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Where can I find more information about thee Overmodulation parameter setting in the ATV630 drives?

Published date: 18 April 2019

Issue:
Where can I find more information about thee Overmodulation parameter setting in the ATV630 drives?

Product Line:
ATV630

Environment:
All 

Cause:
Overmodulation 

Resolution:
The PWM (Drive output) is done regarding DC voltage (continuous voltage), but voltage on DC bus include a ripple.
 
So, the drive sees from this ripple a value from DC bus maximum, DC bus average and DC bus Minimum. To regulate the PWM the drive need to define if the available DC voltage is the minimum, the average (VBUS average/rootsquare 2 ), or the maximum (max of drive input voltage) of DC bus ripple.
 
DC bus ripple (which is about 50VDC at full load) could have impact of 35VAC on output voltage vs input drive voltage if voltage output voltage is limited to minimum voltage ripple/rootsquare 2.
 
Depending of the limit (min average or max) the result is different on drive output : if limited to minimum, then the available output voltage will be low regarding drive input voltage, but if limited to maximum, frequency of DC bus ripple (300Hz) will be added to output voltage (and impact on torque)
 
So, OMVA permit to adjust this limit it’s overmodulation activation, it will permit to increase limitation of voltage limitation. The drive changes the PWM modulation rate to increase the max. output voltage.
Overmodulation is to modulate above available voltage (DC bus voltage/rootsquare 2 < output voltage) so reduce the gap between input voltage level and output voltage level, but that could generate flat top on output voltage.
 

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