VFD overvoltage fault ?
VFD overvoltage fault ?
(OP)
Hello,
I have (2) vfd's controlling 2 motors(conveyors) with a input voltage of 460 volts in real life I measure 494 volts at the input. The drive manufacturer says voltage input in good for +10%. 460*1.10=506
But over the past 2 weeks both drive's have faulted on a overvoltage fault numerous times.The fault has occured when the drive is running at a constant speed. I do not have a line reactors or chokes installed.
Both of the drives, motors are new . In addition to the new conveyor motors at the other end of the plant are 2 new 1000HP 4160 volt compressors DOL starting. We are going to monitor the voltage for spikes etc.. later this week.But while I wait any suggestions?
I have (2) vfd's controlling 2 motors(conveyors) with a input voltage of 460 volts in real life I measure 494 volts at the input. The drive manufacturer says voltage input in good for +10%. 460*1.10=506
But over the past 2 weeks both drive's have faulted on a overvoltage fault numerous times.The fault has occured when the drive is running at a constant speed. I do not have a line reactors or chokes installed.
Both of the drives, motors are new . In addition to the new conveyor motors at the other end of the plant are 2 new 1000HP 4160 volt compressors DOL starting. We are going to monitor the voltage for spikes etc.. later this week.But while I wait any suggestions?





RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
Nothing much more to add to what jraef has mentioned other than to measure (or monitor via a parameter)the DC link voltage rather than just the AC input.
Your steady state DC link voltage will be 690~710Vdc on this AC line voltage leaving little margin for the other effects as jraef describes.
The +/-10% mentioned by the VFD manufacturer will normally be for short durations rather than continuous duty. Most VFD's have their power devices (rectifiers, transistors) rated for the nominal DC voltage based on the AC supply voltage range specified. Some drives show a voltage range of 380~500Vac and this means the power devices are of a higher rating.
So if your drive has a nominal rating of 460Vac then you really are pushing the boundry by connecting to 494Vac as a nominal as this will not take into consideration any peaks.
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD overvoltage fault ?
Since late January
RE: VFD overvoltage fault ?
My last job (this week-end) was for them. It is a long standing relation.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD overvoltage fault ?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: VFD overvoltage fault ?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD overvoltage fault ?
and Gunnar, I hope you mean "general dogsbody" rather than the other meaning I've heard in the beer halls of Hamburg...
RE: VFD overvoltage fault ?
Not that it is from Roman time. But nearly...
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD overvoltage fault ?
I would like to lower transformer tap ahead of vfd's but that involves shutting down half the plant and that is not an option for about 8 weeks, So if anyone is still interested I might have more info at a later date.
Non Semper Erit Aestas.
RE: VFD overvoltage fault ?
always interested in feedback.
RE: VFD overvoltage fault ?
At the risk of embarrassment, what brand of VFD are they? There are a few out there which are really 415V designs that, unfortunately, some engineer was tasked with upgrading to handle "460V motors in the US", but did so without having investigated the fact that 460V is a utilization voltage, based upon a 480V distribution system. We have that discussion in this forum from time to time; a lot of people not from North America have a difficult time with that concept. I'm curious to know who made that design error.
RE: VFD overvoltage fault ?
The +10% should still be the operating range and the DB resistor operation and trip points should both be above that level. So, the drive should not be tripping if the input voltage reaches 506V. It should have to go another 5% to 10% over 506V to trip.
RE: VFD overvoltage fault ?
I agree, the drive shouldn't trip within the +10% range of nominal but I was referring to continuous operation in the +10% range. This should be avoided as it will impact on the lifetime of the components within the drive and also limit any tolerance between the nominal DC link voltage and any AC surge or regenerated DC back onto the link.
If the drive nmark has is indicating 460Vac+10% then it is because lower voltage rated components are used compared to drives stating 480Vac or 500Vac +10%.
A typical trip limit of a "400Vac" drive will be 810~820Vdc and this is obviously beyond the +10% voltage range of the 460/480 or 500Vac nominal input.
RE: VFD overvoltage fault ?
The drive does not have a dynamic brake resistor.
It is controlled via a analog input but it consist of a HMI with a setpoint screen and the operator has to manually enter a speed as a percentage to increase or decrease and I am positive multiple overvoltage faults occured without operator changing speed.
The drive does not have a dynamic brake resistor.
From the drive I am able to get D.C.bus voltage and today it was running pretty close to 700v.
The input was at 500volts ac today.
And the drive is rated at 460v +10%, -15%. The manual says that it faults on a dc bus voltage exceeding 820.So far there has only been a voltage dip in the line momentarily -40 volt but no more faults.
RE: VFD overvoltage fault ?
Is there commanded conveyor speed changes or do they just start up, get to speed, and sit there all day long, faulting occasionally?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: VFD overvoltage fault ?
New information I have learned today is another drive controlling a fan (different manufacturer) has smoked.
RE: VFD overvoltage fault ?
they will be turned off and on while I am there.
RE: VFD overvoltage fault ?
Monitoring the DC bus on the drive display is ok but will not be fast enough to capture transients or spikes on the network. The spikes will not need to be too big wither if the AC is 500V. you will need a scope on the DC link to capture what is happening on the DC link when it trips.
Are the motors driving the gearboxes via belts? sometimes if you get slackness in belts the slip can cause an OV trip if the DC link is already high.
RE: VFD overvoltage fault ?
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VFD overvoltage fault ?
In view of that, it seems to me that two possibilities exist. One would be to drop the incoming voltage either by transformer or by adding at least 5% reactance. The second would be to change the drive to one build to international voltages which typically are 380-10% to 500+10%. These are much more tolerant of voltage variations than drives built to 460V +/-10% or even 15%
RE: VFD overvoltage fault ?
In all the years I have used those "name sounds similar to Yamaha" drives (if I'm interpreting that correctly), for some reason I never noticed that their input voltage specs are 380 - 460V +10%, but I just checked and they are! Wow, the details we can miss sometimes when we are blinded by technology I guess. I cut my drive teeth on that brand 20+ years ago, but have never had that problem. Even as a competitor today I still have respect for their products. Was I just lucky all those years?
RE: VFD overvoltage fault ?
I would still have a DB resistor in this application. It should not have to be very large because you should just need it to dump some energy when any temporary over-voltages appear on the buss.
You have never answered if the conveyor can drive the motor? The drive may have that decel feature but it likely will not allow the motor to run over 60hz. So, if the conveyor drives the motor over 60hz the drive will hold the frequency there and trip.
Another thing, saying your operators are not changing the frequency doesn't mean there isn't a problem with the analog circuit changing itself.
RE: VFD overvoltage fault ?
Seems unlikely here but, absent anything more obvious, it wouldn't hurt to check. Of course, if running open loop scalar V/Hz, that wouldn't be a possible cause.
RE: VFD overvoltage fault ?
I had that problem on roll handling conveyors at a paper mill. They used vacuum grapplers to handle the rolls, which took 2 x 400HP vacuum pumps. When they cycled on and off while the paper rolls were moving, the conveyor drives would trip on OV. We just disabled the stall prevention, I don't really like that feature much anyway. It's one of those things that tends to create more problems than it solves.
RE: VFD overvoltage fault ?
The line feeding the drive is seeing peeks of 690v to 710v. But at sometime in the wee hours last night 1 drive faulted twice on OL.After investigating wiring methods which are not up to par looking at installing load reactors between drive and motor.Will try and go about upgrading wiring also( having motor wires installed in own conduit instead of PVC conduit with multiple motors).Half the length is in pvc the other half is metallic wireway with everything but the kitchen sink in it.Motor wire lengths are less than 150 feet from drives.
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
I guess we can stop asking nmark about overriding. He ain't gonna tell us....
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
That's good, and removes a likely cause of your over-voltage errors.
Thanks nmark.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: VFD overvoltage fault ?
What I mean by that is, your conveyor is undoubtedly moving a load (otherwise, why have it?). That load represents a mass and we all know that a mass in motion wants to stay in motion. So your VFD is running the conveyor at say, 40Hz which represents 80FPM just to keep it simple. Suddenly the voltage drops and the stall prevention feature changes the VFD output speed reference to 25Hz, without a change in your external speed command reference. The mass on the conveyor is still moving at 80FPM and even though the speed is decaying, will take a certain amount of time to slow down to where the VFD speed is telling it to be. During that time, the mass on the conveyor is "pulling" the conveyor belt along with it as the speed decays, spinning the motor at a speed greater than the frequency output of the VFD. So it becomes an external driving force on the motor shaft spinning the motor at super-synchronous speed. All the while, the VFD output is keeping the windings excited. AC motor + excitation current + external driving force at super-synchronous speed = AC induction generator!
I still think you should try just disabling that stall prevention feature. That's why I don't like it. As itsmoked's question points out, it seems almost counterintuitive to do it this way. But that feature is intended to be used primarily when power constrains dictate that you CANNOT increase current as the motor begins to slip more, so it pulls back the speed command in an attempt to decrease the load on the motor. That works on some types of loads, but NOT inertia loads like a conveyor can be.
OK, I'm done. I wanted to be clear about what I have experienced but I could very well be all wet here anyway, so no more soap box. I promise...
RE: VFD overvoltage fault ?
So anti-stall should really be called the reduce-speed-to-match available-voltage feature.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: VFD overvoltage fault ?
RE: VFD overvoltage fault ?
What I was referring to is that if you set the maximum frequency to 60hz then this is usually a hard fixed limit. If the motor is forced into generating past 60hz the drive needs to have the capability of getting rid of the regen energy or it will trip. The drive will not allow the frequency above 60hz to protect itself from the trip.
Now, in this case, the conveyors are not supposed to be able to drive the motors so it likely does not apply. But, it can apply in some applications (pump jack).
So, it would seem we have a case of too much supply voltage.
nmark - The reactor needs to be between the source and the VFD. I still don't like this solution because the reactor has little voltage drop at low load or when the VFD is off so you'll likely still get trips at those times. The solution is that you need to lower your plant voltage. If the voltage is rising on Sundays you need to see if the utility will do something about it.
Now, having said that, I have seen a VFD trip on overvoltage due to a crappy job on the VFD to motor wiring. I believe there was ringing on the buss that was affecting the buss voltage sensing circuit. When it did happen the drive was tripping constantly though which doesn't seem to be what's happening in your case. I really think it was just luck the drive did not fail in that case I saw.
RE: VFD overvoltage fault ?
This parameter is the reference for the drive protective features such as overvoltage, brake resistor turn-on, stall prevention etc..
(This is right out of the manual for one of the drive series of a company that has the same first and last letters mentioned above)
RE: VFD overvoltage fault ?
Currently the stall parameter is disabled and the input voltage parameter is set to 500volts.
So far only 1 fault on overload 3rd shift on Wednesday and no faults over the weekend.
RE: VFD overvoltage fault ?