Introduction
The new power factor controllers DCRK have been designed to meet the technical requirements of the modern electrical industrial plants and the latest customer needs. Due to electronic power devices, voltage quality has been getting worst in recent times and power factor applications are thereby becoming critical. As a result, reliability and the ability to properly operate in all conditions have become the main requirements for power factor regulators but they must also be able to detect any critical condition in order to protect power factor equipment. At the same time, users want easy to use devices as well as functions that consent to check the correct working of the whole power factor correction system.
In addition to the above-mentioned technical requirements, DCRK regulators come equipped with many useful functions that satisfy the most demanding applications.

Range
• DCRK5   - 5 steps, in flush mount 96x96x65mm enclosure
• DCRK7   - 7 steps, in flush mount 96x96x65mm enclosure
• DCRK8   - 8 steps, in flush mount 144x144x62mm enclosure
• DCRK12 - 12 steps, in flush mount 144x144x62mm enclosure
These are standard-supplied with 380VAC –15% and 415VAC +10% voltage range.
But the following voltage ranges are available on request: 110…120VAC, 220…240VAC, 440…480VAC and 480…525VAC. For DCRK8 and DCRK12 types, the 525…575VAC range is also available.

Operation
DCRK conduct all control operations in a totally digital way, thanks to the latest generation of microprocessors. This type of control allows accurate and reliable readings and is not affected by errors caused by electronic component aging. The voltage and current monitoring inputs are equipped with digital band-pass filter, warranting reliable device operation, also in systems characterised by high harmonic content. A special algorithm is able to calculate current overload of the capacitors and they are disconnected when necessary to avoid all damages. According to the cosj set-point, a control algorithm calculates the exact reactive power needed to correct the power factor of the system. The adjustment is conducted in a precise manner and not by consecutive attempts. Each step is provided with one operation counter and one hour meter, in order to provide an equal usage of capacitors with the same rating. The results are radical reduction of the number of operations, longer life and efficiency of both the capacitors and contactors along with a homogeneous wear of capacitor banks when these are of the same rating.

Measurements
• Actual cosj
• Actual L-L voltage              and maximum value (1)
• Actual current                     and maximum value (1)
• Dkvar                                  and Skvar
• Weekly average P.F. (1)    and actual P.F.
• Capacitor overload percentage          and maximum value (1)
• Actual panel temperature and maximum value (1)

(1) Measurement logged in non-volatile memory and keypad clearable.

Alarms
• A01 Under compensation
• A02 Over compensation
• A03 Low current
• A04 High current
• A05 Low voltage
• A06 High voltage
• A07 Capacitor overload
• A08 Overtemperature
• A09 No voltage release.

Built-in protections
Capacitor current overload and over-voltage - The capacitor overload can be caused by over-voltage or, more often, by non-linear loads that cause harmonic distortion on the voltage line. The voltage waveform is analysed by a special algorithm that calculates the exact percentage of the current flowing in the capacitors. Once the set current overload threshold limit is exceeded, the capacitors are disconnected within a time inversely proportional to the exceeding limit. It is important to be aware that some regulators, available on the market, consider the THD (Total Harmonic Distortion) only as an indicator of capacitor current overload.
As shown in the traces below, two waveforms with the same THD cause different capacitor current, since  the harmonic frequencies are not considered.

Panel over-temperature – The DCRK controllers include an internal temperature sensor, which monitors the temperature variation of the electric panel. This temperature value is displayed and the maximum value is logged. By setting the related parameters, a threshold can be set to switch a relay on to operate a ventilation system. It is also possible to set a higher threshold to generate an overtemperature alarm.

No-voltage release - This function can prevent damage to the capacitors by disconnecting them from the mains when short power losses are detected.

Set-up

Basic setup with most common settings - (6 parameters)

Advanced setup with special settings - (16 parameters)

Fast PC setup – By using the DCRK SW software and the TTL/RS-232 interface, it is possible to access all setup parameters in four languages and Save / Load / Print parameters, avoiding in this way possible parameter setting errors.

Fully automatic setup – Allows the installation of the DCRK controllers without programming any parameter. By just pushing two keys, the user is able to put the DCRK into operation.

TTL/RS-232 port and DCRK set-up SW
By using the DCRK SW software and the TTL/RS-232 interface, one can obtain fast PC setup, alarm properties customization, automatic test of electrical panel and full system monitoring.
Fast PC setup - Quick commissioning of a controller can be achieved via PC, avoiding in this way, possible parameter setting errors. The DCRK programmed parameters can also be stored on the PC and quickly downloaded into an unlimited number of units, which require the same programming.
Alarm properties customization – Every alarm is arranged with the following alarm properties: enable, relay activation, step disconnection and trip delay; each of these can be changed.

Automatic test of electrical panel – An automatic panel testing is available in order to check the reactive power installed and to printout a test report.

Full system monitoring – Graphic and numeric measurements display, DCRK status and virtual front panel. In addition for each step: function assignment, status, reactive power, operation counter and hour meter.

Utilities

Automatic identification of CT current flow – At power up, the DCRK controller automatically recognises the current flow direction through the Current Transformer (CT). This avoids inverting the CT connections during installation. In cogeneration plants, where it is necessary to operate in four quadrants, the CT connection sense must be manually set.

Easy CT setting for end users – The manufacturer of power factor correction panels can program all of the DCRK set-up parameters except the CT primary since it depends on the end user’s system. In this case, during the system installation and once the controller is powered up, the display will show a flashing CT which denotes the CT has not been programmed. Just selecting the correct value from the displayed list and storing it with one key will enable the DCRK operation.

Keypad lock function - The activation of this function is made by a combination of keys. Once programmed, the following operations will be locked:
• Access to parameter set-up
• Change of cosφ setpoint
• Change of the operating mode (AUT/MAN)
• MAX values clearing
However, all the measurements will still be viewable.
Four-quadrant operation - When a plant is equipped with a co-generation system, it means there are conditions where energy is imported (consumed) and others where it is exported (generated). In these circumstances, the displacement angle between voltage and current can vary between 0° and 360° (four quadrants) so the DCRK must be programmed accordingly. It is possible to set two independent cosφ setpoints, one for import energy and the other for export. When working with cogeneration plants, the automatic CT connection feature cannot be used.

Autotrimming - Consents to the ongoing control of the installed power of each step. In case of step wear, all the relative power parameters are automatically recalculated. This allows the DCRK unit to work rapidly and efficiently that is with fewer and quicker operations.

Technical specifications

TRMS = True Root Mean Square - DCRK measurements are calculated in TRMS, to give exact values also in presence of harmonic distortion.

Cosj= Displacement power factor - It is in the cosine of the displacement angle between voltage and current. DCRK regulators can read correctly the D.P.F. regardless of the presence of harmonics on current and voltage waveforms.

Power factor - The Power Factor (P.F.) or Total Power Factor (TPF) is the ratio between active power and apparent power (PF= W/VA). In a system without harmonics, the power factor is the same value as Cos j
In other conditions, the power factor is less than the Cos j. Power factor correction systems can adjust the Cos j.  to the required value and can thereby obtain the best possible power factor.
Measurement of weekly average power factor - This reading considers the last 7 days of the DCRK operation. It is calculated in the same way used by energy suppliers, storing active and reactive energy meters in DCRK internal memory.  This value is therefore a true efficiency index of the entire reactive power correction system. It is calculated in the same way used by energy suppliers, storing active and reactive energy meters in DCRK internal memory. This value is therefore a true efficiency index of the entire reactive power correction system.