# 1 phase system and 3 phase system

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#### shermaine

##### New Member
Where can i get the notes or information for 1 phase power supply and 3 phase power supply. What is lagging, resistive(Resonant) .

I dont know what you mean by resistant (resonant), but lagging is a term that refers to the power factor. The power factor is a metric that says the amount that the current wave leads or lags the voltage wave by. lagging means you have an inductive load, and the current is lagging the voltage waveform.

Here is one URL, i didnt read it, but it looked like what you might want Link.

I assume by "resistive (Resonant)" you are asking about a resonant circuit.
A resonant circuit is comprised of inductance and capacitance. Either in series or parallel. Resonance is when the frequency of the applied signal is equal to the resonant frequency of the circuit. this is given by

f = 1/{2 Pi sqrt(L C)} where L = the inductance and C = the capacitance.

The inductance also has resistance. At resonance, the inductive reactance is equal and opposite to the capacitive reactance and so they cancel each other out. Thus only the resistance is left and so the circuit is said to be resistive.

This is difficult to explain in a post, I suggest you search for a suitable book or Internet site.

Len

I remember learning about this (the basics) in "AC Circuits 101" and have since found several used college texts since that are excellent references. If you have access to any used books this might help narrow the search. I use the word basic to help you more quickly locate what you need - not as a measure of your abilities or knowledge.

The book I used while a student (30 years ago) was Electric Circuits by Joseph A Edminister. It is very good as it has worked examples and test questions. Chapter 8 is entitled - Series and Parallel Circuits.

It may not be available now, but some libraries may have it.

Len

Hello,

Thanks for all the information.
At least, i understand 3 phase power supply now.
Thanks.

Btw, how do we know if it is leading or lagging Power factor.
Thanks

Leading and lagging refer to the phase angle between the current and voltage, ie. whether the current leads or lags the voltage. If the circuit is inductive, the current lags the voltage (ie. the phase angle is negative)

If the circuit is capacitive, the current leads the voltage (ie. the phase angle is positive)

Incidentally, what does "btw" mean?

Len

BTW means "By The Way".

Hello, 