Interested to Buy Any Domain ? << Click Here >> for more details...
Transformer calculation
- 1 Answers
- 7379 Views
- Aramco, LMW Lakshmi Machine Works Limited, I also Faced
- E-Mail Answers
Answer Posted / faiyaz
We know that, Transformer always rated in kVA. Below are two simple formulas to find the rating of Single phase and Three phase Transformers.
Rating of Single Phase Transformer:
P = V x I.
Rating of a single phase transformer in kVA
kVA= (V x I) / 1000
Rating of a Three Phase Transformer:
P = √3. V x I
Rating of a Three phase transformer in kVA
kVA = (√3. V x I) /1000
but lets me try to explain.
Here is the rating of Transformer is 100kVA.
But Primary Voltages or High Voltages (H.V) is 11000 V = 11kV.
And Primary Current on High Voltage side is 5.25 Amperes.
Also Secondary voltages or Low Voltages (L.V) is 415 Volts
And Secondary Current (Current on Low voltages side) is 139.1 Amperes.
In simple words,
Transformer rating in kVA = 100 kVA
Primary Voltages = 11000 = 11kV
Primary Current = 5.25 A
Secondary Voltages = 415V
Secondary Current = 139.1 Amperes.
Now calculate for the rating of transformer according to
P=V x I (Primary voltage x primary current)
P = 11000V x 5.25A = 57,750 VA = 57.75kVA
Or P = V x I (Secondary voltages x Secondary Current)
P= 415V x 139.1A = 57,726 VA = 57.72kVA
Once again we noticed that the rating of Transformer (on Nameplate) is 100kVA but according to calculation…it comes about 57kVA…
The difference comes due to ignorance of that we used single phase formula instead of three phase formula.
Now try with this formula
P = √3 x V x I
P=√3 Vx I (Primary voltage x primary current)
P =√3 x 11000V x 5.25A = 1.732 x 11000V x 5.25A = 100,025 VA = 100kVA
Or P = √3 x V x I (Secondary voltages x Secondary Current)
P= √3 x 415V x 139.1A = 1.732 x 415V x 139.1A= 99,985 VA = 99.98kVA
Consider the (next) following example.
Voltage (Line to line) = 208 V.
Current (Line Current) = 139 A
Now rating of the three phase transformer
P = √3 x V x I
P = √3 x 208 x 139A = 1.732 x 208 x 139
P = 50077 VA = 50kVA
| Is This Answer Correct ? | 4 Yes | 0 No |
Post New Answer View All Answers
gas turbine genrator reactances
Define newton's law of viscosity.
A 100W electric lamp is supplied from a 115V, 60HZ source. The peak instantaneous power dissipated in the lamp filament is
WHAT IS SITTING AMPS IN OVER-LOAD RELAY FOR 1PH OR 3PH MOTORS?IF ITS NAME PLATE GIVEN MAX AMPS 10AMPS?
What are the components of feedback control system?
why did youi choose this career?
15hp motor wound by 0.9mm & 0.95mm magnet wire. at no load test it draw 4.2A current. Another motor with same condition draw 9.2A current. How can that occur? pls help
IF I KNOW THE AREA OF CROSS SECTION OFTHE WIRE , WATTAGE OF THE LOAD ,VOLTAGE SUPPLY WHAT IM GIVING TO THE LOAD AND ALSO POWER FACTOR OF LOAD ....... SO GIVE ME FOR WHAT AMOUNT OF CURRENT I SHOULD USE WHICH TYPE OF CABLE?
how to calculate sizing of NGTR (Transformer rating,Loading resistor value and Current rating of resistor) and what is the X/R ratio. Details : 11kV,Capacitance 1.73532 micro farads,40kA for 1sec.
how to design coil turns ?
Is it possible to connect a safety device in to parallel?
any earth foult trip the relay but in welding time not trip by earth foult
Hi friends, i m electrical engineer i want a cdr for migration purpose so anybody have information about this then send me on jayesh_ee88@yahoo.com.please try to me
hello friends this is krunal here.. i have applied for he officer train in hpcl electrical stream.. any one who have applied before for electrical stream please help me out.. post ur reply to my mail id: krunal_airforce@yahoo.com.. any tips, old questions for paper or any help will do.. plz help me.. your faithfully, Krunal Darji
how to calculate the power factor when instantaneous voltage and current has harmonics in it ?
