Reaccelaration Logic for Medium Voltage Motors 3

[durgeav]

Hi,

Please help me out on the topic of reaccelaration logic for medium voltage motors in bus-transfer scheme. I have tried reading a few papers on this, but everything's put up in tedious mathematical equations. Sending a relevant website link would be an additional help.

Regards,
durgeav

 

[Laplacian]

Here is a link with pertinent information you seek.

http://www.mastercontrols.com/EngInfo/Articles/Nailen/TA_RNail.htm

The general questions for you are:

Is this a single motor, or multiple motors?

How are the motors fed; breaker or contactor?

How much time do you have to reaccelerate?

What type of reacceleration event are you trying to recover from? Blips that drop out magnetics (contactors), or complete outages?

For the fastest recceleration without risk of equipment damage, you need to implement residual voltage detection on the motor side to wait until the motor voltage decays to a nominal level for reacceleration. If time is not that important, you can base reacceleration on a suitable time delay (2-10 seconds). If multiple motors are involved, you need to step the reacceleation based on process needs and your distribution system strength. If the motors are breaker fed, just let them ride through unless source voltage goes to zero.

There are many options and considerations depending on your requirements. Post more specific questions if further information is required.

 

[7anoter4]

Hi durgeav
I agree with Laplacian you have to be careful with your equipment.
But from my experience many of Power Stations, where work continuity is vital, are provided with ATS [Automatic Transfer Switch] .Usually the most of consumers are centrifugal pumps, fans and blowers and seems the ATS succeeds to hold them in operation without any damages. But, I guess, the outage frequency is very low here: may be once in a month, I think.
Also there are many articles on the web "pro and contra". There is a link for example:

http://www.firetrol.com/Products/ATS/atsfactors.html#ats

Best Regards

 

[7anoter4]

I have agreed once again with Laplacian. In a Power Station no soft start is provided-no VFD, no vector driver, even no star-delta start. Also there is no contactor on medium voltage side and a few contactors on low voltage bus bar. Even a 10000 HP boiler feed pump is directly started by a breaker closure. This policy is based on reliability theory according which all supplementary device added to a circuit loop compromises the entire system reliability.
Best Regards

 

[electricpete]

7anoter4 - can you share the secret code buried in your handle?

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[7anoter4]

Thank you electricpete.
Your secret code is also very interesting [more than mine, I am positive!]. But if you already asked, my handle is "patience" and my password is "listening Shostakovitch Symphony no. 9"
Best Regards

 

[7anoter4]

Sorry, "the smileys" it is my wife idea!

 

[electricpete]

The internet is about the only place where my wife doens't tell me what to do.

electricpete is not a code. But once I was kicked off of another forum for participating in a nasty personal argument (which was not my fault of course). I wanted to log back in under a new handle without sacrificing my previous identity as electricpete. So I came up with
ITIXI-4
Can anyone decode it?

7anoter4 is 7 letters and patience is 7 letters, but I don't see the connection.

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[electricpete]

Maybe it's easier to read without the caps:
itixi-4
Can anyone decode that?

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[7anoter4]

Hi electricpete
As for a veritable engineer it took enough time to catch it, but I see now your actually question. Do you mean how the handle was chosen?
It is a long story, I remember now. The old QuickBasic required a string length of maximum 8 characters for a password. So I start with 7."An outer" was the original. But with 7 was already 8 .So I reduced the "outer" to "oter" and in order to remember it I put 4 at the end. Very complicate and to remember I took "patience" as a model to count the letters [no more than 8!].I think once upon a time was a song [French, may be?] "Patience, you are an outer man [outsider]!". But now, I take it as my actually name. Your code ITIXI-4 is a puzzle!
Best Regards

 

[electricpete]

If you put into Matlab:
» char ('itixi'-4)

You get back:
ans =
epete

e is 4 letters before i, p is 4 letters before t, and t is 4 letters before x.

I was proud of myself for finding a good code because if you put itixi into google you get a bunch of hits which have nothing to do with me (for example itixi is a place in Saudi Arabia).

But... it didn't work for my purposes. I tried to register at the forum mentioned and above (after being kicked off) and was blocked from registering because they knew who I was from my IP address. Being sneaky in the internet world requires more than disguising your handle.

When I saw your handle it looked somewhat similar. I knew there had to be some kind of thought process behind it and was just curious. Sorry for hijacking the thread.

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