Siemens A1 Manuel D’Utilisation
International English
Selecting a Drive
MICROMASTER Applications Handbook
15
3.4.2 Other
Loads.
Many other loads have non-linear or varying torque relationships. The torque
requirement of the load should be understood before the inverter and motor is
selected.
requirement of the load should be understood before the inverter and motor is
selected.
By comparing the load/speed requirement with the motor capability, the correct
motor can be selected. Remember a different pole pair arrangement may give a
better match to the load needs.
motor can be selected. Remember a different pole pair arrangement may give a
better match to the load needs.
Starting torque may need special consideration. If a high starting torque is
required this must be considered during rating.
required this must be considered during rating.
Torque
Speed ( X 50/60)
0
0.5
1.0
1.2
1.5
Continuous operation possible
100%
150%
Short term (e.g. starting)
operation possible
Load
Characteristic
Figure 3-7
Matching the load to the Motor/Inverter Capabilities
3.5
Acceleration and Braking requirements
If the load has high inertia and there is a requirement for fast acceleration or
braking, the load due to the inertia must be considered.
braking, the load due to the inertia must be considered.
During acceleration, additional torque will be needed. The total torque needed will
be the sum of the steady state torque and this additional torque. Details of these
calculations are described in Appendix B.
be the sum of the steady state torque and this additional torque. Details of these
calculations are described in Appendix B.
During braking, the inertial energy of the load must be dissipated. If a mechanical
brake is used this is no problem, providing the inverter is disabled during brake
operation. If the motor is decelerated by reducing the inverter output frequency,
the energy from the load will be returned to the inverter. Other options such as DC
braking and Compound braking will minimize regeneration to the inverter, but in
this case the energy will be dissipated in the motor windings. Braking methods and
options are described in detail in section 8.2.
brake is used this is no problem, providing the inverter is disabled during brake
operation. If the motor is decelerated by reducing the inverter output frequency,
the energy from the load will be returned to the inverter. Other options such as DC
braking and Compound braking will minimize regeneration to the inverter, but in
this case the energy will be dissipated in the motor windings. Braking methods and
options are described in detail in section 8.2.