Answer / p.aruna devi

ONAN -Oil natural air natural
ONAF-Oil natural air force

Answer / gowhar

The above answer is true.Moreover ,there is a two stage
forced cooling in some of the transformer
(ONAN/ONAF1/ONAF2.on First stage forced cooling(ONAF1) the
MVA rating increses 33% of the actual rating and on second
stage cooling(ONAF1) MVA rating increases to 66% of the
actual rating.

Answer / shashank

ONAN type cooling:
The generated heat can be dissipated in many ways. In case
of smaller rating of transformers, its tanks may be able to
dissipate the heat directly to theatmospheric dry while
bigger ratings may require additional dissipating surface
in form of tubes/ radiators connected to tank or in the
term of radiator tank. In these cases, the heatdissipation
is form transformer oil at atmospheric air by natural
means. This form of cooling is known as ONAN (Oil Natural,
Air Natural) types of cooling.

ONAF type of cooling:
For further augmenting the rate of dissipating of heat,
other means such as fans blowing air on the cooling
surfaces are employed. The forced air takesaway the heat at
a faster rate, thereby giving better cooling rate than
natural air. This type8
 
of cooling called ONAF (Oil Natural Air Forced) type of
cooling. In this coolingarrangement, additional raring
under ONAN condition viz. after shutting off fans,
isavailable, which is of the order of 70-75%.

Answer / abdullah ibrahim

The generated heat can be dissipated in many ways. In case
of smaller rating of transformers

Answer / s c sharma

CORRECT

will three phase energy meter run without one phase

2 Answers  

What is the use of doing meggering for a cable

2 Answers  

why current flows from +ve to -ve terminal

7 Answers  

How to take the Vector Group Test in Transformer? What is the purpose of doing Vector Group Test?

2 Answers  

Draw the vector diagram and condition for the following: 1) Dyn1 2) Ynd0 3) YnYn0

0 Answers  

What is a Phase shift meter? Where can I get one?

0 Answers  

what happened if power factor is "1"

9 Answers   Reliance,

Why the resistance grounding (NGR) is better than Solid grounding?

5 Answers  

What happen if 1200KW/1500KVA alternator runs at no load and high R.P.M.for one minute?

6 Answers  

in a dc motor we supply current only to the armature conductors,from where is the field winding gets excited then??

3 Answers   RRB, Siemens,

Can the Neutral and Body Earthpits of a transformer conncted together by Earth strips under ground.

4 Answers   SanDisk,

how will calculate the safe starting current of 3-phase squirrel cage induction motor?

0 Answers