my last boss was the worst. he was an unrealistic old school asian workaholic. needless to say, i quit after a year. He said we could work on "flex-time" outside of normal 8am to 5pm. So I came in at 7am but when I tried to leave at 4pm, he says "flex time" doesn't mean I can leave early. It...
Hi all,
Just a quick simple question. I had a problem with an elevator and the contactor was returned to me. It looks like one of the poles is slightly damanged so it looks like the motor was probably single phasing, causing burn out. My question is can a motor even drive any load with only 2...
But since the ac/dc motor generator failure coincided with the power outage, its hard not to draw any conclusion that doesn't include the fact that power integrity was not optimal. Maybe it was already in bad shape and maybe power did blink during the power outage causing an out of sync...
yeah... that sounds like a reason. I don't really know why they are using power surge and outage together. When power is reapplied after an outage, is there usually an above normal surge of voltage/current? Is that a misconception?..or are surge protectors at home made to protect against...
Actually, the motor shop says it was due to a power surge, but a consultant is saying that it wasn't likely. So I was hoping someone might be able to shed some light. Thanks!
Hi all,
We had a failure of an AC to DC converting generator on the AC side. The failure coincided with a power outage. Would someone help give reasons as to how a power surge could have caused failure of the generator?
Thank you in advance for any response!
Hi all,
I have a question about motor wire sizing. NEC says we gotta follow table 310-16 if we will have motor wire in a raceway. However, it looks like our motor supplier provides leads that are smaller than NEC code would require in a raceway. It looks like they provided leads following table...
So does it just mean that power can be "weak" (meaning voltage can drop more during motor start) not just between buildings but even within a building? Are there any remedies to this or is it just a "fact of life" type deal?
Hi all,
I was wondering if anyone could enlighten on the following.
Why do some building power supplies have more voltage drop during motor starting than others? Lets say one 50HP motor causes momentary 5% voltage drop due to transient current surge during y-d transfer. Then lets say in another...
Hi all,
Would anyone chime in on what they think is the best measuring equipment for motor and motor circuit analysis? I've seen some engineers at our sister factory with portable oscilloscopes that cost close to 10,000 dollars, but I think that's overkill for motors.
Would a 300Mhz. bandwidth...
I still wonder about Y-D Open transition transient torque vs. DOL starting torque. What's worse? 1-2 cycles of auto reclose current / torque? or 5-6 cycles of starting current / torque. (5-6 cycles for motors I deal with)
I didn't originally design the elevator systems I deal with using...
Hi all,
I saw the subject on contactors come up again.
http://rapidshare.de/files/1496465/hb.pdf.html
Please download the above.
Page 3 of attachment (hb.pdf) shows wye delta starting of a 40HP/200V motor using 208V/60Hz/3Phase power supply.
Scale is 250A / div. (A) and 50ms/div (horizontal)...
For a typical AC-3 Application, a certain sized starter, or more specifically, the contacts of the starter are tested to be good for 1,000,000 electrical operations under its rated application. And tests are done at a high frequency, almost 20-30 make/breaks per minute.
However, for elevator...
I have been looking around online and have come across a lot of contradicting information concerning motor characteristics under variations in voltage.
According to G.E. if voltage is increased say 10% on a particular motor power factor will reduce by 4%, and full load current will decrease by...
