Power factor (PF) is a measure of how efficiently the total current supplied by the utility company is converted into useful work. PF is the ratio of real power (kW) divided by total power (kVA). Utility companies indicate PF on power bills as an average value for the billing period. Average PF is calculated by dividing real energy consumed (kW-hours) by total energy consumed (kVA-hours).

The ideal power factor (PF) is unity. Anything less than unity means extra current is being supplied by the utility company than is needed to achieve the actual task at hand. This extra current is defined as reactive current. Since a PF of unity is somewhat impractical, a good PF is one that is greater than the PF penalty threshold value. The penalty threshold value varies from utility company to utility company but is usually between 85% to 95%.

Power factor (PF) correction is the term given to a technology in use since the turn of the 20th century to increase the present PF to a desired or corrected PF value. This is achieved by connecting power factor correction capacitors (PFCCs) to the electrical system. PFCCs provide the reactive power to the inductive load by supplying the reactive current. The result is that the utility company is not required to supply the reactive current since the reactive current is supplied by the PFCCs. This significantly reduces the amount of total current required from the utility supplier. PFCCs can be installed at the main service or at the load. Myron Zucker was the first person to apply Capacitors At the Load (CAL method) to achieve optimal power factor correction.

Inductive loads result in low power factor (PF). Typical inductive loads are induction motors, induction heaters and magnetic ballast fluorescent lights. The PF of induction motors is further reduced when motors are lightly or intermittently loaded.

  • Energy Charge:
    The total amount of kilowatt-hours (kW-h) consumed during the billing period.
    The total amount of kilovolt amperes-hours (kVA-h) consumed during the billing period.
  • Demand Charge:
    This type of charge compensates the utility for the capital investment required to serve the facility’s peak load. Demand charges may be a large portion of the total electric bill, as much as 75%. Demand charges are usually expressed in kilowatts (kW) but can also expressed in kilovolt-amperes (kVA). Demand charges are usually calculated by determining the average demand of either a 15 or 30 minute period during which the greatest amount of energy was consumed. Demand charges, if expressed in kW, can be reduced by reducing energy peaks. Demand charges, if expressed in kVA, can be reduced by reducing energy peaks or increasing power factor (PF).
  • Power Factor Penalty Charge:
    This is a rate structure charge imposed to encourage the industrial, commercial and institutional user to increase PF. The PF penalty charge is not always easy to recognize on the utility bill. Methods of indicating the PF penalty charge vary from utility company to utility company. The charge is obvious if shown as a PF penalty or PF adjustment. The charge is less obvious if demand is billed as kVA or energy consumption is billed as kVA-h. With many utility companies, penalty billing is imposed when the PF drops below 95%. In most cases, the least expensive, most efficient and most reliable method to reduce this charge is to increase PF by adding properly designed fixed or automatic power factor correction capacitor systems.
  • Reduced electrical utility cost
  • Increased electrical distribution capacity
  • Less total plant kVA for the same kW working power
  • More kW working power for the same kVA demand
  • Reduction in the size of transformers, conductors and switchgear in new installations
  • Reduced power losses in distribution systems
  • Improved voltage regulation due to reduced line voltage drop
  • Decrease carbon footprint on the environment

Power factor correction capacitors (PFCCs) provide the necessary reactive power (kVAr) for inductive loads by supplying the reactive current. This is accomplished by the way capacitors and inductors function together. Both capacitors and inductors absorb and release current. The difference is capacitors and inductors function 180º out of phase. In other words, when the capacitor is releasing, the inductor is absorbing and vice versa. The result is that the utility company is not required to supply the reactive current since the reactive current is supplied by the PFCCs. This significantly reduces the amount of total current required from the utility supplier.

The location that provides most benefits is at the load. Power factor correction capacitors (PFCC) supply reactive current resulting in reduced total current. Reduced total current occurs within the electrical system form the point of PFCC connection back to the source. This results in additional benefits. These benefits are increased distribution capacity, reduced losses and improved voltage. Individual, at the load, correction is not always practical. Since all facilities and operations are different, the most effective capacitor location is also different. In some cases it is more practical to connect larger capacitors on the distribution bus or install an automatic system at the incoming service along with fixed capacitors at the load.

Every application and installation is different. The greatest savings result from reducing or eliminating PF penalties charged by utility companies. In most cases, the pay back is less than two years. Review our Power Factor Correction Application Guide for details on how potential savings can be calculated. Also review our Capacitalk 101 for a case study.

Harmonics are multiples of the fundamental frequency distortions found in electrical power, subjected to continuous disturbances. In a 60 Hz electrical system 350 Hz is the 5th harmonic, 420 Hz is the 7th harmonic, and so on. Harmonics are created by the use of non-linear devices such as UPS systems, solid state variable speed motor drives, rectifiers, welders, arc furnaces, fluorescent ballasts and personal computers. Individual harmonic frequencies will vary in amplitude and phase angle, depending on the harmonic source.

Some indications are overheating, frequent circuit breaker tripping, unexplained fuse operation, capacitor failures, electronic equipment malfunction, flicking lights and telephone interference, insulation melting off of conductors (skin effect).

The solution can be accomplished by: 1. Adding or subtracting capacitance from the system to move the parallel resonance frequency to one that is not harmful. 2. Adding tuned harmonic suppression reactors in series with the capacitor to prevent resonance. 3. Altering the size of the non-linear devices.

The 5th harmonic is generally considered to be the most offending. It is important that the tuned frequency for the 5th harmonic be at least at the 4.2nd harmonic. Tuning slightly below the offending harmonic will accommodate for standard tolerances in the manufacturing process, but remove the largest offending portion of the 5th harmonic. Parallel resonance will occur around the 4th harmonic, at a much lower amplitude and in an area that does no harm to the capacitors or system. Many other systems are designed at the 3.78th harmonic to help extend the life of the capacitors. This tuning frequency does not remove the majority of the 5th, 7th, etc. harmonic from the system.

I have a machine, originally built for U.S. 480Vac 60 Hz. We are revising the machine where the voltage will be 380Vac 50 Hz. The motors are 3HP and 5HP, 1800 RPM, 460V, 3-phase, 60 Hz. Can I use the same Calmount capacitor or do I need another unit?

A. These units will be fine to leave as is. The units may be derated to lower voltages along with derating to lower hertz. The units will have a lower kVAR rating at 380 volt 50 Hz than they would at 480 volt 60 Hz but will still work normally in that setting. The following link is a derating chart for these types of applications.

A capacitor is an energy storage device. The energy stored in a capacitor when power is disrupted will remain until dissipated by the load or by discharge resistors. This takes a few minutes. Problems can occur when power is disrupted and the capacitor is re-energized before the stored energy has time to dissipate. In this case, the applied voltage can be over twice the rated voltage. This extreme voltage and associated excessive current and heat results in capacitor cell damage and premature failure.

The solution is to provide for a two- to five-minute time delay prior to re-energizing the capacitor after power loss. This time delay is a function of the controller on our automatic systems (Autocapacibank™, Autocapacitrap™). For fixed systems, the time delay can be accomplished by the addition of an auxiliary contactor and timer circuit. This option is available in the Calmount®, Traymount®, Caltrap™, Capacibank®, and Capacitrap® systems.

The dimensions of our capacitor cells can be found in our cylindrical and rectangular capacitor cell specifications.

We plan to sell several low voltage 6-pulses drives in Columbia, SA. These drives are coming from New Berlin, WI. They are looking for a passive filter supplier to include in the drives to mitigate the harmonic level and to fulfill IEEE 519. What does this require?

A. For IEEE-519 there are five different harmonic current distortion limits depending on the transformer size and impedance (determines available short circuit current) and the individual load ratings. For several VFDs (at one location) it then becomes a system solution whereby you might combine AC line reactors along with filters to achieve compliance at the lowest cost. It would be helpful to know the model of drive.

What size wire and circuit breaker will I need when I install a 200 kVAR, 480 Volt, 3 Phase, 60 Hz capacitor bank?

A. Per the NEC, the recommended wire size for a 200kVAR, 480V, 3Phase, 60 Hertz capacitor bank is 500MCM – 90 degree, C-Type THHN, XHHW or equivalent and a 400 amp circuit breaker or disconnect switch. Please view our recommended wire sizes, switches, and fuses chart.

My company is in the process of re-building a 1979 Vertical Boring Mill, at our Lykens PA facility. The main electrical control panel has a bank of 4 Myron Zucker capacitors. We cannot read the Catalog number. There is a stamped phrase on top of the capacitors that reads “Contains ECCOL.” My concern is whether that material is PCB-based.

A. The capacitors used in the units you’ve described were manufactured by Commonwealth Sprague. The ECCOL line of capacitors were filled with a non-PCB fluid. Click here for additional information on capacitors with PCB.

Why would I want to place a capacitor at the load (CAL) instead of at the service entrance or substation? Do capacitor banks at the service entrance provide better power factor correction?

A. If your facility has power factor (PF) correction capacitors at its service entrance, those capacitors are probably there to prevent a utility penalty. What they don’t do is improve power factor at the load, which means your actual energy consumption is higher than it needs to be. This, of course, means your company pays for electricity it doesn’t use.

Have you been unable to get approval to pay for a site power survey to see where your energy losses are? Try shrinking the scope. Start with a one-line diagram of your distribution system, and limit the survey so it goes no further than the major loads. If you identify energy savings with this limited survey, the money you save can help you justify a more detailed follow-up survey.

Even with PF correction at the service entrance, you may be surprised to find that you have unacceptably low PF at some loads.

Before implementing any load-level PF correction, determine the effects on your entire distribution system. Corrections at the load will change the PF capacitor size you need at the service. Make sure you regularly inspect PF correction capacitors. Power events can damage these capacitors — and that damage may not be readily apparent. If you can’t remove individual capacitor cells for testing or replacement because the lid of your PF unit interferes with this, consider replacing that unit with one that has a maintenance-friendly lid design.

Capacitors-at-Load (CAL) pay more dividends than power factor correction at the substation. Many utilities reward better power factor or lower KVA demand. But equally compelling reasons for adapting CAL are:

  1. CAL decreases I2R losses in conductors, thereby reducing total KW
  2. CAL enables all equipment in the plant system to furnish more real power
  3. CAL keeps voltage steadier at the load, enabling full torque from motors and full light from lamps, without burnouts due to improper voltage
  4. CAL can be obtained and installed quickly and easily
  5. Capacitors ordered with new equipment give you all these benefits right from the start.

I have some Myron Zucker KIM43005-3 power factor capacitors installed on some equipment. My customer has told me that some of the fuse lights are lit on the Myron Zucker units. Can you tell me the type and size of the fuses that are installed on these units? I’ve downloaded your instructions for diagnosing the lights and replacing the fuses but I can’t find any information that identifies the fuses.

A. Our KIM43005-3 Calmount capacitor uses (3) 20 Amp fuses. The type of fuse is a Class CC – Fast-Acting, Current-Limiting, rejection type fuse. You should always consult the factory if the fuse being replaced cannot be easily identified.

I’ve made measurements in a tissue factory fed from the secondary side of a distribution transformer 800KVA, 11/0.4 KV, X=5% after the erection of a fixed capacitor (100 kVAR)

The results were as follows:

With Capacitor Bank Disconnected
With Capacitor Bank Connected
Voltage (volt)
Power Factor
Voltage Total Harmonic
Total Demand Distortion

The greatest harmonic was the fifth.

I want to know the rule that made the 6.8% TDD to become 31.75%? Is this due to parallel resonance? But the capacitor doesn’t burn nor its fuses blown. Does this factory need to erect a harmonic filter (detuned type)? Note: the same distribution transformer fed other factories that also have capacitor banks.

A. I believe your problem is due to the capacitor being a low impedance device therefore attracting any harmonics that are in the system. This will include any harmonics that are produced on the load-side of the 800kVA transformer. The fact that your greatest harmonic is the 5th tells me that you probably have some 6-pulse drives that represent a good portion of the load.

If you were experiencing resonance you would have burnt conductors, capacitor cells, or blown fuses so we don’t believe that this is a concern. Your fuses are not blowing because they are probably sized large enough to handle the 32% increase in amperage.

I would suggest that you obtain a complete one line diagram of every thing on the load side of this 800kVA transformer and examine your non-sinusoidal devices such as VFD’s, UPS’s, and all other devices that change AC to DC. This will give you a good idea of where the harmonics are being generated from and how to properly size a filtered bank. Since this is a tissue plant I would say that you have VFD’s that are spooling and un-spooling large rolls of paper.

You can learn more by reading our manual on solving harmonics. We would be happy to assist you in resolving this power quality issue and look forward to hearing from you in the future.

No. Induction Heaters are normally listed in voltages and hertz ratings that are not found in our product line.

The following link will take you to our white paper for testing capacitor cells. A capacitor is supposed to draw given amperage at a given voltage based on its kVAR rating. If the capacitor is not drawing enough amperage then it is probably aging and losing some of its capacitance. If it is drawing too much amperage then it is likely that there are harmonics present in the facility and further testing would be recommended to determine if that is the case. These measurements can be taken with an amprobe while the capacitors are on line and without disconnecting wires.

Our manufacturing facility was recently visited by a power quality “expert” from another company (not Myron Zucker Inc.) who recommended we install transient voltage surge suppressors (TVSS) as a way to protect equipment and save energy costs. I know enough to be dangerous, and from what I understand about TVSS, it seems unlikely to save energy. What type of energy savings will I see with Transient Voltage Surge Suppressors?

A. Follow your instincts. TVSS devices are, by and large, designed to do one thing: protect downstream equipment from voltage surges and spikes. They are NOT an energy savings device. You may be interested in reading Mike Holt’s website, which specifically addresses the false claims of some TVSS manufacturers. Mike Holt is a leading National Electrical Code consultant and instructor.

Plugging is understood as stopping or reversing an induction motor rapidly by reversing motor primary connections while the motor is running. Inching, also referred to as jogging, is understood as energizing an induction motor once or repeatedly for short periods to obtain small movements of the driven mechanism.

The IEEE Std 739-1995 which refers to “Reduced power losses when capacitors are located at the load” uses a formula based approach and when I apply it to my data I get a 35% reduction in line losses, also referred to as I2R losses, on my load. But the standard also says that a typical reduction is 2% to 5%. What am I missing?

A. The IEEE equation for I2R losses is as follows: % loss reduction = 100 x (1 – (original PF2 / desired PF2))

This is a percentage of total losses, not total power. So, if your building consumes 1,000kW and you have a total loss of 100kW then the savings from the power factor correction will be based on the 100kW portion not the total 1,000kW.

Let’s say your original PF is 72% and your desired PF is 95%. The loss reduction savings equation on the same example system would be 100 x (1 – (.722 / .952)) , which would be 43% of the losses or 4.3% of the total power. This would fall into the percentage range explained in the IEEE standard.

A. Even though we would consider an isolation transformer to be adequate protection against line harmonics, we have experienced situations where they still have allowed enough harmonics back into the system to cause problems.

This is not the case for a properly sized and tuned line reactor. By selecting the proper reactor based on voltage, hertz, horsepower, and percentage of impedance, we can offer an IGBT compatible reactor to either protect your drive against power spikes and motor current surges (3% impedance) or comply with IEEE 519 requirements for mitigating harmonics (5% impedance).

Line reactors are often a more economical approach as well.

A. It is highly unlikely. Since most residential homes in the US are billed in KWH, the benefit of installing power factor correction capacitors is minimal, if any. The only possible benefit you could achieve is the reduction of I2R line losses. I2R lines losses are typically achieved by either reducing the resistance of conductors (increasing the size of wires) or reducing the current flowing through it. Either one of these methods will reduce heat generated in the circuit. This directly translates into a reduction of KWH usage. On loads with poor power factor, the reduction of current is achieved by simply placing a capacitor at that load. Keep in mind that even in an industrial environment with loads operating around the clock, these line losses are usually minimal, below 3% for each treated load. In a residential environment, electrical line runs are typically short and electrical loads (ex., refrigerators, AC units, air compressors, etc.) generally have a very good power factor, above .90) Therefore, it is not usually justifiable to install capacitors in a residential building unless you are trying to achieve unity power factor or improve overall energy efficiency. This will not necessarily reduce your electrical bill but may reduce your overall carbon footprint.

If interested in learning more about residential power factor correction, please visit the following links:

A. UL does not validate any claims of energy savings when using power factor correction capacitors. UL only evaluates and Lists power factor correction capacitors for safety reasons. Please click here to read an informative article regarding energy savings claims and UL’s involvement.

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