Overvoltage trip on Siemens VFD

[pittengineer]

I have a siemens MicroMaster 420 VFD. It is a 5hp 480V VFD. Ocasionally the VFD will trip on overvoltage. When looking at the line voltages on the drive we read right around 493V L-L. Should this L-L voltage be enough to drive the DC bus into an overvolatge? I would think this would still be within tolerence.

We think that this drive is only in the overvolage condition when the drive is stopping. We are going to try increasing Decel time as well as look into a brake resistor.

Someone here mentioned however that installing line reactors could help with the 493V and bring it closer to the 480V. Will installing line reactors on this drive help to reduce the voltage by much on the line side of the drive? I always thought these line reactors were primarily for harmonics and surges, but I guess they could present an inpendance and thus drop some of the voltage across them? Are these reactors a possible solution?

 

[itsmoked]

Could be the drive is going bad too. The nervousness has increased to a point of nuisance(paranoia).

Keith Cress
kcress -

http://www.flaminsystems.com

 

[mohamedone]

helo pitt
Inductive loads cause transient voltages when switched off.You must shutt off the power to the vfd before swetching the off the load ,umless it is programmed for that.How did you choose the programming parameters for the vfd.
if the problem persists, I suggest the use of varistors or rc filters as close to the motor as possible.

mohamed

 

[ozmosis]

What is the firmware version of the drive?

 

[amptramp]

Most of the the Powerflex 70 drives come standard with built-in MOV protection and common mode capacitors to provide transient suppression. This may explain why the Powerflex 70 drive is not tripping and may provide a hint to the solution to your problem.

 

[PQ101]

The 493volts line-line voltage reading in normal and well within utility 10% tolerance (based on nominal 480volts). With respect to overvoltage reading, it is possible that the VFD controls may see the voltage fluctuation on incoming voltage, or you may have start-up of some other device that is connected to the same panel that's serving the VFD, or there may be capacitors that switch ON/OFF, causing momentary voltage rise. I recommend that you check for proper system-equipment grounding and check the grounding on 480V-208/120V stepdown transformer serving the load, and most important set Dranetz PowerVisa, or Dranetz 658 (or equal) on you VFD motor terminal to collect data and see exactly what is it that VFD is experiencing or reacting to. Once you have collected data you'll be able to troubleshoot the problem based on factual data, because there are many possibilities.

 

[DickDV]

Since all power networks may experience transients from time to time and from a huge variation of sources, trying to find that source and stop it is generally very time-consuming and often unproductive.

I suggest adding a 5% line reactor and a TVSS between the reactor and the drive. That way, regardless of the source, you've protected the drive and probably stopped the nuisance tripping.

Go with what's simple.

(This is my last post on this thread!)