Capacitors increase power factor to the minimum required eliminating surcharge. Sometimes you could get credit for high power factor. KW demand with reactive demand charge. Utility companies bill for KW demand plus a surcharge for excessive reactive demand.
Capacitors reduce reactive demand thereby eliminating surcharge. A Factory is operating several induction motors plus other loads. Its power factor is 0. Calculate the total energy bill for the month and the savings when power factor improvement was made. Assume a 30 day billing period. Labels: Power Factor. Newer Post Older Post Home. You May Also Like:. Resistors Incandescent lights Toasters. Billing Type. Billing Concept.
The leading current drawn by such capacitors neutralizes or corrects the lagging reactive component of the load current. The static capacitors have many advantages since they are lightweight, easy to install, have low losses and require lesser maintenance. However, the disadvantages are quite notable where if the voltage is exceeded then the capacitors will be damaged quickly and their repair would be costly.
They also have a shorter service life years. Another way to improve the power factor is to use a 3 phase synchronous motor which is over excited and runs on no load.
This setup is known as the synchronous condenser. The interesting part is that the synchronous motor can operate under leading, lagging or unity power factor. If there is an inductive load present, then the condenser will be connected to the side of the load and will act as a capacitor to correct the power factor. The synchronous condenser has many advantages since it requires low maintenance, can run for up to 25 years and is not affected by harmonics.
However, its disadvantages include the high maintenance, cost and noise. It also requires an additional equipment to start the motor as it has no self-starting torque. The improved power factor changes the current required from the utility company, but not the one required by the motor. Capacitors should not be selected as a means of correcting poor power factors that are the result of oversized motors or unbalanced pumping units.
Choosing a capacitor for this purpose might cause overcorrection, which can result in a leading power factor. A leading power factor, in turn, might cause overvoltages that would cause control-component failure or power-cable failure. This potential problem generally is avoided by connecting the capacitors downstream of the motor contactors and switching them on and off, along with the motor contactors. Power factor correction capacitors could be applied to each individual motor to correct the power factor of that motor, or could be a single unit connected to the main bus of the switchgear.
In the latter case, the unit should have power-factor-sensing circuits that automatically determine the amount of capacitance required for maintaining a preset power factor. The required amount of capacitors are automatically added to or removed from the switchgear bus to maintain the required power factor. The cyclic kW load on a pumping-unit motor can cause the power factor to vary from 1. Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read.
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro. Electrical distribution systems. Hazardous area classification for electrical systems. Alternating current motors. NEMA motor characteristics.
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