Siemens SINUMERIK 840C - Manual (Page 756)

10 Axis and Spindle Installation 09.95
10.5.4 Curved acceleration characteristic (SW 4 and higher)
10.5.4 Curved acceleration characteristic (SW 4 and higher)
When induction motors are used (spindle operation), allowance must be made for their speed-
dependent acceleration capability in position-controlled operation:
Fig. 1 Torque characteristic of induction motor
TorqueM Constant
torque
Breakdown limit
M = const
Constant
power
M 1/n M 1/(n*n)
Rated speed Speed n
n
n
n
k
n
max
At speeds (n) above rated speed (n
n
), the drive acceleration capability decreases in relation to
the speed. Immediately above rated speed nn, there is a range of "constant power" in which
the torque (and thus also the acceleration capability) drop in proportion to 1/n. When speed n
increases further, there is a range ("breakdown limit") immediately above speed nk in which
the torque decreases in proportion to 1/(n*n).
The required parameters are selected and set in the MSD drive unit.
Fig. 2 Speed characteristic during acceleration (thick line)
Speed
Setpoint
The obtainable linear ramp-up time constants
increase out of proportion for higher speeds
T2 Time
n
n
n
k
T1
10–66 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)