Transformers

Design, selection and operation of distribution transformers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],deutsch English

The German Copper Institute, DKI, is the central information and advisory service dealing with all uses of copper and copper alloys. We offer our services to: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

1. Basics: “Gigantomania” or a necessity of economics? ,[object Object]

This one weighs 300t and does 600MVA... ,[object Object]

[object Object],It's a law of physics: Higher energy density in larger plant

Structure of the public mains 0.4kV 20kV 10kV 380kV 220kV 110kV 50 Hz 3~ 27kV, nuclear 21kV, e. g. coal 10kV, e. g. hydro 0.5kV, e. g. wind

2. Design here of a distribution transformer Wooden spacers (not depicted in the following drawings) HV winding LV winding Current Current

Yoke spanning bar Winding spanning bolts Yoke lamination spanning Wooden winding spacers HV winding Yoke lamination spanning bolts LV winding Off-load tap changer

3. Operating behaviour ,[object Object],[object Object],[object Object],[object Object],Load R Fe X 1  ‘ X 2  X m R Cu1 ‘ R Cu2

By the way, what really is short-circuit voltage? ,[object Object],U SC I N X m R Fe R Cu1 ‘ R Cu2 X 1  ‘ X 2  A V

By the way, what really is short-circuit power? ,[object Object],[object Object],X m R Cu1 ‘ R Cu2 X 1  ‘ X 2  V A R Fe

R load (rated load) ,[object Object],Tricky: C load Voltage across the load ( ≈ 107%!) Equivalent input voltage U 1 ' (100%) Inductive drop u X Ohmic drop u R in the trans-former Total drop u SC in the transformer Voltage across the load ( ≈ 94%) Equivalent input voltage U 1 ' (100%) Inductive drop u X Ohmic drop u R in the trans-former Total drop u SC in the transformer Voltage across the load ( ≈ 99%) Equivalent input voltage U 1 ' (100%) Inductive drop u X Ohmic drop u R in the trans-former Total drop u SC in the transformer Inductive drop ( u X = 5.916%) Ohmic drop in the transformer (e. g. u R = 1%) Total drop inside the transformer (e. g. u SC = 6%)

Theoretical deduction of the load current Short circuit current I SC =16.7* I N  16.7*rated load magnitude ( Z SC = Z load : “half a short-circuit”)  E. g. non-detuned static Var com-pensator 1670kvar on a 100kVA transformer  Rated load

Excerpt with the actually occurring values  Nennlast  Rated load

No-load current ,[object Object],R L ≈400m Ω R Fe ≈400 Ω X 1  ‘ ≈12m Ω X 2  ≈12m Ω X m >4k Ω R Cu1 ‘ ≈2m Ω R Cu2 ≈2m Ω

Vector groups ,[object Object],230V 400V

Vector groups ,[object Object], Yes Why? No  U V W U V W u v w n u v w n

Vector groups ,[object Object],Approximate equivalent circuit of a Yyn vector group R L ≈400 m Ω R Fe ≈400 Ω X 1  ‘ ≈12m Ω X 2  ≈12m Ω X m >4k Ω R Cu1 ‘ ≈2m Ω R Cu2 ≈2m Ω R Fe ≈400 Ω X 1  ‘ ≈12m Ω X 2  ≈12m Ω X m >4k Ω R Cu1 ‘ ≈2m Ω R Cu2 ≈2m Ω L1 N L2 R L ≈ 400 Ω

Prerequisites for parallel operation: ,[object Object],[object Object],[object Object],[object Object],[object Object],u X = 3.91% u R = 0.9% u SC = 4% u X = 2.95% u R = 2.7% u SC = 4% 630 kVA transformer according to HD 428 list C 50 kVA transformer according to HD 428 list B

4. Efficiency ,[object Object]

Division into classes according to the present HD 428

Division into classes according to the future HD 428

Comparing 8 designs of a 40 kVA transformer by Riedel transformer factory

Amorphous steel could cut the no-load losses down to a fraction ,[object Object],[object Object],[object Object],[object Object]

So the replacement of old transformers pays off for a variety of reasons ,[object Object],[object Object]

[object Object],Improvement of efficiencies Load loss of a 400 kVA 16 kV / 400 V distribution transformer

5. Too hot from “hot” loads ,[object Object],Mutual influences between the trans-former and its load

The power loss in a transformer is: ,[object Object]

“ supplementary” additional losses in transformers can be calculated rapidly using the following two simple formulae: where: Oh well, perhaps a practical example is clearer: 1000 compact 11W (15VA) energy-saver lamps powered by a 15kVA transformer, u SC =4%, P ad =0.1 P Cu 81.4% etc. etc.

To some extent the transformer protects itself... ,[object Object],[object Object],701.7% etc. etc.

A tool is available for this, too: The K Factor Calculator by www.cda.org.uk www.cda.org.uk/frontend/pubs.htm#ELECTRICAL/ENERGY%20EFFICIENCY

Deutsche Leonardo Schriften ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],The European Union 3 Projects out of about 4000 awarded – one of them was: www.lpqi.org www.leonardo-energy.org

Transformers

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Transformers

Similar to Transformers (20)

More from DKI Deutsches Kupferinstitut

More from DKI Deutsches Kupferinstitut (16)

Recently uploaded

Recently uploaded (20)

Transformers

Editor's Notes