Why not both?
I'm 'burnt' over space heaters to maintain winding insulation integrity due to my service area being adjacent to the Gulf Of Mexico. High humidities are a constant, and the 'normal' space heaters often are not sufficient to keep windings dry. Talking our engineers into...
There comes a time in the life of a circuit breaker when it needs a complete tear-down and inspection, followed by reassembly using the proper lubricates.
WD-40 and its numerous imitations are NOT lubricants. Our substation crews called it "PM (preventive maintenance) in a can" because if a...
We had a transformer failure in a station using 6.9 kV. Search for a possible replacement or temporary rental until the original unit was repaired quickly confirmed what I suspected - 6.9 kV is NOT common. We found ONE rental, and it was less than 2/3 of the capacity we needed. Of course we...
Per your drawing:
The common practice was to have a sizable resistance as part of the lamp assemble so that shorting the lamp itself or its socket would not result in a trip of the circuit breaker.
I can't remember ever seeing the green light wired through the trip coil.
old field guy
Had a client send a 7000HP 4160V motor in for rewind. It came back with the same symptoms you describe.
Got with the rewind shop. Instead of 2300-volt windings to connect in a wye for 4160, they did 4160 windings. When hooked in a wye, those expect 7200 volts.
Motor ran well when...
davidbeach:
EM relays are why modern relays have torque control equations and time dials.
An SEL-411L is a device capable of may wondrous functions, but an HZ or a KD was the work of a genius. Once you have everything as numbers you can do anything that math and the available computational...
Older CT's used to be susceptible to magnetization due to the DC offset of starting inrush. Older electromechanical relays managed to work through the few cycles of distorted waveform before things evened back out.
The CT's I experienced with this problem were part of a motor differential...
I worked nine years in a petrochemical plant with THREE operating electrolyzer units producing chlorine and caustic soda. Small leaks were a common thing. We all carried personal escape respirators. One of those would 'load up' pretty quick in any kind of release.
I got gassed a couple of...
hokie66-
You know that and I know that, but it made the news cycle. I don't think it was much of a transformer, judging from the smoke cloud.
OFG
old field guy
What's your oscillography look like from the 387?
A quick look at the transformer should give you a good idea about the 'low oil' alarms. It takes a good amount of leakage to reach 'low level'. You should see that easily. If that's the case, the question arises as to what caused that amount...
Per Artisi:
"Trained and licenced operaters using approved designed equipment as it is blatantly obvious by now that what is currently being used and operated is dangerous."
Just exactly what we need. I can see the legislature in its "If it saves ONE child" and "We must do SOMETHING" modes...
We always did the polke drop test using a AC, the rationale being that AC might be better to detect issues with the magnetic components as well as shorted turns.
old field guy
When you bench-tested the transformer, did you use full voltage on the primary? Absent a full voltage test because a lot of shops don't have 4160 easily available, did you perform a reverse excitation test?
In this test, using a variable voltage source and taking safety precautions because you...
I too would like to see vectors.
In the normal world most VFD's exhibit near unity power factor, so you'd expect that when the majority of your load is on VFD, the power factor would be near unity, and when you bypass the VFD, you're back in the world of induction motors, where a power factor...
IBRCAN-
Thanks for the response. I've found a couple of 1200-RPM units on the used/surplus/rebuilt market, but nothing has made me move towards buying one.
A lot of my older stations still have original generation and those are 'big iron', heavy, slow - 750 RPM, 200 KW. Unfortunately I have...
LittleInch-
No, I'm looking at buying replacements. I have extensive installed base of backup generation in my five-state area of responsibility, but most units are 1800 RPM units of various outputs.
I have three offshore platforms, all with oversized generators that are 20-40 years old...
