P46 Motor Overload Hot/Cold Ratio PFN 16
LED Display LCD Display
Range 0 – 99% (Default 60%)
Description The Motor Overload Hot/Cold Ratio parameter defines the steady state overload content (OL
ss
) that is reached
when the motor is running with a current less than full load current (FLA) * Service Factor (SF). This
provides for accurate motor overload protection during a “warm” start.
The steady state overload content is calculated by the following formula.
The rise or fall time for the overload to reach this steady state is defined by the Motor Overload Cooling Time
parameter.
The default value of 60% for Motor Overload Hot/Cold Ratio parameter is typical for most motors. A more
accurate value can be derived from the hot and cold locked rotor times that are available from most motor
manufacturers using the following formula.
z NOTE: Consult motor manufacturer data to determine the correct motor overload settings.
z NOTE: During a warm start the starter would be Class 10, and if it's a cold start, the starter would be a
class 25.
See Also Motor Running Overload Class (P3 / QST 03) parameter on page 76.
Independent Starting/Running Overload (P44 / PFN 13) parameter on page 106.
Motor Starting Overload Class (P45 / PFN 14) parameter on page 107.
Motor Overload Cooling Time (P47 / PFN 17) parameter on page 109.
Relay Output Configuration (P52-54 / I/O 05-07) parameters on page 112.
Theory of Operation section 7.1.6, Hot/Cold Motor Overload Compensation on page 135.
Theory of Operation section 7.1.4, Current Imbalance/Negative Sequence Current Compensation on page 134.
108
6 - PARAMETER DESCRIPTION
100%x
Time Rotor LockedColdMax
Time Rotor ckedMax Hot Lo
1 Ratio H/COL
÷
ø
ö
ç
è
æ
-=
Factor DerateImbalanceCurrent
1
FLA
Current
Ratio H/COLOLss ´´=
PFN: OL H/C Ratio
16 60 %
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