How to Select Power Transformers             Image credit: Allen-Bradley / Rockwell Automation | Allied Electronics | RS Electronics   Power transformers convert power-level voltages, as opposed to electrical signals, from one level or phase configuration to another.   Understanding Power Transformers Power transformers are used to increase or decrease voltage to suit a specific application, and are widely used in electrical...
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Q & A on Power Transformers

We asked our users for their input on Power Transformers. Here are the results of 114 users familiar with Power Transformers.

Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice

Who Took Our Poll?Top

Design TrendsTop

Q:
What new technologies are influencing power transformer design?
18 answers
Answers:
I am not sure. I like the ferrite core type that can handle high frequencies, though I'm not sure if that is new by what you are asking.
~Engineering, Consulting, Bayfield, CO
Built-in protection system against fire, On-line conditioning monitoring, electronics tap-changing mechanism
~Damodar C, Engineering Consultant, Jaipur, India
Installation of fibre optics into coil windings to monitor the condition under load.
~Gregory Smith, Technical Trainer, Cleveland, South Africa
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Q:
From your perspective, which companies are creating the most innovative power transformers?
20 answers
Answers:
In our installation, mostly in the 50 MVA size, the Takaoka units were operating for more than twenty years with the oil leak from its OLTC as the only major defect it encountered.
~Engineer, Gen.santos city, Philippines
Earlier transformers were imported from foreign countries. Now transformers are manufactured in Sri lanka.
~Krishnamoorthy K, Engineer, Kandy, Srilanka
I cannot say. I look at every type I can, but I have not made such a comparison.
~Engineering, Consulting, Bayfield, CO
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Applications and UseTop

Q:
What are some of the applications you have used power transformers for?
32 answers
Answers:
Complete Supply, Installation, commissioning, testing and maintenance of 132KV, 220KV AIS and GIS type Grid Station including Power Transformer of 132/11 KV and 60 MVA Power Transformer for Pakistan Water and Power Authority (WAPDA) GRID System operation under world Bank and Asian development loan. We have complete tools for maintenance including Dehydration of Transformer oil with the plant of regeneration of Transformer oil under World Environmental Authority being approved to regenerate Power Transformer oil due to its use in bulk. Further we witness the all IEC Type Test in Short Circuit Labor try Holland. With this experience our Team has develop SOP for some routine test at site prior to energize the repaired Transformer.
~Khalid Malik, General Management, Lahore, Pakistan
We have used power transformers for step up application from 21 KV to 400 KV to feed power generated by 500 MW generator to grid. We have also used Unit auxiliary Transformers (step down) from 21 KV generator out put to 6.6 KV for auxiliary power consumption of power plant. Station transformer step down from 33 KV to 6.6/11 KV for station auxiliary application. Tie transformers (stem down from 33 KV to 11 KV) for common station auxiliaries applications. CVTs , ICTs in 400 KV grid etc.
~Project Management, Vikash Bhawan, korba, India
I use them for a variety of research projects. Sometimes to step down the voltage and rectify the output for electroplating. Sometimes I used high voltage transformers for ozone generation or even rectify the high voltage for applications such as electrostatic separation of valuable minerals from dirt. I also use high voltage transformer in a hobby...building Tesla coils. There are just too many applications to list here.
~Engineering, Consulting, Bayfield, CO
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Q:
Please share with us any “non-standard” applications that power transformers have been used for.
8 answers
Answers:
Any kind of special rectifying system Water treatment Explosion proof Submerged Earthquake proof
~Bertini Antonino, Engineering Consultant, Perugia, Italy
Parallel operation of different sizes/MVA ratings of power transformers
~Engineer, Gen.santos city, Philippines
Special three-phase resin transformers (kl H) for mining
~Kris S, Project Manager, Myszkow, Poland
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Q:
Do you know of any disastrous mistakes that occurred due to the incorrect usage of power transformers?
7 answers
Answers:
Our one Grid Station caught fire due to use of unbranded Transformer oil. During investigation it was found that the Transformer oil Pour point and flash point were very not up to the standard of IEC rules and regulation. When Transformer was fully loaded and working in the month of June where open temperature was 55 Deg C. Where the Transformer was designed on 45/55 ambient Temperature.
~Khalid Malik, General Management, Lahore, Pakistan
Yes. people over-loads the tr. in winter stating that the outside temperature is low. People use them without getting the oil and dissolved gas analyzed. people making tries after tries even on differential trippings or gas-relay operation.
~Damodar C, Engineering Consultant, Jaipur, India
-Common transformers for rectifying use or for wind turbines - Paralleling transformers with different characteristics - Surcharge or overvoltage due to capacitive loads
~Bertini Antonino, Engineering Consultant, Perugia, Italy
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FeaturesTop

Q:
What would your design or feature "wish list" be for this product?
12 answers
Answers:
Core-quality, Copper quality and section, protection systems, ease of over-hauling, leak-proof joints, minimization of losses etc.
~Damodar C, Engineering Consultant, Jaipur, India
Include an on line oil filtering device in their transformer equipment cause the one we have in our installations doesn't have it.
~Engineer, Gen.santos city, Philippines
Appropriately sized and tested. Accurate drawings for the form factor. Fast turnaround for quotes based on the application.
~John Boomer, Marketing/Sales, Mentor, OH
Good price All design factors within spec Low maintenance Protection against lightning and MV surges
~Willie B, Engineer, Luanda, Angola
% IMPEDANCE TRANSFORMER PROTECTION BIL SEISMIC FACTOR ALTITUDE TEMPERATURE RISE
~MOZAMMEL H, Design Engineer, MOSSOSSAUGA, CANADA
Transformer should be repairable and it should not be seal type.
~Krishnamoorthy K, Engineer, Kandy, Srilanka
Ideally, minimal heat, noise, and vibration. Inexpensive.
~John H, General Management, San Salvador, El Salvador
Noise, dimensions, temperature control, optimized losses
~Bertini Antonino, Engineering Consultant, Perugia, Italy
I don't get into the design of transformers.
~Engineering, Design, Havre de Grace, MD
No loss No heating Small and light weight
~Alain CROSET, Architect, TOULOUSE, France
Efficiency of transformers and load rating
~Derick P, Engineer, Dartford, United Kingdom
The standard time
~Marketing/Sales, RIYADH, Saudi Arabia

Q:
Is there any advice you want to share with users to help them avoid common errors in selection or usage of power transformers?
9 answers
Answers:
Varnished transformers are not really impregnated , they are just dipped into varnish , so we have to ensure that these are fully varnished up to the bottom layer of the transformer .
~Sreedhar Naidu, Production Engineer, Coimbatore, India
Insulation paper and use of International Brand of OLTC like Rein Heusen Germany and Insulates selection. These are the main factor where failure rating will be low.
~Khalid Malik, General Management, Lahore, Pakistan
Never change transformer percentage selection with the transformer under load. This can create spark and carbon deposit and possible failure of the transformer.
~Willie B, Engineer, Luanda, Angola
I would again state that intensive training on the design, components and their functioning and on the analysis of fault/breakdown is a must.
~Damodar C, Engineering Consultant, Jaipur, India
Make sure the KVA specified and the temperature rise specified is what you expected from the transformer from a CC, FAC and WC standpoint.
~John Boomer, Marketing/Sales, Mentor, OH
Transformer should be transported carefully. After transport we should allow some time to energize the transformer.
~Krishnamoorthy K, Engineer, Kandy, Srilanka
- First define exact requirement in use and environment and check the seller guarantees.
~Bertini Antonino, Engineering Consultant, Perugia, Italy
If there is enough budget,buy a transformer that's rated a bit higher than needed.
~Derick P, Engineer, Dartford, United Kingdom
Transformers should be over-sized 150% to allow for over-load conditions.
~John H, General Management, San Salvador, El Salvador

Buying AdviceTop

Q:
Do you have any advice for people relative to buying or using power transformers?
8 answers
Answers:
My experience is that people have very little knowledge on the OLTC components, their significance and the uses. In India, OLTC is provided on most of the power transformers but as far as 400kV tr. are concerned, they are never operated for voltage or load-flow control. Even on 220kv and 132kV, people have even instructed not to use them. Very few people filter the diverter oil. The faults or damages are not analyzed. Thorough training to the buyers and users is required. In case of 33kV and 11kV system either OLTC are not provided or they are never operated.
~Damodar C, Engineering Consultant, Jaipur, India
-Temperature limits for used insulating materials - Losses and temperatures with high harmonics content -Mechanical stability
~Bertini Antonino, Engineering Consultant, Perugia, Italy
Look at the design of the percentage selection switch. Care has to be taken with this as failure happens in this area often.
~Willie B, Engineer, Luanda, Angola
Losses at different frequencies are sometimes not mentioned in datasheets.
~Alain CROSET, Architect, TOULOUSE, France
Please use transformers standards and operating instruction manual.
~Kris S, Project Manager, Myszkow, Poland
Make sure all the transformer parameters are understood.
~John Boomer, Marketing/Sales, Mentor, OH
Do some resurge first and know what you are looking for
~Derick P, Engineer, Dartford, United Kingdom
Shop around and compare.
~John H, General Management, San Salvador, El Salvador


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