Understanding Phase Angle: Voltage and Current Readings in RLC CCT

[Elliot_Bennett]

How can taking voltage and current readings from an AC supplied CCT with either a resistive, capacitive or inductive load (gradually increasing the load for each) show the difference in phase angle between voltage and current for each component? Many thaks for any help.

 

[cnh1995]

Welcome to PF!

How can taking voltage and current readings from an AC supplied CCT with either a resistive, capacitive or inductive load (gradually increasing the load for each) show the difference in phase angle between voltage and current for each component? Many thaks for any help.

Could you elaborate?

 

[Elliot_Bennett]

Welcome to PF!

Could you elaborate?

I recently did an experiment whereby an AC generator supplied a capacitive, resistive or inductive load, for each readings of voltage and current were taken from the AC Generator showing how it reacted to various levels of RLC load. On a capacitive load as the load value was increased the current and voltage both increased, on an Inductive load as the load was increased the voltage rose and current fell and on a Resistive load as the load was increased voltage rose and current dropped (but showed less change than a purely inductive load).

 

[cnh1995]

I recently did an experiment whereby an AC generator supplied a capacitive, resistive or inductive load, for each readings of voltage and current were taken from the AC Generator showing how it reacted to various levels of RLC load.

So did you use a series RLC circuit and changed the componemt values one at a time or did you use purely resistive and purely reactive circuits?

On a capacitive load as the load value was increased the current and voltage both increased, on an Inductive load as the load was increased

What do you mean by 'load' here? Did you increase the capacitance?

 

[Elliot_Bennett]

So did you use a series RLC circuit and changed the componemt values one at a time or did you use purely resistive and purely reactive circuits?

What do you mean by 'load' here? Did you increase the capacitance?

No we did not use a series RLC circuit. Purely resistive, purely capacitive and purely inductive circuits with only the relevant component in each circuit, for each the value of the inductor, capacitor or resistor was increased. I.E for resistive from 50-450 ohms at 50 ohm intervals.

 

[cnh1995]

If the ac voltage source were ideal, there would be no change in voltage with the change in load. The voltage is changing because of the internal impedance of the source.
When you increase the resistance and inductance, you are decreasing the load. Here, the current drops and hence, the voltage across the internal impedance also drops, which gives more voltage across the resistance or inductance.
In case of purely capacitive circuit, increasing the capacitance means increasing the load. Here, the current is expected to increase, but since the voltage is also increasing, it is something like the 'Ferranti effect'.
https://googleweblight.com/i?u=http.../wiki/Ferranti_effect&grqid=ErPULSLj&hl=en-IN

 

[cnh1995]

In #3, you only described the magnitude changes of voltage and current while in #1, you were asking about their phase difference. What is your question about the phase difference?

 

[jim hardy]

Can we assume that generator has a voltage regulator ?

AC generator supplied a capacitive, resistive or inductive load, for each readings of voltage and current were taken from the AC Generator showing how it reacted to various levels of RLC load

To understand what's going on you need to lock the excitation,, ie switch the voltage regulator from "Auto" to "Manual". Otherwise you're just testing the voltage regulator.