xd Negative deviation
1 Transmitter
2 Setpoint adjuster
3 Control amplifier
4 Electropneumatic
signal converter
5 Pneumatic final
control element
Fig. 1/5 Continuous controller,
functional diagram
Two-position or three-position controllers are used to activate relays, contactors or thyristor
switches for switching electric heaters or coolers. The two-position controller (Fig. 1/6) switches, if
the controlled variable goes below the value x1 or above x2. A continuous oscillation occurs whose
frequency depends on the delay time of the controlled system and the switching hysteresis of the
controller.
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SIPART DR20 Project Planning Manual
Since the control result thus obtained does not completely meet the requirements in most cases,
the switching frequency is increased and the amplitude of the oscillation is thus reduced. The
performance of a P or PI controller can thus be achieved in many cases using a two-position
controller. In the SIPART DR20 the control amplifier is followed by a duty factor converter with
adjustable period, resulting in a PID two- position controller (Fig. 1/7).
w
2
1
xy
z
+
-
1. Controller
2. Controlled system
x
x1
x2
OFF
ON
y
ON
OFF
t
t
Fig. 1/6 Two-position controller without feedback
w
21
x-
+xd 34
5
1. Setpoint adjuster
2. Control amplifier
3. Duty factor converter
4. Controlled system
5. Transmitter
Fig. 1/7 SIPART DR20 two-position controller
In the case of controllers with mechanical contacts, the switching frequency possibly is limited
because of the contact life. However, if thyristor units are used as switching elements, the
switching frequency can be increased.
The control problem often requires the controller action to be divided between various final control
elements or manipulated variables, e.g. for heating and cooling. Two- position controllers are used
for these problems where the manipulated variables are divided into two sections and assigned to
two outputs. An adjustable dead zone is present between the two sections. A duty factor of 0 to
100 % is possibly in each section.
These controllers are also referred to as three-position controllers.
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Project Planning Manual SIPART DR20
2. The SIPART DR20 Controller
2.1 Application
The SIPART DR20 is a stand-alone process controller for a wide range of applications in process
engineering, mechanical engineering and apparatus engineering. It is available in the following
designs:
• K controller with continuous output
for connection of pneumatic or hydraulic actuators with proportional action
• S controller with step output,
programmable either as:
- three-position step controller for electric actuators
- two-position controller with two outputs for heating and cooling
Its flexibility means that SIPART DR20 is suitable for designing simple control loops as well as for
solving control tasks in meshed controls. It can be used in conventional parallel wiring via its
analog and digital interfaces. In addition, it can be connected to higher-level systems (process
computers or control systems) via an addressable serial interface which can be retrofitted at any
time or incorporated into a central operating and monitoring system with a personal computer and
the SIPART software, if applicable also together with devices from the TELEPERM D range.
The SIPART DR20 can be programmed to the most common types of controller:
• Fixed setpoint controller with and without disturbance variable feedforward at
input and output
• DDC backup fixed setpoint controller
• Follow-up controller with and without local/remote switchover (SPC)
• Synchronization controller for controlled variable
• Ratio controller
In addition, the device can also be used as a ratio station, manual/automatic control station (also
DDC manual control station) and process indicator.
The control and display unit (front module) of the SIPART DR20 is sealed by a plastic foil so that
degree of protection IP 64 is possible with a suitable installation configuration. The mounting depth
of the device is very small so that it is not only suitable for panel and switchboard mounting but
also for direct installation in machines and equipment.
An extremely high reliability for the device has been achieved by extensive and expensive
measures during development and manufacture. In addition to appropriate selection of the
components used, a worst-case design of the circuits and a 24-hour burn-in with subsequent
computer-controlled final test, special measures have been included to provide an interference-free
design of the circuits and high noise immunity towards RF sources.
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