Basler Electric BE1-11m - Manual (Page 108)

96 9424200996 Rev L
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 5. Hot Curve
t = τ ∙ ln
I
eq
2
I
eq
2 − (S ∙ SF ∙ FLA) 2
Equation 6. 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 = IEC Curve 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
User Curve
This curve is a combination of up to three acceleration curves and one locked rotor curve. The multiple
acceleration curves allow a different curve to be created for up to three different voltage levels for reduced
voltage starting. Voltage levels between those selected for the curves are interpolated between curves.
The locked rotor curve combined with the acceleration curve provides protection for high inertia starts
when the current is close to locked rotor levels for a long duration during acceleration.
When the 49TC element is set in User Curve mode, the Locked Rotor Curve is used when the Locked
Rotor logic input is true. When the Locked Rotor logic input is false, the Overload Curve is used.
Figure 66 shows the Overload Characteristic Curves screen.
Thermal Curve (49TC) Protection BE1-11m