Transformer efficiency varies with load. When the transformer operates near its rated load, the efficiency is highest. At lower or higher loads, core losses or copper losses become more significant, reducing overall efficiency.
What is the main cause of eddy current losses in a transformer?
A Resistance
B Magnetic flux
C High current
D Voltage imbalance
Eddy current losses occur when a changing magnetic flux induces circulating currents within the transformer’s core. These currents generate heat and waste energy, reducing the efficiency of the transformer. Laminated cores help reduce these losses.
Which of these losses are considered constant in a transformer, regardless of load?
A Iron losses
B Load losses
C Stray losses
D Copper losses
Iron losses, also called core losses (including hysteresis and eddy current losses), are constant in a transformer and do not vary with the load. These losses depend on the design and material of the core and occur even when the transformer is idle.
What does the voltage regulation of a transformer indicate?
A Core saturation
B Efficiency
C Voltage drop
D Current flow
Voltage regulation in a transformer refers to the difference in voltage between no-load and full-load conditions. It indicates how much the secondary voltage drops as the load increases. Lower voltage regulation implies better transformer performance.
What happens when a transformer is operated below its rated voltage?
A Increased current
B Reduced efficiency
C Reduced current
D Increased voltage
Operating a transformer below its rated voltage results in reduced efficiency. The voltage drop can cause under-utilization of the transformer’s design, leading to increased energy losses and reduced performance, especially in power transmission.
What is the primary function of a load test in transformer testing?
A Measure efficiency
B Identify faults
C Calculate losses
D Check insulation
A load test is used to evaluate a transformer’s efficiency by applying a known load and measuring the input and output power. This test helps in determining the actual performance of the transformer under normal operating conditions.
What is the result of increasing the current in a transformer’s primary winding?
A Increased voltage
B Decreased flux
C Increased flux
D Decreased voltage
Increasing the current in the primary winding of a transformer increases the magnetic flux in the core. Since the induced voltage in the secondary winding depends on this flux, any change in flux directly impacts the output voltage.
Which type of transformer is typically used for large power transmission over long distances?
A Distribution transformer
B Step-down transformer
C Power transformer
D Isolation transformer
Power transformers are used in large power transmission systems to step up voltage for long-distance transmission. Higher voltage results in lower current, minimizing energy losses over long distances, which is critical for efficient power distribution.
What is the function of a tap changer in a transformer?
A Adjust voltage
B Decrease current
C Change current
D Increase efficiency
A tap changer is used in transformers to adjust the output voltage. By changing the number of active turns in the winding, it can regulate the voltage according to the system’s requirements, especially under varying load conditions.
Which of the following factors has the greatest impact on transformer losses?
A Insulation
B Core material
C Load type
D Frequency
The core material significantly impacts transformer losses, specifically core (iron) losses. High-quality materials, such as silicon steel, reduce hysteresis and eddy current losses, improving the transformer’s overall efficiency.
What happens to a transformer’s efficiency when it operates at very low loads?
A It remains constant
B It fluctuates
C It decreases
D It increases
At low loads, the core losses remain constant while copper losses become proportionally higher. This causes the transformer to become less efficient as it operates below its optimal load, resulting in higher relative energy losses.
In which type of transformer is the primary and secondary winding electrically connected?
A Isolation transformer
B Step-up transformer
C Step-down transformer
D Autotransformer
An autotransformer has a single winding that serves as both the primary and secondary winding, with the primary and secondary electrically connected. This configuration makes it more efficient for voltage adjustment, but it lacks the isolation provided by a conventional transformer.
How is the primary current related to the secondary current in a transformer?
A Inversely proportional
B Unrelated
C Equal
D Directly proportional
The primary and secondary currents in a transformer are inversely proportional to their voltage ratios. This relationship is governed by the law of conservation of energy, where an increase in voltage results in a decrease in current, and vice versa.
Which transformer type is commonly used for high voltage transmission in industrial settings?
A Isolation transformer
B Distribution transformer
C Power transformer
D Step-down transformer
Power transformers are used for high-voltage transmission in industrial settings, especially when stepping up or down large voltages is necessary for effective transmission. These transformers are designed to handle heavy loads and high voltage ratings.
What is the main difference between a dry-type and oil-filled transformer?
A Efficiency
B Cooling method
C Voltage rating
D Size
The main difference between dry-type and oil-filled transformers is the cooling method. Dry-type transformers use air for cooling, while oil-filled transformers use oil for both cooling and insulation, allowing for higher power ratings and more efficient heat dissipation.