Is this adder added to my ambient temperature 86 f or is the adder added to the wire type rating 60 , 75 , 90

Sent from my iPhone using Tapatalk ]]>

Thanks, ]]>

I was reviewing my code book and got to thinking about duplex service conductors and I did my own practice load calcs and here is what I came up with.

1.Unit A & B each calculated load is 67A and 62A

2.Minimum service rating for each is 100Amps based on 230.79(C)

3.Single overhead riser conduit with single set service conductors is based on 129 amps

4.Based 310.15(b)(16) my over head service conductors are based on the calculated load of both units 129 amps = #1 copper conductors

Am I correct?

Or size of the service conductors is based on the main over current protection times two (so 200Amp and use 3/0)

Thank you ]]>

I am upgrading my system to bear load of 600 amperes,

Is it ok to do 70mm2 x 4 or 185mm2 x 2 would be better

Conditions:

Copper xlpe/pvc

Non armored

400 volts

temperature ambient 40C

Cable would be sandwich between two missionary wall filled with sand.

Commercially laying 70mm would cost me less than 185mm

Would support your help!!

Regards

Salman ]]>

I need some help. Can someone differentiate the two in a much clearer way? My understanding is that the prime power runs at a certain percentage of load while continuous runs at 100% load.

For example I need a 40 kVA continuous rating generator set. What will be its equivalent for the prime power generator. If possible, can you show some computations.

Thank you very much. ]]>

They will most likely be SquareD / Schneider. Max design amps is 150 but nominal load is about 120 amps.

1.) How much energy will the transformers consume through magnetizing current?

2.) How much effeciency is lost when you have to introduce a small auto transformer?

Thanks! ]]>

we have an 2500A , 480/277 V meter-service with 2500A, 3p GFI main C.B installed in corner of the property

feeding a 2500A, 480/277 V distribution gear with 2500A GFI main C.B at the exterior of the building.

Thank you ]]>

I need to take advice if its ok to install 70mm2 - 3 core non armored cable carrying 380 volts each in parallel of 4 cable to have load of 600 Ampere?

Each cable have capacity to carry 192 Amperes so 4 would be 768 Ampere!!

What should be installation technique? is gap of 20 CM enough between each cable?

Regards

Salman Khan ]]>

I'm using various amperage of the same Allen Bradley Breakers

1489-A1D020 - 2 Amp

1489-A1D030 - 3 Amp

1489-A1D050 - 5 Amp

1489-A1D200 - 20 Amp

These breakers feed power to I/O module,Power Supplies, and various transmitters in the field (Ultra Sonics, Flow Meters, Gas Analyzer).

The Engineer reviewing my Panel Drawings is requesting a coordination study for the breakers and main breaker in my panel that gets power from the distribution panel.

I would believe if a fault (Line-Ground) were to occur the branch circuit breaker that is experiencing the fault would trip first. None of these breakers have adjustable trip curves.

My response for the my Main breaker to the distribution panel would be for the Arc Flash firm who is doing all the calculation on new equipment.

Do these response have a case? ]]>

I have 100 Amp mains for units, and 1200 Amp main for the building.

Being that residential loads are non-continuous, I don't agree the mains should be required to be 100% rated.

Any suggestions on code reference to support my opinion? ]]>

I have a client who needs to replace their overcurrent protection devices as they are obsolete.

The CTs are mounted externally of the transformer, so line currents are used.

The transformer is an arc furnace transformer, rated 3750 kVA, 13.8 kV primary.

The transformer primary can be reconfigured on the primary between delta (157 A) and wye (90 A). So winding current is rated for 90A.

The secondary is wye, with voltages varying between 400V to 87V through series and parallel bus connections. Let's say that the current rating is 12390 A for now.

The reason for the primary voltage changes is for varying the voltage on the secondary for the arc furnace application.

What I need to know is:

1) Do I need to provide two overcurrent settings for the transformer when the client needs to change the primary? Is this due to the line currents changing?

2) Does changing the primary configuration affect the kVA rating? i.e. for delta, my rating is 3750 kVA, and for wye, 3750/sqrt(3) kVA?

Thanks in advance.

How r u?

Hope all is well

Pls help me to resolve the Electrical Problem. I am getting huge ampere in Earthing Cable. Earthing Cable is coming from Earth Pit. Then this Earthing Cable is fitted on Earth Bar. On this earth Bar, I am getting 135 Amp on Main Earthing Cable. When i am going to check Randomly on any panel like Sub Distribution Panel

Main Incomer Breaker 1000 Amp MCCB

R Phase- 81 Amp

Y Phase- 92 Amp

B Phase- 80 Amp

Neutral - 18 Amp

Earth - 18 Amp

I am thinking that may be Phase Cable Insulation failure or Neutral Cable inter change with Earthing Cable.

Outgoing Branch 100 Amp MCCB

R Phase- 3.4 Amp

Y Phase- 0.5 Amp

B Phase- 0.3 Amp

Neutral - 2.8 Amp

I am thinking that may be due to Unbalance Load

What do you think, where is the problem and what can be a cause?

Please Advise

Ajay Kumar Gautam

Electrical Engineer

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