Myron Zucker, Inc. Frequently Asked Questions
1. What is power factor?
A. Power factor is a measure of how efficiently electrical power is consumed. Power factor is the ratio between active power (KW) and total power (KVA). Active power does work and reactive power (KVAR) produces an electro-magnetic field for inductive loads. PF(%) = (KW / KVA)*100.
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2. What is the ideal power factor?
A. The ideal power factor is one (1) or 100% efficiency. Anything less than one means that extra power is required to achieve the actual task at hand. This extra energy, known as Reactive Power, is necessary to provide a magnetizing effect required by motors and other inductive loads to perform their desired functions.
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3. What is power factor correction?
A. Power factor correction is the term given to a technology that has been used since the turn of the 20th century to restore Power Factor to as close to unity as is economically possible. This is normally achieved by the addition of power factor correction capacitors to the electrical network, which compensate for the Reactive Power demand of the inductive load and thus reduce the burden on the supply. Myron Zucker was the first person to apply Capacitors At the Load (CAL method) to achieve optimal power factor correction.
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4. What types of equipment cause low or poor power factor?
A. Lightly loaded or varying load inductive equipment such as: inefficient motors, HVAC systems, induction furnaces, molding equipment, etc.
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5. What are the factors that affect your electric utility billing?
A.
- Energy Charge:
Number of kilowatt-hours used during the billing period
Number of kilovolt amperes (KVA) used 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 can be reduced by reducing KVA, which can be achieved by reducing energy peaks and improving power factor.
- Power Factor Penalty Charge:
This is a rate structure charge imposed to encourage the industrial, commercial and institutional user to improve power factor. With many of the electric utilities, penalty billing is imposed when the power factor (PF) drops below 95%. In most cases, the least expensive, most efficient and most reliable method to reduce this charge (improve PF) is by adding properly designed fixed or automatic power factor correction systems.
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6. What are the benefits of power factor correction?
- Electricity bills reduced
- Electrical energy efficiency improved
- Less total plant KVA for the same KW working power
- More KW working power for the same KVA demand
- Improved voltage regulation due to reduced line voltage drop
- Reduction in size of transformers, cables and switchgear in new installations
- Reduced power losses in distribution systems
- Decrease carbon footprint on the environment
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7. What do power factor correction capacitors do to improve power factor?
A. Power factor correction capacitors supply the necessary reactive portion of power (KVAR) for inductive devices. Because the capacitors supply this necessary power, the electric utility does not have to supply it, resulting in reduced generation costs for the utility.
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8. Where is the most efficient location for power factor capacitors?
A. The location that provides maximum benefits of power factor correction is at the load. Capacitors work from the point of installation back to the generating source. Therefore, they provide additional savings in recovered heat losses. Individual motor correction is not always practical, sometimes 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.
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9. What kind of savings can I realize by installing power factor correction capacitors?
A. Every application and installation is different. However, in those areas of the country where the electric utilities have a penalty based rate structure, power factor correction capacitors and systems can generate a one year or less payback. 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.
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10. What are harmonics?
A. 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.
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11. What is harmonic resonance?
A. When a capacitor bank is added to a power system, it is effectively connected in parallel with the system's impedance, which is primarily inductive. As far as the harmonic source is concerned, it sees a capacitor in parallel with an inductor. Since the capacitive and inductive reactance are frequency dependent, there is a frequency at which these two parameters will be equal. This frequency is called the system's natural resonant frequency. At this frequency, the system's impedance appears to the harmonic source to be very large; therefore, a harmonic current at the resonant frequency flowing through this impedance will result in a very large harmonic voltage.
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12. What are some indications of harmonic resonance?
A. 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).
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13. How to solve harmonic resonance?
A. 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.
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14. Why tune to the 5th harmonic?
A. 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.
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15. I have machines that need to be converted to a different voltage and frequency; Can I use the existing capacitors in this application?
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.
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16. What are the dimensions of your individual capacitor cells?
A. The dimensions of our capacitor cells can be found in our capacitor cell specifications.
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17. How do I fulfill IEEE 519?
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.
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18. What wire size and circuit breaker size do I use?
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.
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19. Do your capacitors contain PCB?
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.
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20. Capacitors at load or service entrance?
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:
- CAL decreases I2R losses in conductors, thereby reducing total KW
- CAL enables all equipment in the plant system to furnish more real power
- CAL keeps voltage steadier at the load, enabling full torque from motors and full light from lamps, without burnouts due to improper voltage
- CAL can be obtained and installed quickly and easily
- Capacitors ordered with new equipment give you all these benefits right from the start.
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21. What type of replacement fuses should I use?
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.
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22. What is the cause of harmonic amplification in the presence of capacitors?
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:
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With Capacitor Bank Disconnected
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With Capacitor Bank Connected
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Voltage (volt)
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409
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411
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Power Factor
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0.568
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0.946
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Voltage Total Harmonic
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4.5%
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5.7%
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Total Demand Distortion
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6.8%
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31.75%
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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.
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23. Do you provide power quality equipment for Induction Heaters?
A. No. Induction Heaters are normally listed in voltages and hertz ratings that are not found in our product line.
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24. What is the proper way to test capacitors?
A. 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.
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25. What type of energy savings will I see with Transient Voltage Surge Suppressors?
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.
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26. What does it mean to plug or inch a motor?
A. 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.
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27. How can I prove a 25% to 35% kilowatt hour savings by installing power factor correction capacitors?
The IEEE Std 739-1995 5.5.3.3 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.
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