It is not desirable to have leading power factor. That can cause overvoltage.
Capacitors and their function in Alternating Circuits
- Thread starter Fishn sparky
- Start date
- Status
It is not desirable to have leading power factor. That can cause overvoltage.
Even without leading power factor, it is possible to have overvoltage. It is due to series resonance between capacitor and system inductance.
The supply would have to be rather soft for that to happen. But I'm sure you know that.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Please explain. Soft=fluctuating?
Soft as opposed to stiff.
Yes. More liable to fluctuate due to higher source impedance.
Iam not sure.
To acknowledge ignorance is the beginning of understanding.Iam not sure.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
171024-1951 EDT
Soft means a higher impedance, more toward a current source. A stiff source means a source where the the voltage source has a very low internal impedance, and thus the instantaneous voltage deviates very little relative to its unloaded value.
.
Soft means a higher impedance, more toward a current source. A stiff source means a source where the the voltage source has a very low internal impedance, and thus the instantaneous voltage deviates very little relative to its unloaded value.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
171024-2432 EDT
Assume an ideal voltage source, zero internal impedance.
Connect any finite inductor to that source. The source voltage will remain unchanged, as will the inductor voltage.
Separately connect any finite capacitor to that source, and the source voltage will remain unchanged, as will the capacitor voltage.
Next connect any combination of finite capacitance and finite inductance to said source, whether the combination is at resonance or not, and the source voltage will remain constant.
Next put internal impedance in the voltage source. Now it is possible to get an increased voltage at the output terminals of the non-ideal voltage source.
.
Assume an ideal voltage source, zero internal impedance.
Connect any finite inductor to that source. The source voltage will remain unchanged, as will the inductor voltage.
Separately connect any finite capacitor to that source, and the source voltage will remain unchanged, as will the capacitor voltage.
Next connect any combination of finite capacitance and finite inductance to said source, whether the combination is at resonance or not, and the source voltage will remain constant.
Next put internal impedance in the voltage source. Now it is possible to get an increased voltage at the output terminals of the non-ideal voltage source.
.
OK. Got examples?
Let me state principle involved. The transformer inductive reactance Xl can combine with line capacitive reactance Xc ( such as due to series capacitor in the line ) to form a series circuit across the supply of voltage E. Then voltage across transforms Et=E/[1-(Xc/Xl)]. If Xc/Xl=0.8, Et=5E ie over voltage at the transformer.
Extremely common
voltage rise due to Xc shunt (Pi config) is a major factor in line design
in reality it is on the order of 10% or so
mitigated with shunt Xl, series Xc, tap adjusting v regulators, and lately FACTS
https://www.google.com/amp/s/electricalnotes.wordpress.com/2011/03/26/ferranti-effect/amp/
Last edited:
I understand the principle. That wasn't my question.
If you can cite no actual examples, that's fine.
Can we leave it at that please?
I'm sure you think so.
The supply source with series capacitor in post#54 is very stiff. Despite it, it was shown five times supply voltage can be impressed upon transformer even when the circuit is inductive. An example for this is an unloaded transformer connected to transmission line with series capacitor.
Not only me
EVERY line engineer
physics/field theory
how about a matlab power sim model?
- Status