18 Questions
When the frequencies of two voltage sets are different, what happens to the phasor difference (VA1 - VA2)?
Its magnitude varies in time
What happens to lamp L1 when the voltage across it passes through zero?
It turns off
What is the advantage of the cross-connected synchroscope method?
It shows whether the incoming machine is running above or below synchronous speed
What is the purpose of the cross-connected lamp synchroscope?
To check for synchronization
What is the result of the cross-connected lamp synchroscope when the lamps are arranged in a cyclic manner?
The lamps light up sequentially
What happens to the brightness of lamp L1 due to the difference in frequencies?
It changes in time
What is a necessary condition to obtain a Lissajous figure on the CRO screen?
Connecting an attenuator (probe) to the X and Y plates
What is required to ensure condition (a) is satisfied?
A simple measurement
What is the purpose of closing the synchronizing switch?
To observe a straight line with a slope less than 90º
What is the voltage across lamp L1 represented by?
V A1 - V A2
What is the frequency of the phasor (V A1 - V A2)?
f
What is the purpose of a synchroscope?
To ensure conditions (a) and (b) are satisfied
What is the primary function of a synchroscope?
To synchronize a generator with an infinite bus-bar system
What is the purpose of a single-phase variac in the synchronous machine starter circuit?
To control the armature voltage of the synchronous motor
What is the significance of the phasor diagram in Fig.1(b)?
It corresponds to the straight-connected lamp synchroscope
What is the purpose of the synchronizing switch (S2) in Fig.3?
To connect the synchronous machine to the infinite bus-bar system
What is the Lissajous figure method used for in synchronization?
To determine the synchronizing conditions
What is the significance of the cross-connected lamp synchroscope?
It provides a visual indication of synchronism
This quiz assesses your understanding of Lissajous figures on a CRO screen, including synchronization and phase connections. Learn how to obtain a Lissajous figure and identify the shape of the figure on the screen. Test your knowledge of CRO operations and Lissajous figures.
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