BENSHAW RediStart MX3 Series, User Manual

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See Also Independent Starting/Running Overload parameter (PFN28) on page 105.
Motor Starting Overload Class parameter (PFN29) on page 106.
Motor Overload Hot/Cold Ratio parameter (PFN31) on page 107.
Motor Overload Cooling Time parameter (PFN32) on page 108.
Relay Output Configuration parameter (I/O 10-15) on page 112.
Theory of Operation section 7.1, Solid State Motor Overload Protection on page 138.
Motor Overload Hot/Cold Ratio PFN 31
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
(PFN32) 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.
See Also
Independent Starting/Running Overload parameter (PFN28) on page 105.
Motor Running Overload Class parameter (PFN30) on page 106.
Motor Starting Overload Class parameter (PFN29) on page 106.
Motor Overload Cooling Time parameter (PFN32) on page 108.
Relay Output Configuration parameters (I/O 10-15) on page 112.
Theory of Operation section 7.1.6, Hot/Cold Motor Overload Compensation on page 141.
107
6 - PARAMETER DESCRIPTION
PFN: OL H/C Ratio
31
60 %
Factor Derate Imbalance Current
1
FLA
Current
Ratio H/C OL OL
ss
´ =
100% x
Time Rotor Locked Cold Max
Time Rotor cked Max Hot Lo
1 Ratio H/C OL
÷
ø
ö
ç
è
æ -
=