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Exhaust Fan Keep Trip

12/27/2008 9:38 PM

Hi,

I got this problem at work, where one of my exhaust Fan keep trip after run for awhile. the Exhaust fan is run on timer with two fan running that one run, the other standby.Both are run with VSD. The First exhaust fan VSD had be replace a couple monts ago where the VSD found to be faulty. The new VSD is getting back the same brand but different model as the existing model had be replace.

This trip is quite happen a few mth ago, after the replace the VSD it gone. But come back again. Both of my VSD and fan contractor found that their equipments are runing fine. We even manual run the exhaust fan, it work and the cable for the exhaust fan is check also to see any current leakage. but found none.

Only the first exhaust fan trip when running, while the second exhaust fan found to had not that problem.

Can anyone advise me on that ?what wrong with that.

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#1

Re: Exhaust Fan Keep Trip

12/28/2008 12:53 AM

VSD trip? What is a trip--A breaker, or is it a fault, if so, what is the fault.

What Brand, size drive and motor?

When does it TRIP? Starting? Running? Ramping down?

Is the trip an overvolt? overcurrent? ground fault?

Both fans in the same duct?

Need way more information to help.

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#2
In reply to #1

Re: Exhaust Fan Keep Trip

12/28/2008 1:05 AM

Hi Kilogore,

The Breaker trip. The Brand is Danfoss and the power is around 45KW. Both fan is connect to the same ducting, but only one run at a time while the other standby. A timer is install for the switch over every week.

For the trip, once that fan (First Fan) switch over. It run awhile then trip. While if the other fan (Second Fan) switch over. Nothing will happen. Sometime, when the First Fan run for a few days then it trip.

We also suspect the earth fault for the fan, but found nothing. Hope that answer ur question. I think mostly not overvolt, bcos we change replace the VSD only without touching the existing layout.

Thanks.

Tan

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#3
In reply to #2

Re: Exhaust Fan Keep Trip

12/28/2008 1:59 AM

Never used Danfoss drives--But if the drive and the conductors are sized properly for the motor and the breaker feeding the drive is tripping(if this is the case) I would look closely at the breaker and it's connections before the drive. All drives I have used fault out at the HMI and really do a good job(sometimes too good) at spotting problems.--The drive does have an HMI and it is programmable, no? The high amps should be caught by the drive if it has a parameter for it and it should be less than the breaker feeding it.

Are the amps what you expect, or are they high?

Are the amps balanced feeding the drive?

Is there anything that changes the volume of air that that fan moves while it is running?

What voltage, HP motor, size of breaker, size of drive?

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#4
In reply to #3

Re: Exhaust Fan Keep Trip

12/28/2008 2:12 AM

Hi Kilgore,

My mistake, on the previous comment onthe VSD trip. While we need to off the breaker in order to reset the VSD.

Tan

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#5
In reply to #4

Re: Exhaust Fan Keep Trip

12/28/2008 2:17 AM

Hello Tan,

Do you have the manual for the drive?

Can you look up fault codes?

It should be able to tell you what it doesn't like--Voltage, amps, ground fault, line votage..............

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#6
In reply to #3

Re: Exhaust Fan Keep Trip

12/28/2008 2:18 AM

Hi Kilgore,

Good questions that you points out on amp. will check first then feedback to u.

A couple months ago there ais change in the volume air flow as more equipments are connect to exhaust Fan.

Thanks.

Tan

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#7

Re: Exhaust Fan Keep Trip

12/28/2008 8:37 AM

Could be excessive loading on the VSD due to the increased loading.

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#8
In reply to #7

Re: Exhaust Fan Keep Trip

12/28/2008 8:41 AM

Hi,

why it happen on first fan not the second one ? both connect to the same ducting and service same place.

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#9
In reply to #8

Re: Exhaust Fan Keep Trip

12/28/2008 2:17 PM

Tan--Is the fault overcurrent? Are the amps high? I still haven't heard.

If it is overcurrent, double check the overcurrent parameters.

Can you take the drive from the good fan and wire it to the bad fan motor(temporarily) and run it to prove that the fan and motor are the problem?

Does the ducting have a Y for the fans? The air inlets to the fans the same and can you partially close the air intakes or restrict the airflow somehow?

Good air fans can get overworked if the air to them is unchecked. If this is the case restrict the air at the intake and set it to full load amps for the motor.

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#12
In reply to #9

Re: Exhaust Fan Keep Trip

12/28/2008 8:42 PM

Hi Kilgore,

My guy is checking on that.

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#14
In reply to #9

Re: Exhaust Fan Keep Trip

12/28/2008 9:12 PM

Hi Kilgore,

Just feedback, when the VSD trip.the error message show is earth fault.

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#15
In reply to #9

Re: Exhaust Fan Keep Trip

12/28/2008 10:56 PM

Hello Kilgore Trout: it seems you have the bases well covered.

I'm not familiar with that particular brand of VFD, so this is a shot in the dark as far as his error code goes.

Some three phase motors are equipped with thermal protection, I'm just wondering if the motor either has excessive amp draw, or is overheating due to some other reasons such as restricted airflow across the motor, if opening the internal safety (assuming the motor is thermally protected) could trigger his error code.

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#25
In reply to #9

Re: Exhaust Fan Keep Trip

12/30/2008 3:36 AM

Hi Kiglore,

I have shift VSD from fan one to fan Two. The First VSD Trip. So i summary that the VSD i change got problem.while the other is ok.Just done.tks for ur idea.

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#26
In reply to #25

Re: Exhaust Fan Keep Trip

12/30/2008 7:36 AM

Tan--Glad to help out(If I did) anytime.

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#10
In reply to #8

Re: Exhaust Fan Keep Trip

12/28/2008 8:29 PM

Each motor has its own VSD, right? So the one that trips may have some problem that causes it to trip under high loading.

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#11
In reply to #10

Re: Exhaust Fan Keep Trip

12/28/2008 8:39 PM

Ya, each motor is control by its own VSD. We have the VSD relay card replace as it still guarantee. After run for a week, it trip on one night.When it restart after that, with two hour it trip again after run for awhile.

What you mean on the last sentence on the trips parts ?

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#20
In reply to #11

Re: Exhaust Fan Keep Trip

12/29/2008 2:38 AM

Exactly what it means, under high loading it trips because it's defective. However, since it's been replaced, the problem may be on the fan motor instead.

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#13
In reply to #10

Re: Exhaust Fan Keep Trip

12/28/2008 8:47 PM

Both of the exhaust fan supply to the same location. Both fan connect to the same ducting.where one act as a standby while the other running. The second fan do not face any problem when running.Only the first fan that get replace new VSD got that problem. That what i quite curious on.

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#17
In reply to #13

Re: Exhaust Fan Keep Trip

12/28/2008 11:14 PM

Hi Tan,

We have used Danfos Vsd's and have found them to be fairly good drive. Just a thought, the fan that is not running, does it spin while the other is running? If so it may be worthwhile enabling the 'flying start' feature, if it has one. As guest mentioned it may be worth looking at adjusting the current limit as well. If you have a ground fault, I would be checking the cable and motor for any faults.

Regards,

Trevor.

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#18
In reply to #17

Re: Exhaust Fan Keep Trip

12/28/2008 11:30 PM

Tan,

I concur tooz

The fault seems to be a ground/earth fault.

If it is in a damp environment open everything and make sure all connections are dry.

I have changed a lot of wiring and motors downstream for A/B drives--They are too good at sensing ground faults in damp, hot environments(my opinion).

Do you have line filters or reactors? You may consider them---The High voltage spikes in the DC wave form can piece even good insulation and the filters can soften the spikes down a bit.

Meg the conductors(make sure you disconnect the drive and don't meg it) and the motor. This may not give you a definitive answer for the drive sensing ground.

Before you replace the motor and/or the conductors try to dry them and make new connections.

I have been stumped by this a few times and replaced motors and conductors that run fine across the line, but a drive won't run them.

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#16

Re: Exhaust Fan Keep Trip

12/28/2008 10:57 PM

The fan is a machine with a cuadratic torque vs velocity curve, but fans has a very high inertia, this means the starting (acceleration) take a long time and the starting current too. There are a tipical mistake with operation with VSD, the VSD can manage a current above the nominal value (above 100%) only for a limited time, if the VSD has a current limit value adjusted above 100% and the high inertia of the fan make a starting take more time than current limit time of the VSD, the VSD trip with a overcurrent or overtemperature (I2t trip).

The solution is set the limit current of the nominal current of the VSD (100%), the starting take a long time but trip free. Other option is oversize the VSD.

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#19

Re: Exhaust Fan Keep Trip

12/28/2008 11:53 PM

Hi,

Check your setting on the over current protection.

Best regards,

Patrick

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#21
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Re: Exhaust Fan Keep Trip

12/29/2008 2:40 AM

Thought you were my son Luke.

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#22

Re: Exhaust Fan Keep Trip

12/29/2008 7:38 AM

First of all, please give us a more detailed description of the situation.

Model and type of VFD, model and type of motor, any accessory on the motor like PTC sensor's.

Second on a normal VFD theire is a display that shows the error, when it happend, at what current at what speed etc. Surrely Danfoss has such a error memory.

Mostly the last 5 errors can be seen.

Please tell us these errors.

Only good informations can lead to a good advice.

good luck

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#23

Re: Exhaust Fan Keep Trip

12/29/2008 8:12 AM

A shot in the dark here but I saw a similar problem on a HVAC fan in a hospital. Brand new installation and would intermittently trip out on earth fault. The VFD was replaced and a bunch of other stuff. Finally the VFD manufacturer called the company I work for in to diagnose the problem. Turned out that at the motor, the installer used regular electrical tape instead of the thicker rubberized tape. The lug used to make the connection had a square edge and when the motor vibrated just right that lug came close enough to the cover that it arced and caused the VFD to trip out on earth fault. I rewrapped the connections with a good rubberized electrical tape and shoved the connections in a little tighter and all was well. Maybe you have a similar issue.

Shawn

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#24

Re: Exhaust Fan Keep Trip

12/29/2008 3:30 PM

Hi Tan

Assuming the VSDs are close then the simplest and most definitive method of checking, as earlier suggested, is to swap the motors /VSDs, assuming they are of equal sizes.

Prior to that check that the ALL the settings on unit 1 and unit 2 are the same.

Regards Chas

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#27

Re: Exhaust Fan Keep Trip

01/07/2009 11:41 AM

I'm not familiar with Danfoss drives but most of the ones we have in our plant have dip switch settings. If yours have dip switches, make sure they're set properly. Have had that problem in the past with a new drive installation.

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