Power Factor Capacitors
by Larry Brunetti
(Eagle, Idaho)
I read an article on your page about power factor capacitors and energy savings. Pretty good article, but missed the fine points.
Motors are inductive loads. However, putting a capacitor across the input of a motor will NOT correct its power factor. The motor power factor cannot be changed externally. Period.
These capacitor boxes CAN improve the power factor TO YOUR HOUSE, but that doesn't change anything about how much energy you use. BEST CASE, if you put a capacitor across the input to a motor in your house, you will reduce the current in the supply wires, which will reduce the power loss of the resistance feed wire.
If you have VERY bad wiring, with lots of resistance, to a big motor you will definitely reduce the current by correcting the power factor and power loss in the feed wires:
Power reduction = current reduction x current reduction x resistance of the wire. (I^2 x R)
Without going through examples, the improvement would be so small (for a well wired house)as to be negligible. If you have this problem, FIX THE WIRES, because it may be possible to burn up the motor by undervoltage, or burn down your house by overheating the wires.
Second, energy companies use capacitors to correct power factor on their power lines, reducing the current and saving I^2 x R loss. If you put a capacitor bank on the input to your house, you will save money for the power company because the current delivered to your house will be at a better power factor. YOU will NOT see a measurable change in your power/energy consumption.
The capacitor must be of a specific value to correct the power factor of any inductive load WHEN OPERATING. That means that the capacitor must be at the inductive load, switched right along with the motor. If it is left on all the time, current will pass through the capacitor, causing heating in the (bad) wires WHEN THE MOTOR IS OFF.
So, 1. Buy a capacitor box to help the power company, and 2. Have your wires checked for the right size so you don't burn your house down.
Because this is a rather complex engineering problem, most laymen don't understand it, and that leaves them open to scammers that make all kinds of wild claims that are just not true.
Comments for
|
||
|
||
© Green Energy Efficient Homes Inc. 2012 Privacy policy