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Anonymous Poster

Load Calculation

05/28/2008 1:02 AM

hi,hope this question will prove futile.

well i m having a site about 8 km of stretch with 2 kw of load .now the problem is to find the voltage drop and the size of the power cable to b used?the load is distributed along the stretch uniformly.

and my second question is that i have a power source at one end .do i need to use transformer in between .if yes that at what distance?and of what rating.

and of course a have source of 440 v transformer.but the load is single phase.

to b presise load discription is like this

load one----------24v ac 15 w---------30 in number

load two----------12v dc 5w----------18 in number

load three--------220 v ac 3w---------12 in number.

i hope u will solve my problem.thanks

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Guru

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#1

Re: load calculation

05/28/2008 2:48 AM

Alternative one

There are 30 nos 15 watts loads .Group them into 3/4 section.for sub distribution.Run higher cross section cable to each Group.Then normal cross section cable to individual loads.

Alternative two

Provide Transformers in each group for distribution.

Cost factor has to be worked out and decided.

Please indicate the allowed voltage drop.

Please identify yourself and place.

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Guru
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#2

Re: load calculation

05/28/2008 2:53 AM

As you hope it will be futile ... I shalln't bother trying.

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#3

Re: load calculation

05/28/2008 3:36 AM

Hello Guest,

Because each load is extremely small, the cheapest way is to use an individual transformer for each load.

A 15W transformer is going to cost approximately $2.50, a 5W around $1.90, and the 3W transformers around $1.60 each (US$ prices), because you are going to use several of the same sizes, so they will be somewhat cheaper than a single transformer unit cost.

Size of transformers: 15W would be approx 25mm cube, 5W approx 25mm cube (including diodes/capacitor assembly for the DC required), and 3W approx 16mm cube.

You haven't bothered to state the Country this mythical installation is in.

You have also not bothered to advise which loads are at which points in the 16km round journey.

You have not bothered to state the frequency of your AC supply either, so I have designated it at either 50Hz/60Hz.

So the above advice is about the best you're going to receive, unless you reply, with , otherwise it is an exercise in futility.

Kind Regards....

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#4

Re: load calculation

05/28/2008 5:06 AM

Well your english is something. However, your question does not have enough information. It appears you are are talking about 415 or 380 volts 3 phase power source. Load 1: Obviously there is a step-down transformer. What is the Volt-Ampere rating? Load 2: Obviously there is a transformer and rectifier. What is the power rating? Load 3: Clear These pertinent questions will help you in finding out the maximum current flow in your circuit and the voltage drop evntually the size of cable.

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Anonymous Poster
#5

Re: Load Calculation

05/28/2008 11:04 PM

As per me if you required 24 V at load end than you put a servo stablizer at receiveing at of rating INCOMING 100-433V OUTGOING 0-50Volt,

voltage drop will not be as high as it drop voltage from 433 V to 50 volt & you will easly received atleast 50 V at receiving End.

I still have voltage issue then install a capacitor of 25 KVAR at receivign end to increase voltage level

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#6
In reply to #5

Re: Load Calculation

05/28/2008 11:38 PM

i would suggest you to refer cable manufactures catalog where you would find voltage drops mentioned for Both AC and DC applications and cable de rating factors due to ambient temperature, method of cable laying in air.in ground& In duct etc based on this information you can decide most economical sizing of cable and transformer as suggested by our friends above.

crm

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#7
In reply to #6

Re: Load Calculation

05/29/2008 12:25 AM

Voted 1 good answer ;o)

I agree, go and check out the manufacturer of the cables, for voltage drops for your distance,

also where are the loads? ok, you have x number of 1 load, and y number of another load, but the distribution? evenly spaced, all grouped at 1 end, are they moving?

Calculate the current draw drop points along your lines, and combine the resistance of the feeder line to calculate the voltage drop on each section, add those drops to get the complete voltage drop, making sure the resulting drop is still within the supply tolarance.

If its outside the tolarance, you may need heavier feed lines, or multiple feed lines, this will come down to cost.

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