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  1. electricpete

    phishing risk as P.E.

    It strikes me there is an attack vector to be phished via the publically available info about you as a PE. Well of course it's not that much a risk if you use normal good phishing resistance practices, but here's how it would work: * starting with either a last name or a PE number, someone can...
  2. electricpete

    [cross post] Portable antenna-based EMI detection of arcing at wound rotor motor slip rings?

    Please see my thread here thread237-518299 If you have any response, please respond in that linked thread on the motor forum rather than here in the EE/Electronic forum. I don't want to create two different threads with different responses, Thanks!
  3. electricpete

    Portable antenna-based EMI detection of arcing at wound rotor motor slip rings?

    We have some noise issues that seem correlated to operation of a particular special purpose crane. During that period we have some wound rotor motors running wound and also some collector rings and brushes associated with the supply on the stator side (to accommodate getting stationary power...
  4. electricpete

    Found Maxima / wxMaxima and pretty happy with it

    I played around with the FOSS/gnu apps maxima and wxmaxima this weekend and found they check all the boxes for me. Maxima is the older program which uses command line interface. wxmaxima is a newer version that adds a GUI front end and a worksheet style interface (saves your input commands and...
  5. electricpete

    for unbalanced voltage, does the phase with lower voltage draw higher or lower current?

    Let's say I have a high resistance in the supply path to the motor such that one phase sees a lower voltage (or maybe it's more accurate to say the two associated phase-to-phase voltages decrease) Would you expect that phase to draw higher current than the other two, or lower current than the...
  6. electricpete

    Refurb of 4kv motor with good global vpi winding - opinions on need for dip and bake?

    My personal approach (spec) for refurbishment of VPI windings is clean/bake/test but no dip and bake unless there’s some good reason. The reason for my approach: about 20 years ago a shop did a dip and bake on one of our motors and the winding temperature went up. Later I saw the cooling...
  7. electricpete

    interpretting temperature rise and duty cycle for an intermittent run motor

    I'm not familiar with rating practices for intermittent duty motors. Maybe some of you are more familiar than me and may have some insights on this question. MOTOR DESCRIPTION: Nameplate on slide 1: 1.5hp, ~1800rpm, intermittent duty, Class H insulation, 115C ambient, 40C rise. FLA=2.25A...
  8. electricpete

    residual problem from filling a transformer with oil without vacuum

    I was asked for urgent input about something but only given some vague details, So of course, I'll turn around and do the same to you guys! This is 25kv / 13.8kv 3 winding oil winding transformer around 50MVA. Normal oil preservation is nitrogen blanket. At beginning of maintenance period...
  9. electricpete

    buying rolling bearing at the small end of the bore tolerance?

    For a bearing like a 6318 / 90BC03, the tolerance range on the bearing bore is 3.5425 - 3.5433. If you're evaluating an undersized shaft that's a pretty big range. We sometimes pull all of ours out of the warehouse and use the smallest one. But that doesn't always work, recently the smallest...
  10. electricpete

    Corroded RTD terminal board points (large motor in outdoor salty environment).

    On our large motors we have (like most) 6 stator RTD’s but we only connect one to our plant computer system. We periodically check to find the hottest one and leave it connected to the computer. We have frequent problems with erratic indicated winding temperatures creeping up. Often when we...
  11. electricpete

    repair shop replies to RFQ with boilerplate and irrelevant questions

    We send out detailed information with our RFQ's. There is one shop that on two consecutive occasions resopnding to a refuribshment RFQ responded with a long list of questions that seemed like a cut/paste. These included items that seemed irrelevant to the bid process, items that could be found...
  12. electricpete

    can overfilling a horizontal sleeve bearing motor cause excess oil usage

    Title should have been: can overfilling a horizontal sleeve bearing motor cause increased oil addition frequency I know that on a vertical motor if you overfill the oil, it can result in increased rate of oil loss from the upper bearing which would necessitate increased oil addition frequency...
  13. electricpete

    transformer highest temperature attained temperature indicator mysteriously spikes twice

    Background * 50MVA H / X / Y transformer 25kv to 13.8kv with LTC. * transformer has 3 local temperature indicators. oil temperature (mechanical / capillary). X and Y temperatures similar to oil temperature indicator except the temperature is boosted by resistive heater circuit fed by ct's...
  14. electricpete

    a session with chatGPT about induction motor testing.

    I hear a lot of buzz in the news about chat GPT... the newest conversational AI that's supposed to be able to do amazing things. So opened up a chat session and asked it a few questions about induction motor testing. My questions are in CAPS and the responses are normal mixed case.The...
  15. electricpete

    submersible sump pump part deux - does it rotate in reverse when flow is reversed?

    This is the same pump described in my previous thread thread407-494946 1/2 HP, 115 Volt, 60 Hz, 3.87″ Impeller, 2″ NPT Discharge, 20′ Cord, 3/4″ Solids. (No, we haven't changed anything since last thread) We "backflush" or "backwash" this pump with pressurized water source applied to the pump...
  16. electricpete

    effect of restricted suction upon pump amps (high speed multi-stage centrifugal pump)

    The pump in question is 10 stage horizontal 7300rpm centrifugal pump. It is driven through gearbox by a 600hp motor. For some context, the pump was operating in steady state at 70% motor load (approx 400hp), when suddenly the current began to increase, speed began to decrease, indicated flow...
  17. electricpete

    space heaters visibly glowing with normal current - is it normal / acceptable?

    We have an 8000hp vertical motor with six 480 volt 500w heaters (3000w total) in the lower bearing bracket area. The current measures 3.5A in each leg as expected. However the heaters are visibly glowing dark orange. I tried to take a picture and they came out more purple looking (both...
  18. electricpete

    an update to vba routine for highlighting the current cell

    In the previous thread below, I had posted a vba routine to highlight the current cell. thread770-485560 Recently I copied that vba code into a new spreadsheet and whenever I changed cell (activating the macro) vba threw a type mismatch error at the line "Set mySheet = Target.Parent" Target...
  19. electricpete

    where to sell old (text) books

    Early in my career (before the internet), I hoarded textbooks. First my college texts, then an assortment of new and used books as I got into new areas in my work. Now I'm late in my career and don't need them as much, and have most of the info available electronically anyway. The dates in...
  20. electricpete

    question about small submersible pump bhp vs current characteristics

    I have a question about Goulds WE0511HH pumps that we use in a sump application: Submersible Pump. 1/2 HP, 115 Volt, 60 Hz, 3.87″ Impeller, 2″ NPT Discharge, 20′ Cord, 3/4″ Solids. I'm not sure where is the best place to find info on this pump (google floods me with distributors), but here is a...

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