Detuning Reactors

[submonkey]

Greetings,

 

The the webpage http://www.lmphotonics.com/pwrfact.htm states:

 

(under "Supply Harmonics")

> Adding the inductance in series with the cpacitors will reduce their

> effective capacitance at the supply frequency. Reducing the resonant

> or tuned frequency will reduce the the effective capacitance further.

 

(under "Detuning Reactors")

> Using detuning reactors results in a lower KVAR, so the

> capacitance will need to be increased for the same level of correction.

 

I'm not convinced! Please consider the reasoning below. I have used

'w' to represent system frequency in radians per second.

 

The detuned reactor is connected in series with the

capacitors. The impedance of the reactor is:

 

Zr = jwL

 

The impedance of the capacitor is:

 

Zc = 1/jwC = -j(1/wC)

 

The total impedance of the reactor and capacitor is:

 

Zt = jwL - j(1/wC)

 

 

Note that the effect of adding the detuned reactor is to

reduce the combined impedance, which in turn results

a higher current. The current still "looks" purely

capacitive, since (1/wC) is larger than wL.

 

I conclude that:

 

1. Adding a detuned reactor makes the capacitor bank

draw more capacitive current.

 

2. A higher capacitive current means a greater supply of

reactive power.

 

3. The apparent kVAr is higher!

 

Thanks,

Submonkey

[marke]

Hello submonkey

 

Welcome to the forum.

 

Yes you are correct, the impedance is reduced and therefore the current is increased. This will of course increase the KVAR of the circuit. - I will correct the comment on the web page. Thank you for picking that up.

No one else has seen this!! It is always a concern that no matter how often you read something, you can miss the obvious.

 

Have a great day,

Best regards,