Instrument Transformer Question & Answers June 7, 2023 By Wat Electrical This article lists 50 Instrument Transformer MCQs for engineering students. All the Instrument Transformer Questions & Answers below include a hint and a link to the relevant topic wherever possible. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up on the fundamentals of the Instrument Transformer. Instrument transformers are devices used in electrical power systems to transform high currents or voltages into measurable and manageable levels for protection, control, and metering purposes. They are primarily used in conjunction with instruments and protective relays. Current transformers are used to step down high currents to lower, measurable levels. They are commonly used for metering, protection, and control applications. CTs consist of a primary winding and a secondary winding wound around a magnetic core. The primary winding is connected in series with the circuit carrying the high current, while the secondary winding is connected to instruments or relays. The secondary winding’s current is proportional to the primary current but reduced in magnitude. Voltage transformers are used to step down high voltages to lower, measurable levels. They are primarily used for metering and protective relaying purposes. VTs consist of a primary winding connected across the high-voltage circuit and a secondary winding connected to the measuring or control devices. The secondary winding’s voltage is proportional to the primary voltage but reduced in magnitude. 1). What is the primary purpose of an instrument transformer? To change the voltage level To change the current level To measure power factor To measure resistance Hint 2). Which type of instrument transformer is commonly used to measure high currents? Current transformer (CT) Potential transformer (PT) Both CT and PT Neither CT nor PT Hint 3). What is the purpose of a potential transformer (PT)? To measure high voltages To measure low currents To isolate the measuring instrument To convert AC to DC Hint 4). Which of the following statements is true about instrument transformers? They are used only in AC circuits They are used only in DC circuits They are used in both AC and DC circuits They are not used in any circuits Hint 5). Which parameter is commonly measured using a current transformer (CT)? Voltage Power factor Current Resistance Hint 6). Who is credited with the invention of the current transformer (CT)? Nikola Tesla Thomas Edison Galileo Ferraris Ottó Bláthy Hint 7). When was the first practical current transformer developed? 1802 1879 1890 1905 Hint 8). Who is known for the development of the potential transformer (PT)? Nikola Tesla Thomas Edison Ernst Alexanderson William Stanley Jr Hint 9). When were instrument transformers widely adopted for electrical measurement and protection? Early 1900s 1950s 1980s 2000s Hint 10). What technological advancement contributed to the improvement of instrument transformers in the mid-20th century? Introduction of digital technology Development of semiconductor devices Integration of microprocessors Use of high-temperature superconductors Hint 11). Which of the following is true about the secondary current of a current transformer? It is the same as the primary current It is higher than the primary current It is lower than the primary current It is independent of the primary current Hint 12). In a current transformer, if the primary current is 100 A and the turns ratio is 1:100, what is the secondary current? 10 A 100 A 1000 A 10000 A Hint 13). Which of the following is a common application of current transformers? Voltage measurement Power factor correction Energy storage Current measurement for protection relays Hint 14). What is the typical secondary current rating of a current transformer? 1 A 5 A 10 A 100 A Hint 15). A current transformer (CT) has a turns ratio of 1:1000. If the primary current is 100 A, what will be the secondary current? 0.01 A 1 A 10 A 1000 A Hint 16). A CT has a rated primary current of 400 A and a rated secondary current of 5 A. What is the current ratio (CR) of the CT? 80 40 5 0.0125 Hint 17). If a CT has an accuracy class of 0.5, what is the maximum allowable error at the rated current? 0.5% 0.05% 5% 50% Hint 18). A CT has a burden resistance of 5 Ω and a rated secondary current of 1 A. What is the burden voltage when the secondary current is at its rated value? 0.005 V 0.05 V 0.5 V 5 V Hint 19). A CT has a saturation current of 200 A and an accuracy class of 1. If the primary current exceeds 200 A, what can be expected? The CT will produce accurate readings The CT will produce inaccurate readings The CT will become damaged The CT will automatically adjust its ratio Hint 20). A 400/5 CT is used to measure a primary current of 200 A. What will be the secondary current? 40 A 20 A 2000 A 800 A Hint Instrument Transformer MCQ for Interviews 21). A CT has a ratio of 800/1 and a burden resistance of 0.2 ohms. What will be the secondary current if the primary current is 1000 A? 0.2 A 2 A 5 A 200 A Hint 22). A CT has a turns ratio of 200/5 and a rated burden of 5 VA. What is the maximum primary current that can be measured without exceeding the burden limit? 25 A 50 A 200 A 1000 A Hint 23). A CT has a turns ratio of 1000/1 and an accuracy class of 0.5. What is the maximum permissible error at rated current? ±0.5% ±1% ±5% ±10% Hint 24). A CT has a burden resistance of 10 ohms and a secondary current of 1 A. What will be the burden voltage? 1 V 10 V 100 V 1000 V Hint 25). In a CT with a turns ratio of 1:200 and a primary current of 500A, what is the secondary current? 0.25A 2.5A 25A 250A Hint 26). Which parameter is commonly measured using a voltage transformer (VT)? Current Power factor Voltage Resistance Hint 27). In a power system, voltage transformers are typically used for ____________________? Metering purposes Protection purposes Both metering and protection purposes None of the above Hint 28). What is the ratio of a voltage transformer (VT) typically expressed as? Primary voltage to secondary voltage Secondary voltage to primary voltage Primary current to secondary current Secondary current to primary current Hint 29). The secondary voltage of a voltage transformer is 120 V, and the turns ratio is 1:10. What is the primary voltage? 1,200 V 12 V 1,080 V 10,000 V Hint 30). The secondary voltage of a voltage transformer is ______________? Equal to the primary voltage Higher than the primary voltage Lower than the primary voltage Unrelated to the primary voltage Hint 31). Which error occurs due to the difference in the transformation ratio of a current transformer? Phase error Ratio error Burden error Saturation error Hint 32). What is the primary cause of ratio error in current transformers? Magnetic hysteresis Core saturation Insulation breakdown Thermal heating Hint 33). Which error is introduced due to the phase angle difference between primary and secondary currents? Phase error Ratio error Burden error Magnetizing error Hint 34). What is the primary cause of phase error in current transformers? Core saturation Insulation breakdown Burden impedance Magnetic hysteresis Hint 35). Which error occurs due to the burden impedance affecting the current transformer’s output? Phase error Ratio error Burden error Saturation error Hint 36). What is the effect of burden error on the current transformer’s performance? Alters the turns ratio Causes core saturation Introduces phase shift Increases the magnetic hysteresis Hint Read more about Transformer 37). Which error occurs when the current transformer’s core reaches its magnetic saturation point? Phase error Ratio error Burden error Saturation error Hint 38). What is the primary consequence of saturation error in current transformers? Decreased accuracy Increased ratio error Higher burden impedance Reduced phase error Hint 39). Which error can be reduced by using a low-resistance burden on the secondary side? Phase error Ratio error Burden error Magnetizing error Hint Instrument Transformer MCQ for Quiz 40). Which error is caused by the magnetizing component of the primary current? Phase error Ratio error Burden error Magnetizing error Hint 41). What is the effect of magnetizing error on the current transformer’s performance? Causes core saturation Increases the turns ratio Introduces phase shift Reduces the ratio error Hint 42). Which of the following errors in a power transformer occurs due to unequal magnetic leakage paths? Magnetizing current error Hysteresis error Leakage reactance error Winding resistance error Hint 43). Which type of error occurs due to the resistance of the transformer windings? Hysteresis error Winding resistance error Leakage reactance error Stray loss error Hint 44). The error caused by the magnetizing current in a power transformer is known as _______________? Hysteresis error Winding resistance error Magnetizing current error Stray loss error Hint 45). Which error occurs due to the variation of the magnetic flux density with the operating conditions? Hysteresis error Eddy current error Magnetic leakage error Core loss error Hint 46). The error due to the circulating currents induced in the conductive parts of the transformer is known as ________________? Hysteresis error Winding resistance error Eddy current error Core loss error Hint 47). Which error occurs due to the losses in the transformer core and windings? Hysteresis error Eddy current error Copper loss error Stray loss error Hint 48). The error caused by the resistance of the transformer windings is known as _______________? Hysteresis error Winding resistance error Magnetizing current error Copper loss error Hint 49). Which error occurs due to the magnetic leakage in a transformer? Hysteresis error Winding resistance error Leakage reactance error Core loss error Hint 50). The error in a transformer due to the losses in the transformer windings is known as _________________? Hysteresis error Eddy current error Copper loss err Core loss erroror Hint For More MCQs Core Transformer Question & Answers Shell Type Transformer Question & Answers Transformer Question & Answers Single Phase Transformer Question & Answers Time's up
