Lenze DSD - Manual (Page 429)

Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23
429
17 Restrictions of the drive dimensioning
17.7 Saturation effects in the motor at > 200 % Mrated
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17.7 Saturation effects in the motor at > 200 % M
rated
If motors are operated above a rated current of approx. 200 ... 250 %, the torque for synchronous
motors no longer increases proportionally to the current, or in the case of asynchronous motors no
longer follows the equations stored in the DSD.
• This effect is considered in DSD.
• DSD generates a "note" if the value of 400 % is exceeded and indicates that the thermal utilisa-
tion of the motor and inverter and an increased current requirement of the inverter result from
this.
Effect for synchronous machines (SM)
For SM, the ratio of torque to current (k
T
) is an important parameter. However, this ratio is non-lin-
ear at high loads and strong speed variations.
Two different effects occur:
• Saturation of iron parts at high currents.
• Speed-dependent, inexact image of the real motor in the motor management of the inverter.
[17-1] Torque-current ratio by means of the example of MCS synchronous servo motors

Note!
Only occurs with regard to dynamic overcurrents > approx. 200 ... 250 %.