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  • Users: patm72
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  1. patm72

    Busbars on edge distance and derating

    Hello, Would anyone have an idea from which distance should derating be applied to busbars run in parallel? My application is at 480V and busbars would be on their edge, one per phase, and sized for about 900A (that is over the FLA by a factor of 1.25 already). Thank you.
  2. patm72

    Uninsulated live parts clearance

    Hello, I am trying to find an Canadian code equivalent to the table for minimum spacings found in NEC 408.56. Can anyone point me to the article that would treat of this subject? Thank you.
  3. patm72

    Transformers dimensions

    Hello, For a given kVA size (~2000kVA), 480V output and other similar insulation characteristics (BIL for example), how much larger could a dry-type 13.2 kV transformer be over a 4.16 kV? Thank you!
  4. patm72

    Crimping tools

    When it comes to crimping open type contacts and ferrules, is the shape of the tool critical? I see that TE, Altiv, Cinch and other manufacturers have these contacts and seemingly an associated crimping tool. Sometimes, those tools are extremely expensive, making their purchase prohibitive for...
  5. patm72

    Electrical machine and removable panels bonding

    Hello, I have a machine in an enclosure with multiple doors and bolted panels. The machine itself has a 25A three-phase 480VAC fused disconnect, for driving two motors of respectively 1 and 5 HP. At the core of the machine is a gas turbine. I'm actually pushing for having all doors and...
  6. patm72

    PMSM unknown voltage withstand rating and using it at higher voltage (600V vs 480V)

    How do motor manufacturers do to obtain a given class of insulation? I am mostly interested in knowing if a motor that I know runs very well with a 480V rated VFD (supplied with the same line voltage), can run well with 600V as the line voltage at the VFD. Obviously, the VFD would be rated for...
  7. patm72

    NEMA MG standard for PMSM?

    Hello, Would anyone be able to point me towards which NEMA standard should a permanent magnet synchronous motor be built according to? What info should appear on the nameplate of such a motor? Same as for induction? These motors of foreign fabrication are used in a packaged unit. The motors...
  8. patm72

    CSA 22.2 No. 14 and MOV

    Can anyone help me shed some light on the following claim found in CSA 22.2 No. 14 (2008) paragraph 4.15.2 regarding MOV's as overvoltage protection devices? Where does it come from? Surge suppressors of the metal oxide varistor type are not considered to be acceptable overvoltage protection...
  9. patm72

    MV transformer in equipment

    Hi, I'm looking for some guidance on how to integrate a MV/LV transformer in a machine. Looking for MV machines on the web, well, only MV motors pop up. If you search for MV equipment with embedded MV transformer, you invariably hit switchgear apparatus. What I have is a packaged machine...
  10. patm72

    Permanent Magnet Synchronous Motor (PMSM) sizing of conductors (with a VFD)

    Hi, I'm trying to validate to which value I should size conductors going to a PMSM. The FLA of this motor will be 304A - and 308V (this is a high speed application, 24 000 RPM, continuous duty). Note that this voltage is developed at the motor which is driven by a VFD receiving 480V, 3 phases...
  11. patm72

    NEC Article 430 Part IV confusion

    On the interpretation of Article 430 part IV from NEC (Motor Branch-Circuit Short-Circuit and Groud-Fault Protection), I am quite confused by the term "Ground-Fault Protection". While I understand the difference with the other member, "Short-Circuit", I am wondering what the use of fuses brings...
  12. patm72

    Fuses for circuit powered by VFD DC bus

    Hi, I'm trying to find fuses for the North American market (UL) to protect a low amperage circuit derived off of a VFD DC bus (650VDC+). The circuit consists in a magnetic bearing controller used to levitate the shaft of a motor driven by the VFD. The manufacturer recommends using 14x51...
  13. patm72

    Transformer connection configuration

    I am wondering about which transformer configuration to use in a 3-phase low voltage system, depending on the 600V feeder configurations below. Both are possible, although I would expect the case 1 to be most probable. The primary of the new transformer has to be 600V, and the secondary 480V...
  14. patm72

    Graphical symbol for Normally Open Held Closed limit switch

    I'm currently trying to hold my ground over the symbolic representation of a Normally Closed Held Open switch with an engineer. He pretends my representation is not per ISA 5.1. As far as I can see from the internet, I do not see a representation of such a switch at all according to this...
  15. patm72

    Industrial Control Panel SCCR

    Does a machine that has terminal blocks wired upstream of a MCCB to allow flexibility of connection in the field have a SCCR equal to that of the terminals? As you know, terminals have a 5kA or 10kA rating at best if unprotected. The reason for that arrangement is to have flexibility to...
  16. patm72

    NEMA MG 1 Part 31

    Can anyone tell me if PMSM’s are subject to the NEMA MG 1 part 31 standard? To me, they should meet a certain voltage insulation level, but is it that? Or is that only for induction motors?
  17. patm72

    Weird VFD impact on feeder bus

    Hi, We have a pair of KEB VFD’s (319 kVA) installed in the field, driving a pair of turbo fans (250hp) within the same enclosure. The power devices in order are MCCB – IR – VFD – Sine Filter – PMSM Motor. As mentioned, two sets are installed in the same enclosure, but they are fed from two...
  18. patm72

    Autotransformer protections

    I work for a company where we are designing machines working at 480V comprising a 75HP PMSM motor driven by a VFD and appropriate controls. The service voltage (480V) enters the unit through a MCCB, from which we split between the “Input Reactor – VFD – Sine Filter – Motor” branch and another...
  19. patm72

    Corner grounded delta transformers theory

    I am currently working on a project where the equipment is to be fed by an MCC powered by a corner grounded delta transformer. I was aware of the many configurations transformer windings could have, but I have a hard time grasping the idea of the corner-grounded delta... Grounding a phase, it...
  20. patm72

    NFPA

    A cable (A) feeding an electric 3-ph motor using a softstart can be disconnected from a machine. Another cable (B) feeds control voltage to the same part of the machine. When this latter cable (B) is connected, it enables a control contactor feeding the 3 phase voltage to the softstart and the...

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