The power factor controller is a device that measures the power factor from electrical signals (voltage and current), calculates the need for insertion or removal of reactive power through capacitors connected to its outputs, and keeps its index within adjustable limits. There are various types of inputs, outputs, parameters, and functionalities. Below, we highlight the main types.
Power factor control based on electrical quantities voltage and current
The equipment is connected to a common point with a group of low voltage loads. The current is measured through intermediate devices such as current transformers and Rogowski coils.
The diagram above shows the input of 3 voltage signals + Neutral, and 3 current signals, which implies a three-phase control in a star system. This type of connection is the most common, as it is recommended for unbalanced systems.
There are also single-phase controller models that receive a voltage signal, a current signal, and based on that, insert the capacitors. It is important to note that single-phase control involves various caveats and precautions, as it is not uncommon to have phase imbalance.
For choosing the type of sensor, the number of phases monitored, among other aspects, an energy analysis is always recommended. This type of study reveals the current dynamics, the incidence of harmonics, how many and which capacitors to place, and other important information for sizing the control system.
Power factor control based on standardized signals
There are controllers that activate the capacitors based on a standardized input signal, such as the ABNT CODI, provided for in NBR 14522. This type of connection is uncommon, as it involves several caveats to be feasible.
Best control practices imply correcting the Power Factor as close as possible to a load or groups of loads. This type of control allows for an increase in current and circulating reactive power since this type of connection is closer to the energy entry point, at the utility meter, and farther from the points that actually cause variations in the power factor.
Types of Power Factor Controllers
Power Factor control can be performed in various ways, with the main methods being:
Fixed and Individual: Dimensioning capacitors connected to the set point without intermediate control.
Automatic in Load Groups: Using power factor controllers or time-based control.
Hybrid: Using fixed capacitor banks and automatic control simultaneously.
For each application, a type of control will be more suitable, depending on the actual need for adjustment. It is at this point that doubts regarding application arise.
Use of fixed capacitors and capacitor banks - unloaded transformers and motors
We start from the principle that power factor controllers act to correct reactive surpluses, so we apply the correction at points where such variation may exist. Fixed capacitors or capacitor banks aim to adjust the phase in motors or the power factor in an unloaded transformer. Note that the capacitors are directly connected to the correction point, as this is an inherent need of the "load."
Use of automatic power factor controllers
É natural dentro de grandes consumidores de energia, termos uma dinâmica de funcionamento variante, ou seja, motores partindo e parando simultaneamente, alternadamente ou aleatoriamente. Máquinas funcionando a plena carga com altas correntes, ou baixas cargas quando em períodos menos produtivos.
Below, we can see a graph of the corrected Power Factor, measured by an energy analyzer. Note that this is an electrical quantity that varies constantly over time.
We are referring to a point higher up on the single-line diagram, where we evaluate the Power Factor at a common point for various loads. In this scenario, we use automatic controllers that continuously monitor the Power Factor, responding as needed by inserting or removing capacitors based on the momentary requirements.
Use of automatic and intelligent power factor controllers
During periods like nighttime or shutdowns, currents and power levels tend toward very low values, approaching zero. In such cases, caution is necessary. Power factor controllers, for the most part, require electrical quantities such as voltage and current to calculate the power factor.
However, when our current is nearing zero, our controller may lack current to assess. What do we do then?
We opt for a hybrid solution! At this point, we maintain our initial fixed and automatic solution simultaneously.
There are devices capable of maintaining fixed capacitor banks while also providing simultaneous control. These controllers can diagnose anomalies, malfunctions, and even insufficient control capabilities.
Which power factor controller to use?
There are periods (nighttime, shutdowns, etc.) where the current and power tend towards very small values, approaching zero. In such cases, caution is necessary. Power factor controllers, for the most part, require electrical quantities such as voltage and current to calculate the power factor.
However, considering that our current is approaching zero, our controller may lack current to assess. What do we do then?
We move towards a hybrid solution! At this point, we maintain our initial fixed and automatic solution simultaneously.
There are devices capable of maintaining fixed capacitor banks while also providing simultaneous control. These controllers can diagnose anomalies, malfunctions, and even insufficient control.
EMBRASUL incorporates concepts ranging from the design of the enclosure, which uses modern materials, to the connectors that ensure high operational safety, following recommendations from international standards.
Through the keyboard/display unit, they provide users with system readings in a practical manner, along with an easy parameterization interface, allowing configuration according to the load profile.
The current models offer intelligent control with alarm systems for cases of insufficient capacity, faults, and also maintain measurement and control logs of capacitors, which can be sent to supervisory systems and energy management. It functions as both a controller and an electrical measurement device simultaneously!
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