Integrated Temperature Limiter Function; Tl Within The Scope Of Trd; Tl With External Predefined Load; Requirements Placed On Sensor And Protection Pocket - Siemens LMV51 Series Basic Documentation

TL within the
scope of TRD
TL with external
predefined load
Requirements placed on
sensor and protection
pocket
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6.7 Integrated temperature limiter function

The temperature limiter function is implemented as a «safety-related» function con-
forming to DIN 3440. This means that the function is single-error-proof. In other words,
a single error cannot negate the protective function of the controller and temperature
limiter. The temperature limiter works similar to the 2-position controller but with a sepa-
rate limit value that can only be changed after entry of a password.
Parameters:
TL_ThreshOff
TL_SD_On
The TL function also ensures that controller setpoints > TL_Threshold_Off cannot be-
come active.
The TL function is only active in connection with the Pt100, Pt1000 and LG-Ni 1000
sensors. These sensors are monitored for short-circuits and open-circuits.
Activation / deactivation of the TL function depends on the parameterization of the ac-
tual value input (parameter SensorSelection) (refer to section 5.5).
Short-circuits or open-circuits of the TL sensors lead to «C = OFF», «TL = OFF» and to
the relevant error message.
Within the scope of TRD (Technical Directives for Steam), 2 temperature sensors are re-
quired to ensure the internal TL function.
Parameter: Inp1/2/4Sel (Pt100Pt1000) or
Inp1/2/4Sel (Pt100Ni1000)
The Pt100 input is always assigned to the TC function. For the TL function, the Pt1000
or LG-Ni 1000 input is used for the second sensor.
The internal TL function can be used in all operating modes, provided the appropriate
actual value input parameterization is made and the associated temperature sensor is
connected.
If the internal TL function is used, the time constant T of the temperature sensor with
protection pocket may not exceed 45 seconds.
1
0.63
T
Instant temperature change of test medium to determine the time constant
ϑ M
Temperature of test medium
X a Output signal of temperature sensor
T Time constant
Basic Documentation LMV5...
6 Temperature or pressure controller (internal load controller LC)
ϑ
M
X
a
7550d19E/0502
Time t
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13.08.2004