In the IEEE Red book, when you are calculating the utility Zpu they just use the simple formula: (KVAbase)/(KVAsource) which is a unit less number.
Thus for a base of 100MVA and a fault MVA of 400 you would get Zpu=100/400=.25pu.
I don't understand the math behind that simple formula as I would...
I am trying to do some energy calculations for an aquaculture project that is trying to calculate different methods of creating flow in a channel and injecting air into water. So I am electrical engineer in background, but have some basic fluid knowledge. They currently want me to evaluate a 2...
An electrician ran 1000 ft of parallel 350 kcmil Aluminum XLPE cables in a PVC conduit underground. The run was from a non-fused disconnect to several large brine pumps on a platform. About 500 ft in to the run they put a non-wet proof splice kit in. About 7 months ago the customer noticed...
Hi,
Awhile back I created a spreadsheet that showed how the current and voltage will change on a wye unbalanced system depending on single phase or three phase loads being added.
I have since tried doing the same thing with a delta high leg transformer. I can't find any real examples on the...
Lets say you have a three phase 208/120V supply and you calculate the kVA on phase A, B, C as following: 7.42, 4.29, 2.62. Now you need to determine the actual current per phase so you can get your wire sizes (don't worry about 1.25% of cont load).
How would you calculate the current per...
Trying to figure out the simplest design for the following:
There is an existing hospital with a 2000A 480V service going in to a GE fused disconnect with GFP and test button. The customer is being required to install an alternate power quick connect in which the customer decided to install at...
Using IEEE Grey book for Volt Drop I get the following:
(sorry about the notications)
VD = I[RCosq + XSinq]
PF = Cosq
Sinq = Sin(Cos-1q)
If I am given the z% of a transformer and I wanted to figure the voltage drop by using the IEEE formula I would first come up with:
z=sqr(R*R +X*X)
R=Zcos(q)...
Here is my design situation: a new generator is being installed that will feed a generator panel with 16 breakers feeding out to 4 pole ATSs. I will have a disconnect in the panel and there will be an electronic breaker in the generator that is about 75 ft from the building. Since the first...
Is there any code that determines when an electrical room is required for panels, service meters, or disconnects for <=600V equipment? In particular I was told that for a commerical service coming in to a strip mall needs to have the meter and disconnects installed inside and not outside. No...
Need some sanity checks. I am looking at a 15 story condo that has the MDP on the first floor. There is a 600A breaker that feeds (2) sets of 350kcmil conductors up to the top floor's Rooftop panel. The conduits leave the MDP in a two PCV conduits and only have three conductors and one...
Does anyone know if there is code or a process to follow for replacement of equipment damaged by fire? I have a customer who had a fire in the bedroom. It burned the paint off the panel, but the wires are still in the breakers. I am thinking that even if the inside looks good the...
I am getting mixed feedback from different sources on how to size the overcurrent protection device for a generator feeding an ATS that is dedicated to the fire pump. When I read 695.4(B) it says overcurrent protective devices between an on-site standby generator and a fire pump controller...
Say you have three motors individually protected off a tap by circuit breakers that was sized at 225% of NEC table 430.250 and the feeder is protected by a fused disconnect would you size the fuse at a) Largest motor breaker size + FLA of other motor taps b) same as previous, but do calculations...
Has anyone used a program called Design Master within AutoCAD and now use AutoDesk Building Systems for their electrical design work? I am curious on anyones opionion on their satisfaction of one over the other.
I have a question about using the Point to Point Short Circuit Current calculations for three situations and need to know how to address them when calculating the "f" factor
1) For Line-to-Neutral Faults most articles assume that the neutral conductor and the line conductor are the same size...
Does anyone have a simple 1-3 page conctract from small electrical design for end users. I am a one man firm that has been issuing Quicken quotes for design. The customer gives me a PO and then I bill it. Now I am starting to think that I should have some time of simple contract to add to my...
I am trying to determine which pump is better for an irrigation pump. My question is can you determine anything about the quality of the pump based on the full load amps if both pumps have the same HP rating (both are standard motor/pump design and not variable speed)? Or do you only look at...
