Application Notes C-11
[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 will cause the motor thermal overload to trip.
The effective overload factor is a combination of [Motor OL Hertz] and
[Motor OL Factor].
Overspeed Limit is a user programmable value that allows operation at
maximum speed, but also provides an “overspeed band” that will allow a
speed regulator such as encoder feedback or slip compensation to
increase the output frequency above maximum speed in order to
maintain maximum motor speed.
The figure below illustrates a typical Custom V/Hz profile. Minimum
Speed is entered in Hertz and determines the lower speed reference limit
during normal operation. Maximum Speed is entered in Hertz and
determines the upper speed reference limit. The two “Speed” parameters
only limit the speed reference and not the output frequency.
The actual output frequency at maximum speed reference is the sum of
the speed reference plus “speed adder” components from functions such
as slip compensation.
The Overspeed Limit is entered in Hertz and added to Maximum Speed
and the sum of the two (Speed Limit) limit the output frequency. This
sum (Speed Limit) must is compared to Maximum Frequency and an
alarm is initiated which prevents operation if the Speed Limit exceeds
Maximum Frequency.
Changing Overload Factor
0102030405060708090100
% of Base Speed
Continuous Rating
OL % = 1.20
OL % = 1.00
OL % = 0.80
0
20
40
60
80
100
120
140
Overspeed
To Next Page
Loading...
Need help?
General
