Normal Operational Status; Pickup Characteristic And Warning Levels; Maximum Continuous Overload Current; Time Constant Τ - Siemens 7UT51 Instruction Manual

9
Thermal Overload Protection (49-1, 49-2)
9.2 Normal Operational
Status
The thermal overload elements (49-1, 49-2) can be
Non-Existent/Disabled, or a choice is made as to
which side (or winding) is to be monitored. A common
practice is to monitor the lowest rated winding. The
choices are made in addresses 7824 and 7825.
7824 49 Therml1
7825 49 Therml2
Existence and monitored winding (or side) of each thermal
overload protection element (49
Option Description
- -
Non Existent/ 49 1 (or 49
DISABLED (default).
-
REFERENCE 49 1 (or 49
SIDE 1 Winding 1 (or Side 1) of the protected
object.
-
REFERENCE 49 1 (or 49
SIDE 2 winding 2 (or Side 2) of the protected
object.
-
REFERENCE 49 1 (or 49
SIDE 3 winding 3 (or Side 3) of the protected object
(7UT513 only).
-
VIRTUAL 49 1 (or 49
OBJECT a separate, object (only available when a
7UT513 is protecting a two
Once a thermal overload element is referenced to a
side , it can be configured. Its normal status is set in
Address 2401 (for the 49-1 element) or 2501 (for the
49-2 element).
2401 49Therml1
2501 49Therml2
Normal operational status of each thermal overload
- -
element (49 1 or 49 2).
Option Description
-
ON 49 1 (or 49
-
OFF 49 1 (or 49
-
BLOCK 49 1 (or 49
TRIPPING trip contacts and signal contacts will not
respond to this 49 element's trip events.
-
ALARM 49 1 (or 49
ONLY trip and signal contacts operate only for this
49 element's alarm events.
108
- -
1 and 49 2).
-
2) element does not exist
-
2) element exists and monitors
-
2) element exists and monitors
-
2) element exists and monitors
-
2) element exists and monitors
-
sided object).
-
2) element is active (default).
-
2) element is inactive.
-
2) element is active except that
-
2) element is active except that
9.3 Pickup Characteristic
and Warning Levels
9.3.1 Maximum Continuous
Overload Current
The maximum allowed continuous overload current is
specified in Address 2402 (or 2502) as a multiple or
fraction of the rated nominal current of the protected
object.
-
2402 K fctr 1
-
2502 K fctr 2
Ratio of maximum continuous thermal
overload current to rated current: I
–
Range: 0.10 4.00 (unitless)
Default: 1.10
From the manufacturer of the protected object, obtain
the protected object's maximum continuous thermal
overload current ( I ) and rated nominal current ( I
max
then calculate the "k factor" using the following
equation:
k
If the manufacturer's data for I
typical value is 1.1, which would require the load
current to exceed 110% of the rated nominal current
before a 49 pickup could occur.
Time Constant τ τ τ τ
9.3.2
Because the appropriate time-until-pickup depends on
a thermal time constant, τ τ τ τ , which is related to the
maximum current the protected object can tolerate for
a short duration (often called the "1 second current").
The unit of τ τ τ τ is minutes . Consult the documentation of
the protected object to obtain the duration and current
of an allowed overload, then calculate τ τ τ τ using the
following equation:
τ
=
allowed duration in minutes
7UT51 v3
/ I
MAX N
I
max
--------- -
=
I
n
is not available, a
max
2
⎛ short-term current ⎞
×
--------------------------------------------
⎝ ⎠
continuous current
PRIM-2330C
),
n
(9.3)
(9.4)