What is the main difference between an auto-transformer and a two-winding transformer?
A
Auto-transformer has two cores
B
Same winding acts as both primary and secondary
C
Auto-transformer works only on DC
Analysis & Theory
In an auto-transformer, part of the winding is common to both primary and secondary circuits.
Auto-transformers are more efficient than two-winding transformers because:
A
They use less copper and core material
C
They have separate cores
D
They operate at high temperature
Analysis & Theory
Auto-transformers are lighter and more efficient due to reduced copper and core material usage.
Which of the following is NOT an advantage of an auto-transformer?
C
Electrical isolation between circuits
Analysis & Theory
Auto-transformers do not provide electrical isolation between the primary and secondary.
Auto-transformers are mainly used when:
A
The voltage ratio is high
B
The voltage ratio is low
Analysis & Theory
They are best suited for low voltage ratio applications where the difference between primary and secondary voltage is small.
In an auto-transformer, the power transferred inductively is:
Analysis & Theory
Power is transferred partly by conduction and partly by electromagnetic induction.
Which of the following is a limitation of auto-transformers?
C
No isolation between input and output
Analysis & Theory
Auto-transformers do not isolate primary and secondary sides, which may be dangerous in some applications.
What is the condition for saving copper in an auto-transformer?
Analysis & Theory
Auto-transformers save more copper when the voltage ratio is low (i.e., primary and secondary voltages are close).
Which of the following applications commonly use auto-transformers?
C
Starting induction motors
Analysis & Theory
Auto-transformers are commonly used to start induction motors with reduced voltage.
If an auto-transformer has a transformation ratio of 2:1, how many windings does it have?
Analysis & Theory
An auto-transformer has only one winding that acts as both primary and secondary.
Which of the following is a disadvantage of using an auto-transformer?
B
Electrical isolation is not provided
Analysis & Theory
Auto-transformers lack electrical isolation, which can be a safety concern in some circuits.