Lenze MC3000 Series - Manual (Page 17)

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CONSTANT TORQUE CONSTANT HP
TORQUE HORSEPOWER
HORSEPOWER
TORQUE
FREQUENCY (Hz)
TOR
QUE (%)
20 40 60 80 100 120
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:
0%
25%
50%
75%
100%
100% 75% 50% 25% 0%
% SPEED
% T
ORQUE
% HORSEPOWER
% FL
OW