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

["Tesla list" <tesla@xxxxxxxxxx>]

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



---------- Forwarded message ----------
Date: Mon, 25 Dec 2006 11:02:05 -0800
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: IGBT long life at 3X rated Ip??  Re: 15kva 14.4 kV  Transformer..
    (fwd)

Industry leaders (Siemans, AB, Yakasawa, Toshiba, etc..) are good but 
they do get really expensive especially in applications such as a 
company buying PLC's to control in-house equipment (simply low 
quantity).  For company's where it's worth the price, sure. The other 
side of PLC use is in end-line equipment and thus high quantities are 
purchased (amazing the difference in price!).

But for the casual purchase (especially say something a coiler might 
play with), I would not recommend the higher end products simply due to 
the cost. PLC's such as Automations DL series and other low end PLC's 
are at least attainable and still have plenty of power for most tasks. 
I've had many PLC brands run into comm issues, but that is often noise 
related such as inverter controlled motors where there is a lot of 
electrical noise in conjunction with insufficient supply filtering.

Take care,
Bart

Tesla list wrote:

>Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Sun, 24 Dec 2006 17:12:20 EST
>From: FIFTYGUY@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: IGBT long life at 3X rated Ip??  Re: 15kva 14.4 kV  Transformer..
>    (fwd)
>
> 
>In a message dated 12/24/06 12:14:40 P.M. Eastern Standard Time,  
>tesla@xxxxxxxxxx writes:
> 
>  
>
>>Automation Direct has a large selection of PLC controllers --- some under  
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>>$200.   These work great for control  applications.
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>    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
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