How is the primary connected to on a pole mounted transformer. Like a small 75kVA, with 240/120 secondary. I only ever see one squiggly line down to a high voltage bushing going in to case, which is also tapped to an arrestor, grounded to the case. The secondary has its three insulated terminals...
I guess I'm okay with the ampacity and voltage drop. I am concerned that we probably will not have all of it off of the reel at once. Meaning that it will have to dissipate whatever fraction x 250W is wound around the reel. Could this prove to be a problem, opinions? Full load operates for about...
Does anyone know, in general what NEC section (table) best describes how to derate SOW type cable. I am unable to verify voltage drop calcs. The application is for (temporary) power disto from smaller portable generators (15kw). The cord reels are specified with 200' SOW cable, 3wire+G #10AWG...
A senior electrical designer is trying to convince me that on a 480 system voltage drop isn't really a consideration. Here's the situation. We have a feed to an 800A MCC with about 434 TCHP / 514 KVA of motor load. He insists that since the voltage drop over the feeder is on 1-2% that the...
Here is a page that has some interesting pictures and videos. Although they are not really educational as you request, they are entertaining. High voltage arcs, sparks, including a substation fuse failure, substation transformer exploding, arc flash demo.
http://205.243.100.155/frames/longarc.htm
I was intending to use LPS-RK fuses to replace FRS-R type, for some FVNR starters (10-40hp), vfd's (40hp), & SMC's (125-150hp) all 460V. According to NEC 430.52, size time-delay fuses at 175% of full load current. I have no nameplate information from the motors, so I assumed that FLA = FLC for...
I am curious about the history of Carbon Monoxide awareness (residential) in the USA. I am a young firefighter. We receive CO alarm activations year around, nearly all false alarms / malfunctioning detectors. The Red-Cross has distributed CO alarms free for about the last 7 years (literally like...
The NEC classifies low voltage as ranging "up to 600 volts nominal", with higher levels being "above 600 volts nominal". No mention of AC or DC I believe. ANSI low voltage range voltage class stops at 600V also. However I generally consider:
Low voltage: 0 to 1000 V
Medium Voltage: 1001 to...
Let us know how many people are asked to leave because they did not have an approved calculator. When I took the FE; of the 200 or so, about 10 people were thrown out of the PE exam section!
Good luck.
Is it appropriate to install both a line ractor and load reactor (dV/dt filter) to combat: harmonics on the source feeders, and IGBT effects on long motor leads, respectively. I am assuming our motors were not spec'd as inverter duty rated. The various drives range from 30, 45, 75, and 100 hp @...
We are working at a plant with 480/277V, and is distributed using 3 wires + ground. The incomming feeders are 13.2kv to a delta - wye transformer. I guess the wye secondary is grounded somewhere at the substation? Although I only see a delta-star diagram on the nameplate. Should / does the sec...
Opinions needed: What does this mean to you?
MCC Incomming Line Disconnect
Circuit Breaker
Frame - 800A MC
Trip - Non-Auto
The first three lines are obvious. What is the reference to Non-Auto (Trip). I was told it was a thermal-magnetic breaker, without the overload ("thermal"). It would...
I suppose you could use any 3v lithium cell that was close right. Is this a a logistics problem? Chances are if you have access to the internet you should find about everything, 2032 - very common size. You could find a calculator or led eychain, and rip one out. Anyways, I would direct you to...
Does the double ended substation have some variety of interlock? One purpose being to prevent backfeeding of a faulted primary feeder. All of ours are spec'd with simple Kirk-Keys. I would investigate trying to balance the loads better before moving to a different topology. Do you have any data...
I ground cable tv connections only at the demarc point, to the the building electrical panel ground (residential water pipe usually). Beware, I have been "shocked" before by cable connections to old tube tv's due to a lack of polarity on the plug, and a part of the chasis becoming hot...
What is the propper pressure to pump into the FDC sprinkler system. I thought it was constant, regardless of building size, assuming the inlet would be sized appropriately to maintain estimated flow rates. So if the building has a standpipe, what is the minimum working pressure that must be...
