Impedance transformers

Thread Starter

DrNick

Joined Dec 13, 2006
110
Has anyone here ever built an impedance transformer that reflects real power and allows the imaginary to pass? I heard that the energy bill for a high power device at MIT was costing them too much money, so they put an impedance transformer in front of it, and reduced their energy bill significantly (because energy companies do not bill for imaginary power!!! heh)
 

JoeJester

Joined Apr 26, 2005
4,325
because energy companies do not bill for imaginary power!!!
And they frown upon someone delibertly changing the power factor.

If MIT is involved in a theft of service, it would be news, and in the Massechuettes court system.
 

Thread Starter

DrNick

Joined Dec 13, 2006
110
So the power company considers it theaft to use energy they dont bill for? Do they say that you can't change the power factor when you sign up for service?
 

kubeek

Joined Sep 20, 2005
5,731
I think it is not theft, because you can connect anything you want after the clock, if it meets some electrical requirements and is installed by some professional.

But is it possible to get purely inductive or capacitive load using some transformer?

Let's say I have a resistive heater connected to single phase. How would the circuit look like, which will transform it to reactive load?
 

JoeJester

Joined Apr 26, 2005
4,325
Don't you think the electric company would investigate why a customer who spent alot of money for their service and suddenly is spending a little would investigate the cause of the drop?

If they were going to say that much, why not install their own 1kW generator and run the 1 MW plant from this "imaginary" power.
 

Thread Starter

DrNick

Joined Dec 13, 2006
110
Well the thing is that I believe that this reflects the real power, so you can't run a larger generater from a smaller one. It just uses power that the energy company doesn't bill for. I am playing around with matching networks for now to see if I can get one of these bad boys working heh.
 

Papabravo

Joined Feb 24, 2006
14,253
Has anyone here ever built an impedance transformer that reflects real power and allows the imaginary to pass? I heard that the energy bill for a high power device at MIT was costing them too much money, so they put an impedance transformer in front of it, and reduced their energy bill significantly (because energy companies do not bill for imaginary power!!! heh)
AFAIK there is no such thing as imaginary power. There is power factor correction but that just means bringing the voltage and current to the same phase. When you do this, the cosine of the phase difference is one and the instantaneous power is V times I. At any other phase difference the cosine will be less than 1 and the power will be less than the power delivered in the matched case which represents a purely resistive load.

I think you are wasting your time and if you're not careful may be a candidate for a Darwin.

Although not entirely clear you might find the following helpful
http://en.wikipedia.org/wiki/Apparent_power
http://en.wikipedia.org/wiki/Electricity_meter
 

kubeek

Joined Sep 20, 2005
5,731
AFAIK there is no such thing as imaginary power. There is power factor correction but that just means bringing the voltage and current to the same phase. When you do this, the cosine of the phase difference is one and the instantaneous power is V times I. At any other phase difference the cosine will be less than 1 and the power will be less than the power delivered in the matched case which represents a purely resistive load.
Yes, but there is imaginary current, eg. out of phase with voltage.
And the initial thought was probably about imaginary current and not power.

It is possible to create power factor correction which will make the cosine 0, but I think the device will never pay back, because for industry it is impossible to use it because off sudden consumption drop.
And for home like for heating it is also unusable, because making corrector for tenths of kilowatts is not a thing for a DIYer.
 

Papabravo

Joined Feb 24, 2006
14,253
I'd be careful. Just because you can represent an AC wavform with a complex number does not mean there is an imaginary current. All currents a real just as all voltages are real.

The magnitude and phase of an actual waveform behave the same way as the phasor quantity, but that does not mean that the current or any component of the current is imaginary.
 

thingmaker3

Joined May 16, 2005
5,084
So the power company considers it theaft to use energy they dont bill for? Do they say that you can't change the power factor when you sign up for service?
What they do say when you sign up for service is that they will bill more if the power factor is below a certain level. TANSTAAFL. ;)
 
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