Basler Electric BE1-11m - Manual (Page 505)

9424200996 Rev L 493
IEC Curve
IEC curves provide the ability to automatically change between two curves based on if the motor is hot or
cold. The hot or cold status is shown on the Motor Status > Thermal Curve metering screen on the front-
panel.
An internal cold-to-hot timer is initiated when the motor is started from a cold state. The timer continues
after the motor is running. The motor is determined as hot when the internal timer exceeds the Running
Cool Time Constant (RCTC) setting and the hot curve shown in Equation 36 is used. If the motor is
stopped before the RCTC setting is exceeded, the motor remains in a cold state and the timer resets at
zero. It is recommended that the IEC Hot Curve Current setting (I
p
) is set no greater than 95% of the
thermal current pickup (S
• SF • FLA).
An internal hot-to-cold timer is initiated when the motor is stopped while in a hot state and the thermal
capacity is less than 10%. The motor is determined as cold when the internal timer exceeds the Stopped
Cool Time Constant (SCTC) setting and the cold curve shown in Equation 37 is used. If the motor is
restarted before the SCTC setting is exceeded the motor remains in a hot state and the timer resets at
zero.
t = τ ∙ ln
I
eq
2 − I
P
2
I
eq
2 − (S ∙ SF ∙ FLA) 2
Equation 36. Hot Curve
t = τ ∙ ln
I
eq
2
I
eq
2 − (S ∙ SF ∙ FLA) 2
Equation 37. Cold Curve
Where:
t = Operating Time
I
eq = Measured Equivalent Motor Current
TD = Time Dial
FLA = Full Load Amperes
SF = Service Factor
S = Overload Scaler
τ = Motor running time constant
I
P
= Specified load current before the overload occurs (IEC Hot Curve Current setting), which
is specified in National Standards, declared by the manufacturer, or calculated from
manufacturer provided thermal curve.
ln = Natural log
BE1-11m Time Curve Characteristics