I have a mcp where I keep getting f5 faults on start ups. It only happens in the early morning hours when I'm not there so the other guy just resets them until they run and then it is fine the rest of the day. This does not happen to all of them just 4 out of about 7. He wants to replace them when they do this because the problem will go away when he puts a new one in place. He says they are just wearing out. I called the AB drive tech line and was told that they don't wear out and there is a power problem or it will not f5. I think DC bus voltage trip is 810v and line trip is around 550. I told the tech guy I never see a high bus or line voltage and he responded I might not ever see it because it happens to quick for a meter. He said to install line reactors. He also said the power company switches when the demand is increased to a higer demand and they have to switch on there side. I'm not sure what he was saying so any info on this will help. So the question is this does anyone know if these vfd's can wear out to throw false faults? I would think that the checkism when the drive checks its self would indicated a problem with the drive.
allen Bradley vfd's
- Thread starter Timboe
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hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
While everything wears out, electronics just does it in a different way then something mechanically.
The F 5 fault is incoming supply over voltage or DC buss over voltage, here is what I could find for you for a 1336 drive which we use quite a few of at work on AB's support web site:
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
I find it strange it is happening on start ups but if it only happens in the early morning hours then I would suspect your utility might have transformers tapped to high because of a voltage drop problem and while during the day when more power is used the voltage stays low, but in the middle of the night the line voltage goes up as loads are turned off, my first thing I would do is get someone who knows how to do a long term power condition study by putting a PQ recorder on your service and or the incoming to the MCC with the drive, to find out what the current and voltage is really doing, the utility could have a bad automatic voltage controller (tap changer) that they don't even know about so if it is an incoming voltage problem then you can show the utility the recorded data and have them find the problem on their end.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
When a drive "wears out", it dies, it does not trip on High DC bus voltage.
One thing that can happen though is that if there are capacitors on the line somewhere, an interaction can take place where the line capacitors can 'ring' with the line capacitance and start to drive the voltage up in little mini-surges, a phenomenon called "resonance". Those mini-surges get through the rectifier front end of the drive and build up in the capacitors of the drive DC bus system if the drive is not using it fast enough.
It's hard to see without a scope sometimes, and can be very transient because the utility will only put the capacitors on-line under certain circumstances. Not only that, but they are VERY reluctant to admit to it. I had it happen once to an entire chemical facility way out in the desert south of Las Vegas once. No matter what brand of VFD we installed out there, eventually they ALL started tripping on High DC bus, even when not running. I suspected capacitor resonance with the line, but the utility steadfastly insisted they did not use capacitors to boost their voltage. So I drove down the road and took PICTURES of a huge cap bank near their sub station. When I confronted them with it, they said "Oh, THOSE capacitors..." They eventually gave in and installed reactors down stream of them and the problems went away.
Installing reactors ahead of the drives can have the same effect. The reactor slows down the rise time of the resonant waves, which allows the drive to use the energy instead of having it over charge the DC bus caps.
One thing that can happen though is that if there are capacitors on the line somewhere, an interaction can take place where the line capacitors can 'ring' with the line capacitance and start to drive the voltage up in little mini-surges, a phenomenon called "resonance". Those mini-surges get through the rectifier front end of the drive and build up in the capacitors of the drive DC bus system if the drive is not using it fast enough.
It's hard to see without a scope sometimes, and can be very transient because the utility will only put the capacitors on-line under certain circumstances. Not only that, but they are VERY reluctant to admit to it. I had it happen once to an entire chemical facility way out in the desert south of Las Vegas once. No matter what brand of VFD we installed out there, eventually they ALL started tripping on High DC bus, even when not running. I suspected capacitor resonance with the line, but the utility steadfastly insisted they did not use capacitors to boost their voltage. So I drove down the road and took PICTURES of a huge cap bank near their sub station. When I confronted them with it, they said "Oh, THOSE capacitors..." They eventually gave in and installed reactors down stream of them and the problems went away.
Installing reactors ahead of the drives can have the same effect. The reactor slows down the rise time of the resonant waves, which allows the drive to use the energy instead of having it over charge the DC bus caps.
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mike_kilroy
Senior Member
- Location
- United States
MAX button meter?
MAX button meter?
You probably have a digital meter in house somewhere with a MAX/MIN button on it: If you use the MAX button and watch the incoming voltage you likely would see anything (like spikes or oscillation from capacitors downstream) show up as higher than your 550v. You must check all 3 lines as the higher voltage being rectified can be only on 1 leg and still cause this. We had a customer in Ontario with such a case; their vfd had db regen and when this happened their db resistor would glow orange. If they ran the machine of course the motor used the excess so it was ok. Power company came in and fixed their problem.
MAX button meter?
You probably have a digital meter in house somewhere with a MAX/MIN button on it: If you use the MAX button and watch the incoming voltage you likely would see anything (like spikes or oscillation from capacitors downstream) show up as higher than your 550v. You must check all 3 lines as the higher voltage being rectified can be only on 1 leg and still cause this. We had a customer in Ontario with such a case; their vfd had db regen and when this happened their db resistor would glow orange. If they ran the machine of course the motor used the excess so it was ok. Power company came in and fixed their problem.
wirenut1980
Senior Member
- Location
- Plainfield, IN
Agree with Jraef. It makes sense that the increase in load in the morning with machines coming online causes the utility steady state voltage to drop enough that their capacitors switch in creating a switching transient which can be passed through from the AC to DC conversion. The variability of whether the drive trips out is probably due to where on the voltage waveform the switches close in on the cap bank, or maybe it just did not switch that morning. Line reactors are the solution, usually try 3% and that typically works, if not try 5%.
kwired
Electron manager
- Location
- NE Nebraska
I have seen drives that give a overvoltage fault when there has been a "blink" or other obvious disturbance on incoming voltage.
I would guess the OP's problem is related to something happening on the input voltage side of things whether from POCO or elsewhere in the premises.
I would guess the OP's problem is related to something happening on the input voltage side of things whether from POCO or elsewhere in the premises.
JoeStillman
Senior Member
- Location
- West Chester, PA
I specify auto-restart after voltage faults whenever the drives are not manually started and auto restart is safe to do. The default is typcally no auto-restart and you have to explicitly program that parameter.
jcormack
Member
- Location
- Pennsylvania
Could also be caused by Regen load.
Could also be caused by Regen load.
A DC buss OV can also be caused by the load attempting to regen. On typical drives (ones without an active regen front-end) the DC buss will absorb the regen energy to a point, if it can't handle the energy the voltage rises to a point the drives says "stop". As has been mentioned you can play with the "free-wheel" setting (if the drive has one) that turns the IGBTs off for a moment, but if it is an actual regeneration coming from the load the best way to handle that scenario is to add an external DC buss dynamic braking resistor - most drives today have the 7th IGBT built in to handle this optional add on - if the drive does not, DB resistors with a control built in are readily available. DB's can be added without changing out the drives. Another solution instead of reactors on the front end is an isolation transformer that you tap to provide a lower voltage to the incoming - a 480 volt class drive typically tends to work better on a 460 volt input, as opposed to a 500 volt input.
Could also be caused by Regen load.
A DC buss OV can also be caused by the load attempting to regen. On typical drives (ones without an active regen front-end) the DC buss will absorb the regen energy to a point, if it can't handle the energy the voltage rises to a point the drives says "stop". As has been mentioned you can play with the "free-wheel" setting (if the drive has one) that turns the IGBTs off for a moment, but if it is an actual regeneration coming from the load the best way to handle that scenario is to add an external DC buss dynamic braking resistor - most drives today have the 7th IGBT built in to handle this optional add on - if the drive does not, DB resistors with a control built in are readily available. DB's can be added without changing out the drives. Another solution instead of reactors on the front end is an isolation transformer that you tap to provide a lower voltage to the incoming - a 480 volt class drive typically tends to work better on a 460 volt input, as opposed to a 500 volt input.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
True, but this doen't explan why it only appears to happen at certain times;
If it were a regen problem, it would likely be happening more consistently and throughout the operation day.
We don't know what the machine is though, so maybe there is some sort of procedure they do only in the wee hours (when nobody is looking?) that puts the drive into regen.
Far more likely to be a resonnance issue though in my opinion.
ghostbuster
Senior Member
- Location
- Great White North
It has been our experience ,the utility in our area generally switches the caps on early in the morning (4-7 am.) in anticipation of increase loading on the grid.In some cases ,it is 2 or 3 separate cap switchings to get them all on.You are also right,it very much depends on what part of the voltage waveform they are energized on.And Yes,it causes grief each time for many customers with sensitive equipment.
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