GE M60, Instruction Manual

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CHAPTER 5: SETTINGS GROUPED ELEMENTS
M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 5-203
5
Figure 5-104: Thermal model cooling
HOT/COLD SAFE STALL RATIO
— The motor manufacturer sometimes provides thermal limit information for a hot/cold motor.
The M60 algorithm uses this data if this setting is programmed. The value entered for this setting dictates the level at which
thermal capacity used settles for current that is below the motor service factor times FLA. When the motor is running at a
level that is below this limit, thermal capacity used rises or falls to a value based on I
equivalent
(average three phase RMS
and the selected setting. Thermal capacity used either rises at the fixed rate of 5% per minute or falls as dictated by the
running cool time constant.
Eq. 5-16
where
TCU
end
=
THERMAL CAPACITY USED
if I
equivalent
remains steady state