Siemens MICROMASTER Eco Reference Manual page 25

ECO REFERENCE MANUAL
High speed operation of standard motors is
usually limited to twice the normal operating
speed (i.e. up to 6000 or 7200 rpm) of a two pole
motor because of bearing limitations. However,
because the motor magnetic flux level will reduce
above base speed (because the output voltage is
limited to approximately the input voltage) the
maximum torque will also fall in inverse
proportion to the speed above base speed.
It is not usually possible to operate a fan or pump
motor over its base speed since the torque
(current) requirement will increase proportionally
to the square of the speed.
Torque
150%
100%
0
Possible limited operation due to motor cooling
Continuous operating area
0.5 1.0
However, if a motor is connected as a low voltage
motor (delta connected motor windings) and
operated on a higher voltage inverter, full torque
may be obtained up to 1.7 times base frequency
if the inverter is correctly set up. Obtain the
correct voltage/frequency curve by setting the
motor parameters as follows:
P081= 87
P084= 400 Hz (or to suit supply)
1.2 1.5
Short term overload
capability (60 secs)
(MICROMASTER Eco)
Speed (X 50/60)
8-7
SC