Power Factor for AC Pumps

[sphelps]

Originally Posted by Goatman

http://www.reefcentral.com/forums/sh....php?t=1989362

I read that thread already, it really isn't what we're talking about here.

[Goatman]

Originally Posted by sphelps

I read that thread already, it really isn't what we're talking about here.

oops, sorry wrong paste...ignore

[mrhasan]

I am not reading online since I am getting infos from electrical engineers. I have, out of curiosity, confirmed with another colleague of mine just now and is also saying that you get billed for the amount of voltage and current you are drawing out from the outlet; NOT how much your device is consuming. There's no such utility meter that can determine which device is consuming what. With the difference in calculation, he came to some conclusion:

1. The motor is really horrible
2. The readings are not taken from the correct point

I am not with number 2 because the DC pump is right on target regarding the readings; so I stick with the motor is horrible

[sphelps]

I cannot find anything to suggest a residential meter measure kVA, only watts.

There are three terms you will encounter when dealing with alternating (AC) power (as opposed to DC or batteries). The first is the kilowatt, abbreviated kW, and it represents real power. Real power can perform work. Power company utility meters on the side of your house measure this quantity and charge you for it.

The second term is reactive power, and it is measured in KVAR which is short for kilo volt amp reactive. Unlike kW, it cannot perform work. Residential customers do not pay for KVAR, and utility meters on houses do not record it.

The third term is apparent power, referred to as KVA. If you hook up two multimeters to measure current and voltage and then multiply the readings together, you get apparent power in volt amps, or VA. To distinguish it from real power, VA is used instead of W.

[mrhasan]

Originally Posted by sphelps

I cannot find anything to suggest a residential meter measure kVA, only watts.

Yap residential meters record KWh, not KVA.

[wmcinnes]

Originally Posted by mrhasan

Yap residential meters record KWh, not KVA.

Thus your meter only counts the real power.


I'm with Steve and his research.

[mrhasan]

Originally Posted by wmcinnes

I'm with Steve and his research.

Then my question is, how would each of the real power of individual components in the household be calculated by the utility meter?

[wmcinnes]

Originally Posted by mrhasan

Then my question is, how would each of the real power of individual components in the household be calculated by the utility meter?

They simply measure kW and not kVA.

They consist of a motor with the stator current being the current into the building and the rotor curreent being proportional to the voltage at the building input. The motor turns a disc (the disc you see rotating in the window) that passes through a magnetic field generating eddy currents in the disc and this regulates the speed at which the disc turns so that the meter can be adjusted to read correctly.

[sphelps]

Originally Posted by mrhasan

Then my question is, how would each of the real power of individual components in the household be calculated by the utility meter?

Because the utility meter measures the exact same thing as the energy monitor, it measures actual power in kWh. It doesn't measure apparent power or vars.

[mrhasan]

Originally Posted by wmcinnes

They simply measure kW and not kVA.

They consist of a motor with the stator current being the current into the building and the rotor curreent being proportional to the voltage at the building input. The motor turns a disc (the disc you see rotating in the window) that passes through a magnetic field generating eddy currents in the disc and this regulates the speed at which the disc turns so that the meter can be adjusted to read correctly.

1. KW is not a direct unit so the meter actually does some conversions within itself

2. That is exactly how it is done. The rotor moves proportionally to the product of voltage and current to shows kWh consumption. No PF involved that's it. So when a outlet draws 1.85A @ 115V, that means the rotor is turning at a proportional rate directly to the product of those two.

The motor needs 82W to run and it is taking in 82W but due to its inefficient manner (age, water, etc.), the pump has to take in more power and hence 1.85*115V.

For this motor, you are bringing 1.85A "in" the house.