Mikro PFCR Explanation

Power Factor Regulator  Industri Teknologi Mikro Sdn. Bhd.

Electric Loads Resistive Load

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Power supplied is totally transformed t ransformed into useful work • Current = Active Current (I A)

Reactive Load

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Power supplied is NOT transformed into useful work Inductive load and capacitive load

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•

Current = Reactive Current (IR)

V-I Vector Diagrams

Power – Resistive Load

Power – Inductive Load

Inductive + Resistive Power 

Power   Active Power (P) Power actually consumed by the load P = V · IA (kW) 

Reactive Power (Q) Necessary power but not transformable in useful energy Q = V IR (kVAR) ·

 Apparent Power (S) Total power that flows toward the load S = V I (kVA) ·

Power Factor (PF) 

PF is a measurement of how effectively a system is converting electric power to useful output power.

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PF always less than or equal to one (1).

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The lower the PF, the lower the efficiency.

Power Factor Readings 

Displacement Power Factor ( DPF) Cos ϕ - Cosine of the phase angle (ϕ) between the fundamental frequency of voltage and current. Only phase shift between V & I.

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Total Power Factor ( PF) True ratio of active power to apparent power  Phase shift and harmonic distortion PF =

 Active Power (P)  Apparent Power (S)

=

kW kVA

Power Triangle 

"Power triangle" without effect of harmonics

Harmonic Effect 

"Power triangle" with effect of harmonics

Causes of Low Power Factor  

Most electrical systems have lagging power factor due to inductive loads such as motor, air -conditioner, fluorescent lighting etc. Typical PF of loads Load

Power factor 

Induction motor 

0.70 – 0.80

Fluorescent lighting

0.70

 Arc welding

0.50

Phase controlled rectifier 

0.40 – 0.90

Benefits of PF Correction    

Reduced electricity bills Gained in system capacity Reduced line losses Improved voltage condition

PF Correction Methods 

Connect capacitors in parallel to the system. Capacitor produces leading PF thus neutralize the lagging PF.

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If low PF due to harmonics is significant, harmonic filter is required. Capacitor will NOT help to improve low PF caused by harmonics.

PF Correction by Capacitor 

Before

 

 After  After 

Calculate Required kVAR

Table of Output Factor k Original PF (Cosϕ1)

Desired PF(Cos ϕ2) 0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

0.98

1.00

0.50

0.40

0.56

0.71

0.85

0.98

1.11

1.25

1.40

1.50

1.73

0.60

-

0.16

0.31

0.45

0.58

0.71

0.85

1.00

1.10

1.33

0.70

-

-

-

0.14

0.27

0.40

0.54

0.69

0.79

1.02

0.80

-

-

-

-

-

0.13

0.27

0.42

0.52

0.75

0.90

-

-

-

-

-

-

-

0.16

0.26

0.48

Power Factor Regulator (PFR) 

What is PFR?  A device to monitor and maintain the required power factor of an electrical network.

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Working principle of PFR PFR continuously measures the network's reactive power (kVAR) and then correct it by switching in/out of the capacitor banks to achieve the targeted power factor.

Mikro's Power Factor Regulator  Model PFR60 – 6 switching outputs Model PFR80 – 8 switching outputs Model PFR120 – 12 switching outputs Model PFR140 – 14 switching outputs

Power Factor Measurement: DPF or PF? 

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Capacitor banks are only designed to compensate the reactive power of the fundamental frequency component. Capacitor banks are not designed to correct total power factor where harmonic currents are included. DPF measurement method is more suitable for power factor regulat or.

How to measure DPF 

Zero crossing method Measures the phase angle difference between the respective zero crossing of the voltage & current waveforms.

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Numerical method The phase angle is computed using mathematical method through the regularly sampled voltage and current waveforms.

DPF Measurement (1)

DPF Measurement (2)

Features of Mikro's PFR 

DPF measurement by numerical method.  Accurate measurement even in the presence of harmonics. Capacitors improve DPF only.

Cause & Effect of Harmonics 

Causes Non-linear loads draw non-sinusoidal currents. e.g. Adjustable-speed motor drive & energy saving lighting.

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Effects Overheating and dielectric breakdown of capacitors. Excessive current caused by resonance Increase losses.

Features of Mikro's PFR (2) 

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Total harmonics distortion (THD) measurement and alarm.  Able to measure current THD. Disconnect all capacitor banks in the event of THD alarm to prevent damage of capacitors due to harmonics.

Features of Mikro's PFR (3) 

Intelligent automatic switching program. Improve switching efficiency by reducing the number of switching operations.  Able to measure kvar required and select the most appropriate switching steps.

Evenly distribute usage of each capacitor bank. Switch in least used capacitor  Switch out longest used capacitor 

Features of Mikro's PFR (4) 

Programmable switching sensitivity. Optimized switching speed. Reaction time inversely proportional to the reactive power required.

Features of Mikro's PFR (5)   Alarm

functions

Under/over voltage alarm. Under/over load current alarm. Under/over compensate alarm. THD alarm. Light indicator for alarm. Programmable last output step as alarm output contact.

Features of Mikro's PFR (6)   Automatic

current transformer ( CT) polarity

 Automatic correction of CT polarity when reversed. 

Programmable rated step Enable flexible usage of capacitor with different sizes.