Power Factor Correction in Cincinnati

Low power factor can cost a large facility hundreds or even thousands of dollars a month in utility penalties, and it wastes capacity in your electrical system. Cooper Electric’s power quality team measures, designs and installs power factor correction for commercial and industrial facilities across Greater Cincinnati and Northern Kentucky.

What Is Power Factor?

Power factor measures how effectively electrical power is being used. It is the ratio of real power (watts) to apparent power (volt-amperes). A power factor near 1.0 means power is being used efficiently; a low power factor means it is not. Many utilities charge a penalty when power factor falls below 0.90.

What Causes Low Power Factor?

The main cause is inductive motor loads running at less than full load. Motors on equipment such as surface grinders, conveyors, air compressors, circular saws, punch presses and plastic injection molding machines are sized for their heaviest load but often run lightly loaded: a conveyor with little on it, a saw spinning without cutting, or a grinder taking a shallow cut.

Inductive loads need two kinds of power: real power (kW), which does the actual work, and reactive power (kVAR), which sustains the motor’s magnetic field. Reactive power does no useful work, but it still circulates through your distribution system and the utility’s. Together, real and reactive power make up apparent power (kVA).

Why Low Power Factor Matters

Utilities build their systems in kVA but bill you in kW. Transformers are sized by apparent power, while meters measure kilowatt-hours and kW demand. Poor power factor forces the utility to build a larger system than your real load needs; at a power factor of 0.70, the supply must be about 43% larger than at 1.0. That is why utilities charge penalties.

• Eliminate penalties: your last 12 months of utility bills can show exactly what low power factor is costing you. Do not count on the utility to point it out
• Free up capacity: raising power factor reduces kVA, so you can add kW load without upgrading transformers or service
• Improve voltage: capacitors reduce current, which improves voltage from the point of installation back to the main service, especially at the end of long feeders or bus duct runs

Not every facility is billed for poor power factor, so a bill review is the first step.

How Power Factor Is Corrected

Standard induction motors seldom exceed a power factor of 0.95 and can fall to 0.60 or lower when lightly loaded. Synchronous motors can supply a leading power factor, but they are rarely practical for this purpose in modern plants.

Most often, power factor is improved by adding power capacitors to the plant distribution system. Capacitors act as reactive current generators, supplying kVAR locally so less current has to be drawn from the utility. They can be installed at individual motors or grouped at one point on the main distribution. Capacitors at each motor reduce current all the way from load to source but cost more up front; grouping them at a single location usually delivers the best return on investment.

Installation Tips from Our Power Quality Team

Protect capacitors with fuses and indicator lights

Power capacitors have no moving parts and need little maintenance. They should be fused, and we recommend blown-fuse indicator lights. A properly sized installation should not blow fuses, so a lit indicator can be an early warning that harmonic currents have entered the system.

Measure harmonics before you install

Non-linear loads, most commonly variable frequency drives, create harmonic currents that can destroy capacitors. Harmonics are specific to each facility and hard to predict, so we recommend a power quality survey with instruments that record over several days rather than a one-time snapshot. If harmonics are significant, filters tuned to specific frequencies may be needed to protect the capacitors.

Check operation and adjust motor overloads

Capacitor cases are normally warm to the touch; a cool case can mean a blown fuse or an open power source. A true-RMS clamp-on ammeter can confirm operation: three-phase capacitors draw about 1.2 amps per kVAR at 480 volts and about 2.4 amps per kVAR at 240 volts. When capacitors are installed on the load side of motor starters, the overload heaters must be adjusted per the capacitor manufacturer’s recommendations.

Avoid voltage rise at light load

Large fixed capacitor banks can cause an objectionable voltage rise when the plant is lightly loaded, such as nights and weekends. An automatic controller that monitors power factor and switches capacitors on only as needed prevents this.

Why Work with Cooper Electric

Capacitor installations involve harmonics, motor protection and voltage control, so experience matters. Our team includes Certified Power Quality Professionals, and we have served Greater Cincinnati businesses since 1946. We will analyze your bills and power quality, recommend the right solution, install it and guarantee the work.