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Drives for Web Handling

Blogmaster: Clarence Klassen

20

AC Drives are fed by  AC mains and produce an AC power output for the motor. Why then is “DC Bus Over Voltage” one of the most common faults on a drive system?

It turns out that most of the Variable Frequency Drives (VFD) used in web handling convert AC mains to DC using a rectifier. Then the DC voltage is chopped into a Pulse Width Modulated (PWM) AC signal using an inverter.

Common VSD’s use a simple bridge rectifier to create the DC bus voltage. Rectifying 3 phase AC voltage increases the dc voltage by a fixed ratio of 35%. For example, with 460 VAC mains, the dc bus voltage will be 621 volts. This voltage is not regulated and assumes that power is being delivered to a motor.

It turns out that the rectifier is not the only source of power for the DC bus inside the drive system. If the motor acts like a generator, the inverter back feeds power to the DC bus. Capacitors and resistors in the DC circuit can absorb a bit (<10%) of the generated power. If the generated power is too much, the DC volts have to rise.

In all cases, you will find the drive was generating when the DC Over Voltage fault occurred. The situations vary but may include:

-          stopping

-          tension is over-hauling the roller

-          unwind is generating all the time

Sometimes the situation is only a very brief event. For instance, when an accumulator completely empties, the web snaps and may cause the motor of an adjacent roller to generate for only a fraction of a second. This may be enough to create the fault.

Solutions are dynamic braking resistors, common dc bus for multiple drives, and VFD’s specifically engineered for regenerative applications.

Comments

#589 rajesh
Saturday, August 11, 2012 10:47 AM

hi expert sir

In my siemens mm430 drive is continnew show fault f0002 (dc link over voltage)not going fault from reset or other setting .what can i do drive again run.
#590 Clarence Klassen
Sunday, August 12, 2012 8:33 PM
rajesh:
I will need more information to provide an answer.
If the fault is always present, the drive is defective or a parameter is incorrectly set.
If the fault 2 occurs during a deceleration only or when the motor acts as a generator, the discussion above applies.

Clarence Klassen
#659 Ugur
Wednesday, November 14, 2012 5:02 AM
hi,
we have belt conveyor running with 2 VFDs, motors are identical and both 55kW, when conveyor is empty and both motors running one is taking 27A and one is taking around 50A, normally it should be almost same around 30A. And after some time- 7 minutes- the motor which is taking 27A trips on DC bus over voltage.
Can you please advise us regarding this one? we have no braking resistors. Also when we tested motor in solo run both motors were taking around 30A and able to run more than 30minutes without any failure.
#662 Clarence Klassen
Thursday, November 15, 2012 8:49 AM
Ugar:
It would seem from the symptoms that the drive with 50A is over hauling the drive with 27A. Has something changed such as a drive belt?

At any rate the solution would be to go to the drive with 50A and reduce the Top RPM parameter, slowing this drive. Then the loads will become balanced. Alternately, increase the Top RPM parameter on the 27A drive. Whichever drive speed is displayed to the operator should be set to show accurate speed.
#663 ugur
Thursday, November 15, 2012 10:57 AM
First thanks a lot for your kind reply on my question.

in fact we had a belt cut incident and this caused to much damage on mechanical structures which are already repaired. for subject 2 VFDs there is only one setting for speed and it is 50 Hz so before the crash they were running smoothly. I agree with you that the loaded motor is forcing the other one to run as a generator but we are also suspecting that some mechanical tension on the belt causing this problem, may i be correct on my assumption?
Best regards
Ugur
#664 Clarence Klassen
Thursday, November 15, 2012 11:05 AM
Tension alone cannot generate power. The source of the power is one of the motors.

Look harder at the specifications for the drive. There must be a parameter which can adjust the speed setpoint. If you cannot find it, contact me directly with the brand of the VSD.

Clarence
#765 tinkul
Sunday, January 27, 2013 8:07 AM
Dear sir,

I am having an toshiba P& 50HP VFD with an error as Over Voltage during Acceleration. i am thinking that it is a problem with DBRs is it ??????.

or I think it is some over voltage protection IC problem .
#767 Clarence Klassen
Sunday, January 27, 2013 5:25 PM
tinkul:

Overvoltage trips on ac drives happen when a drive is generating. This is during stopping,decelerating or being pulled by another section. We would not expect a drive to experience overvoltage trips during acceleration, when motoring torque is required.

This indicates there may be a problem with Inertia Compensation (IC) on this section or the immediate upstream section.

If the section with the trip does not have enough inertia compensation, it will be pulled by an upstream section. If this is the problem, more inertia compensation is required on this drive.

If the upstream section has too much inertia compensation, it will accelerate more quickly that the line and will pull the section with the trip.

If one section is wrong, you should check inertia computation for each section in the entire line.

To determine where inertia compensation is wrong with web in the line compare speed between the line pacer and each other section while accelerating. There should be no speed error. Another hint is to look for tension variations during speed changes.

Clarence Klassen
#772 John
Monday, February 04, 2013 12:27 PM
I have a customer w/ several drives, of various sizes, in a system of MCCs. The majority of these drives, 27 of 42, control 1HP motors with the others controlling 40-75HP motors. The drives on the 1HP motors are faulting due to DC bus over voltage when the motors they are controlling are not operating.

The vast majority of these motors operate diverters (very similiar to valves) which simply move from one position to another. The faults occur only at night when the entire system is out of operation and no maintenance is being performed. Any thoughts?

John
#773 Clarence Klassen
Monday, February 04, 2013 8:15 PM
John:
I really have no idea. I expect some other part of the plant is producing spikes that raise the volts enough to cause the OV trip.
Every think of shutting them off overnight?

Clarence Klassen
#827 Ripu
Thursday, April 18, 2013 11:29 AM
Hello Mr. Klassen... Our plant have got ACS850 ABB drive which runs 15 motors in scalar mode for driving conveyors.. We have two different sections -plate mill & stackel mill... this drive is located in the stackle mill.. Our problem is that the drive trips in "dc overvoltage" whenever the conveyors in plate-mill run at some load.. The dc voltage in the drive reaches at 800 Vdc whilst the drive is idle.I would really appreciate if you could help me in this situation.
#830 Clarence Klassen
Saturday, April 20, 2013 9:50 AM
I have received more comments on overvoltage trips than any other topic.

I will make another entry on over voltage in the next week. It will discuss some of these problems in general. I am unable to give detailed long distance support on problems around the world.

Clarence
#853 ravikannan
Thursday, May 16, 2013 4:30 AM
we are using ELIN EBG dyno control panel . it is used to control the speed of transient dyno.dyno also act as a generator,thiacings dc voltage again convert in to ac and used for incoming of this panel ,now we are facing a problem of overvoltage in dc link,of converter section, immediately the dyno will be trip.kindly give me reason for this error and solution
#854 Clarence Klassen
Thursday, May 16, 2013 7:33 AM
Dynamometer run in regeneration most of the time. This they are subject to dc bus overvoltage. Did this dyno ever run correctly?

Perhaps someone else has experience with this brand.
Clarence
#947 Davoud sajadi
Tuesday, August 27, 2013 12:38 PM
DC over voltage (3210) fault occurs when we are going to start one of ABB, ACS800-04 frequency convertor. our application is pump and this drive was working for 2 month. I really apprecate if you could to help me to solving it.
#949 Clarence Klassen
Tuesday, August 27, 2013 1:06 PM
Davoud:
Generally dc overvoltage occurs when the process is driving the motor faster than the setpoint for the drive. For a pump, there may be flow in the pipe driving the impeller. Reduce the flow upstream of your pump for starting, or provide a fast setpoint and fast ramp time to prevent generating long enough to produce an overvoltage.

Clarence
PS. let us know how you solve this.
#954 Mark Shirah
Wednesday, September 04, 2013 10:58 AM
There is one issue that has not been mentioned that many times is overlooked. Utility Substation capacitor rings can cause High DC Overvoltage trips on VFD's. When a 3600 Kvar capacitor is turned on or off, it can create a ringwave which causes the signwave to cross zero unexpected and out of sequence, therefore causing a direct short across the VFD. The drive will reset and run the remainder of the day without any issues until the Utility Capacitor is operated again.

There is usually a simple fix for this. The drive manufacturer can size a Line reactor ahead of the drive ( usually around 3% ) which will dampen the ring to where the signwave does not cross zero. If you are within 2 miles or so from a Utility Substation, this could be a possible cause.
#958 Clarence Klassen
Wednesday, September 04, 2013 7:24 PM
Makes sense that voltage spikes are introduced when switching capacitors. I have not solved a problem this way. Does the 3% impedance of the new reactor provide better isolation than the existing 5% impedance of the isolation transformer?
Clarence Klassen
#965 GHANIM
Saturday, September 07, 2013 5:59 AM
dear sir
i have ingersoll rand comperssor nirvana N37 , with HPM motor , with start signal the comperssor trip and give massage ( dc bus overvoltage )
pls , how can i solve this
#966 Clarence Klassen
Saturday, September 07, 2013 2:51 PM
GHANIM:
I am sorry I cannot help with your overvoltage trip problem. The compressor is not being oversped by the process. Therefore the high voltage must be coming from switching transients.

Please see the comment above by Mark. The transient my come from the utility, but if it only occurs on starting, some contactor must be closing to create the over voltage spikes.
Clarence
#1048 Robert Carpenter
Thursday, November 21, 2013 4:13 PM
I am trying to set up a Nord SK205 E with a C4-REL control box for use on a tilt table with a large load (over 2,300 lbs) We have a 200 Ohm - 4,000w capacitor system set up in series to try to deal with the overvoltage problem, as well as a 1,750 lb counterweight. We are getting a DC Link OV error of 997V whenever the table reverses directions. I have tried extending the deceleration time as well as setting the parameters for the DBR to the correct ohms and wattage. Any hints?
#1049 Clarence Klassen
Saturday, November 23, 2013 6:11 PM
Robert Carpenter:
I am not familiar with this drive nor have I put a drive on a tilt table, although I have used drives on carts lowering wound rolls.

It should be possible to lower the load with a large enough braking resistor and slow enough ramp time. I can't offer much help. Call your vendor tech support and ask yourself:
does the table tilt properly unloaded?
is dynamic braking working at all? the braking electronics or resistor may have failed.

Clarence Klassen
Does slowing ramp time help?
#1058 srinivas
Wednesday, December 11, 2013 5:15 AM
dear sir, I had a problem with my Yaskawa varispeed G7 drive, this is used for a weigh feeder 2.2 kw motor, and with constant set point and rpm it was tripped with DC bus over voltage, can u please explain...
#1059 Clarence Klassen
Wednesday, December 11, 2013 10:43 AM
I have worked with this drive including braking resistor and had no problems with dc overvoltage problems while running or generating.
Clarence Klassen
#1142 Armand
Saturday, March 29, 2014 11:28 AM
Hi Clarence,

I would like to ask question regarding on the inverter we are using. Brand is Reliance Electric gv3000 v5.5. Currently I am encountering two problems regarding on the drive.
1. The first problem is we have potentiometer mount outside the panel so operator can adjust the speed depending on the production needed. The problem is the once we rotate clockwise the potentiometer, instead of adjusting the speed its decreasing. Same as happening once we rotate the potentiometer counterclockwise, instead of decreasing its increasing. We already checked the said potentiometer and found working. Is there already problems on one of the card in the drives?
#1145 Clarence Klassen
Wednesday, April 02, 2014 8:46 AM
Armand:
I suggest reversing the two outside wires on the speed pot. This may be easier where they connect to the drive or on the pot itself.
#1151 Rao
Monday, April 07, 2014 11:53 AM
Hi
We have issue in MM440 drive used for magmixer in vessel.
Its connected to DCS through profibus and in DCS it is programmed for all common error to trip the VFD irrespective of warning or alarm.
We are getting occasionally " VDC max" warning from vfd and due to programming in DCS it is tripping the VFD. But if we run the VFD locally, its not tripping.
Is it ok if we introduce time delay (say 2-5 sec) in DCS to avoid tripping of VFD ?
Rao
#1152 Clarence Klassen
Monday, April 07, 2014 8:48 PM
Rao:
The drive will protect itself. change the DCS to not trip the drive or delay tripping
Clarence Klassen
#1160 bourne
Sunday, April 13, 2014 1:25 AM
Any parameter setting related to dc bus overvoltage of yaskawa drive 1000series besides acc..deacceleration?? Because the tension of conveyor belt at times comes into effect at higher speed...any advice sir..thank you
#1161 Clarence Klassen
Sunday, April 13, 2014 2:46 PM
Bourne:
It is possible to add a braking resistor to this A1000 drive to reduce the dc overvoltage while generating. Contact your distributor.
Clarence
#1162 bourne
Monday, April 14, 2014 2:45 AM
Thank you sir but the panel vfd so compact to add or modify ...is there any other parameter related to dc bus overvoltage fault??like the v/f pattern or negative torque..or any.....thanking you in anticipation
#1166 Clarence Klassen
Monday, April 14, 2014 9:21 PM
bourne:
What can I say. You have a compact drive that is subject to faults. I don't think you can fix this with parameter changes. You will have to:
1- stop pulling on the drive
2 - add a braking resistor

I don't know what is pulling your drive on the conveyor. Perhaps it is another drive pulling too hard because its speed is wrong. Perhaps it is the mass on the conveyor as it rolls down hill.
Clarence Klassen
#1167 Clarence Klassen
Monday, April 14, 2014 9:24 PM
I am tired of this DC Bus overvoltage topic, have nothing more to contribute and will no longer respond. Perhaps some of our readers or drive vendors can continue the thread.

Clarence Klassen
#1217 Gabriel
Monday, June 23, 2014 3:36 PM
Great information, thank you.
#1310 M L SHARMA
Sunday, October 05, 2014 8:21 AM
i am suffering with vfd model acs800-04-140-3 sr no 1062005204 working at agitatore driving motor max load 140amps but vfd tripping at 100amps load after many compliance there no service engineer attend same fault.
#1319 Derek
Tuesday, November 04, 2014 11:45 AM
Well, I have an interesting one;
I have a Yaskawa v1000 drive model number: 4A0031AAA
The drive is running at v/hz mode.
The motor is 20hp and is connected to a gear box running a positive displacement pump.
The drive will ramp, run, and decelerate fine as long as the hz are under 35hz.
But at any time the drive hz is between 35hz and 45hz the drive will trip on over voltage. Occasionally it will go past 40hz and will continue to run fine above 50hz, used to trip on deceleration until I set the drive to coast to stop.
When I decouple the pump the same problem occurs. When I decouple the single gear gearbox the motor runs fine.

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Blogmaster

Clarence Klassen photo

Clarence Klassen

Clarence Klassen is president of KlassENgineering (incorporated in 1999) and is a Licensed Professional Engineer with Professional Engineers Ontario (PEO). Clarence applies 31 years in the Pulp and Paper industry to solving problems with drives for web handling. He has 10 years of experience as a drives engineer with GE Canada and 10 years of experience with Opcode Systems Inc., a PLC and Drives Systems Integrator. Much of Clarence's experience was gained in onsite installation of new equipment and troubleshooting of existing equipment. KlassENgineering performs Pre-Start Health and Safety Reviews as required by the Ontario Ministry of Labour.

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