ATV12 OSF

[mk268]

I have 3x ATV12 VSDs that come up with an OSF fault when sitting idle while powered from a generator when another pump starts. 
I know that the voltage is low then high for less than a second when the other pump starts due to the generator compensating. 
Is it possible to increase the tolerance before the OSF fault comes up?

[Bastian_Schmitz · Accepted solution]

I did not see a parameter for this on ATV12. There is an advice in the manual 

On ATV320 there is a Parameter called URES / VRES for this purpose. You find here a FAQ post to this topic. But unfortunately only in german.

[ismailozinan]

Hi

Excessive increase of the DC bus voltage in drives may damage the DC bus capacitors inside the drive. To prevent this risk, drives are equipped with OSF (Over Supply Voltage) protection.

When a frequency converter is supplied by a generator, during sudden or heavy load conditions the generator governor increases the fuel input in order to recover the engine speed. At the same time, the AVR (Automatic Voltage Regulator) attempts to regulate the output voltage, which may result in short-term voltage overshoots. This can cause excessive AC voltage at the drive input and consequently lead to an increase in the DC bus voltage.

As a first measure, it is recommended to increase the drive acceleration ramps and, if possible, avoid starting the motor under load. If the issue persists, the governor and AVR parameters on the generator control unit should be reviewed in accordance with the generator manufacturer’s recommendations.

In VFD applications, it is a common field practice to select the generator with at least twice the required power capacity, depending on the load characteristics. Therefore, it is also advisable to verify the generator sizing criteria.

Best Regards,