ট্রান্সফরমার সম্পর্কে গুরুত্বপূর্ণ ১০০ টি প্রশ্ন ও উত্তর ।

 

What is a power transformer? A power transformer is an electrical device used to transfer electrical energy between two or more circuits through electromagnetic induction.
How does a power transformer work? A power transformer works on the principle of electromagnetic induction, where a varying current in the primary winding induces a voltage in the secondary winding.
What are the primary components of a power transformer? The primary components of a power transformer are the core, primary winding, secondary winding, and insulation.
What is the purpose of the core in a power transformer? The core provides a low-reluctance path for the magnetic flux generated by the primary winding, which helps in efficient energy transfer.
What are the different types of power transformers based on their applications? The different types of power transformers include distribution transformers, power transformers, autotransformers, and instrument transformers.
What are distribution transformers used for? Distribution transformers are used to step down voltage levels for distribution to residential and commercial areas.
What are power transformers used for? Power transformers are used to step up or step down voltage levels in high-power transmission systems.
What is the difference between a step-up transformer and a step-down transformer? A step-up transformer increases the voltage level from the primary to the secondary winding, while a step-down transformer decreases the voltage level.
How is a power transformer cooled? Power transformers are cooled using methods such as oil cooling, air cooling, or a combination of both.
What are the cooling methods used in power transformers? The cooling methods used are ONAN (Oil Natural Air Natural), ONAF (Oil Natural Air Forced), and OFAF (Oil Forced Air Forced).
What is the purpose of transformer oil? Transformer oil provides insulation and cooling for the transformer windings.
How is the insulation level of a power transformer specified? The insulation level is specified in terms of the Basic Impulse Insulation Level (BIL) to withstand lightning surges.
What is the difference between an oil-filled transformer and a dry-type transformer? Oil-filled transformers use transformer oil for cooling and insulation, while dry-type transformers use air for cooling and have solid insulation.
What are the advantages of dry-type transformers? Dry-type transformers are more environmentally friendly, require less maintenance, and have no risk of oil leakage.
What is the typical life expectancy of a power transformer? The typical life expectancy of a power transformer is around 30 to 40 years, but it can vary based on the operating conditions and maintenance.
What are the factors that affect the efficiency of a power transformer? Factors such as core losses, copper losses, and load losses affect the efficiency of a power transformer.
How is the efficiency of a power transformer calculated? Efficiency is calculated by dividing the output power by the input power and multiplying by 100 to get the percentage.
What is a tap changer in a power transformer? A tap changer is a device used to vary the turns ratio and adjust the output voltage to compensate for variations in the input voltage.
What are the different types of tap changers? The different types of tap changers are on-load tap changers (OLTC) and off-load tap changers (OLTC).
Why is routine testing important for power transformers? Routine testing helps in identifying any issues early and ensures the reliability and safety of the transformer during its operation.
What are the routine tests conducted on power transformers? Routine tests include turns ratio test, winding resistance test, insulation resistance test, and magnetic balance test.
What is the turns ratio test, and why is it important? The turns ratio test checks the turns ratio of the transformer and helps ensure that it meets the specified voltage transformation requirements.
What is the purpose of the winding resistance test? The winding resistance test helps in determining the health of the transformer windings and identifying any potential faults.
What is the insulation resistance test used for? The insulation resistance test measures the resistance of the transformer insulation and detects any deterioration or contamination.
What is a sweep frequency response analysis (SFRA) test? SFRA test is used to analyze the mechanical integrity and condition of transformer windings by measuring their frequency response.
What is Dissolved Gas Analysis (DGA), and why is it performed on transformers? DGA is a method used to analyze the gases dissolved in transformer oil to detect potential faults or overheating.
What are the major fault types that DGA can detect? DGA can detect faults like overheating, partial discharge, arcing, and insulation degradation.
What is the purpose of a power factor test on a transformer? The power factor test helps to determine the insulation condition and losses in the transformer.
What are the different types of transformer insulation? The different types of transformer insulation include paper, pressboard, and Nomex.
What is the purpose of the Buchholz relay in a transformer? The Buchholz relay is a gas and oil-operated relay used to detect internal faults such as short circuits or winding damage.
What is the typical temperature rise limit for a power transformer? The temperature rise limit is usually specified as 55°C for oil and 80°C for winding.
What is the purpose of the Conservator tank in a power transformer? The Conservator tank acts as a reservoir for transformer oil, allowing for expansion and contraction due to temperature changes.
What is an On-Load Tap Changer (OLTC)? An On-Load Tap Changer (OLTC) is a tap changer that can adjust the transformer's voltage while the transformer is under load.
What is the function of the Neutral Grounding Transformer (NGT)? The Neutral Grounding Transformer (NGT) limits the fault current during an unbalanced fault in a power system.
What is the purpose of an isolation transformer? An isolation transformer is used to isolate electrical equipment from the power supply, providing safety and reducing interference.
How is the efficiency of a transformer affected by load variations? The efficiency of a transformer generally decreases as the load decreases, and it operates closer to its no-load condition.
Can a power transformer be used in reverse to convert high voltage to low voltage? Yes, a power transformer can be used in reverse to step down a higher voltage to a lower voltage.
What is the maximum capacity of power transformers used in power transmission systems? Power transformers can have capacities ranging from a few kVA (kilovolt-amperes) to several MVA (megavolt-amperes).
How is the capacity of a power transformer specified? The capacity of a power transformer is specified in terms of the kVA rating or MVA rating.
What is the function of a bushing in a transformer? A bushing is used to provide a connection between the transformer windings and external electrical equipment.
How is the insulation level of a transformer bushing specified? The insulation level of a transformer bushing is specified in terms of its BIL rating.
What is the purpose of a surge arrester in a power transformer? A surge arrester protects the transformer against voltage surges and transients caused by lightning or switching events.
Can a power transformer be connected in parallel with another transformer? Yes, power transformers can be connected in parallel to share the load in a power system.
What precautions should be taken when paralleling power transformers? Precautions include ensuring that the transformers have similar voltage ratings, impedance, and tap settings.
What is the purpose of the Overload Relay in a power transformer? The Overload Relay protects the transformer against excessive current and prevents damage due to overload conditions.
What is a vector group in a power transformer? The vector group indicates the phase displacement and connection of the primary and secondary windings.
How many vector groups are there for power transformers? There are 11 standard vector groups used for power transformers.
What is the purpose of an Earthing Transformer? An Earthing Transformer provides a low-resistance path to the ground for fault currents, protecting the power system from ground faults.
How is the efficiency of a power transformer affected by operating at lower or higher frequencies? The efficiency of a power transformer decreases at higher frequencies due to increased eddy current and hysteresis losses.
What is the purpose of a Magnetic Oil Gauge (MOG) in a power transformer? The Magnetic Oil Gauge is used to indicate the level of transformer oil inside the tank and monitor any oil leaks.
How is the insulation resistance test conducted on a power transformer? The insulation resistance test is conducted by applying a DC voltage between the windings and the transformer tank and measuring the insulation resistance.
What is the purpose of the Pressure Relief Device (PRD) in a power transformer? The PRD is a safety device that relieves excess pressure inside the transformer tank to prevent tank rupture during internal faults.
How can you determine the polarity of a transformer? The polarity of a transformer can be determined by conducting a polarity test using a known voltage source.
What is the typical noise level of a power transformer during operation? The noise level of a power transformer is generally low, but it can vary depending on the size and cooling method.
How is the no-load current of a power transformer determined? The no-load current is the current drawn by the transformer secondary when the primary is open-circuited. It is typically a small percentage of the full-load current.
What are the factors that contribute to transformer losses? Transformer losses are mainly due to core losses (eddy current and hysteresis losses) and copper losses in the windings.
What is the purpose of the Breather in a power transformer? The Breather is a desiccant-filled device used to keep the air inside the transformer tank dry by absorbing moisture.
Can a power transformer be used to convert DC (Direct Current) to AC (Alternating Current)? No, power transformers work only with AC voltages due to the principle of electromagnetic induction.
What are the differences between a power transformer and a distribution transformer? Power transformers are used for high-voltage transmission, while distribution transformers are used to step down voltage for distribution to end-users.
What are the typical dimensions and weight of a power transformer? The dimensions and weight of a power transformer can vary widely depending on its capacity and design.
How often should a power transformer be tested for routine maintenance? Routine maintenance testing should be performed at least once a year.
What are the signs that a power transformer may be failing? Signs of a failing power transformer include excessive noise, overheating, oil leaks, and abnormal vibrations.
How is the load loss of a transformer determined? The load loss is determined by measuring the power consumed by the transformer when operating at rated load and rated voltage.
Can a power transformer be operated at reduced load continuously? Yes, a power transformer can be operated at reduced load continuously, but it may lead to decreased efficiency and increased losses.
What is the purpose of the Magnetic Shield in a power transformer? The Magnetic Shield is used to reduce the stray magnetic fields generated by the transformer.
How is the impedance of a power transformer specified? The impedance of a power transformer is specified as a percentage and represents the voltage drop from the rated voltage when the transformer is loaded at its rated current.
What is the typical voltage regulation of a power transformer? The typical voltage regulation of a power transformer is around ±5%.
What are the common causes of power transformer failures? Common causes of power transformer failures include insulation breakdown, short circuits, and overheating.
How is the Short Circuit Impedance of a power transformer determined? The Short Circuit Impedance is determined by applying a known voltage to the transformer secondary and measuring the current.
What are the safety precautions when working with power transformers? Safety precautions include ensuring proper grounding, using personal protective equipment, and following safety procedures during maintenance and testing.
How is the efficiency of a transformer affected by the load power factor? The efficiency of a transformer is reduced when operating at low power factors due to increased copper losses.
Can a power transformer be connected in series with another transformer? Yes, power transformers can be connected in series to step up or step down voltage levels depending on their ratings.
What is the purpose of a Radiator in a power transformer? The Radiator is used to dissipate heat from the transformer by increasing the surface area for better cooling.
Can a power transformer be operated without any load connected to the secondary winding? Yes, a power transformer can be operated without a load, but it will consume some no-load current.
What is the purpose of the Tap Changer Controller in a power transformer? The Tap Changer Controller automatically adjusts the tap settings based on the load and voltage conditions to maintain a consistent output voltage.
How is the impedance voltage of a transformer specified? The impedance voltage is specified as a percentage of the rated voltage and represents the voltage drop across the impedance when the transformer is loaded at its rated current.
What is the purpose of the Marshalling Box in a power transformer? The Marshalling Box is used to house and protect the electrical connections of the transformer.
How is the polarization index (PI) test conducted on a transformer? The polarization index test involves measuring the insulation resistance at 10 minutes and 1 minute and calculating their ratio.
What is the function of the Thermometer in a power transformer? The Thermometer is used to monitor the transformer's oil temperature to prevent overheating.
Can a power transformer be used in a DC (Direct Current) circuit? No, power transformers work only with AC (Alternating Current) circuits.
What are the factors that determine the cost of a power transformer? The factors that determine the cost of a power transformer include its capacity, voltage rating, cooling method, and other features.
What is the purpose of the Radiator Fan in a power transformer? The Radiator Fan is used to enhance cooling by increasing air circulation through the radiator.
Can a power transformer be operated with a reversed polarity connection? No, a power transformer cannot be operated with a reversed polarity connection as it will cause a phase shift and an incorrect voltage transformation.
How is the impedance voltage different from the impedance percentage of a transformer? The impedance voltage is the actual voltage drop across the impedance, while the impedance percentage is the ratio of the impedance voltage to the rated voltage.
What is the purpose of a Control Cabinet in a power transformer? The Control Cabinet houses the tap changer controls and protection relays for the transformer.
What is the typical insulation class for transformer windings? The typical insulation class for transformer windings is Class A (105°C) or Class E (120°C).
Can a power transformer be used to step up or step down a single-phase supply? Yes, power transformers can be used to step up or step down a single-phase supply.
What is the function of the Pressure Relief Device (PRD) in a power transformer? The Pressure Relief Device is a safety device that releases pressure from the transformer tank during internal faults to prevent tank rupture.
How is the impedance of a transformer calculated using the impedance percentage? The impedance of a transformer is calculated by multiplying the impedance percentage with the rated voltage.
What are the advantages of a three-phase transformer over a single-phase transformer? Three-phase transformers are more efficient, cost-effective, and compact than single-phase transformers for high-power applications.
How is the Oil Temperature Gauge calibrated in a power transformer? The Oil Temperature Gauge is calibrated to display the correct oil temperature corresponding to specific temperature levels.
What is the purpose of the Tap Selector Switch in a power transformer? The Tap Selector Switch is used to manually change the tap positions for voltage adjustment.
Can a power transformer be operated at higher than its rated voltage? Operating a power transformer at higher than its rated voltage can lead to increased losses and reduced lifespan.
What are the safety measures to be taken during transformer oil testing? Safety measures include wearing appropriate protective gear and ensuring that the testing equipment is properly grounded.
How is the phase sequence determined in a power transformer? The phase sequence is determined by measuring the voltages across the transformer windings.
What is the purpose of the Oil Level Indicator in a power transformer? The Oil Level Indicator is used to monitor the level of transformer oil inside the tank.
Can a power transformer be used to convert one voltage frequency to another? No, power transformers do not change the frequency of the input voltage.
How is the Short Circuit Withstand Test conducted on a power transformer? The Short Circuit Withstand Test involves applying a short-circuit current to the transformer to verify its ability to withstand short-circuit conditions.
What is the purpose of the Protective Relay in a power transformer? The Protective Relay monitors the transformer for abnormal conditions and initiates protective actions when necessary.
How is the polarity of a power transformer determined during installation?

1. The polarity of a power transformer is determined by connecting a low voltage AC supply to the transformer primary and observing the direction of the induced voltage in the secondary winding.