For example, 222k metal film capacitor, 224j 250VCIB metal film capacitor, 683 chip resistor, 4R30 chip resistor, 3R90 chip resistor, ect.

I have the numbers, but unsure know how to get exact electrical values. ]]>

I know that in the case of a wye-wye transformer built out of 3 separate single phase transformers, the 'neutral impedance' would be very high. The reasoning is to consider the arrangement with a single phase load connected line-neutral on the secondary. This secondary current requires primary current on the connected leg. However there is no secondary current on the other two legs of the wye, and thus the primary current on the other two legs of the wye is just magnetizing current.

But in the case of a common 3 leg core, each secondary coil interacts with all three primary coils, so current on only one of the secondary coils can cause current on all of the primary coils.

I was hoping for a pointer to how to calculate this case.

Thanks

Jon ]]>

I've seen fire pump feeds require the 2-hour rating MI cable provides, but this engineer has MI Cable feeding two life safety panels on his riser? The runs are insanely long too so it's going to be very expensive. Is this required? Why would he have drawn it this way?

I thought it was just fire pumps that required the 2 hour rating. Any help is appreciated.

]]>I thought it was just fire pumps that required the 2 hour rating. Any help is appreciated.

How do you compute the impedance of this transformer? It's 500va 230vac to 115vac isolation transformer with this specs:

https://www.hammfg.com/electronics/t...s/line/172.pdf

The 500VA step down isolation transformer would be put before the type 3 SPD in the following. I'd like to know the impedance of the transformer and how many length of say AWG 10 it is equivalent to so I can decrease the length of the wire which can be done.

Thank you. ]]>

Actual voltage drops vary greatly from average:

Circuit 1 (coils 1,2, 5, 6, 9, 10, 13): 14.3, 10.1, 6.4, 24.3, 8.4, 14.8, 24

Circuit 2 (coils 3, 4, 7, 8, 11, 12, 14): 19.6, 29.2, 6.1, 7.4, 27.5, 32.5, 6.5

Could the position of the rotor poles in relation to the stator iron affect individual pole voltage drops (maybe due to inconsistent reluctance paths)? Or is this actually an indication of a failing rotor/shorted field windings?

Apartment:

19 feet by 50 feet 3va 2850 Va

3 small appliance circuits 4500

stove 8000

no washer

no dryer

no heating or cooling

No other appliances

total usage: 15350

first 8000

15350 â€“ 8000 = 7350 * 0.40 = 2940

/240 45.6 50 amps

no stove__ 7350 amps/240v 30.6 amps

Whole house calc with apartment:

4 floors including basement and apartment

33 by 50 times 4 floors times 3Va = 19800

11 small appliance circuits over three floors 16500

garbage disposal 1176

2 ranges 16000

2 laundry 3000

0 dryers 0

2 dishwashers 2400

3 waterpumps 3528

total usage 62404

first 8000

62404-8000=54404 *0.40 = 21761 =29761

= 124 amps

if take out both stoves: 46404 so 23361 = 97.35 amps.

If I take out the circuits for the apartmentâ€¦ I get

47054 Va = 23621 = 98.42 amps. Or 85 amps without stove...

So somehow I get less amps with apartment than without apartment. What am I doing wrong?

Apartment is one range probably gas but...set for 8000 electric just in case

3 small appliance circuits

no washer or dryer

no extras.

Am I messing up somewhere??? ]]>

200,000 kA

X/R = 10 (test X/R for LV fuses is 4.89)

Due to the high X/R ratio when I run my analysis the actual fault current used for the fuses in the service boards is over 200k. Does this mean the 200k fuse is actually not rated adequately in this example? ]]>