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  • Users: sibeen
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  1. sibeen

    Motor current during soft stop operation

    I have been asked to do a review of an incident at a site that occurred over 6 months ago and where the site conditions have changed considerably since. The information gathered from the site, by others, during the events was sparse. The site has a 2 pole, 400V, 30 kW pump which was used to...
  2. sibeen

    Schneider Masterpact NW Breaker issue

    Something that I was notified about today and thought may be of interest to some on the forum. Haven't posted here for quite a while and had to go looking for my login details. This is an excerpt from a notice that Schneider has sent out regarding Masterpact NW Circuit Breakers (3P, 4P, 6P, &...
  3. sibeen

    Switchboard Short Circuit Rating

    I'm doing a study on a relatively old building and have run across something that I'm not sure how to handle. The building has a main switchboard which has a design kA rating of 63 kA for 1 second. The main ACB circuit breakers have a Icu / Ics / Icw rating of 75 kA. The board is fed by three...
  4. sibeen

    LV Genertator feeding Transformer

    I have a site which is currently fed via a centre tapped 480 volts giving two 240 volt supplies (j240 and -j240). All the loads on site are single phase 240 volts. The site requires a new generator(s) system to provide back up power in the event of a main fail. The site load is approximately 40...
  5. sibeen

    Simple circuit analysis

    I was having a look at a dual op-amp intergrator today - something that I haven't done for a very long time. I thought to myself "this couldn't be too hard" and quickly worked out what I assumed the output of the circuit would be, using some vaguely remembered formulas from long ago. Turns out...
  6. sibeen

    regeneration on customers' supply lines

    fab1961, I believe that when they talk about the short circuit power they mean the maximum fault current rating of the upstream transformer. In this case a 1 MVA transformer will have a maximum short circuit current of approximately 27 kA (I'm using a system voltage of 415 V) and therefore the...
  7. sibeen

    NER & 3 phase short

    A friend has a site currently under construction which utilises a 22 kV incoming feed. This is then stepped down to 400 V for the LV. The site also contains four back-up generators which operate at 11 KV. This is stepped up to 22 kV and then stepped down by the normal feed transformers for the...
  8. sibeen

    Computer room Power Factor

    I'm trying to track down some 'historical' figures on what the normal rnage of power factors could have been expected in large computer/data centres, approximately 10 to 15 years ago. It's one of those things that I used to have a heap of reports on, but that was two or three employers ago...

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