impact 1336 drive faults

[skiier]

Have recurring faults from AB 1336 impact drives.
The faults are occurring on two diferent machines.
One machine has 2 drives and the other has 3.
These machines are enviromental test cells which mostly test automotive parts.
The loads on the drives are very light usually but the test durations average probably 50 to 200hrs per test.
These machines are about 15 yrs old but have only recently begun to have problems with faults.
The drives are also set to ramp from one speed to another whenever a speed change occurs.
Some general info;
The faults tend tocome randomly and have no set pattern or fault type. For example; I have recorded from the drives (via the HMI interface) an "overload", "overvoltage", and "HW fault".

The load is very light on these drives and "overhauling" is not a problem I do not think?

Both machines arw connected to the same distribution bus.

I think , and help me out on this point if anyone can , the combination of age and a noisy distribution bus is tending to cause individual drive DC bus voltage swings and hence faults.
Capacitors only last so long and I am thinking that maybe this could be the problem.

Now I know there can be a million questions regarding more info about this post but pls be reasonable and do not split hairs over the most trivial details. I wish to hear from people who have experience with three phase voltage problems and particularly those who have reviewed with multiple drives.
These machines are well maintained. The motors and bearings and belts are routinely checked.
The faults are occuring on five impact 1336 drives that are running and ramping simultaneously and they are connected to the same 600v three phase bus.
Also this equipment is located in a plant that has a lot of industrial machinery and a very large main service. Equipment such as other large vfds, welders, and other inductive loads are all part of the noise in this system and every year it seems more and more noisy equipment is added to the plant.
Like I stated before could the combination of 600v distribution bus voltage swings and noise cause faults with older drives?
Anyone?

 

[ScottyUK]

I think you could be on to the problem with capacitor aging. It may be slightly more subtle in that the main bus capacitors may not be at fault, but the control supply. I can't remember if the 1336 has a separate converter for the control bus: gut feeling says yes but it's a while since I opened one up.

A quick & dirty test if the main reservoir caps are on their way out would be to install a large external capacitor wired direct to the DC bus and see if things improve. If the problem is on the control supply then it probably won't help much. Keep the connections short and run close them to each other.

 

[ozmosis]

I would agree with Scotty. The 1336 impact is quite an old series and once the DC Bus caps start drying out, you will get spurious trips etc. your drive will be more susceptible to 'noise' on the network. Light loads mean a higher DC bus voltage and additional distortion will only push the drive to an over-voltage condition.

 

[jraef]

In addition, the 1336 used an SCR based front-end converter (instead of a DC bus charging resistor circuit) and over time, the firing board for that might be starting to fail, ie pulse transformers etc.

Just so you know, Rockwell (my employer) has a lowered cost upgrade/replacement program for 1336 drives in effect, but only for a limited time since announcing the cessation of support for it last year. You may want to take advantage of the upgrade opportunity. Spare parts are NO LONGER AVAILABLE for the 1336.

"Will work for (the memory of) salami"

 

[Drivesrock]

I would tend to agree with capacitor aging. I found this text:

The Effects of End of Life of DC Link Capacitors

Manufacturers of capacitors usually define “end of life” as that point when the ESR (Effective Series Resistance) of the capacitor doubles from its original ESR value. This does not mean that the capacitor stops working, blows up or dies. In fact, the capacitor will continue to behave as a capacitor but with degraded performance.
The effect of this on the drive will generally be an increase in the peak to peak ripple voltage on the DC link. This may or may not be significant depending on the application and other factors.
The increased ripple will also lead to increased ripple current which in turn will create more heating effect in the capacitor. This increased heating will further degrade the performance.

____________

AB will have selected capacitors with an expected lifetime and this is heavily dependent on a number of factors which will increase or shorten the expected lifetime. Temperature could be the most critical and I have been advised that each change in 10 degrees C up or down will halve or double the lifetime. Also, if the supply voltage is lower than rated or the drive does not run at FLC then the life will be increased.

One solution may be to replace the capacitors.

 

[ozmosis]

Drivesrock
It is not just the 'obvious' DC link capacitors that degrade over time but also capacitors that are mounted on the control/power boards. These are not as easy to replace and the cost compared to a new one can be quite prohibitive. (especially if, as with most companies, offer incentives to replace old for new)

 

[jraef]

That was the basis of my comment on the SCR firing boards. The pulse transformers (I should have said pulse generators) used to gate the SCRs on at the right time are also dependent on capacitors. As those age, you get more misfires and with that, voltage spikes on the unfiltered DC side of the rectifier. Combined with a decreased DC bus capacitance to help take care of it, you can get OV faults. Also, deficient bus capacitance starts a ringing interaction of the ripple from the rectifier and the ripple caused by firing the IGBTs that can cause severe DC bus voltage spikes. That can stress the IGBTs as well and a few misfires on those babies means the instant demise of the VFD.

"Will work for (the memory of) salami"

 

[JadeYork]

Yes, you are on the right track with the capacitators weakening. This will cause all sorts of faults, especially in a unit that has been continuously ran for 15 years without a recondition.

I have also seen problems with power quality affecting the operation of VFD's. You can install a line reactor/filter to clean up the power going to your machine. This will works as long as you are not completely dropping a phase or two.I found a great resource on servo components here.