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  1. buzzp

    Looking for ideas on Electrical Enclosures

    Conduits can also contribute to this...if not properly sealed. The dust could actually be pulled in from a conduit, depending on your intake/exhaust fan. I have seen this more than once.
  2. buzzp

    Looking for ideas on a DC disconnect.

    Seems like you already ate up the $2500 you were trying to avoid spending by designing something different....you must be making more than one of these.
  3. buzzp

    X/R

    I am in the US and have an ONAF transformer rated for 20MVA with a 100kV delta primary and 21.6kV Y secondary. The %Z is 6.03% at 100k-21.6k. The X/R is unavailable. If I remember correctly, the X/R ratio I can safely use for a transformer this big is 20 when determining my maximum fault...
  4. buzzp

    CT Question

    You can hook up the 5A to the 1A input with some caution. Your short circuit current is only 1600A so the relay should be able to handle 4A on its input without causing damage. If you want to be sure, ask the relay manufacturer but you should be fine. selinc.com has some good papers on this subject.
  5. buzzp

    Testing of Three Phase Capacitors & Surge Arresters

    This won't be a comprehensive test but I have used an insulation resistance tester to see if the caps are breaking down with voltage applied. This was also on LV caps in a VFD - kept tripping drive and found bad caps in the DC bus. You might have some luck with doing something similar since your...
  6. buzzp

    CT Question

    Those burdens are likely the max burden so I think you are fine. If the 1A and 5A are wired to different points on the relay, you can't wire up a 5A secondary to a 1A terminal. However, usually, they are the same terminal and its just a programming change.
  7. buzzp

    Does a Motor Thermal Overload Relay Physically Break The Circuit?

    Hey Waross - I didn't realize CT's were used in thermals as well. I suppose it makes sense. I haven't seen a UL listed OL that uses Hall Effect sensors. I have seen current monitors with hall effects but no listed OL devices. I once was designing an OL using hall effects. They are extremely...
  8. buzzp

    Does a Motor Thermal Overload Relay Physically Break The Circuit?

    I can't see your drawings either. I agree with Waross. You are talking about two different kinds of overloads: thermal and electronic. Thermal's are typically associated with the older style overloads that heat up a bi-metallic strip as Waross said (they carry next to no current - they deflect...
  9. buzzp

    Cap bank issues when tripping 8850HP

    There is a lot to think about here...thanks for the info. I will be working on an ETAP model and for short term, changing when all these banks are energized.
  10. buzzp

    PLC and HMI in a Explosion Proof Enclosure

    I believe MSHA requires XP and I fall under their regulations, including the 1968 version of the NEC (no joke). I'll try to find some time to revisit the page turner suggestion, etc. that I told you about in the other thread and give you some more details...its been 6 years since I did this.
  11. buzzp

    Cap bank issues when tripping 8850HP

    I don't have a lot of faith in the company that designed the cap banks, nor do I have faith in their drawings as far as accuracy (based on their work since I started here). The equipment was installed before my time. I don't know if 16A fuses were ever installed. I do know, they used to have 80A...
  12. buzzp

    PLC and HMI in a Explosion Proof Enclosure

    I responded but in the other thread...at least I thought. Cross posting causes mass confusion...
  13. buzzp

    Cap bank issues when tripping 8850HP

    We have a 100kV/21.6kV substation. On the secondary side we have 4 cap banks, 300kVAR each, setup in a delta. We then go through 13000 ft of 636 to another cap bank (3 banks at 900kVAR each). After another 2500 ft of 636, we go to a 21.6kV/4160V transformer, which has a cap bank of 600kVAR and...
  14. buzzp

    Class I, Division 2, rated accesories inside of typical NEMA 4X enclosure

    My quick thoughts: I don't think you can use a 4X enclosure - this is dust tight and water tight, not gas tight. This wouldn't be allowed by the NEC. You have to use an explosion proof panel or pressurized. You can also use IS components and proper wiring techniques and/or nonincendive circuits...
  15. buzzp

    How will the COVID-19 pandemic change the face of business...

    Some people aren't cut out to work at home, while others thrive. Me, I get way more done at home not only because I don't have interruptions but I also don't have a 1.5 hour commute so I tend to work a little longer when at home. Unfortunately, it is going to take time for this to be widely...
  16. buzzp

    Workplace Ethics

    I have been a part of too many unethical companies and employees. Some very blatant, others not so much. I have seen NERC reports fudged by federal facilities (this one caught up to them). I have also seen an all out blatant disregard for electrical safety in general. Originally, I thought it...
  17. buzzp

    Noiseless / Clean Ground for Motor Power Cable Shields

    I would just use as big of buss bar as practical. I believe the idea is to create a low impedance path, with a large surface area, to give the noise a chance to dissipate before it reaches the main ground, which could cause other issues with sensitive electronics. I haven't really checked into...
  18. buzzp

    Using Ethernet hubs in an ATC system

    Whether the connections are in a secured room or on the production floor, the risks are virtually the same...the one cable is always exposed whether the switch is in the locked room or on the floor. If the switch is set-up right, I don't see any more risk, other than more ports available to try...
  19. buzzp

    Using Ethernet hubs in an ATC system

    I don't think the original poster is referring to wireless, at least I never seen that mentioned in his original post. I think the IT guys are more worried about having a switch, in an unsecured room, for anyone? to access. However, if someone wants too, they simply unplug the ATC device the...
  20. buzzp

    Can anyone recommend a VFD brand and a good supplier?

    All for LV: I prefer not to use AB drives. They don't seem to perform well in other than an ideal environment. The support is not very good without a contract either. I like ABB drives for less than an ideal environment. Comms is somewhat of a clunky setup for Ethernet. The support is horrible...

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