Home Page News Search Contact Us Language Bar فارسی English
If you have faced with a case that needs conferring during your work or studies, you can submit it here as a "New Riddle" and we'll show it in your name. Notice: Site owners have the right to accept a riddle or not, or make a little changes in submited riddles.
Submit New Riddle

Voltage transformers are occasionally used to adapt voltage protective relays and instruments with nominal voltage of main circuit in low voltage switchgears.
Author : Hamid
A power transformer manufacturer which was located in economical boycotted country met some problems in material provision.
Author : Hamid
A power transformer manufacturer decided to decrease their production budget by reduction of material amount used in transformer construction.
Author : Hamid
Regarding to physical size of national power systems, rate of power exchange and transmission lines capacity are increased by using of high voltage technology.
Author : Hamid - From: Iran
As you know, because the B/H curve of the magnetic material forming the transformer Core is not linear.
Author : Shahbazi - From: Iran
Our utility specifications calls for VTs of burden 100VA. As the connected burden is low and due to switchgear compact designs (for indoor applications), manufacturers are offering VT of burden 30VA or less.
Author : thamee97
In an industrial project, the customer decided to change first order for new power transformer. ...
Author : Hamid - From: IRAN
we face a problem that our generator output terminal has a phase sequence U-V-W (clockwise) but the transformer terminals arrangement is W-V-U (anticlockwise) with a vector group Dy-11.
Author : GUEST
A 3-core cable was installed to supply a DC UPS system and it was realised they actually needed a 4-core cable , 3 phase & neutral.
Author : WALKERP
Transformer No1 is having Primary tapping for 11275V and at secondary 445V v getting. Similarly  Transformer No 2  tapping position is at 10725V and at Secondary 415V v getting.
Author : Adarsha - From: INDIA
I was carrying out a fault current distribution for an earthing design for a primary or zone substation when I found the transformer to be used was Yyn0 (33/11 kV). Apparently the lines company here have many substations with these transformers.

Author : Marcos
R core transformers are very popular in control circuits due to the advantage of negligible leakage of flux.
Author : Mak - From: India
Hi I was hoping someone can assist me with some information regarding methods for detecting partial discharge in transformers and power cables.

Author : GUEST
please help!!!!!!! i need to to know the advantages and disadvantages of an air gap on a ferrite core, of a transformer.
Author : GUEST
Can i used step down transfprmer 6.6KV/415V as a 415V/6.6KV application area?

Which kinds of factor affected for this job?
Author : ANKUR PATEL - From: india
How the electrical energy flows from one side of transformer to other side?
Author : Baran - From: IRAN
Is there any special recommendation for converter transformers sizing?
Author : Arash - From: IRAN
How can we do power transformer insulation resistance test as an acceptance test?
Author : Parham - From: IRAN
How do the transformer vector group influence on permissible neutral loading and level of system ground fault currents?
Author : Arash
For making of a current injection source with 2000 A rating current, can we use an ordinary current transformer with ratio 2000/1 A, and connect 1 A side to one ordinary low current injection source ( 1 A) for obtaining of 2000 A in other CT side?
Author : Hamid - From: IRAN
What parameters shall be checked in power transformers parallel operation?
Author : emad - From: Iran
2700kVA 33000/1050 volt
Dd0 and Dy5 configeration cyclo convertor transformers generating large amounts of hydrogen gas. Various modificationd to the clamp config have been done the Dd0 as proven to be a succes but this hasnt worked on the Dy5.
Author : Claudio - From: South African
Optimum pulse in Rectifier transformer
In a erectifier transforemr it is preferred to go for more and more no of pulse operation . For example in a Bridge configuration 48 pulse operartion is adequate .
Author : R K Mohapatra - From: India
Whether a Tertiary winding is essential in  a 3 phase 3 leg power  transformer and not in 5 leg configuration ?
Author : R K Mohapatra - From: India
Is there any link between Odd Harmonics causing Partial Discharge in Medium/High Voltage ( in this case 15 KV ) Cast Resin Current Transfomers , Voltage Transfomers or Power Transformers.
Author : Shane Alfonso - From: South African
I got the below of the Internet, what I want to know is the following, will the noise being measured be different in auto than in manual, will the noise also be different if the tap changer is in different settings in manual i.e. 3,5 or 6
Author : Lucas van der Merwe - From: South African
Why cannot we use whole of parallel power transformer bank capacity for power transfer in practice?
Author : Alvina - From: Armenia
Can somebody share the  experince of a 100 MVA 220 kV class transforemr working at a continuous  oil pressure of 4 kg.
Author : R K Mohapatra - From: India
Can a tertiary winding on a power transformer be used for station supplies? if so how is its connection to the auxillary transformer. what other use does it have other than 3rd harmonic suppression and compensation for unbalanced loads.
Author : Hatisari Kujinga - From: Zimbabwe
On a substation 3 phases tranformer 34500 V / 480-277 V, I would to know what is better or recomended.
Author : Ronald Vincenti - From: Costa Rica, Latin America
A 20 MVA transformer can be change to 25 MVA is possible without change in the winding?
Author : A.Selvakumar - From: India
I have created a model of a transformer comprising a figure 8 core with face 1 of the primary and face 1 of the secondary coils in the first 'hole' of the figure 8 and ...
Author : Barry Fleming - From: Scotland
i want to know how we detrmine (ngr)value in power transformer protection.
Author : Hindi - From: Sudan
How to design a choke/reactor for 3phase 18amps 1.1mh

Author : Sudharsan - From: India
How to design a three phase to single phase transformer for 10kva 415v/230v it is possible?
Author : sudharsan - From: India
I know basic equation for Arc furnace trafo cal Q= m C . delta T
Can anybody explain what the major consideration for Arc furnace trafo calculation is?
Author : ASAD MALIK - From: Saudi Arabia
Are there any recommendations for power transformer reactive compensation?
Author : Ebrahim - From: Iran-Tabriz
Is the megger test necessary for new power transformer and are there any accepted values for measured megohm in insulation resistance test?
Author : Ahmed - From: Egypt
Load calculation for t/f and cable capacity determination of /cable size for any load.
Author : Gajendra - From: India
How do u choice a Transformer Being a Client?
Author : Baba - From: Qatar
How we can calculate the total power transformers capacity which are installed in parallel?
Author : Saeed ahmed - From: Qatar
How do you model a single coil of a Power transformer?
Author : Nixon Pambirei
In Oil or Dry Type Transformers, Why do they lay 7×1Core Single Core 800 or 630 Sq.mm Cables Instead of 3×Core cables like the Primary Side of the Tx.
Author : BABA - From: Qatar
I need to harvest power from a high voltage line using the Faraday's law. i.e. whenever current flows in a conductor, magnetic field is produced around the conductor.
Author : Kotteeswaran - From: Chennai, Tamil Nadu
Which side of a loaded transformer contains the magnetizing current?
Author : Hamid - From: Iran
During magnetic balance test in auto transformers, It is experienced that ...
Paralleling of two tramnsformer with various secondary group vector, is it possible?
Author : Rahgozar - From: Iran
Anyone can teach how to calculate the temperature rise of the transformer,especially for up to 20kVA?
Author : Ajei - From: unknown
Can anyone teach how to calculate the per phase ohmic value of a 220/132 kV, 160MVA T/F with an example for different taps?
Author : Kazi - From: unknown
In utility transformer 20/0.4 KV, Yd11, shall we ground the primary side of transformer?
please explain in detail.
Author : Dayita - From: India
Is there any way to calculate the no-load loss of transformers?
Author : Shahab - From: Iran-Tehran
What happen when we apply dc voltage to the primary winding?
Author : Nycknikki - From: India-Gujrat
Please explain us about parallel transformer equipment and protection.
Author : Rizah Julianto - From: Singapore
Runing 3x40MVA transformers in a setup of 66/11 KV system! how risky is it? what is the fault current if the circuit is at fault?
Author : BABA - From: QATAR
Can any body tell me what is the permissible value of tangent delta of windings for commissioning of Transformers?
Author : Sreelatha Gajjala - From: India- Hyderabad
In one of Transformers, sometimes megger value is good, Polarisation index is of the order of 2 and the dryout of insulation is as per established VPD process, still the tandelts is high. What could be the reason?
Author : Gajjala Sreelatha - From: India- Hyderabad
Could high tan delta be the reason of Hydrogen generation in Transformers?
Author : Sreelatha Gajjala - From: India- Hyderabad
Can you please tell me whether low aromatic content in oil (less than 4%) and high aromatic content (more than 8%) can lead to stray gassing for example Hydrogen generation?
Author : Sreelatha - From: India
When an OLTC is mounted accidentally  in such a way that the tap position (say 4)indicated on top of OLTC do not match with that(say 3) shown in the motor drive when...
Author : Sinnadurai Sripadmanaban - From: Srilanka
What are the functions of matching transformer,isolation transformer,zig-zag transformer,lighting transformer,high impedance transformer etc?....
Author : Sinnadurai Sripadmanaban - From: Srilanka
What's the effect of core saturation on magnetizing current, i know it increases but why, I think may be I m not clear about basics of magnetizing current???????
Author : Abhishek Kumar - From: India
What are some techniques/ requirements to increase the power transfer efficiency of an IPT system?
Author : Hendrik - From: South Africa
Please explain with fig. how neutral point is created with a zig-zag connection type earthing transformer. ...
Author : V.K.Nambiathiri - From: India
Can you please tell me is there any possibility that 5th harmonics can be higher than 3rd harmonics in outer two phases of the transformer?
Author : Sreelatha - From: India
Can you Please tell me what is internationally accepted definition of " Failure Rate of Transformers"?
Author : G.Sreelatha - From: India
In order to increase the impedance to tertiary winding in a single phase autotransformer tertiary winding is placed on outer limb of a 3 limbed single phase or a 4 limbed single phase configuration....
Author : Sreelatha - From: India
Please tell us the calculation of impedance for the transformer with windingd placed on different legs (not on the same leg). It is required for 500MVA, 765 kV Power Transformer design. ...
Author : Sreelatha - From: India
I have tried to calculate inductance using FEM analysis for one of our transformers. we are getting the solution in matrix form (self and mutual inductances for LV, HV and Tap windings) as given below:
Author : Sreelatha - From: India
I want to know about basics of vector group.
Can you please tell me for what application what type of transformer vector group we have to select?
Author : Sreelatha - From: India
To prevent rusting on hardware various kinds of plating are restored to.
Zinc plated or stainless steel hardware react with transformer oil to produce stray hydrogen which is often mistaken as an offshoot of partial discharges. ...
Author : G.Sreelatha - From: India
Can you please tell me the saturation flux density of CRGO material used in transformers?
Author : Sreelatha - From: India
Can Dy5 and Yd5 vector group transformers be paralleled?
Author : Unknown - From: Unknown
How can we caculate the maximum load to be connected to A 3-Phase, 4wire 480:208Y/120V 150KVA Transformer?  
Author : Khalid Ameen - From: Yemen
We have received a enquiry with 63/63/0.25MVA, 80/23/??/0.42kV PT. In this we have to decide the ?? winding and the vector group connection is Ynyn0+d+syno. ...
Author : Sreelatha - From: India
Normally impulse test shall be conducted on transformer with negative polarity. ...
Author : M.RAJKUMAR - From: India
If some knows about short circuit impedance calculation of split winding arrangement in power transformers, kindly let me know.
Author : Sreelatha - From: India
In a Transformer Bushing, there is a mention about the tan δ, that represents the loss factor of the bushing. What does the two values of tan δ indicate? ...
Author : Vinayak - From: India
We have 2 transformers at my work that are Dyn5.5 and Dyn6.5 respectively.  Now, I get that they are 30-degrees out of phase with each other.  But, I've never seen another transformer with ...
Author : Brian - From: USA
How does this kind of transformer works, where these are used? Why does the Y phase current is almost double than the other phases? ...
Author : Vinayak - From: India
Rating of a furnace transformer in delta primary is ok but if primary in star transformer kva rating is less than of the rated capacity why?
Author : Unknown
Can you please tell me the definition for knee point voltage of core (CRGO) material used for power transformers?
Author : G.Sreelatha - From: India
How is to decide the kVAR rating for the no load compensation of the transformer and where the capacitor is connected?
Author : Unknown
Non Identical phase displacement transformers are  operating in parallel. How?
Author : Soman - From: India
Question: The nameplate on a 50 kVA transformer shows a primary voltage of 480 V and a secondary voltage of 120 V.We wish to determine the approximate number of turns on the primary and secondary windings.....
Author : Encoder - From: Complex
Explain the Functioning of Oil Surge Relays in OLTC transformers
Author : soman - From: India
We have the following problem with tank shielding (i.e magnetic shunts for reducing tank stary losses):
We are fixing the shield with bolts leaving 75-200mm on the taop and bottom portions of the vertical shield without bolting. ...
Author : G Sreelatha - From: India
why transformer rating in terms of KVA / MVA
Author : jayesh b sathwara - From: India
In one of our 50MVA, 132 kV class transformers tested recently, stray losses are coming around 100kW more than the calculated although all other losses are with in the limites. ....
Author : Sreelatha - From: India
Would you please let me have enough information about the situation in which a 3 phase transformer has 1 phase broken and supplied with 2 phases while on its secondary side. it has:
Author : Kazemi - From: Iran
please guide, how to calculate Neutral Ground Resistance for transformer (630kVA, 11/0.433kV) for neutral earthing to limit the earth leakage current to 750 mA as per recommendation in hazardous area locations.
Author : Tarun Panwar - From: India
If we change the phase sequence of Power Transformer, will it change the vector group of Transformer? If yes/No Why
Author : Deepak Tardalkar - From: india
How much voltage can be steped up or down by a transformer?
Author : Unknown
I want to know what should be the limits of C & DF for normal threshold, Specially when previous results are not available to compare with.
Author : Talha
Clarify the difference between the terms Buchholz relay and oil surge relay as applied to the transformer protection
Author : Ajay John - From: India
In the case of transformer with on load tap changing,percentage impedence changes with the tap changing and fault level reduces when percentage impedence changes. ...
Author : Ajay John - From: India
Is over surge relay necessary in transformer with OLTC with rating less than 500 kVA?
Author : Ajay - From: India
Upto what transformer rating we can use fuses as primary and secondary protection is there any limit like > 1 MVA Fuse on primary and ...
Author : Ikhan - From: UK
i need to build an AC current injection, to test CT, circuit breakers etc. the device should be small and portable. can you please help me or give me a ...
Author : Enas - From: Sudan
Secondary voltage measured at secondary of a 500kVA, 11kV/433V, transformer at no load was found 430V. But when measured at 200kVA loaded condition it was 460V.Why
Author : V.K.Nambiathiri - From: India
What should be the rating of Zig-Zag type Earthing Transformer to be placed at 3.3kVside of a 66/3.3kV ,YNd1 transformer for providing E/F protection at 3.3kV side?...
Author : V.K.Nambiathiri - From: India
Two numbers of transformers (1600 KVA & 750 KVA ) are running  in parallel . Bus coupler is inserted in bus for different type operations. ...
Author : kannan - From: India
Why we are using only Dy5 vector group for the transformer for Static Excitation System?
Author : Deepak
What is the difference between power & distribution transformers, I have heard a lot about it that power transformer designed for max efficiency at  full load and ....
Author : Deepak
I was working in a transformer manufacturing unit in India as per my company 222va ac 98.25 f 50 maximum flux 0.58 , 3 phase inductor 0.69 mh and ....
Author : Manoj - From: India
How 20 degree phase possible in transformer which is used for VFD
Author : Mrithun - From: India
Hi How can we size the three phase transformer when we have three different unbalanced loads.
Author : Iqbal - From: UK
Can you advise what will be the Voltage to Earth on delta side.

The Data is

400/650 STAR / DELTA Dyn11 5.75%
Author : Iqbal - From: UK
Why transformer energy transformation principle is based on electromagnetic or inductive as we have seen two inductors representing primary and secondary. ?....
Author : Debabrata Das - From: INDIA
I have referred many books regarding choke design..But I'm not able to design the chokes..i need a clear guidance to develop my design  knowledge.
Author : Deepak - From: India
Change Language :