In an electrical system, the term power factor is the ratio of usable real power to non-usable apparent power sometimes called reactive power. It not only controls energy consumption but also how that energy consumption is billed.
The lower the power factor the higher the required necessary current draw, which will require a more robust infrastructure and the use of appropriately heavier gauge wires to minimize the dissipation of power. This means that on-premises utility usage will be more costly, and facilities operating with low power factors will be charged at a higher usage utility rate than facilities with high power factors.
Fortunately, there are ways to correct sub-par operating power factors and greatly reduce or eliminate frequency harmonics to ensure higher cost efficiency of an operating electrical system.
There are two scenarios causing power factor displacements – operating power factor and harmonic power factor. The first displacement is caused by any inductance in an electrical load, (such as a motor) causing the delivered current to be out of phase with the supply voltage, while the latter displacement results from any non-linear switching of the utilized supply voltages, such is the case when using power semiconductor devices and rectifier circuits.
For an electrical system to function properly, any harmonic resonance present and/or harmonic distortion must be eliminated
When there is a large supply of individual currents from a number of harmonic current sources, the system could resonate. This is especially true if one of the harmonic frequencies of the current sources coincides with the resonant frequency created from the combination of the supply transformer’s and the capacitor circuitry combination which is being used for power factor correction.
The large flow of current going to a major supply transformer (such as in a data center) can lead to a large harmonic voltage distortion. This event increases the risk of increased heating which will cause the loss of some of the transformer’s power output, possible malfunction of connected equipment, possible premature failure of other connected power factor correction capacitors and motors, and interference in some communication systems.
Harmonic Filters – A Practical Solution
To reduce or eliminate harmonic resonance and distortion, a true harmonic filter needs to be used at strategic operating circuit points.
What is a harmonic filter?
As previously mentioned, harmonic filters are used to eliminate harmonic distortion caused by excess currents in and out of appliances. It can prevent large quantities of harmonics from causing damage to equipment, downtime of operation, and preventing an increase in operating costs.
What is a harmonic filter made of?
The interior of a harmonic filter is made up of an array of resistors, inductors, and capacitors that are capable of deflecting unwanted harmonic currents, sending them to ground. Some of these filters are designed to deflect harmonics of a specific frequency or frequencies.
What are the various types of harmonic filters?
Passive Harmonic Filters – These filters are typically used in industrial installations with loads representing more than 500kVA. These filters require power-factor correction during installation.
Active Harmonic Filters – Also known as active harmonic conditioners, these filters are often used in commercial installations with loads less than 500kVA. They help to reduce current distortion that could lead to equipment heating and circuit overloads.
Hybrid Filters – A system that combines passive and active filters for industrial installations with loads more than 500kVA. It has the advantage of the previous two types of filters and covers different power and performance levels.
Each of these options has their place in the market. It is important that a user identifies the amount of harmonic distortion that needs to be eliminated before a filter is chosen. Active filters, for example, are ideal when there is more than one type of load present, such as UPS, VFD, and DC drives
These various types of Harmonic Filters are readily available from Staco Energy. Staco Energy is an 80 year old midwestern company engaged in designing and supplying harmonic filters, voltage regulators, and UPS power conditioning equipment. Please contact Peninsula Technical Sales for further information regarding what type of harmonic filters might be appropriate for you.
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