Lenze MCH Series - Manual (Page 21)

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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 following diagram illustrates these
relationships.
0%
25%
50%
75%
100%
100% 75% 50% 25% 0%
% SPEED
% T
ORQUE
% HORSEPOWER
% FL
OW