Lenze AC Tech M3103S Installation & Operation Manual page 17

CONSTANT TORQUE
150
130
110
90
70
50
30
10
6 .1 .1 VARIABLE TORQUE VS . CONSTANT TORQUE
Variable frequency drives, and the loads they are applied to, can generally be divided
into two groups: constant torque and variable torque . Constant torque loads include:
vibrating conveyors, punch presses, rock crushers, machine tools, and just about every
other application that is not considered variable torque . Variable torque loads include
centrifugal pumps and fans, which make up the majority of HVAC applications .
Variable torque loads are governed by the affinity laws, which define the relationships
between speed, flow, torque and horsepower . The diagram below illustrates these
relationships:
100%
75%
50%
25%
0%
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TORQUE
20 40
FREQUENCY (Hz)
0%
25%
CONSTANT HP
HORSEPOWER
60 80
75%
50%
% SPEED
M301L
100 120
100%
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