Transformer:
A
transformer is an electrical (static) device which transfers power from one
circuit to other circuit magnetically at a constant frequency. In fact
transformer works for AC power. The two circuits namely primary and secondary
(LV- low voltage & HV- high voltage) are electrically isolated but coupled
magnetically. The power levels of LV side and HV side are same and maintain a constant
frequency however the voltage and current parameters varies based on the turns
ratio. Turns ratio (K) is the ratio of Secondary turns to primary turns. Transformer
is generally rated in KVA.
If one side
of the transformer circuit has less turns compared to other side it is treated
as LV side (as voltage directly depends on the no. of turns of a coil) and HV
side is the one which has more no. of turns. On LV side the transformer operates
on low voltages, high currents and on HV side its opposite.
Transformer structure
Transformers in Solar PV
applications:
Particularly for solar PV power plant applications
transformers are generally used to step up the voltages to higher values (Several
KV’s). In detail, Transformer’s input is
connected to the inverter output and its output is connected to the utility
grid. It functionality includes stepping up the voltage levels of the generated
power from the PV panels , equaling it to the grid voltage levels so as to have
safe on grid operation.
On other
side it also provides galvanic isolation between DC input and AC output side
(Grid) & filters the harmonic content from the inverter output.
The High voltages in transmission and primary distribution sides
leads to low power losses, so generally engineers prefer transformers for
having high voltages to cut down losses.
Transformers in PV application are generally categorized as:
1. Distribution transformers
2. Power transformers
Distribution Transformer: Pole, pad mounted are two types of
distribution transformers. Pad mounted distribution transformers are common
type of transformer used in solar array fields, while pole types are frequently
used in conventional distribution systems. Typical power rating varies between 50KVA
-2500KVA. In general, primary sides are connected to the inverters (string type)
output (typically 230V, 440V AC), Outputs of distribution transformers (33KV
maximum, however some vendors offer higher voltages on request)are connected to
substation lines or power transformers in the case of large solar PV plants.
Distribution transformer
Power transformers: Power transformers are step-up transformers;
these will step-up the voltages to very high levels (66KV, 132KV, 220KV, 400KV)
and transmit the power. Higher voltages are preferred to reduce the losses. Typical
power rating is 200MVA & above. For large PV power plants power
transformers are used to synch with the grid to allow the transfer of generated
power to the utility grid.
Power transformer
Solar PV plant incombination with
Distribution and Power transformer
Again, two
types of distributed transformers based on the coolant used Dry and Liquid type. Liquid type (windings
are of oil immersed - NONA (Natural Oil Natural Air)) because it dissipates
heat quickly, also it is smaller in size (doesn’t require thick insulation, core
material) and comparatively has lower cost.
For typical
indoor installations Dry type (transformer windings are encased with Epoxy
resin) transformers are used, however these are fire proof and non- explosive.
These are not design flexible and are of particular ratings & complex manufacturing
process makes it more costly.
Single Line diagram of solar PV plant:
The pointer
indicates the use of transformer in PV power Plant.
Important parameters of transformers:
Voltage, basic
impulse level, winding connections, impedance, efficiency, winding material,
temperature rise, cooling, insulation class, seismic resistance, altitude derating.
Voltage: It is important to mention the
voltage rating (ranges b/w 300 – 700AC), as inverter output determines the low voltage
(LV) level of the distribution transformer. The output voltage of the
distribution transformer will determines the voltage level of power
transformer.
Winding connections: It is important to mention the
winding connection type for the design of protection scheme, the
most common 3-phase distribution configuration for transformers in solar
applications is the delta-to-wye configuration, with the wye grounded or
ungrounded. This configuration allows for an independently derived neutral on
the wye-connected secondary winding, which not only is essential for safety
purposes but can also provide multiple voltages at the inverter pad without
requiring additional transformers. The delta-connected primary winding provides
a reliable configuration for the utility, because it allows harmonic currents
to circulate within the transformer. This prevents harmonics from flowing into
the electrical distribution system.
Substation
transformers usually use the grounded wye–to–grounded wye
configuration. However, substation transformers are multi winding transformers
that also have a tertiary delta winding. This delta winding prevents harmonics
from circulating in the electrical transmission system and stabilizes the
neutral point when loads become unbalanced.
BIL (Basic impulse level): In terms of product safety BIL is
very important as it determines the withstand capacity of the winding
insulation inside the transformer. Normally the transformer is subjected to impulse
voltage levels which are very high than the rated voltages (max./operating) to
make sure will defend themselves in case of any faults or malfunction.
Impedance: It is the opposition to the AC power,
characterized by Z (can be reactive, resistive). Normally it is rated as %Z, it
is used to determine the voltage drop and at no load it can be taken the
voltage drop of the transformer.
Transformers
under 50KVA have impedances of less than 2%, for 75KVA – 2500KVA transformers;
the standard nominal impedance value is 5.75%. The IEEE standard allows a
tolerance of +/- 7.5% for two winding transformers and 10% in multi winding
transformers.
Efficiency: Transformer efficiency is defined as
the ratio of output power to the input power, it depends on the capacity of the
transformer. According to NEMA (National Electrical Manufacturers Association)
for 75KVA – 1000 KVA transformer the range of efficiencies would be normally
98% - 99%. The loss of power is due to the internal losses of the transformer.
Winding material: Manufacturers offer transformers
with copper or aluminum windings. Copper offers better electrical conductivity
by volume than aluminum but aluminum offers better electrical conductivity by
mass. Copper made transformers are more likely compact and are more costly.
Temperature rise: During the operation of transformer
the losses inside will result in heat which inturn results in temperature rise,
this effect reduces the performance of the machine. Technically it is defined
as the average temperature rise of the windings compare to the ambient
temperature is about 40 deg Celsius when the machine is at its nominal rating.
For liquid
filled transformers are 55 – 65 deg Celsius, dry types are about 115 – 150 deg Celsius.
If a technician installs a liquid-filled transformer with a
temperature rise of 65°C in a 40°C environment and loads it at its nameplate
rating, the average temperature of its windings should not exceed 105°C.
Transformers used at PV projects experience more thermal cycling
than a typical utility distribution transformer. A solar project transformer
starts cold in the morning and reaches its peak temperature midday during peak
ambient and peak energy periods. Then it cools back down and starts the cycle
over again. Special consideration needs to be given when selecting a solar
project transformer to ensure that the cooling system can handle the
temperature swings. An O&M team is also important to carefully monitor and
reset the pressure system in some geographic locations.
Insulation class: A
transformer’s insulation class correlates to its temperature-rise value. Manufacturers
provide electrical isolation in the transformer with enamel-coated wires and
insulating material between the winding layers, and they vary materials and different thickness to achieve different insulation-class ratings. After they have insulated
the transformer winding, they impregnate the coils with varnish to minimize the
possibility of moisture intrusion, increase mechanical strength and improve
heat transfer, and they then mount the transformer winding in a protective
enclosure.
Cooling: Dry-type transformers
are self-cooled and rely on passive methods conduction, convection and
radiation to transfer heat from the transformer to the environment. Liquid-type
transformers are more common in solar applications.
Transformers steel enclosures filled with a nonconductive dielectric
fluid, which insulates the internal components and helps keep them cool,
protect liquid-type transformers. The heat that the windings generate transfers
to the dielectric fluid, which circulates via natural convection. The heat then
dissipates into the environment via the transformer’s oil cooler, which is an
external heat exchanger or radiator. This is a rather elegant and
energy-efficient cooling method.
As shown in following, the industry classifies liquid-filled
transformer cooling according to internal cooling medium, internal cooling
mechanism, external cooling medium and external circulation method.
For example, pad-mounted
distribution transformers have a cooling classification of ONAN: O indicates that the cooling medium in
contact with the windings is an oil with a flash point of 300°C or less; the
first N indicates that the oil
circulates via natural convection; A indicates
that the external cooling medium is air; the second N indicates that the air
circulates via natural convection.
Substation transformers of 10 MVA and larger typically have multiple
capacity ratings, such as 12/16/20 MVA, which correspond to different cooling
classes, such as ONAN/ONAF/OFAF. In this example, the lowest rating, 12 MVA,
represents the self-cooled transformer capacity and has the ONAN cooling class
rating. The next one, 16 MVA, is the capacity of the transformer when it uses
fans to force air through the oil cooler radiators; this rating has the ONAF
cooling class rating. The highest rating, 20 MVA, is the capacity of the
transformer with both internal coolant circulating pumps and external fans, and
it has the OFAF cooling class rating. Each cooling level typically adds
approximately 25% more capacity.
Dielectric fluids can be either mineral oil or less-flammable
vegetable-based oils, such as Envirotemp FR3 and BIOTEMP. Transformer products
designed for solar applications often use the latter because they are derived
from a renewable resource and are biodegradable.
Seismic resistance: According to the International
Building Code contain
specific seismic resistance requirements for transformers at certain places.
Installations at health care facilities, emergency response locations (such as
fire and police stations) and critical government facilities frequently must
have seismic certification.
Altitude de-ratings: Because the air is less
dense at higher altitudes, the effectiveness of the cooling system and the
dielectric strength of the transformer decrease at higher elevations.
Therefore, you must either de-rate transformers installed above 3,300 feet or
specifically design them for the location. The product safety standard that
applies to liquid-filled distribution and substation transformers requires that
you de-rate transformer capacity by 0.3% for every 330 feet increase in
elevation above 3,300 feet.
Technical parameters of aTransformer:
Transformer configuration: Type of winding connection of the
transformer.
Rated power (KVA) : The maximum power the transformer can
withstand. It differs for different types of transformers.
Primary voltage (KV): The LV winding of the transformer
which is based on the inverter output. It depends on the transformer rating.
Efficiency: It is defined as the ratio of output
power to input power of the transformer.
BIL(basic impulse level): It is the maximum withstanding
capacity of the insulation winding during the faults/abnormal conditions.
SIL(switching impulse level): It is the maximum withstanding
capacity of the insulation winding during the switching operations.
Rated frequency: The maximum deviations with respect
to the desired frequency, this should not be high for a good machine.
Type of coolant: The coolant used to dissipate the heat
produced inside the machine, the cost does depend on the type of insulation
used. Dry type transformer is more costly compared to liquid type. Ex. ONAN,
epoxy – resin (dry type).
Tapping (%): Various ranges of voltages can be
obtained within a single transformer avoids multi transformer operation if
required.
Secondary voltage (KV): Rated output voltage of the
transformer. It depends on the capacity transformer.
Temperature rise: This discloses the rate of heat rise
inside the machine. It shows significant effect on the efficiency of the
transformer.
Liquid Insulation temperature: It is the maximum withstand
temperature of liquid (coolant) used inside the transformer.
Impedance (%Z): Percentage impedance data is used to
find the voltage drop, voltage regulation.
Load losses @ 75oC (W): The transformer losses (power) during
the loaded condition & at 750C.
No load losses @ 75oC (W):
The power losses of
the transformer during no load & at 750C.
Winding materials: The materials used for the
transformer winding (LV,HV) usually Aluminium or copper.
Total weight: The total packed weight of the complete
transformer.
Datasheet of transformer:
The
following datasheet gives the information about a transformer specifically on
the different parameters which are mostly discussed above.
Follow the
link (open in the new tab):
Pricing of Transformer:
The cost of
transformer mainly depends on the active materials used i.e., copper/steel (for
making core, windings), no load losses (efficiency) & the type of
insulation used (liquid/dry).
Generally
the active material costs 50% of the total cost of the transformer. However,
the different vendors have different price lists. But the below information
will give us a rough idea about the price.
Eg: A 100KVA typical distribution transformer is around 3000 euros, 400KVA is around 7000 euros and 1000KVA is around 12000 euros.
Eg: A 100KVA typical distribution transformer is around 3000 euros, 400KVA is around 7000 euros and 1000KVA is around 12000 euros.
Manufacturers:
The
following are the well known Transformer manufacturers across India.
Name of the company
|
Address
|
|
ABB India
|
NA
|
|
Transformers and
Rectifiers india ltd.
|
Survey No. 427 P/3-4, & 431 P/1-2,
Sarkhej-Bavla Highway, Moraiya, Sanand, Ahmedabad–382213, Gujarat,
INDIA.Phone No. +91 2717 661661
Email ID: marketing@transformerindia.com, purchase@transformerindia.com |
|
Alstom T&D India
|
A-18, First Floor, Okhla
Industrial Area, Phase – II, New Delhi – 110 020,Contact Number - 011-
41610660.
|
|
Siemens India
|
130, Pandurang Budhkar
Marg, Worli, Mumbai, Maharashtra 400018
Phone - 022 2498 7000 |
|
Kirloskar Electric
Company Limited
|
||
Gujarat Transformers Pvt.
Ltd
|
JD Nagar, Maneja,
Vadodara, Gujarat 390013
Phone - 0265 264 2422 |
|
Uttam Bharat
|
B-189/A , Road No.9 (F),
VKI Area, Jaipur - 302013 Rajasthan India
|
|
Urja Techniques (India)
Pvt. Ltd
|
B-17 Shriram Industrial
Estate, G.d. Ambekar Road, Wadala.
|
|
Kotsons Pvt. Ltd
|
C-21, U.P.S.I.D.C.,
Site-C, Sikandra, Agra, Uttar Pradesh 282007
Phone:0562 264 1422 |
|
Danish Private Limited
|
F-679, Sitapura
Industrial Area, Jaipur- 302022. INDIA
|
|
Century transformers pvt.
Ltd.
|
Century Transformers Pvt.
Ltd, 5, Jatia Road, Bally, Howrah – 711201, India,Mobile : 09830258414, +91
9903256404
E-Mail: swarup_t@yahoo.co.in, info@centurytransformer.com |
|
Technical associates ltd.
|
Technical Associates
Ltd., 8th km., Faizabad Road, Ismailganj, Lucknow, U.P. – 226016.
Phone No. +91(522) 4053600 E-mail: contact@techasso.com |
|
LE transformers india
ltd.
|
LE TRANSFORMERS INDIA LTD,
Old No. 2, New No.10,Bagavathi Amman Street , Lakshmi Amman Nagar, Erukkancherry. Chennai – 600118. Tamilnadu, India Phone : +91-44-25595271, Fax : +91-44-25594271 E-mail: kucheraa@yahoo.com / letindialtd@gmail.com |
|
Vaibhav Group
|
Vaibhav Group, 1 – Ra- 11
Vigyan Nagar, Kota, Rajasthan.
Phone No: +91 744 2427809 E-mail ID: info@vaibhavgroup.com |
|
RUNTHALA INDUSTRIES
|
A-68, Road No. 1,
Vishwakarma Industrial Area, Jaipur-302013 (Raj.)
Phone No. +91-141-2330875, +91-141-3130875 Email ID: info@runthalaindustries.com, purchase@runthalaindustries.com |
|
Prima transformers
|
Mr. Ajit M. Pimple
(technical Director), Prima Transformers Pvt. Ltd, Plot No.809/2, Kothari Ind
Estate, Kothari Cross Road, Santej, Gujarat, India – 382721.
Phone No. +91-2764-286115/02764286645(j), 9825866827 Email ID: info@primatransformer.com |
|
Mahashakti energy limited
|
MAHASHAKTI ENERGY
LIMITED, A-8, New Focal Point, Dabwali Road, Bathinda -151 001, Punjab, India
Phone No. +91-164-2280058, 2281778 Email ID: info@mahashaktienergy.com |
|
Vijai Electricals ltd.
|
Vijai Electricals Ltd,
6-3-648/1&2, Off Raj Bhavan Road, Somajiguda, Hyderabad – 500 082. Andhra
Pradesh, INDIA.
E-mail ID: websales@vijaielectricals.com |
|
Bharat Bijlee pvt. Ltd.
|
Corp. office : Electric
Mansion 6th Floor
Appasaheb Marathe Marg Prabhadevi Mumbai 400 025 T: +91 22 2430 6237 / 6071 Email: bblcorporate@bharatbijlee.com |
|
Synergy transformers
|
"Diksha Parva"
Maheshwar Madhi Main Road, Pipaliya Nagar, Mangrol Road, Keshod. Dist: Junagadh. (Gujarat) INDIA Phone : +91 02871 231791 +91 02871 253077 Web : www.synergytransformers.com |
|
MAHENDRA TRANSFORMERS (P)
LIMITED
|
Add : F – 10, South Side of G.T. Road Industrial Area Near N.H. 24, Ghaziabad – 201009 (UP), INDIA Phone : 0120 –4561635, 2840474, 2840781 Mobile : +91-9818140474, +91-9818450084 Fax : 0120 – 4561635 Email : mahendratransformers@gmail.com & ag.mktg@hotmail.com URL : www.mahendratransformers.com |
|
Kappa electricals pvt.
Ltd.
|
KAPPA CONSOLIDATED PVT.
LTD., SOUTHERN ELECTRIKS
19, MOUNT ROAD, SAIDAPET, Chennai, TN, 600 015, Phone : +91 - 44 - 22454709, 22454516, Fax : +91 - 44 - 22351662, 22451693 |
|
Marson's Electricals
|
Artoni, Mathura Road Agra, DH, 282 007 Phone : +(91)-(562)-2642327 Fax : +(91)-(562)-2641435 |
|
Muskan power infra
structure ltd.
|
Muskaan Power
Infrastructure Ltd
Sua Road, Industrial Area - C Dhandari Kalan Ludhiana, PN, 141014 Phone : +91-161-2510641/2510642 Mobile : +91-9417033948 Fax : +91-161-2510645 |
|
P.M. electronics ltd.
|
B-10 & 11, Surajpur
Site C,
Surajpur Noida, UP, 201306 Phone : +91-120-2560890 Fax : +91-120-2560891 |
|
Prismatic india
|
Prismatic India
Prismatic Engineering Pvt Ltd.Plot No 308,Link Road Jigani Industrial Area Bangalore, KK, 560105 Phone : +91-80-27826274 Fax : +91-80-27826278 |
|
Raksan transformers pvt
ltd.
|
Raksan Transformers
Private Ltd - Mohali, Punjab.
Plot No.1413 HSIDC Industrial Estate-rai Sonepat, HY, Phone : +91-130-6535990 Fax : +91-130-2366991 |
|
Tesla transformers
|
30 "B", Industrial Area, Govindpura Bhopal, MP, 462023 Phone : +91 - 755 - 2586778 Fax : +91 - 755 - 2581865 |
|
Reacon power equipments
pvt. Ltd.
|
Recons Power Equipments
Pvt. Ltd
Plot No. 38 Sector – 25 Faridabad, HY, 121004 Phone : +91-129-4062114/4062115 Mobile : +91-9871921777 Fax : +91-129-4151323 |
|
Roland electronics and
devices
|
152C, Sarat Ghosh Garden
Road
Kolkata, WB, 700031 Phone : +91-33-4155525 Fax : +91-33-4158723 |
|
Standard transformers
pvt. Ltd.
|
Standard Transformers
Pvt. Ltd.
P.B.No.8, Plot No-95 GIDC Industrial Estate Canacona South Goa, GO, 403702 |
|
T.S. international
|
Level 6, Chennai Citi
Centre. 10/11
Dr.Radhakrishnan Salai Chennai , TN, 600004 |
|
Transformers and
electricals kerala ltd.
|
Angamally South
Ernakulam District Cochin, KL, 683573 Phone : +91- 484 -2452251 Fax : +91-484 -2452363, 2452873 |
|
UP transformers india
pvt. Ltd.
|
UP Transformers (India)
Pvt. Limited
UPSIDC Industrial Area, Site – 2, Plot No. B1 - B2 Amawa Road Raebareli, UP, 229316 Phone : +91-535-2217110 Mobile : +91- 9415335102 |
|
Mahindra electrical works
|
Plot No. A-433, Road No.
28 Wagle Industrial Estate,
Thane , MH, 400604 Phone : 91-22-2582 3743/2580 1110 Fax : 91-22-2582 2461 |
|
EMCO
|
1st Floor,Piramal Tower,
Peninsula Corporate Park, G. K. Kadam Marg, Lower Parel, Mumbai - 400 013 Email: emco.corporate@emco.co.in |
|
Sukam power systems. Ltd.
|
SU-KAM POWER SYSTEMS LTD.
Corporate Office Plot No. 54, Udyog Vihar, Phase VI, Sector-37, Gurgaon - 122001, Haryana, India |
* Note: The above information may subject to vary without any notice and we will be not responsible for such happenings.
Here, the information source manufacturers list is companiesinindia.net and indiacatalog.com
