Configuring
2.3 Selecting and dimensioning induction motors
1PM6/1PM4 Hollow-Shaft Motors for Main Spindle Drives
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Configuration Manual, PPMS, 04/2008, 6SN1197-0AD23-0BP0
2.3.3
Selecting induction motors
A differentiation must be made between 3 applications when selecting a suitable induction
motor:
Case 1:
The motor essentially operates in continuous duty.
Case 2:
A periodic duty cycle determines how the drive is dimensioned.
Case 3:
A high field weakening range is required.
The objective is to identify characteristic torque and speed operating points, on the basis of
which the motor can be selected depending on the particular application.
Once the application has been defined and specified, the maximum motor torque is
calculated. Generally, the maximum motor torque is required when accelerating. The load
torque and the torque required to accelerate the motor are added.
The maximum motor torque is then verified with the limiting characteristic curves of the
motors.
The following criteria must be taken into account when selecting the motor:
●
The dynamic limits must be adhered to, i.e., all speed-torque points of the relevant load
event must lie below the relevant limiting characteristic curve.
●
The thermal limits must be adhered to, i.e. the rms motor torque at the average motor
speed resulting from the duty cycle must lie below the S1 characteristic curve (continuous
duty). The rms value of the motor current within a duty cycle must be less than the rated
motor current.
●
In the field-weakening range, the permissible motor torque is restricted by the voltage
limit characteristic (stability limit). A margin of 30 % should be observed.
2.3.4
Motor operates continuously
The following motor must be selected: P
N, Motor
≥ P
required
An overload is dimensioned for transient overloads (e.g. when accelerating). The peak
torque must lie below the stability limit.
It must then be verified that the selected motor can supply the necessary output over the
desired speed range. If this is not the case, a larger motor or a different winding variant must
be selected.
