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  1. Gr8blu

    Safety Class Vs Construction Class

    In what country? Under whose rules?
  2. Gr8blu

    Commutator marks in DC Motors

    If the brush "span" is wrong (the brush contact does not span enough bar surface in circumferential direction), we can end up with one or both of the following. 1) The brush face area may be less than ideal, which translates to high current density - which in turn tends to start burning the...
  3. Gr8blu

    Commutator marks in DC Motors

    THe spacing for bar burning is going to be related to the number of coils per slot. If the burn is every second bar, then the commutator most probably has (BARS) = 2 x (SLOTS) However, I did see the same thing once, when (BARS) = 4 x (SLOTS) and only every second bar was equalized.
  4. Gr8blu

    Help Understanding MIL Specs

    MIL-P-23377 Epoxy Polyamide MIL-P-23377H MIL-PRF-23377 MIL-P-23377 ( MIL-P-23377H ) ( MIL P 23377 ) ( MIL-PRF-23377 ) is a two component, corrosion inhibiting, polyamide primer. This epoxy primer offers excellent corrosion and chemical resistance over properly prepared aluminum and steel...
  5. Gr8blu

    NEC Temperature Class

    The issue is igniting the combustible/flammable material. The normal concern is that having the material come in contact with a surface that has enough heat to ignite the material (since there is almost guaranteed to be oxygen present as well). Then the matter becomes whether 1) the material...
  6. Gr8blu

    Commutator marks in DC Motors

    Probable causes: 1) Incorrect brush alignment / off neutral. This can be because of the physical positioning of the brush contact face relative to the commutation zone, or it can be a result of dissymmetry in the magnetic field (interpole or main pole winding is exhibiting shorted turns...
  7. Gr8blu

    Electrical Check Lists - Engineering Phase

    Question (as written) is too vague. Note that an internet search should turn up at least a handful of reference documents, provided you input the appropriate search terms. You may have to choose portions of them and merge into a "custom" document to facilitate what you're trying to accomplish.
  8. Gr8blu

    How are you managing capital or client projects in your ERP without losing visibility?

    To some extent, all the options amount to "customizing the ERP". The biggest difficulties I see are: A) project(s) definition is lacking so that materials and resources can be tracked appropriately. B) not adjusting the project plan when new information is developed (e.g. the material now has a...
  9. Gr8blu

    A Conceptual Modification to the Continuing Education Requirements

    I will be the first to admit that mentoring is a MUST - both during the school portion of becoming an engineer and afterward, in the practical experience realm. Looking back, I was incredibly lucky in both areas compared to a lot of my classmates - and even more so when compared to those other...
  10. Gr8blu

    DC Motor Drive - Imbalanced input (line/neutral) and output (motor + / - ) current

    1) All three DC systems are NOT wired the same, according to the image appended. Units 1 and 2 take power from "Phase 2" to neutral; Unit 3 takes it from "Phase 3" to neutral. I suspect the Unit 1 connection was intended to be from "Phase 1" to neutral - it would be a good idea to physically...
  11. Gr8blu

    Fan blade worn out

    Step 1: Determine WHY the blade (or judging by the images provided, the WELD) failed in the first place so you can fix the problem and not just apply a bandage to a symptom. Step 2: Figure out where the missing material went. Are the piece(s) now causing trouble in the downstream direction by...
  12. Gr8blu

    Hole size with tolerance for Shaft

    First decision; is the key meant as a location device or as a torque transmission device? If locating, the fit between shaft and sleeve will be tighter than if the intent is for the key to transmit the majority of the torque. Second decision: is the process driven by the shaft going to require...
  13. Gr8blu

    Paper or online engineering journals?

    If you use online storage, be sure to check the fine print. Most of the time, the online storage entity owns the copyright - not you.
  14. Gr8blu

    GE Vertical Motor - Spherical Roller bearing with springs

    @RM12 Is your vibration in the radial or axial direction? More details on vibration in the following links. https://ludeca.com/blog/balancing/10957/1x-rpm-vibration-is-not-always-caused-by-an-unbalance-here-are-9-other-faults/ https://power-mi.com/content/misalignment
  15. Gr8blu

    How to test short in alternator rotor winding inside the slots?

    SA07 - In addition to the Baker, there are two other fairly common testers in use. one is manufactured by Schleich, and the other is called a "PJ Tester". http://www.pjelectronics.com/ https://www.motordiagnosticsystems.com/products/schleich_advanced_test_technologies/MTC3_Series My personal...
  16. Gr8blu

    black start using aeroderivative turbine

    The basics behind it can be found in documents such as the one at the following link. https://www.netl.doe.gov/sites/default/files/gas-turbine-handbook/1-1.pdf
  17. Gr8blu

    A Conceptual Modification to the Continuing Education Requirements

    First time I heard the NEC mentioned was during the summer between my first and second year of my degree. I was working a summer "intern" type of job for the local utility to help pay for the following year's tuition. After I completed my degree, I had to verify one of our more complex designs...
  18. Gr8blu

    How to test short in alternator rotor winding inside the slots?

    For industrial equipment, the allowable variation is dependent on the type of test. DC Drop Test (Apply DC to circuit, measure DC voltage across each pole). Allowable variation is 5% from average (most shops will raise concern at 3%). AC Drop Test (Apply AC to circuit, measure AC voltage...
  19. Gr8blu

    PLF Load based on 16" spacing

    ...use the formula above. FOr distances in inches, convert the distance to feet by dividing the inches by 12. Example 1: 24 inch spacing. PLF = PSF * 24/12 = PSF * 2 Example 2: 16 inch spacing. PLF = PSF * 16/12 = PSF * 1.3333 A uniform load is a continuous load along the entire length of...
  20. Gr8blu

    A Conceptual Modification to the Continuing Education Requirements

    There was always more to learn - it hasn't gotten less so as I've progressed through my career. In part that is because my level of responsibility (and therefore the areas covered by my responsibility) has increased, as well as the complexity within a given sub-category. In a typical year, I...

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