Transformers
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Define the percentage voltage regulation and efficiency of a power transformer.
Voltage regulation is the difference between no load voltage and full load voltage by no load voltage.Voltage regulation = No load voltage – Full load voltage / No load voltage. Voltage regulation is mentioned in % (percentage).% Voltage regulation = No load voltage – Full load voltage * 100 / No loRead more
Voltage regulation is the difference between no load voltage and full load voltage by no load voltage.
Voltage regulation = No load voltage – Full load voltage / No load voltage.
Voltage regulation is mentioned in % (percentage).
% Voltage regulation = No load voltage – Full load voltage * 100 / No load voltage.
Efficiency of a transformer is the ratio of output in watts and input in watts.
Efficiency = Output in watts / Input in watts.
% Efficiency = Output in watts * 100 / Input in watts.
% Efficiency = Output in watts * 100 / Output in watts + losses.
See lessWhat is the design basis of 6.6 kV aluminium bus bars?
a) Temperature rises not exceed 90 ºC. b) Withstand short ckt stresses. c) Take care of thermal expansion.
a) Temperature rises not exceed 90 ºC.
b) Withstand short ckt stresses.
c) Take care of thermal expansion.
See lessWhat is the purpose of header breaker in water circuit?
The header breaker ensures oil pressure greater than that of water pressure always. Therefore there is no leak of water into oil.
The header breaker ensures oil pressure greater than that of water pressure always. Therefore there is no leak of water into oil.
See lessWhy all 415V transformers are chosen Dyn 11? What are the protections provided for the 415V transformers?
a) To facilitate interchange. b) To have momentary parallel during changeover. Protectionsa) Door interlock to trip HT and LT breakers. b) LT breaker can on only after HT breaker is in on position. c) Instantaneous O/C and inverse O/C (50 + 51). d) Instantaneous E/F (50N). e) IDMT E/F and restrictedRead more
a) To facilitate interchange.
b) To have momentary parallel during changeover. Protections
a) Door interlock to trip HT and LT breakers.
b) LT breaker can on only after HT breaker is in on position.
c) Instantaneous O/C and inverse O/C (50 + 51).
d) Instantaneous E/F (50N).
e) IDMT E/F and restricted E/F (51N + 64).
f) Winding temp high trip (140°C trip and 130°C alarm)
See lessWhy twin secondary SUT?
As per is, the rating single secondary power transformer is limited to 25MVA (6.6 kV) or 40 MVA (11 kV), in order to limit the 3 phase symmetrical fault level with in 26-40 kA (contribution from grid and local machines)
As per is, the rating single secondary power transformer is limited to 25MVA (6.6 kV) or 40 MVA (11 kV), in order to limit the 3 phase symmetrical fault level with in 26-40 kA (contribution from grid and local machines)
See lessWhat is the use of Tertiary winding?
Star connected circuit, which has an isolated neutral there can be no zero sequence components. Since the zero sequence components are by definition in time phase with another their sum can not be zero at the junction point as per kirchoff’s law. It follows that there are limitations upon the phaseRead more
Star connected circuit, which has an isolated neutral there can be no zero sequence components. Since the zero sequence components are by definition in time phase with another their sum can not be zero at the junction point as per kirchoff’s law. It follows that there are limitations upon the phase loading of a bank of transformers connected in star – star unless the neutral points are connected to the source of power in such a manner that the zero sequence components of current have a return path or unless the transformer are provided with tertiary winding.
See lessWhat is the advantage of Pressure relief device in TELK type GT over explosion vent of BHEL, even though in both cases oil will be expelled out during sudden pressure rise?
During internal fault, the internal pressure rise is relieved by the expelling out of oil through Pressure relief device /explosion vent. However the Pressure relief device closes back when the pressure drops. Hence the oil exposure to atmosphere is minimised, thus saving large quantity of costly trRead more
During internal fault, the internal pressure rise is relieved by the expelling out of oil through Pressure relief device /explosion vent. However the Pressure relief device closes back when the pressure drops. Hence the oil exposure to atmosphere is minimised, thus saving large quantity of costly transformer oil from oxidation and moisture absorption. Fire hazard due to transformer oil does not exist after the closure of Pressure relief device.
See lessWhat is E/F current limit for SUT and UT?
400a limited by 10 ohms resistor.
400a limited by 10 ohms resistor.
See lessWhat are the advantages of dry type transformer?
No fire hazard. It can be mounted indoor.
No fire hazard.
It can be mounted indoor.
See lessWhy the tap changers are always connected to HV side of the transformer?
During tap changing action the load current has to be shifted from one tap to another tap. In case HV wining the load current will be less. Hence lesser arcing will take place.
During tap changing action the load current has to be shifted from one tap to another tap. In case HV wining the load current will be less. Hence lesser arcing will take place.
See less