42
Constant Torque Loads.
When the motors output current exceeds 103% of the motors protective
electronic thermal characteristics during the start operation, the Inverters protective (OL1) will
allow operation of the drive for 150% of rated current for 60 seconds before shutting the Inverters
output off.
Variable Torque Loads
(Fans, Pumps...etc.) When the motors output current exceeds 113% of the
motor’s protective electronic thermal characteristics during the start operation, the Inverters
protective (OL1) will allow the drive to operate at 123% for 60 seconds before shutting the
Inverters output off.
Constant Torque Loads:
With a Constant Torque Load, the
torque loading is not a function of
speed. This is a characteristic of
traction drives, conveyors, positive
displacement pumps, etc.
As the speed changes, the load
torque will remain constant and the
horsepower will change linearly with
the speed.
Variable Torque Loads:
With a Variable Torque Load, torque
loading is a function of speed. This
is characteristic of centrifugal
pumps, and certain types of fans
and blowers. As the speed is
increased, typically the torque will
increase with the square of the
speed and the horsepower will
increase with the cube of the speed.
100
50
0
50
100
Torque
Horsepower
Pe
rc
en
l T
o
rqu
e an
d Ho
rse
p
o
w
er
Percenl Speed
+
0
P
er
cen
l T
o
rq
u
c and
H
o
rs
ep
ow
er
Percent Speed
Torque
Horsepower
50
100
12.5
25
100
