dogleg43

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About dogleg43

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    Sparky

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  • Country Afghanistan
  1. I can't tell you where to actually get hands on experience with 3 Ø but here is a short list of what I believe is important to know: Read up on and understand transformer connections: wye, delta, open delta, grounded leg, etc. Understand where & how to identify the different phases (legs) in a panel and MCC. Be able to properly test L1-L2, L1-L3, L2-L3, etc. Know how to hook up a 9-lead motor on hi-voltage and low-voltage. Know the various wire color codes.  NEC rules are different from UL, NFPA-79, residential, and commercial color codes. Hope this helps.
  2. Yes, and UL508A, NFPA-79, and others.  Why wouldn't we?  It's just another necessary tool.  No different than owning a socket set, multi-meter, etc.
  3. You would need the entire NEC because every section in it constantly references following another section.  That being said, here are some the the main sections to become familiar with: 250 (grounding), 310 (conductors), 409 (industrial control panels), 430 (motors and motor controllers), 725 (Class 1,2,& 3 circuits), & 800 (communications) There are a bunch of good NEC guides out there.  Can't think of the names offhand.  Probably one by Mike Holt.
  4. Ground Loop

    To help things out make sure you grind the paint off of the backpanel where the ground bar is mounted. Also, ground the doors and the enclosure itself. Sometimes when checking continuity with a meter between ground and the backpanel I have'n't had a good connection.
  5. Why break the neutral? It is not required. If you do break it then make sure you don't use a fused disconnect.
  6. wire markers

    You could try these: http://www.grafoplast.com/ We have used them in a steel mill. They are kinda labor intensive to make but they are the absolute best if a wire label needs to remain readable.
  7. Machine Full Load Amp calculation

    NEC section 430.24 should get you what is needed unless the customer has some more specific rules: 430.24 Several Motors or a Motor(s) and Other Load(s). Conductors supplying several motors, or a motor(s) and other load(s), shall have an ampacity not less than the sum of each of the following: (1) 125 percent of the full-load current rating of the highest rated motor, as determined by 430.6(A) (2) Sum of the full-load current ratings of all the other motors in the group, as determined by 430.6(A) (3) 100 percent of the noncontinuous non-motor load (4) 125 percent of the continuous non-motor load.
  8. The major concern to look at is will the project work if interposing relays are added? If it is a high speed operation will the additon of the the response time of the relays be fast enough to control the process (in addition to the program scan time + the input card's response time + output card's response time)?
  9. Panel pictures

    Have to agree with BobLfoot here, but not sure that 4" is needed between the terminal and wireduct. One thing to do that helps is to use the hi-rise dinrail.
  10. Hand - Off - Auto Control Philosophy

    Sparky, From your description this a very common and accepted control scheme in my experience as a controls engineer (over 25 yrs). The Start and Stop/Hold buttons are bypassed in AUTO and then some sort of limit switch or other device will start and stop the motor/machine in an orderly process. My question is, in HAND should the Start PB always start something or should there be some sort of control device to inhibit the running of the machine? Example: If the machine is in HAND should the operator be able to start it and run an engine block off the end of the conveyor or should there be a photoeye wired/programmed in to stop the line if the engine block gets to the end of the line? Believe me, I've seen this happen. Management said HAND means HAND.............until two engine blocks were run off the end of the line. Then they said well, what we really meant was that HAND should still prevent stupid things from happeining. Yeah, right.
  11. Engraving Machine Recommendation

    We are also interested in an engraving machine. Do any of these interface to AutoCAD? We show the tags in our drawings and see no need to type things in again for tags.
  12. I cannot quote the NEC code section, but voltages may be mixed in the same raceway as long as ALL of the wires in that raceway have the same insulation rating. Now here can be your "out": the NEC does not apply to control systems, only premises wiring.
  13. What is a PSO? Cycle test or not, how are companies in the USA supposed to compete with this type of disregard for safety? We are forced to spend more time setting up to safely do a task than it takes to actually perform the task.
  14. In the past we've just used regular silicone and it works real well as long as both surfaces are clean when it is first applied. If something needs to change they come loose easily. Then apply a new bead of silicone when re-attaching.
  15. I/O wiring to terminal?

    We built panels for several customers whose spec called for fusing every output, ex: Chrysler. Their reasoning was it made things easier to troubleshoot. Costly, yes; but I have to agree with them. Whatever the customer wants. Also, regarding the original question about wiring from the I/O module to a terminal strip; that is how I like to see it. Over the last 20 years I've been on several projects where the PLC I/O was being upgraded and it made it easier if it was all wired to terminals.