efficiency improvement using capacitor

[star882]

I have heard that by installing a capacitor in parallel with a compressor, the total current will decrease without any impact on operation. That would imply an efficiency increase.
Is that true? Does it only work on older equipment?
I have heard about someone doing that with an old refrigerator and actually got a very significant decrease in operating costs, but I cannot verify that.

[lana]

Hi there,

There is a way to use capacitors to make the reactive part of the power zero (if I explained this correctly , I am not an electricity expert, I just know that it kills ).
And this decreases the cost dramatically.
We have this system installed at our home engine room and also in the factory. It does make a real difference.

I am sure Peter1 can help you on this one.
Cheers

[Josip]

Hi, Star882

maybe you can find out more here:
http://www.shockfamily.net/triplehex/40hp.html

I'm not electrical engineer and this is some kind of "dark area" for me and will be nice if someone can explain this in layman's terms.

sounds very interesting. Thanks.

Best regards, Josip

[NoNickName]

Reactive power is wasted power due to induction caused by windings of electrical motors. Basicly induction causes a disalignment between the phase of voltage and current.
This disalignment produces a parasite power called "reactive power", caused by the vector product of current x voltage. Users pay for reactive power more than for active power, without any benefit in terms of work done.
Capacitors also induce a disalignment, but with inverse sign. So when induction is causing unbalance between current and voltage, than a capacitor can be used to realign the phase.
Unfortunately, capacitors have a drawback of increasing the RMS voltage, so the life of motors can be reduced accordingly to the quantity of rephasing.
The ration between total power and active power is called power factor or cos(fi) and it generally is 0.70 to 0.85 for non-rephased motors, and up to 0.97 for rephased motors.
Please note that rephasing capacitors induce harmonic distortion to the sinusoidal profile of voltage, and this may cause EMI and power surges into fan speed regulators or other triacs.
If harmonics are found after the capacitors along the power line, than it may be necessary to install detuning reactance resistance in series with the capacitors.

[US Iceman]

WOW. NoNickName, that was impressive. That's about the best explanation I've seen in such a short space!

[Brian_UK]

I've read, but am still bemused, albeit amazed.

But as you say, an excellent description and one that makes me realise why I avoid electricity if I can.

[Josip]

Hi, NoNickName

Thanks for nice explanation. So far I know (not familiar as you are ) about capacitor banks because today that is a must for each refrigeration plant here.

Sorry, I made mistake; the question was abut explanation regarding this article:

http://www.shockfamily.net/triplehex/40hp.html

from this thread:
http://www.refrigeration-engineer.co...ead.php?t=7889

3-phase motor to work as single phase motor

I'm not going to build it, just curious.

Best regards, Josip

[NoNickName]

I never heard of that type of motors.

[frank]

Did NoNickName get a Rep point for that??

Great explanation

[ultralo1]

Star882,
I cant explain exactly but if you talk to an electrical engineer They maybe familair with the saying "Eli the Ice man"

ELI= Voltage leads current in an inductor
E=voltage
L=inductor
I=current
inductor=coil

ICE= Current leads voltage in a capacitor
I=current
C=capacitor
E=voltage

As you can see they can cancel each other out if you know the equations.

Unfortunatley this is one concept that I could never wrap my head around and understand fully