🔍 Key Concepts

• Relationship between frequency difference of bus and incoming machine and the speed of synchroscope rotation • How the direction of phase shift (incoming wave leading or lagging the bus wave) relates to the FAST vs SLOW side of the dial • Interpreting the spacing of zero crossings in the waveforms to see if the incoming machine is faster or slower than the bus

💭 Think About

• Look at the waveforms in figure A: as time (phase angle) increases, does the incoming machine’s waveform move ahead of or behind the bus waveform? What does that imply about its frequency? • If the frequency difference between the bus and incoming machine is small vs large, how would that change the rate at which the synchroscope pointer goes around the dial? • On a typical shipboard synchroscope, when the incoming machine is slightly faster than the bus, which way does the pointer move: toward the FAST or SLOW direction?

✅ Before You Answer

• Identify clearly which sine wave is the bus and which is the incoming machine, then note which one completes a cycle first. • Estimate whether the two frequencies appear very close or significantly different based on the gradual change of the error angle in figure A—this tells you if the pointer motion is slow or rapid. • Match the lead/lag of the incoming machine relative to the bus with the labeled FAST/SLOW directions on the synchroscope face in figure B before choosing an option.