Internship Autumn2011

Murshedur rahman

ID:#0731084

TRANSFORMER DESIGN

&

MANUFACTURING AT

GEMCO LTD

Transformer

Distribution

Core type

Straight cut

Angular cut

Shell type

PowerAccording to application

Construction type

Design form

ONAN(Oil natural Air natural)Cooling type

Categorizing the transformer production at GEMCO

Comparison between power & distribution transformer

Power Transformer

DistributionTransformer

Power transformer

Distribution transformer

Installation

Connection

Capacity

Voltage rating

•Cooling system

At substation (generation

side).

Δ- Δ or Y- Δ, 3 wire.

MVA.

Usually stepped down to 11kv.

ONAF, OFAF, ONWF, OFWF

At distribution and transmission (consumer side).

Δ-Y, 4wire.

KVA.

Usually stepped down from 11kv

to 415v.

Usually ONAN.

Comparison between power & distribution transformer

Primary Distribution Transformer’s parts

rRod Gap Arrester

Core type transformer

Transformer type

Winding

Core

Comparison between core & shell type transformer

The advantages of each type are:

core-type (or three limbs) is the most commonly used method of construction, the smaller core means less weight and expense.

shell-type (or five limbs) is used for larger transformers because of a reduced height and better mechanical protection to the winding because it is surrounded by core.

From a manufacturing standpoint, core-type & shell-type designs are very similar.

Transformer Core type

Angular StraightPerformance Reduce reluctance

against the magnetic flux by reducing the gaps between sheets. Hence lessen the iron loss and betters the performance.

Provides more reluctance to magnetic flux due to more number of gaps. So performance is well below angular.

Cost Cost is more as huge amount of core is wasted due to the cutting off at corner to make it angular.

Cost is well below the angular cut.

Preference Preferred where efficiency is vital.

Mostly used due to the less cost.

Comparison between core & shell type transformer

I ) Transformers: Power Transformer, 3 Phase, 33/11KV, 1 MVA to 5 MVA Distribution Transformer, 3 Phase, 33/0.415 KV, 100 KVA to 250 KVA Distribution Transformer, 3 Phase, 11/0.415 KV, 50 KVA to 500 KVA Distribution Transformer, 1 Phase, 6.35/0.24 KV, 5 KVA to 50 KVA Distribution Transformer, 1 Phase, 11/0.24 KV, 15 KVA to 25 KVA

Apart from these, other rated transformer could manufactured as per requirements of clients up to 5MVA

II)Repair & Miscellaneous Works:Damaged Distribution & Power Transformers up to 20 MVA

Products / Services:

Process flow diagramPPM •Design product

•Estimate cost

CPL •Test raw materials•Report

Plant •Electrical•Mechanical

Testing •Test completed transformer•Report

Name of Raw Materials Specification of materials

CRGO Silicon Steel Sheet

Grade M-5 (width 0.3mm, density-7.65kg/dm3, Core loss 0.97-1.39 for 1.5-1.7T)

Copper Strips Electrolytic Copper of 99.9% purity

Super Enameled Copper Wire

SWG -14 to 21 Copper of 99.9% purity

Mild Steel Sheet Prime Quality

HT Insulator Electrical Porcelain Insulator

Transformer Oil As per IEC-296 Class-1

Insulated Paper & Board

Electrical Grade 100% Sulphate/Kraft Pulp

Raw material specification LT Coil dimension,

Thickness=5.6mm, width=11.2mm, insulation=.45mm, density=61.92x10^-6 kg/m3

HT coil type- SWG17 , supper enameled dia-1.42-1.53, density= 8.9x10^-6

kg/m3 CRGO Silicon Electrical Steel Sheet with thickness

0.3mm &flux density Bm≤1.7Wb/m²IEC Standard: 76Vector group: DYN-11

Design specification

The design is usually 6 step core section with Cylindrical coils

In design calculationDesign specification

Summarizing the design:

•Specification of the transformer to be designed

•Chose Ez, Bm,

•Calculate Area and Diameter for core•Find conductor size of HT & LT winding and calculate current density•Choose layout of windings-- numbers of turns per layer , numbers of layers, distance between coils

•Calculate R, X, Z.

•Calculation of performance

•Designing the tank

Transformer leg

Active Part

Tapping

Core

InsulationBoard

Insulation Paper over winding

Each transformer undergoes following routine tests as per IEC 60076 requirements:

•Di-electric strength test of transformer oil.

•Measurement of Insulation Resistance.

•High Voltage Test.

•Induced Over Voltage Test.

•Ratio Test.

•Vector Group Test.

•Measurement of No-Load Loss and Excitation Current.

•Measurement of Load-Loss and Impedance Voltage.

•Measurement of Winding Resistance.

•Temperature Rise Test. 

Testing

THANK YOU