Power Transformer are used for
stepping-up the voltage for transmission at generating stations and for
stepping-down for further distribution at substation. Usually naturally cooled,
oil immersed, On type, two winding. three phase transformer are used up to the
rating of 10 MVA. The transformers of rating higher than 10 MVA are usally
Air-blast cooled. For very high rating transformer the forced oil, water
cooling or air blast cooling may used.
For regulating the voltage the
transformers used are provided with on load tap changer. They are put in
operation during load hours and disconnect during light load hour, that is they
are usually operated at approximately full load condition. This is possible
because they are arranged in bank and parallel with other unit or
disconnected at will.
Design: Power Transformer
So power transformer are designed to
have maximum efficiency at or near full load condition. that is iron loss to
full load copper loss ration is 1:1.
Power Transformer are designed to
have consider leakage reactance than permissible in distribution transformers
because in power transformers inherent voltage regulation is not as much
important as current limiting effect of the higher leakage reactance.
Power Transformer usually make use
of flux density of 1.5 to 1.77, have percentage impedance ranging from 6-18%
and regulation 6-10%.
SPECIFICATION OF TRANSFORMER :
- KVA rating
- Rated voltage
- Number of phase (single phase or three phase)
- Type of Core ( shell type or core type )
- Tapping - if any
- Frequency (in INDIA 50hz, USA- 60hz)
- Construction ( Delta type or Star Type in case of three
phase)
- Type of cooling ( air cooling, oil cooling)
- Ambient Temperature ( Average 40° C)
- Voltage Regulation
- No-load Current in ampere or percentage of rated
current at at rated voltage and rated frequency.
- Efficiency in percent at full load, half load,
3/4 load at unity or 0.8 pf (power factor).
INSTALLATION:
Power Transformer are generally
installed upon lengths of rail fixed on concrete slab having foundation 1 to 1½
meter deep.
No comments:
Post a Comment
Please do not enter any spam link