Domestic Power Factor Correction

Q.  Can power factor correction save KWHrs in a domestic environment?
No, The addition of pwer factor correction may reduce the current drawn, but will not cause your meter to run slower.

Q.  Does power factor correction make motors run more efficiently?
If you connect the correct value of capacitors in the supply to an induction motor, you will reduce the current flow from the supply to the point where the capacitors are connected. If you measure the current in the supply between the capacitors and the motor, you will find that the current does not change. The current into the motor is independent of the connection of the capacitors. The efficiency of the motor is unchanged.

Q.  Does power factor correction make motors run cooler?
No, the motor losses are not changed so the temperature rise of the motors remains the same.

Q.  Does power factor correction reduce energy consumed?
No, the addition of power factor correction will reduce the current drawn from the supply in situations where there is an inductive current flowing and the correction is equal to or less than the inductive current. The reduction in current can reduce the losses in the supply, but no appreciable loss reduction will occur within the residence.

Technologies.

Power Factor Definition : Power factor is the ratio between the KW and the KVA drawn by an electrical load where the KW is the actual load power and the KVA is the apparent load power. It is a measure of how effectively the current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.

The current drawn by an inductive load such as an induction motor, comprises two components: the resistive current that actually does the work, and the inductive or magnetic current that does no work. The resistive component of the current is in phase with the supply voltage and draws KW as measured by the power meter. The inductive current, commonly referred to as the reactive current is at 90 degrees to the supply voltage and does not contribute to the KW measured by the power meter.

When you connect an ameter in series with an induction motor to measure the current, you measure both the resistive current and the reactive current at the same time, and due to the phase angle between them, they do not directly add. For those with a mathematicaal bent, the resultant current measured, is the square root of the sum or the square of the resistive current and the square of the inductive current.
KW = V x I_resistive

KW = V x I_motor x pf

where pf = Cos(ø) and ø is the angle between the resistive current and the motor current.
Any change in I_magnetising does not alter the KW in the formula above.

Adding power factor correction to a circuit that has an inductive current flowing, will add a capacitive current. The capacitive current is also a reactive current, but it is in the opposite direction to the inductive current. It is 180 degrees out of phase. In effect, the capacitive current subtracts from the inductive current. If they are equal, they wil cancell out to zero. If the capacitive current is less than the inductive current, the total reactive current will reduce. If the capacitive current is greater than the inductive current, the resultant current will be capacitive.
If capacitive current is added to a resistive load, the net current will increase.

To correct the power factor, the amount of capacitive current needs to be constantly adjusted to match the amount of inductive current drawn. This can not be done by adding a fixed amount to the supply. An automatic switching unit is required.