[SOLVED] measuring AC current frequency

When would a tech want to measure the AC current's frequency?
for what kind of circuits or applications?

my DVM manual says it's for line and load regulation

Mostly I have measured the AC voltages frequency but never the AC current frequency

We would a tech want to measure the AC current frequency for what kind of circuit or application

Frequency of current and voltage same. I don think any load will take a current in diff frequency than voltage and it is no possible.

There is more two things about analysing current,
1, current phase for power factor but direct measurement is possible
2, current harmonics taken by loads cause harmonics in the AC line

1, current phase for power factor but direct measurement is possible

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for single phase or 3 phase power supplies?

current harmonics taken by loads cause harmonics in the AC line

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I would need a O-scope that has FFT or a spectrum analyzer using a current probe to measure the current harmonics?

UPS systems load the AC line or AC generator causes current and voltage harmonics?

Or machine equipment connected to the 120VAC causes loading harmonics and in rush current

Is the currents frequency higher during in rush current?

how would u measure in rush current?

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Does designers measure the currents frequency for TTL and CMOS inputs to outputs for each state or from Logic IC chip to the next IC chip to test the legacy speed?

Because the currents frequency plays a role in the legacy of the circuit

for single phase or 3 phase power supplies?

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That is not depend on number of phases.

I would need a O-scope that has FFT or a spectrum analyzer using a current probe to measure the current harmonics?

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Yes, you will need.

UPS systems load the AC line or AC generator causes current and voltage harmonics?

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Yeah most of them.

machine equipment connected to the 120VAC causes loading harmonics and in rush current

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Not all time, in initial condition for 2 or 3 cycles, but I heard about some machines will generate 3 or 5 th harmonics which will affect lines.

Is the currents frequency higher during in rush current?

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Actually they are same frequency in nature, but it can happen some cases but not with a huge current.
for example the reason for transformer (it will also take inrush current) taking inrush current is for magnetizing the inductance. in that case if that kind of low inductance create any resonance it may oscillate.

how would u measure in rush current?

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If you want you can have a CT and a peak detector.

Does designers measure the currents frequency for TTL and CMOS inputs to outputs for each state or from Logic IC chip to the next IC chip to test the legacy speed?

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They will measure it in terms of delays and capacitance.