Motor Protection Example
Figure 2-64 illustrates an example of a complete motor protection characteristic. Such characteristic usually
consists of different protection elements, and each element is responsible for special motor malfunctions.
These are:
•
Thermal overload protection: to avoid overheating of the motor due to inadmissible load
•
Load jam protection: to prevent overheating and mechanical damage due to a locked rotor
•
Motor starting protection: protects the motor against prolonged startup procedures and the consequent
thermal overload of the rotor
•
Overcurrent and high-current elements: for motor shutdown due to electrical faults
[motorbelastungsgrenze, 1, en_US]
Figure 2-64
Example of a complete motor protection characteristic
Example:
Motor with the following data:
Nominal voltage
U
Nom
= 10 kV
Nominal current
Ι
Nom
= 436 A
Long-term current rating
Ι
max
= 135 A
Startup duration T
startmax
= 8.5 s
Current transformer
Ι
NomCTprim
/ Ι
NomCTsec
= 500 A / 1 A
The setting for address 4402 Load Jam I> as secondary value is calculated as follows:
Functions
2.8 Motor Protection
160 SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016
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