Learning Center

Understanding Power Factor

From Basic Electricity to SVG

A simple guide to understand how electricity works, why power factor matters, and how a Static Var Generator (SVG) can help you use electricity more efficiently and reduce your costs.

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1

Electricity starts with voltage and current

Electricity comes down to two things: voltage and current. When voltage pushes current through a load, the equipment gets the energy it needs to do its work.

V

Voltage (V)

The push. The force that moves electricity along a wire, just like water pressure in a pipe.

A

Current (A)

The flow. How much electricity is actually moving, just like the water flowing through the pipe.

In shortThink of voltage as water pressure and current as the water flow.
Pressure (Voltage) Water Flow (Current) Water turns the turbine (useful work)
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Pressure alone does nothing until the water actually flows
2

Single-phase and three-phase electricity

Mains electricity does not sit still. It rises and falls in a smooth wave, 50 times every second.

Single-phase (L-N)

+V 0 −V Time → Voltage (V)
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Common in homes and small loads · 230 V · 50 Hz

Three-phase (L1-L2-L3)

L1L2L3 120°120°120° +V 0 −V Voltage (V)
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L1L2L3
Used in buildings and industrial loads · 400 V · 50 Hz
In shortThree-phase is just three of these waves, evenly spaced 120° apart. Bigger buildings use it because it delivers power more smoothly.
3

Types of electrical loads

Different equipment pulls current in different ways. Whether the current keeps in step with the voltage is what sets your power factor.

Resistive load (R)

Example: heater, lamp

V A
V = VoltageA = Current
In phase (φ = 0°) · PF = 1.0
Converts electrical energy directly into heat or light.

Inductive load (L)

Example: motor, pump, fan

lag V A
V = VoltageA = Current
Current lags voltage · PF < 1.0
Needs a magnetic field, so it draws reactive power.

Capacitive load (C)

Example: capacitor bank, electronics

lead V A
V = VoltageA = Current
Current leads voltage · PF < 1.0
Stores energy in an electric field and can supply reactive power.
Why it mattersMotors are the problem child. They pull the current out of step, and that is what drags a building's power factor down.
4

The power triangle

When current falls out of step, your supply carries two kinds of power at once: the useful kind, and the wasted kind.

φ P = 80 kW Active power, does the real work Q = 60 kVAr Reactive power, no useful work S = 100 kVA Apparent power, total supplied
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Drawn exactly to scale: 80² + 60² = 100², so φ = 36.87°

S² = P² + Q²

PF = P / S = cos φ

P · Active powerkW
Q · Reactive powerkVAr
S · Apparent powerkVA
In shortPower factor is simply how much of the power you are supplied actually does work. Here, 80 out of 100, so 0.8.
5

Why does low power factor matter?

A low power factor means you need more current to get the same work done, and every cable and transformer in between has to carry it.

Higher current in cables and transformers

Increased losses and energy waste

Voltage drop and reduced system capacity

Possible reactive-energy charges or power factor penalties

Less efficient use of electrical infrastructure

6

Same useful power, different power factor

Two buildings doing exactly the same work, 100 kW each, but with different power factors.

Low power factor

Useful load100 kW
Power factor0.70
Apparent power143 kVA
Reactive power102 kVAr
Current at 400 V206 A
▲ Higher current drawn from the grid

Corrected power factor

Useful load100 kW
Power factor0.98
Apparent power102 kVA
Reactive power20 kVAr
Current at 400 V147 A
▼ Lower current drawn from the grid
In shortSame useful work, far less current. Both buildings do 100 kW of work. The one with the poor power factor just drags 206 A through its cables to do it, instead of 147 A.
7

How can power factor be corrected?

There are three common answers. They all add reactive power back into the building. The difference is how well they keep up when demand changes, and in a real building demand changes constantly.

kVAr 02550 75100125 Bank reacts late, then over-corrects by 67 kVAr SVGBankFixed lift starts two lifts pumps time →
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What the building needs SVG Capacitor bank Fixed capacitors
The green line runs exactly along the top of the grey area · that is the SVG matching demand as it happens
Read it like thisThe grey area is what the building is asking for. A solution is good when its line follows the top of that area. Only the green SVG line does. The blue bank arrives after the surge has already passed, and then leaves too much connected.

Fixed capacitors

Always on, always the same amount. It cannot be told to do anything else.

Reacts innever
Controlnone
Can absorb leadingno
Average miss24.2 kVAr
Sized small on purpose, because anything bigger over-corrects when the building is quiet. So it under-delivers nearly all day.

Automatic capacitor banks

Switches blocks of capacitors in and out. Better, but only in fixed chunks.

Reacts inseconds
Controlfixed steps
Can absorb leadingno
Average miss17.6 kVAr
A capacitor has to discharge before it can be switched back in, so the bank is always a beat behind. Short surges are over before it reacts, and every switch wears the contactors.
SVG
Best match

Static Var Generator

Electronically generates the exact amount needed, moment by moment.

Reacts inmilliseconds
Controlstepless
Can absorb leadingyes
Average miss0 kVAr
No steps to round to and no contactors to wait for, so it simply follows the load. It can also absorb reactive power, which neither capacitor solution can do at all.
8

What is an SVG and how does it work?

Think of it as a machine that makes reactive power on site. Instead of the grid shipping the wasted power all the way to your building, a cabinet next to your distribution board produces it right where it is used. It does that in three steps, thousands of times a second.

1

It watches

A sensor clipped around the main incoming cable reads exactly how much current the whole building is pulling right now.

2

It works out the waste

From that reading it separates the part doing real work from the reactive part that is only sloshing back and forth.

3

It gives the waste back

It generates that exact reactive amount itself and feeds it into the board. The grid is left sending only the useful part.

Utility / Transformer 400 V, 3-phase 1 CT (current transducer) measures total current Main Distribution Board (MDB) ElevatorsPumpsHVACOther loads SVG in parallel 2 3 Compensating current (kVAr) measurement signal to the SVG controller
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Power cable SVG connection Measurement signal
1CT watches the current 2SVG works out the waste 3SVG gives the waste back
The red numbers are the three steps above · the SVG sits in parallel, so it adds current without interrupting the load
In shortNothing is switched off and nothing runs through the SVG. It sits to one side and quietly cancels the waste, so the grid only has to send the power that does real work.
9

Before and after SVG

Here is the whole point of this page in one picture. Take one building doing 100 kW of real work on a 400 V supply, and look at how much current has to travel down the cable to deliver it.

Before SVGpower factor 0.70 206 A After SVGpower factor 0.98 147 A 59 A more, for the same work
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Same building · same 100 kW of useful work · only the amount of current changes
29%less current in every cable, breaker and transformer feeding the building
~49%less heat wasted in those cables, because losses rise with the square of the current

Before SVG

  • ▲The grid has to send a lot of reactive power all the way to you
  • ▲Cables, breakers and the transformer run hotter and closer to their limit
  • ▲Reactive-energy charges or low power factor penalties may apply

After SVG

  • ▼The reactive power is made on site, so the grid only sends useful power
  • ▼The same equipment now has spare capacity for more load
  • ▼Potential reduction in reactive-energy charges, depending on tariff
In shortNothing about the building changed. The same lifts, pumps and chillers do the same work. The SVG simply stops the waste from travelling down the cable, which frees up capacity you have already paid for.
10

How can an SVG reduce electricity costs?

An SVG does not cut the kWh your equipment uses. It cuts the wasted power your building pulls from the grid. If your tariff charges for reactive energy, low power factor or kVA demand, that shows up as a lower bill.

Lower reactive-energy charges

More efficient use of existing infrastructure

Reduced losses and voltage drop

Increased available capacity

Supports a more sustainable and efficient building

The actual saving depends on the load profile, the existing power factor, reactive energy consumption, the electricity tariff and correct SVG sizing. We measure your installation before quoting a figure.
Next step

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