Synchronus Machine Characteristics (AFNL & AFSC)

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SUMMARY

The discussion centers on the characteristics of synchronous machines, specifically the Open Circuit (No Load) and Short Circuit Characteristics. It is established that for both generators and motors, the short circuit field current (AFSC) is larger than the no load field current (AFNL), resulting in a short circuit ratio (SCR) that is always less than 1 for generators and greater than 1 for motors. The participants conclude that the textbook contains inaccuracies regarding the SCR calculations, as both synchronous generators and motors operate on the same principles, differing only in energy flow direction.

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  • Understanding of synchronous machine operation principles
  • Familiarity with electrical circuit characteristics
  • Knowledge of short circuit ratio (SCR) calculations
  • Basic concepts of generator and motor functionality
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Electrical engineering students, educators, and professionals involved in the study or application of synchronous machines and their characteristics will benefit from this discussion.

cpscdave
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Hi everyone,
I'm a little confused what is going on in our textbook. There are a number of questions that state the table below has the Open Circuit (No Load) and Short Circuit Characteristics of some synchronous machine.
But then the columns don't seem to match that wording (I'd think that open circuit would be first)

I'm wondering if someone can confirm this thought process is right.

If you are looking at a GENERATOR the short circuit filed current (AFSC) will be larger than the no load field current (AFNL) resulting in a short circuit ratio (SCR) less than 1

If you are looking at a MOTOR the AFSC will be SMALLER than the AFNL resulting in a SCR greater than 1?

Does this seem correct?? Or am I way off base here??
Thanks
 
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No, it isn't correct. Short circuit currents are larger than no load currents for motors too
 
So then you can never have an SCR > 1?

This textbook is borked it has a couple examples where they calculate the SCR to be > 1
 
Sync generator and sync motor are in principle same things. Only the direction of the flow of energy is reversed. Therefore, I don't know what they are talking about (or I misinterpreted )
 

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