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radha5520
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India - Member - New Member

Join Date: Feb 2011
Location: Bangalore
Posts: 7

Isolation Transformer

12/02/2011 6:24 AM

Why we are using isolation transformer before power supply, for plc control circuit?
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Anonymous Poster #1
#1

Re: Isolation Transformer

12/02/2011 8:14 AM

I think this replies.

Of course there are certain other points (or applications that makes the Isolation Transformers useful) too not answered here.
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Anonymous Poster #1
#2
In reply to #1

Re: Isolation Transformer

12/02/2011 8:21 AM

Always try to think upon the subject before asking a question since that would make you understand better.

What is an Isolation Transformer ?

- ratio 1:1

- Electrically uncoupled.

What it would do?

- Same voltage on primary and secondary

- DC Bias would be isolated on one side (whatever it might be)

- High frequencies would be provided with higher impedance.

- Secondary may be separately grounded (unaffected by primary neutral)

...

What is the feature that you find is useful here and wouldn't be so easily, relaibly or economically achieved by other means?

(All these advices are assuming you are still in the early career/ student stage)
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Anguraj Chelladurai
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Join Date: Nov 2011
Location: Chennai, India
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Good Answers: 2
#3

Re: Isolation Transformer

12/02/2011 9:07 AM

It can be also termed as 'Insulation transformer'. Because both primary and secondary windings are separated by physically each other.

An isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits.

Isolation transformers block transmission of DC signals from one circuit to the other, but allow AC signals to pass. They also block interference caused by ground loops

Have you got it?

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SHOCKISCAN
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Join Date: Sep 2008
Posts: 196
Good Answers: 6
#4

Re: Isolation Transformer

12/02/2011 10:28 AM

The isolation transformer removes/stops induced noise (voltage) and harmonics from the AC signal before it reaches the power supply primary. Basically it "cleans" the AC sinewave by restoring it's symetry and magnitude thereby stablizing the power supply output. If any noise induced into and reflected by a PLC power supply into the PLC backplane and/or CPU or I/O card circuitry reaches a magnitude higher than the TTL gate threshold value, it can and usually does produce random, uncontrolled TTL gate triggering. This results in incorrect and uncontrolled execution of I/O card and program logic execution. This condition can cause machine and/or system control runaway.

Hope this helps.
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Anonymous Poster #1
#5
In reply to #4

Re: Isolation Transformer

12/02/2011 11:40 AM

The isolation transformer can only stop the DC bias. It is magnetically coupled so most of the harmonics especially lower order would pass through with minimal suppression. The suppression would only be depending upon the impedance offerred by the transformer's inductance.

For the other purpose (cleaning etc) it won't be that useful.

Isolation transformer's basic function is to electrically isolate and allow only the AC portion to pass through.
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PWSlack
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#6

Re: Isolation Transformer

12/05/2011 3:41 AM

Undefined "we". Very abstruse.

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