Multiple inverter failures

[JonAW]

Hi guys

I'm really ****** off at the moment. The company I work for got a contract to supply and fit the electrical control panel and wiring to motors etc of a waste recycling plant. We have done about 50 of these plants, maybe more, with the stipulation that we bear no responsibility for the electrical supply to our control panel, that lies with the customer. We have had no faults in the past.

This contract required a slightly larger panel than anything we have done before but not by much. It consists of a large PLC controlling about 30 motor starters and 10 variable speed drives (inverters). Plus a few other bits and pieces. Each VSD has its own input reactor (choke). The supply is from a 550kva generator, under full load our plant only draws around 120kva. (there is a terrible power factor of 0.6 so the apparent power used is only 80kw.)

Basically what is happening is that every day or so a vsd fails, always at the input side ie. the dc link is completely wiped out. We have tried different generators with varying degrees of success. With one generator we had no failures for 2 weeks but then the generator itself failed. We put a power analyser on the panel and see very little voltage fluctuation, about 5volts as the plant comes on and off load. We have measured harmonics with a result that we have 2.5% deviation on the voltage and 3% deviation on the current. Frequency could not be more stable at 49.9hz. Nothing else has failed on the plant except a 230vac/24vdc psu which failed this morning.

We tried changing the input chokes to output chokes to see if that would make any difference but we are still having failures. There has also been a power quality expert on site and he can find no fault with the supply and no fault with our installation. I know the supply has nothing to do with us but we have to help in finding a solution as we are replacing the vsd's until a conclusion has been found. Plus I have now been onsite for nearly 4 weeks incase there is a failure so that I can fix it as quick as possible. The thing is I am fixing the symptoms not the problem.

Can anybody offer any help or advice, we have completely run out of ideas and the company that bought this plant is losing money hand over fist as the downtime spent in solving different situations is crazy.

thanks

Jonny

 

[Griffin]

Hi,

Is it the same inverter that fails??
What manufacturer is it i.e Siemens, Mitsubishi.
Most modern types of inverters trip (with a fault code) if there is a problem with either supply or load.
What about the protective device for the inverter does this trip? what is it

A couple of years ago we had multiple failures of siemens inverters (90 kw) at a large manufacturing plant too.

I can understand how frustrating it is

Regards

G

 

[JonAW]

There are a number of inverters which trip more regularly than others but all of the vsd's have faulted at some point. This is not a normal trip. We have had an inspection done on some of the drives and were told that the DC link on the input side has completely failed. There are no warning trips just a huge bang like a thunder strike and the drive dies. Each drive is protected by its own manual starter which always activates but it is not quick enough to protect it. The failure could only have happened with a large voltage surge more than double of what the drive is capable of handling. The largest drive we are using is a 5.5kw. All the drives are manufactured by WEG. We are using a power logger to inspect the supply, but in almost 3 weeks have found nothing. There is not even a voltage surge at the time when a drive dies. Very very frustrating!!

 

[djandyryan]

Does any one here know what an OCL error is on a KASUGA inverter?

 

[Steve D]

All my experience is of Mitsubishi inverters, not KASUGA, but I would guess an OCL error code may be overcurrent.

 

[ericks]

Hi Jonny,
I have quite a bit of exp. on WEG inverters. Need some more info though:
1) What supply to the weg, single or three phase?
2) What is the application?
3) You say they trip often, what is the error code/codes?
4) Do the same one fail or is it random one's?
5) Why do you have a manual starter fitted to the drive???
6) How often is power switched on and off to the drive ???

If you give me a description of the application and the model of the drive and above i can advise you more.

Greetings
Erick