Siemens SIPROTEC 5 7UM85 Manual page 27

For a reduced voltage, the starting current almost reduces linearly. At 80 % of the rated voltage, the maximum
starting current is 0.8 ⋅ I
The current threshold for detecting a motor starting must be bigger than the motor secondary rated current
and must be smaller than the maximum starting current. If no other influencing factors are present (peak
loads), the value for Curr.thres.starting, which is configured in the Motor-state detection function
block, can be an average value as follows:
Set the Curr.thres.starting = 2.1 A.
The Tempr.thres. cold motor parameter is used to set the threshold for the cold motor. If the rotor
temperature exceeds the Tempr.thres. cold motor, the motor is in
in Cold state. The setting value of the Tempr.thres. cold motor parameter depends on the permissible
numbers of the cold and warm starts as follows:
Considering a safety tolerance, Siemens recommends setting the Tempr.thres. cold motor parameter to
40 %.
Step 5: Motor Restart Inhibit
Thermal Replica Rotor Function Block in the Motor Function Group
(_:104) Perm.no. of warm starts = 1
(_:105) Perm.no. of cold starts = 2
(_:106) Factor T-const. at oper. = 5.0
(_:107) Factor T-const. standstill = 10.0
(_:108) Starting time = 8.2 s
(_:109) Equilibrium time = 1.0 min
(_:112) Start.cur./mot.rated cur. = 5.2
Thermal Stage
(_:1) Mode = on
(_:11221:103) Min. restart inhibit time = 6.0 min
Step 6: Determining the K-Factor
Take the maximum permissible current I
Thermal Overload Protection, 3-Phase - Advanced
(_:106) K-factor = 1.1
Step 7: Selecting Overload Protection and Tripping Characteristics
Thermal Overload Protection, 3-Phase - Advanced
(_:101) Threshold current warning = 1.1 ⋅ I
0.88 A
(_:104) Threshold thermal warn. = 90 %
(_:110) Thermal time constant = 150 s
SIPROTEC 5, Additional Information on the Protection of Explosion-Proof Motors with Type of Protection Increased Safety e,
Manual
C53000-H5050-C078-1, Edition 03.2019
= 3.3 A.
starting
as 1.1 times motor rated current I
max, perm.
=
rated,sec
Warm state. Otherwise, the motor is
The permissible number of warm starts
The permissible number of cold starts
The extension factor for the cooling time constant
when the motor is running
The extension factor for the cooling time constant
when the motor is stopped
The maximum permissible starting time of the motor
The time of the standstill state for a motor
The starting current which is a per-unit value with the
motor rated current as reference
The mode of the stage
The minimum duration for the restart-inhibit time
rated, motor
The parameter which is used to describe the limiting
value for the maximum permissible continuous load
The threshold to the maximum permissible contin-
uous current I
max, perm
The threshold to indicate the thermal warning
The thermal time constant
Setting Example
.
27