Re: IGBT long life at 3X rated Ip?? Re: 15kva 14.4 kV Transformer.. (fwd)

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Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 24 Dec 2006 17:23:32 -0700
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: IGBT long life at 3X rated Ip??  Re: 15kva 14.4 kV  Transformer..
    (fwd)




Sorry to hear this bad news.  I've used about 40 of them over the past years 
and so far, knock on wood, absolutely none of them have failed in any 
manner.

Curious --- with all your experience Phil, what brand do you recommend?

Dr. Resonance
>
>>Automation Direct has a large selection of PLC controllers --- some under
>
>>$200.   These work great for control  applications.
>
>
>
>    Not to rain on D.C.'s post, but I work with a  variety of PLC's every 
> day
> as my job - very common in industrial  machinery.
>
>    The Automation Direct PLC's are made by Koyo. In my  experience with
> their modular PLC's:
>
>    1) Power supplies fail. Some sort of bad solder  joint problems. But 
> I've
> had problems with *all five* of the ones I've ever  dealt with, and they 
> were
> of different ratings. They might last a few  years, but eventually they 
> will
> die. And as they mate into the PLC modular  rack, they are proprietary.
>
>    2) Software/capabilities are a bit weak compared to  the other industry
> standard PLC's. Timer values are limited, inputs/outputs  assignment are
> limited and somewhat idiosyncratic. Just makes things more of a  pain to 
> casually
> play with them.
>
>    3) I've had one of their "com interface" modules  die (the thing that
> allows connection between the programming PC and the  PLC).
>
>    4) Tech support is iffy quality.
>
>    You get what you pay for. While I'm sure  Automation Direct must have
> some decent deals, I never found them to  be worth the gamble for any 
> components
> I was willing to install in machinery I  was tasked with 
> building/maintaining.
>    FWIW, I'd go with either a Siemens or Allen-Bradley  micro PLC. Siemens
> has micros that are incredibly compact and powerful, and they  love to 
> *give*
> you all the support and software you need. Allen-Bradley has the  better
> programming software, but they are very "snooty" about tech support 
> unless you've
> *bought* a support package.
>    Just be careful about running too much current  (especially with
> inductive loads) through the PLC's outputs -even relay  outputs. I've had 
> Siemens
> micros "bounce back" after their contacts "stuck" from  too much current, 
> but best
> to include a separate glass fuse for each and every  output. Saves
> programming time spent on re-assigning an output to a  spare...
>    Also hard to find a Siemens micro PLC with  120VAC inputs. A-B still
> makes those, tho. Most micros, except the very cheapest  models, have the
> capability for expansion modules if you find you run out of I/O  for some 
> reason.
>
> -Phil LaBudde
>
>
>