Siemens A1 User Manual
International English
Selecting a Drive
MICROMASTER Applications Handbook
13
Torque
Speed ( X 50/60)
0
0.5
1.0
1.2
1.5
Possible limited
operation due to
motor cooling
Short term overload capability
(60 seconds)
Continuous operating area
100%
150%
Figure 3-4
Operating Capabilities of Motor/Inverter Combinations
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 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.
operating speed (i.e. up to 6000 or 7200 rpm) of a two-pole motor because of
bearing limitations. However, because the 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.
However, if a motor is connected as a low voltage motor (delta) 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. The correct voltage/frequency curve may be
defined by setting the appropriate motor voltage (e.g. 400 V) and frequency
(87 Hz).
higher voltage inverter, full torque may be obtained up to 1.7 times base frequency
if the inverter is correctly set up. The correct voltage/frequency curve may be
defined by setting the appropriate motor voltage (e.g. 400 V) and frequency
(87 Hz).
3.4 Load
Considerations
The inverter and motor requirements are determined by the speed range and
torque requirements of the load. The relationship between Speed and Torque is
different for different loads. Many loads can be considered to be Constant Torque
loads. That is, the torque remains the same over the operating speed range.
Typical constant torque loads are conveyors, compressors and positive
displacement pumps. See Figure 3-5
torque requirements of the load. The relationship between Speed and Torque is
different for different loads. Many loads can be considered to be Constant Torque
loads. That is, the torque remains the same over the operating speed range.
Typical constant torque loads are conveyors, compressors and positive
displacement pumps. See Figure 3-5
Torque
Speed
Extruder, Mixer
Pump, Fan
Conveyor, Compressor