Allen-Bradley PowerFlex 70 User Manual page 114

Appendix C Application Notes
114
Operation below 100% current causes the temperature calculation to account for
motor cooling.
Motor Overload Curve
100000
10000
1000
100
10
100 125 150
Full Load Amps (%)
[Motor OL Hertz] defines the frequency where motor overload capacity derate
begins. The motor overload capacity is reduced when operating below [Motor
OL Hertz]. For all settings of [Motor OL Hertz] other than zero, the overload
capacity is reduced to 70% at an output frequency of zero.
Changing Overload Hz
120
100
80
60
40
20
0
0 10 20 30 40 50
% of Base Speed
[Motor NP FLA] is multiplied by [Motor OL Factor] to select the rated current
for the motor thermal overload. This can be used to raise or lower the level of
current that causes the motor thermal overload to trip. The effective overload
factor is a combination of [Motor OL Hertz] and [Motor OL Factor].
Trip Amps = P42 [Motor NP FLA] x P48 [Motor OL Factor]
0.7 x Trip Amps
P47 [Motor OL Hertz]
P1 [Output Freq] (Hz)
The motor overload, if enabled, enables continuous operation at or below the
line. Above the line, the overload trips after a time delay. The further above the
line, the shorter the trip time.
Rockwell Automation Publication 20A-UM001N-EN-P - July 2013
Cold
Hot
175 200 225 250
OL Hz = 10
OL Hz = 25
OL Hz = 50
60 70 80 90 100