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KARTHIKA BHASKER
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CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/11/2011 11:32 PM

I WANT TO DESIGN A TRANSFORMER FOR A SHIP. I HAVE ALL THE LOADS CONNECTED TO IT. IT HAS A 415V INPUT AND 230V OUTPUT. NOW I WANT TO CALCULATE THE POWER. FOR THAT I NEED CURRENT. HOW CAN I FIND IT?
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pnaban
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#1

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/11/2011 11:52 PM

If you know load and voltage assume a pf and calculate the current.

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Tornado
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#2

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 12:13 AM

Add up the watts of all the concurrent loads (or all of the connected loads adjusted by a diversity factor). If the power factor (PF) is known, divide the kilowatts by PF to determine the required KVA of the transformer (allowing for some extra to start the largest motor). If the PF is not known, a common assumption is 0.80.

I'm not sure why you need a transformer in the first place. 415 volts in delta equals 230 volts in star.

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KARTHIKA BHASKER
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#4
In reply to #2

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 8:22 AM

i need a transformer to step down the three phase which is generated by a diesel generator. for light loads in ship and all i need a 230 V supply.
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Aseer
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#7
In reply to #4

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 12:12 PM

Tell me do you have neutral along with 3 phases which is generated from the diesel generator ?

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KARTHIKA BHASKER
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#9
In reply to #7

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 11:25 PM

I am not sure about the neutral coming from the diesel generator. Is it necessary?
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Tornado
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#10
In reply to #9

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 11:41 PM

It might not be necessary, but it could be convenient, eliminating the need for a transformer. Please revisit post 2.

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zamanengineer001
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#11
In reply to #9

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/13/2011 12:39 AM

If your power is coming from diesel generator, you dont need any transformer, definitely it has neutral, use it to get 220v a.c
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KARTHIKA BHASKER
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#5
In reply to #2

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 8:28 AM

the supply to the DC distribution board is given by the transformer which i mentioned earlier. If you don't mind please tell me that how to determine the current rating of a fuse which is connected to the loads.
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TonyS
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#6
In reply to #5

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 9:07 AM

Where did the the DC distribution board come from?

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KARTHIKA BHASKER
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#8
In reply to #6

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 11:22 PM

It is not dc distribution board. it is 230V ac distribution board
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Aseer
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#12
In reply to #8

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/13/2011 1:28 AM

You are confused man.Even I understood what you need to ask but you don't know how to ask ....Sum up all the connected load (watts) the voltage is 415V so;

Ampere = Watts/ (415 x 1.732 x .8)

Calculate the current as above way...

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KARTHIKA BHASKER
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#13
In reply to #12

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/13/2011 11:28 PM

is there any problem in overestimation of loads ?( as per that loads we are designing the fuses)
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Aseer
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#14
In reply to #13

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/14/2011 12:05 AM

Why overestimation? get the complete Electrical diagram of the system or physically figure out and count all the loads,then consider 20% extra rating for the fuses If you want.

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KARTHIKA BHASKER
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#15
In reply to #14

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/14/2011 7:43 AM

we are overestimating because we are designing the system. so, all datas regarding the lighting points and all are assumptions. The requirements will change depending on the customer. that's why we are planning to overestimate.
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Aseer
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#3

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/12/2011 12:14 AM

Dear, find below few usefull basic formulas for electrical system design.Do it by your self man...


Symbolic:

E =VOLTS ~or~ (V = VOLTS) P =WATTS ~or~ (W = WATTS) R = OHMS ~or~ (R = RESISTANCE) I =AMPERES ~or~ (A = AMPERES) HP = HORSEPOWER PF = POWER FACTOR kW = KILOWATTS kWh = KILOWATT HOUR VA = VOLT-AMPERES kVA = KILOVOLT-AMPERES C = CAPACITANCE EFF = EFFICIENCY (expressed as a decimal)

DIRECT CURRENT
AMPS=WATTS÷VOLTSI = P ÷ EA = W ÷ V
WATTS=VOLTS x AMPSP = E x IW = V x A
VOLTS=WATTS ÷ AMPSE = P ÷ IV = W ÷ A
HORSEPOWER=(V x A x EFF)÷746
EFFICIENCY=(746 x HP)÷(V x A)
AC SINGLE PHASE ~ 1ø
AMPS=WATTS÷(VOLTS x PF)I=P÷(E x PF)A=W÷(V x PF)
WATTS=VOLTS x AMPS x PFP=E x I x PFW=V x A x PF
VOLTS=WATTS÷AMPSE=P÷IV=W÷A
VOLT-AMPS=VOLTS x AMPSVA=E x IVA=V x A
HORSEPOWER=(V x A x EFF x PF)÷746
POWERFACTOR=INPUT WATTS÷(V x A)
EFFICIENCY=(746 x HP)÷(V x A x PF)
AC THREE PHASE ~ 3ø
AMPS=WATTS÷(1.732 x VOLTS x PF)I = P÷(1.732 x E x PF)
WATTS=1.732 x VOLTS x AMPS x PFP = 1.732 x E x I x PF
VOLTS=WATTS÷AMPSE=P÷I
VOLT-AMPS=1.732 x VOLTS x AMPSVA=1.732 x E x I
HORSEPOWER=(1.732 x V x A x EFF x PF)÷746
POWERFACTOR=INPUT WATTS÷(1.732 x V x A)
EFFICIENCY=(746 x HP)÷(1.732 x V x A x PF)
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nesubra
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#16

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/19/2011 9:33 AM

First of all stop using capitals .It amounts to shouting.Now do u want to design a transformer or select a suitable transformer.Both are different.I don't think designing a transformer is your job.It is an expert job.

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KARTHIKA BHASKER
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Join Date: Oct 2011
Location: Cochin
Posts: 12
#17
In reply to #16

Re: CALCULATE THE AMPS OF A LOAD CONNECTED TO THE TRANSFORMER

10/20/2011 12:31 AM

i want to select a transformer
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