Power Factor for AC Pumps

[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.