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Anonymous Poster

DC Drives

02/13/2010 2:33 AM

Dear Sir,
One of our client using the Dc drives for their applications. In that plant we comissioned our compressor 22Kw. For our compressor we have the Controller which have the Digital O/p , relay O/p, Analog I/p (electronic Circuit PLC) to control the Star Delta circuit & other purposes for compressor. It requires 24v Ac. So we have transformer 50VA to stepdown 415v Ac to 24v Ac. But only at the time when customer starts the DC motor for their application means our compressors stops & Controller (electronic Circuit PLC) also get hangs automatically by itself. But it getting the 415v 50Hz 3phase supply & for I/p of (electronic Circuit PLC) also getting 24vac 50Hz. But it doesnt give any command just in hang position. But our compressor run when their DC motor in stop condition. So plz give me the soluton whether we should use any filters before I/p of (electronic Circuit PLC) to activate..?? I also checked volage there was no DCv in the supply..........We thought there will be prblm due to the harmonics. So plz give me the soluton whether we should use any filters before I/p of (electronic Circuit PLC) to activate..?? Rgs

Thiruvenkatam.S.P| Engr-After sales I ELGI-Equipments ltd | 23,Shivaji Marg,karam Pura| New Delhi,15| India M: +919910016727 | P: 011-25928095, 8593 | f: 011-25459375 | e: thiruvenkatam@elgi.com

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Anonymous Poster
#1

Re: DC Drives

02/13/2010 7:44 AM

System earth?

You have an isolation transformer, what you have done with the neutral of the secondary?

Check the harmonics on the line as the motor starts that should give you sufficient idea.

Most of the DC drives have their own PLCs (?) Why they are not interfering with each other?

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Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1372
Good Answers: 80
#2

Re: DC Drives

02/14/2010 10:10 PM

There are many possible causes identified previously.

Others could include:

Wiring error on the motor/drive causing a ground/return loop affecting the low voltage supply (analog) of the PLC.

Reduction of the line voltage caused by the low power factor, especially if running at hight torque and low speed.

Maybe harmonics but more likely other causes.

Bad wiring in your plc panel, loose wire etc... Don't underestimate small things. It is probably a simple cause.

Try a divide and conquer approach by a competent engineer/technician. Use somebody who understand the technologies involved.

Good luck.

Give us the result once the problem is solved. We would like to know.

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Commentator
Engineering Fields - Electrical Engineering - New Member India - Member - New Member

Join Date: Dec 2009
Location: Bangalore,India
Posts: 80
Good Answers: 1
#3

Re: DC Drives

02/15/2010 12:29 AM

Dear Mr.Thiruvenkatam.S.P,

Thanks for the question and your doubt. if you could explain in detail (electrical diagram and block diagram preferable) regarding the DC drive application and your compressor drive application, then the forum members will be in a position to give a better explanation and solution. is it possible that the PLC is programmed in such a way that when DC motor is ON , the compressor is OFF??.. what is the application? please check with the electrical designer or electrical consultant.

Thanks

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Power-User
Engineering Fields - Power Engineering - New Member

Join Date: Nov 2009
Location: Abuja, Nigeria.
Posts: 126
#4

Re: DC Drives

02/16/2010 12:36 AM

U have not indicated the the capacity of ur power supply equipments or stand by generator. U have also not indicated the the capacity of the DC motor.

What starting and running method are they useing for the DC motor?

If the dedicated transformer is not properly rated or ur standby Gen is small and or ur supplied directly from a public line, U may expirience that.

If the above is ur or not ur case, U need a voltage stabulizer and not a filter for ur equipment since a contributing cause might be from the outer vicinity

Such equipments as urs are very sensitive to voltage fluctuations.

Dickson.

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