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Connection Types for Power Factor Correction Capacitors

Connection Types for Power Factor Correction Capacitors

Connection Topologies for Power Factor Correction Capacitors & Capacitor Banks

In this article we will breifly explain the 4 types of capacitor connection topologies for Power Factor Correction capacitors, along with rules to apply for series or parallel connected capacitor banks. 

1) Single Phase 

Single Phase PFC capacitors are simply connected from line to neutral.

2) 3 Phase Four Wire Y (Star) connected loads

The Capacitors are generally connected between L1 and Neutral, L2 and Neutral and L3 and Neutral in order to reduce the voltage seen by the capacitors, any external fuses, and the cabling/busbar system which rediuces cost and is generally safer due to the lower voltages.

4 Wire Star

3) 3 Phase 3 Wire Y (Star) connected loads

Capacitors are connected in parallel to each load, or Line to Line, L1 to Star Point(L2,L3), L2 to Star Point(L1,L3) L3 to Star Point (L1,L2)

3 Wire Star

Many Low Voltage Capacitors in the market come interally connected in 3 Wire Star configuration.

3) 3 Phase Delta (Most Common for Low Voltage) connected loads

Capacitors are connected in parallel to each load, or Line to Line, L1 to L2, L2 to L3, L3 to L1

Delta Connected Loads

Most Low Voltage Capacitors in the market come interally connected in Delta configuration.

5) If you need to increase Kvar rating due to capacitor design limitations

In this case we connect multiple capacitors in parallel to increase the Capacitance (uf) and therefore the kVar rating.

 

PFC Caps in parallel

The basic formula is as follows where Q = Kvar

Q=2π*fn*Un*Un*C

6) Higher voltages than 22kV

In this case we need to connect multiple capacitors in series. Note that in series the capacitor value must be identical, and connecting in this way will decrease the effective capacitance seen by the circuit/load.

PFC Caps in Series

 

The Effective Capacitance (CT)will be 1/CT = 1/C1 + 1/C2 +1/C3 

In many cases to achieve the reqired voltage and capacitance rating, a bank of parallel and Series connected capacitors are required.

Real world applications

PFC with short circuited Motor

PFC Cap connection to a motor with starter on rotor

PFC Cap connection to a motor conected by ordinary star-triangle switch

PFC Cap connection to a motor conected by special star-triangle switch for motors of any rated power

PFC Cap connection to an automatic star-triangle switch for motors of any power rating

Contact us for design and manufacture of Power Factor Correction Capacitor Banks

For more detailed design information on selecting and connecting capacitors you can download Iskra Systemi guideline here

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