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Vfd Failure


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#1 rahuljadhav1

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Posted 21 March 2008 - 04:04 AM

Dear All
It's festiv time in India,but not for me.Reason ?

My question is If for a AC drive- Ready ,Run,Speed ref. signals are coming along with the Power will cause
any damage to drive?

Or any arching at input side contactor will cause any damage?

One of our customer reported MPCB tripping upon power-up? MPCB seting done.


Regards

Rahul

#2 Carl

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Posted 21 March 2008 - 10:06 AM

It is usual practice to keep the power and control cable separate as this reduces the likely hood of interference from the power cable…….as this can inductively couple……..especially in inverters as you have a rapidly changing signal on the leading and trailing edge of the output waveform to the motor……… if memory serves me correctly a square a wave is rich in odd harmonics.

sorry I should have mentioned that cables running in parallel have a greater likely hood of causing interference……..basically it is a transformer in a straight line

#3 chaterpilar

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Posted 22 March 2008 - 04:42 AM

QUOTE (rahuljadhav1 @ Mar 21 2008, 07:04 AM) <{POST_SNAPBACK}>
Dear All
It's festiv time in India,but not for me.Reason ?

My question is If for a AC drive- Ready ,Run,Speed ref. signals are coming along with the Power will cause
any damage to drive?

Or any arching at input side contactor will cause any damage?

One of our customer reported MPCB tripping upon power-up? MPCB seting done.




Regards

Rahul


I am trying to understand your question..are you saying that by mistake, the ref signals shorted with a live line?

In that case VSD will have problems in the control card.

However if it is tripping, the incoming breaker then it is a serious problem.

Personally, i avoid using contactors in input/output side of VSD.

Try opening the drive cover and see for some arcings or blackspots. Power supply card or some thyristors might be grounded.

Cheers...and do not let problems spoil the spirit... wink.gif

#4 rahuljadhav1

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Posted 31 March 2008 - 08:43 AM

QUOTE (chaterpilar @ Mar 22 2008, 10:12 AM) <{POST_SNAPBACK}>
I am trying to understand your question..are you saying that by mistake, the ref signals shorted with a live line?

In that case VSD will have problems in the control card.

However if it is tripping, the incoming breaker then it is a serious problem.

Personally, i avoid using contactors in input/output side of VSD.

Try opening the drive cover and see for some arcings or blackspots. Power supply card or some thyristors might be grounded.

Cheers...and do not let problems spoil the spirit... wink.gif




Dear sir

I think my post was not clear.
Well in this case power cables and control signal cables are running seperatly.Also no case of signal shorted with live line.
What my question is when I am switching the i/p power contactor for my drive, at the same time Ready ,Run ,and Ref. are going to drive.So will it cause any malfunctioning?

#5 chaterpilar

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Posted 31 March 2008 - 12:04 PM

QUOTE (rahuljadhav1 @ Mar 31 2008, 11:43 AM) <{POST_SNAPBACK}>
Dear sir

I think my post was not clear.
Well in this case power cables and control signal cables are running seperatly.Also no case of signal shorted with live line.
What my question is when I am switching the i/p power contactor for my drive, at the same time Ready ,Run ,and Ref. are going to drive.So will it cause any malfunctioning?



It should not cause problems...but wait till some other members chime in...with their views.. cool.gif

But what is the duty cycle? should not be started/stopped more than 3 times per hour.

#6 Carl

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Posted 31 March 2008 - 03:16 PM

it could cause problems if you are switching the drive on and off via the mains contactor as a stop start thats if the duty cycle of the on off is very short..............I've seen this problem on the old mitsi drives ....it used to burn out the surge resistor.....and then in turn it would weld the surge contactor........and then it would pop the input bridge due to the repeatd high inrush current.....and if you where really unlucky it would feed AC to the capacitor bank....the caps would then explode.............fortuanatly I've only seen one catch on fire and that was on a work bench.......mind you the ringing in my ears lastd about an hour and my boss was not to pleased

its called........... learning the hard way




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