As shown in the illustrated diagnostic setup...

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Question 1 of 2066636ef128f7522a1c522e8f

As shown in the illustrated diagnostic setup for locating a shorted field coil of a ten-pole salient pole alternator, if 240 VAC/60 Hz is applied across the brushes, what would be the voltage drop across field coil No.4 if that field coil had shorted turns and the other field coils were free of shorts? Illustration EL-0202

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Question 1 of 20

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🔍 Key Concepts

• Series circuits and how applied voltage divides across equal resistances • Effect of shorted turns in a field coil on that coil’s resistance and its share of the total voltage • Ten-pole alternator means 10 coils in series between the brushes when using this test method

💭 Think About

• First, assume all 10 field coils are healthy and have equal resistance. With 240 VAC applied across the brushes, what would be the approximate voltage across each coil? • Now, if coil No.4 develops shorted turns, does its resistance go up or down compared to the others, and will its voltage drop be higher or lower than the healthy coils? • Given the four choices, which one best represents a reduced voltage on the bad coil, while the remaining nine coils must now share a little more than before?

✅ Before You Answer

• Confirm that all coils are connected in series between the brushes in this diagnostic setup • Calculate the normal per-coil voltage when 240 VAC is divided equally by 10 coils • Make sure the option you select is less than the normal per-coil voltage, since a shorted coil will have less resistance and therefore a smaller voltage drop in the series string

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