DC motor speed control 1

[lukin1977]

Hi

I need to replace an old DC drive. The machine is a wire drawing machine. The drives works in speed control. Actual speed input comes from a tachometer mounted at the end of motor shaft. Set speed value is set manually with a potentiometer and there is another potentiometer signal coming from a “dancer” that is moved by the wire drawn by the machine. This dancer is used to syncronize one motor with the next

All 3 inputs are processed in a separeted board (I mean separeted from the SCR converter) and then an output signal from this board goes to the converter to control the firing angule of the SCRs.

Questions:
What is the function of this board?
A Modern DC drive have this board or microprocessor inside?
Can I replace the converter and control board with a modern DC drive?

Thanks!

 

[Skogsgurra]

An Arboga machine?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[lukin1977]

yes

 

[Skogsgurra]

Then you can easily use a Siemens DC Master with option 'Free Function Blocks' and build the corresponding functions with them.

Their 6RA70xxxx works also.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[lukin1977]

That is exactly the DC Drive that I am aiming. SIEMENS DC Master SIMOREG 6RA7018
In fact just before I wrote the first post a local Siemens representative visit our plant. But he could not answered my question. He is "going to check". He told me they have very low experience with DC Drives

Can you explain me some more about how this speed control works and what is this "free funtion blocks" that you mentined?

Thanks!

 

[Skogsgurra]

You can find manuals for the drives on the Siemens site. The free function blocks are very well described there.

Short description: There are logic and analogue function blocks that you select and connect using binectors or connectors. Very easy once you start using them. I have done several 'transitions' from old drives to modern ones using these drives.

You could (almost) use the diagrams for the existing analogue functions and calculate things like time constants, gain, integral part and such things* and then use the data in the function blocks. I would say it can be done in a three-five days, including testing with wire. You have to find someone used to it, though. Or you do it yourself. Depends a lot where you are.

*or estimate them from recorded step responses.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[lukin1977]

I will ask the DC Drive seller to do it or help me do it or I help him do it

 

[Skogsgurra]

I think you will be helping him!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[lukin1977]

Skogsgurra

I have being looking the Siemens Catalog and they offer 2 alternatives:

Base Drive Panels: SCR semiconductors and controls + contactor + fuses + trasformer

Power Module Drive: only SCR semiconductors and controls

I think we only need the Power Module because we can use our existing contactors, fuses, etc

Is this correct?

 

[Skogsgurra]

That's how it is done in most cases. The old panels are often well built and that goes for existing contactors, fuses also.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

I found a picture from 2006. It is a winder that we rebuilt in Tenth of Ramadan City in Egypt. Very smooth. The local guys learned quickly. Lots of spare room after the original thyristor sets and control card cages had been removed.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[etom]

Depending upon the HP of the drives, it is cheaper to retrofit new control onto the existing scr bridge. We call this a "front end" retrofit....usually about 100 hp and up.
TMGE makes very versitle digital front ends that will easliy do this application.

 

[lukin1977]

etom

Each DC motor is 12,6 kW. We want to replace the drives and control card because they are continusly failing