System power factor

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anbm

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Why most installed generators and motors I saw, the nameplate typically has power factor (pf) data as 0.8 but not higher?

If the client wants to increase their overall electrical system power factor from 0.75 to 0.95, they ask how much overall power
they can gain by doing this, is it safe to say 20% as pf will be increased from 0.75 to 0.95?
 
anbm said:
Why most installed generators and motors I saw, the nameplate typically has power factor (pf) data as 0.8 but not higher?

If the client wants to increase their overall electrical system power factor from 0.75 to 0.95, they ask how much overall power
they can gain by doing this, is it safe to say 20% as pf will be increased from 0.75 to 0.95?
Click to expand...
IMHO. None. Increasing PF will reduce the KVar load but not the KW load. :)
 
It's not about increasing real power, it's about reducing apparent power by keeping reactive power local, which reduces metered energy and line losses.
 
I find that overall plant power factor has been going up with all the VFDs. But with all these 6 pulse drives we are starting to see harmonic problems
 
What is the advantage to increase power factor anyway? save any bills???
 
Increasing power factor means available power will go up if kVA capacity is the limiting factor.

Say you have a 1 MVA transformer supplying a plant. The true power that transformer can deliver is 1/of. If you had some weird 1 MVA pure capacitive load with zero power factor, that transformer would be fully loaded with zero real power delivered.

But sometimes kVA capacity is not the limiting factor. Generators are often designed specifically with the expectation of 0.8 power factor. The alternator might be rated 1 MVA but the prime mover only rated for 800kW. If you connect a poor pf load, then you hit the 1 MVA limit. But if you connect a > .8 pf load you will hit the 800 kW real power limit of the prime mover.

Jon
 
EC Dan said:
It's not about increasing real power, it's about reducing apparent power by keeping reactive power local, which reduces metered energy and line losses.
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Except for determining a demand-based multiplier, reactive power is not a component of metered power. There is no direct charge by POCO for reactive energy. To the extent that reactive power features current which can dissipate real power in line resistance, there can be a billed energy saving, but that is a small effect.
 
anbm said:
How, please explain in detail, assuming I am a non-technical person ... lol
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See the beer picture. The less foam, the smaller a glass needed to deliver the desired amount of beer.

If you improve power factor, you need less current to deliver the same power at a given voltage. Less current means smaller cables or lower cable loss.

Jon
 
anbm said:
How, please explain in detail, assuming I am a non-technical person ... lol
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There is not to a lot to explain. If you operate at say 0.8 pf the current is lower than at 0.5 pf.
 
Besoeker3 said:
There is not to a lot to explain. If you operate at say 0.8 pf the current is lower than at 0.5 pf.
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Or the voltage is higher. Or the wattage is higher. It really all depends on the load and how you're achieving a higher power factor, doesn't it?

Also the NEC doesn't really care, unless my power factor solutions actually change the nameplate watts or VA of the loads.
 
winnie said:
Increasing power factor means available power will go up if kVA capacity is the limiting factor.

Say you have a 1 MVA transformer supplying a plant. The true power that transformer can deliver is 1/of. If you had some weird 1 MVA pure capacitive load with zero power factor, that transformer would be fully loaded with zero real power delivered.

But sometimes kVA capacity is not the limiting factor. Generators are often designed specifically with the expectation of 0.8 power factor. The alternator might be rated 1 MVA but the prime mover only rated for 800kW. If you connect a poor pf load, then you hit the 1 MVA limit. But if you connect a > .8 pf load you will hit the 800 kW real power limit of the prime mover.

Jon
Click to expand...
we have a winner.
 
Just remember that reactive power still needs to circulate actual current in the conductors. Let's pretend you're a utility and a big customer just changed all the ballasts in their fluorescent lighting from good power factor to bad power factor models but they keep the same foot-candle levels. They are using the same amount of power in the building (and metering the same amount) but because they have more reactive power the actual current flowing in the utility's wiring goes up. That's why big users are penalized for having overall bad power factors (the utility only sees the net power factor of all the different device power factors in the building), thus often making power factor correction (adding the proper capacitance or inductance to the system) a cost effective solution.
 
anbm said:
What is the advantage to increase power factor anyway? save any bills???
Click to expand...
In my area the ultility company would charge commercial customers a surcharge if power factor was below 90% . We had to add capacitor banks at several locations. Now with everybody using LED every where you have to watch their power factor. They usually do not list PF on spec sheet or boxes but have seen it as low as 80%. Hope the government make LED manufacturers only produce LED lamps & luminares with a PF of at least 95%. Never install PF capacitors on output side of any VFD'S. We had a contractor install two 30 HP drives on 40 year old air handlers that each motor had a PF capacitor. Drive would not run until I disconnected capacitors.
 
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