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Saturday, January 16, 2016

Power Factor Correction

Recently, a few buddies of mine have been very interested in products that will improve the mains power. There are many products of such nature, like isolation transformer, mains regulator, power factor corrector, power bank, and etc. Isolation transformer, mains regulator and power factor corrector are widely understood, but what is power bank? Can we really store power?

One of the gist of better power transmission is power factor correction. This has been widely used in industrial or commercial buildings to correct the phase relationship between voltage and current to achieve better (close to 1) power factor. Power factor of 1 means there is perfect alignment of voltage and current phase to achieve perfect 100% power transmission. Power factor of <1 means there is a phase shift between Voltage and Current, and power delivery is less than idea.

The phase relationship of the Voltage and Current is dependent on the electrical equipment connected on the load. Say, if we fixed the Voltage phase as reference (as usual, we always need a reference point), there shall be loads that shifts the Current forward and backward in relation to the Voltage phase. In general, inductive load will shift the current backward since inductor prohibits current flow (high impedance to current change), and capacitive load will shift the current forward, in relation to Voltage. Resistive load, is phase neutral - does not shift the current in relation to voltage.

Most solid state uses very big capacitor bank and therefore causes current to advance in phase in relationship with voltage. On the other hand, tube amplifier uses a lot of chokes and transformers, with low capacitance but high voltage capacitors, therefore current will retract in relationship with voltage.

Current / Voltage Phase Relationship

How do you correct this relationship? Simple! The answer is already there! If the current advances in relationship with voltage, use inductor to pull it back, and vice versa! This is called power factor correction (PFC)in lay man's term! One of the difficulties with power factor correction is that how much is enough and how much is too much? There is NO benefits in over-correcting. A close to 1 power factor will not only make your system sounds better, but saves you money too!

In industrial designs, usually a micro-controller is used to monitor the current versus phase relationship, and change the compensation in a controlled feedback loop. Less complicated system can use fixed PFC, like switch mode power supplies with PFC integrated.

PFC works, but can passive PFC like the above work for your system? Yes, it can, but not always the case since everyone's systems are different! Once would have to get the right PFC factor right to have the optimal correction and optimal sound. A one size fits all solution does not work. If it works, you are lucky, or it is just sound changes instead of optimization with over or under-corrected power factor.

In the next article, we shall come up with a simple user configurable power factor correction device. Once can flip switches to change the PFC factor to customize it to their own systems. It might be hard without measurement devices but at least one can still use their ears and that's what matters!

J&K Audio Design
1/17/2016

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Level 0: link 1

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Level 3: depends on type, size and complexity. Email us for details.

Iso-trans: link 1, link 2

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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