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

what is different between DIGITAL and ANALOG?

3 Answers  

What happens if the negative to earth voltage is greater than positive to earth voltage in the battery of substation?

0 Answers  

with out name plate details , how to find the metering ct and protection ct.?pls brif explaination about that.

3 Answers   APNPDCL,

why should the primary of transformer be connected in delta in a heat run test?

0 Answers   Bhel,

can we use HPSV LAMP in HPMV LAMP fixture ?and viseversa.

5 Answers   OPS,

The coulomb is a unit of:(a) Energy(b) Voltage(c) Power(d) Quantity of electricity

1 Answers  

What can a fresh(without experience) electrical engineer contribute to NTPC( Or any PSU company) growth?

3 Answers   NTPC,

why the check zone and main zone are used for Busbar Protn. scheem?

0 Answers  

how to convert star network in delta or vice versa...?

1 Answers   Toyota,

Hi, i want to know is meant by power quality? How it can calculated ? How we can improve?

1 Answers  

What is critical disruptive voltage?

0 Answers  

what is the effect of power factor to (a) voltage (b) transformers (c) generators (d)transmission lines

4 Answers