0 5 . PR OT EC T I O N F U N C T I O N S 41
M10x simulates thermal conditions in the motor
for all operating modes (running or stopped).
This permits maximum utilization of an
installation and assures safe protection of the
motor. Thermal overload protection simulation
accounts for the temperature rise of both the
stator winding and the iron mass of the motor. It
gives thorough consideration of the effect of
motor overheating due to three-phase unbalance
during the simulation calculation of motor
thermal overload.
There are two thermal models supported by
M10x: standard and Eex e. The standard model
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32 Principle picture of motor thermal simulation
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33 Trip curve from cold condition
makes use of parameters trip class t6 in thermal
overload calculation. The protection of explosion
proof three-phase motors with type of protection
‘increased safety’ EEx e is done with two special
parameters, the Ia/In ratio (stall/nominal current
ratio) and te time.
The following diagram offers the characteristic
curve of overload protection, in which the
characteristics are adjusted by changing t6 (trip
time for current IL max=6xIn from the cold state).
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