EVERGREEN METAL WORKS

Bommasandra, Bangalore, Karnataka

Transformer core lamination for Power & Distribution transformers is manufactured from various grades of Cold Rolled Grain Oriented ( CRGO ) steel. Lamination in various shapes & sizes are slit and cut to required accurate geometrical shapes with 90 & 45 cutting systems. The manufacturing of Cold Rolled Grain Oriented CRGO Quality Lamination involves a high degree precision engineering.Transformer lamination can be of various sizes for single or three-phase transformers, made with overlap joints or step lap joints (CrossLongitudinal). They are cut, punched and V-notched in order to fit in a particular transformer. Cutting, Punching and Notching of different shapes of sheets are possible in width up to 1000 mm and length up to 5500 mm.

Transformer core lamination for Power & Distribution transformers is manufactured from various grades of Cold Rolled Grain Oriented ( CRGO ) steel. Lamination in various shapes & sizes are slit and cut to required accurate geometrical shapes with 90 & 45 cutting systems. The manufacturing of Cold Rolled Grain Oriented CRGO Quality Lamination involves a high degree precision engineering.

Transformer lamination can be of various sizes for single or three-phase transformers, made with overlap joints or step lap joints (Cross/Longitudinal). They are cut, punched and V-notched in order to fit in a particular transformer. Cutting, Punching and Notching of different shapes of sheets are possible in width up to 1000 mm and length up to 5500 mm.

Toroidal Transformer Basics

GeneralA toroid is a doughnut-shaped object whose surface is a torus. Its annular shape is generated by revolving a circle around an axis external to the circle.

A coil of insulated wire in a doughnut shape (usually with a core of iron or similar metal) is an example of a toroidal object. These are used as inductors in circuits such as low frequency transmitters and receivers because they possess higher inductance and carry greater current than similarly constructed solenoids. They are also used as transformers in main power supplies. Toroidal coils reduce resistance, due to the larger diameter and smaller number of windings. The magnetic flux in a toroid is confined to the core, preventing its energy from being absorbed by nearby objects.

In the geometry of torus-shaped magnetic fields, the poloidal flux direction threads the "donut hole" in the center of the torus, while the toroidal flux direction is parallel the core of the torus.

Advantages of Toroidal Power TransformersToroidal transformers offer many advantages over standard laminated power transformers. Toroidals provide quiet, efficient operation with very low stray magnetic fields. Their small size and weight support a package that is easy to design into any application.

The Step-lap CRGO Transformer Laminations design leads to low no-load losses and a low noise level, lateral step-lap enables a favourable assembly for the upper yoke. Every type of CRGO Transformer Cores can be produced in a form of Step lap, over lap, 45 cut, with hole or without hole from every required quality electrical steel up to 800 mm width. Evergreen uses the newest, computerized version of Cut to Length Machines in order to produce Step-Lap CRGO Transformer Laminations Cores.

The Step-lap CRGO Transformer Laminations design leads to low no-load losses and a low noise level, lateral step-lap enables a favourable assembly for the upper yoke. Every type of CRGO Transformer Cores can be produced in a form of Step lap, over lap, 45 cut, with hole or without hole from every required quality electrical steel up to 800 mm width. Evergreen uses the newest, computerized version of Cut to Length Machines in order to produce Step-Lap CRGO Transformer Laminations Cores.

Slitting is the first and foremost manufacturing process in order to obtain any type of cut lamination. Indeed, it is the heart of the whole manufacturing process and to ensure it continuous beats, it should be tuned with fine accuracy and high quality standard.

the first and foremost manufacturing process in order to obtain any type of cut lamination. Indeed, it is the heart of the whole manufacturing process and to ensure it continuous beats, it should be tuned with fine accuracy and high quality standard.Slitting process is the origin where quality standard starts, and subsequently it is maintained by the different types of cutting process. Quality of the material is always on top priority at Evergreen and thus we stress more on slitting process for better quality in every single process.we have set up essential quality check-points during slitting process to ensure that the burr level of material is well within the tolerance. The precise slitting process can undoubtedly slit the material without any generation of scrape. (I.e. slitting of a coil of 120 mm in two different 60 mm coils is promising task).

The Slitting Machine gives 18 adjustable strip widths. Tool geometry is of critical importance for eliminating burrs of CRGO.

CUTTING ACCORDING TO LENGTH (CRGO)

AUTOMATIC METHOD OF PROCESSING CRGO POWER TRANSFORMER LAMINATIONEvergreen uses the newest, computerized version of Cut to Length Machines in order to produce Step Lap Transformer Laminations Cores.

MANUAL METHOD USED FOR DISTRUBUTION CRGO TRANSFORMER LAMINATION.The SECOND stage of the CRGO Lamination manufacturing process is "Shearing" at 45 or 90 as required by the customer. Strict tolerances are maintained (as per the tolerance chart) and a unique three point location method ensures accuracy in dimensions in terms of angle and length. Burs are controlled by ensuring the blades are always sharp. Continuous line inspection ensures all parameters are strictly maintained within acceptable limits.

The THIRD step of CRGO Lamination manufacturing process is to fabricate "V-Notch" or holes at per customer's design. Accuracy is utmost importance and specially designed jigs and fixtures ensure that all dimensional tolerances specified by the customer are maintained.

STRESS RELIEF ANNEALING

The FOURTH step of the manufacturing process of CRGO Transformer Lamination is to deburr and stress relief anneal the material by other health annealing furnace. This is done as per the mill's specification at 820 C for a few minutes depending upon the thickness and grade of CRGO material.

TESTING

Final Inspection of CRGO Lamination for Manufacturing Tolerences as per International Standard OR as Per Customer Requirement. Checking of Core Losses on the Finished CRGO Lamination and No Load losses on CRGO Built Up Cores. Issue a Test Certificate for Every Despatch.

PACKING

We are able to deliver CRGO lamination as leg or sheet packet, according to your packing requirements, inside of wooden box or on the pallets.

Production Processes For Crgo (Grain Oriented Steel) Toroidal Transformer Cores SLITTING

CRGO Electrical steel comes in the form of wide coils having widths of 750 mm to 1000 mm. These coils are to be slit in various widths in steps ranging from 10 mm to 100 mm.

WINDING

These slit coils of CRGO are wound on semi automatic winding machine as per the dimensions given by our customers.

SPOT WELDING

On winding the CRGO Toroidal cores to the exact size the start and finished ends of the core are spot welded on spot welding machine.

STRESS RELIEF ANNEALING

During the winding process of CRGO, severe stresses are induced in the gains of the raw material. Theses stresses are relieved in our specially designed annealing furnace equipped with automatic temperature controller, circulating fan and inert atmosphere. The annealing cycle (at 800C) improperly controlled to get uniform and best annealing results.

TESTING

Since the CRGO electrical properties of cores are very critical, every core is tested on a specially designed test bench. The ampere turns/cm (magnetization current) are measured on every core to ensure that they are within the specified limits.

PAINTING

After testing the 'PASSED' cores are painted with N.C. paint to prevent the CRGO Toroidal cores from corrosion.

PACKING

The Electrical Properties of CRGO Toroidal cores are very sensitive to bad handling during transit. We take great care while packing the cores in wooden boxes with cushioning material to prevent stresses on the cores during dispatch.

Wound Cores for Single and Three Phase Transformers

Wound Core for Single Phase Transformer, Pole Transformers, and Pad Mounted Transformers etc.

Unlike c.r.g.o. C-Cores each turn of c.r.g.o. are cut into a separate lamination and resulting but-joint are distributed over the wide area to reduce no load losses.Other advantages of c.r.g.o. wound cores comprise the reduction of assembly time and savings in copper and low core losses.

Electrical Testing

All cores, unless otherwise state, are individually tested to the standard guarantee specifications. Special test conditions, when required, can be applied and guaranteed to suit customers' individual requirements.

BLANKING LAMINATION

Blanking lamination are been processed and produced with best raw material under precession engineering tool room.