| Power Factor Explained
Energy costs are on the rise, and facilities everywhere are looking to reduce energy consumption and the costs related to it. But if you haven’t analyzed your monthly energy usage, traced it to operational components or broken out utility fees; how can you make smart decisions to reduce consumption?
To learn more about power quality download any of these free application notes or watch a webinar:
Power Quality (PQ) covers a wide range of issues, from voltage disturbances, to performance wiring and grounding. The symptoms of poor PQ include intermittent lock-ups and resets, corrupted data, premature equipment failure, overheating of components for no apparent cause, etc. The ultimate cost is in downtime, decreased productivity and frustrated personnel.
By adding basic power quality measurements to production equipment maintenance procedures you can head off unexpected failures in both production equipment and your power system.
Power quality problems can originate from inside or outside the facility. How do you find the problem(s), how do you quantify it and how do you correct it?
6 Simple ways to reduce costs through power quality Join a Fluke power quality expert for this 45 minute webinar on the fundamentals of power quality. Learn how to diagnose power quality problems by conducting a systematic power quality survey and how to troubleshoot power quality problems and save money by improving power quality.
Recorded Version - Duration 32 minutes
Watch Now » | What is Energy? The first step in making an informed plan that will reduce your energy consumption is to learn how energy differs from simple volts and currents. When we talk about the energy that is supplied by a utility, we are really talking about the two components of energy - power and demand.
Power is measured in Watts (usually expressed as kW, that’s 1,000’s of Watts), which is an indication of the rate that energy is instantaneously expended, and is what delivers the useful work in driving loads or lighting your plant. Watt-hours, or kWh, are the summation of the amount of kW consumed in one hour, and are commonly used as a billing unit for consumer electric utilities.
Demand, also referred to as apparent power, is expressed in kilo-Volt-Amperes (kVA), which is the product of the voltage and the current. This is a value that does not consider the efficiency, or actual work produced by the delivery of this energy. To make a rough estimate of your demand, you can use a regular digital multimeter with a current probe and measure the voltage and the current. By multiplying the two values, you get the demand of a circuit which is measured in kVA, however, as you don’t measure both quantities at the same instant this method is very likely to be an inaccurate representation of the true demand.
What is Power Factor, and how does it affect me? If a circuit is operating at 100% efficiency, then the demand (kVA) and the power (kW) are exactly the same thing. But, as most technicians will tell you, this is rarely the case. Most of the time power (kW) is less than the demand (kVA). The ratio of power and demand, kW/kVA, is called power factor. Power factor is measured on a scale of 0 to 1.0.
Power factor is significant because utility companies provide customers with Volt-Amperes but bills them for Watts. If a circuit’s power factor drops below 1.0, the utility must generate more than the minimum Volt-Amperes to supply power to the circuit. This in turn increases a utility company’s generation and transmission costs which lead to the utility charging additional fees. In fact some utilities may charge a rate for every percentage point between .85 and .97; you should check the details on your electricity bill to find out exactly what you are charged.
To give you an example of how costly low power factor can be, let’s assume that the utility adds 1% charge for every point you are below a power factor of 0.97. Let’s also assume that your power factor average is 0.86 every month and that your demand charge is $7000.
(0.97 – 0.86) * 100% = 11%
(11% * $7000) * 12 months = $9,240
In this example you could be spending an additional $9,240 a year due to a low power factor.
What causes low power factor? Low power factor is typically caused when reactive loads, such as capacitors or inductors, are present. Some common examples of circuits containing inductive or capacitive elements are motors, transformers, and lighting.
Another contributor to low power factors are harmonic currents. These are currents that are reflected back into the system and are present in the load current, but not in the voltage. Harmonic currents don’t contribute anything to the power supply system but can lower your power factor; the only loads that will not introduce harmonic currents are purely resistive, like heaters and incandescent lamps.
“Imaginary” power is another component to low power factors. This type of current flow, measured in Volt-Amperes reactive (VAR), is strange in that it is present on your electrical distribution system, but produces no work.
The most common cause of imaginary power is motor inductance, and is greater when motors are not loaded to their recommended capacity.
 What can be done to maintain power factor close to 1?
Now that you understand what power factor is, how it affects you and what can cause low power factor, you are ready to create a strategy to reduce your consumption and create a more efficient system.
Your first step is to start taking base line readings of your systems and to do that you need a meter that can simultaneously measure voltage, current, and the associated values of kVA, KW and power factor. A regular digital multimeter can’t do that, but Fluke has a full line of power quality meters that, depending on the make and model you select, can test single phase , split-phase, and three phase measurement configurations as well as measure or record V, A, W, VA, VAR, Power Factor and Harmonics. Some of the logging models even provide the means to accumulate measured values over time in kWh, kVAh, and kVARh, the same energy readings used by utility companies. Now the only hurdle standing in your way to understanding your systems energy consumption is time, after all you can only measure energy as the work that your electrical system delivers to your loads and that takes time to gather.
One way to estimate the energy usage is by observing power use over a short period of time and then, using some simple math, to project what your longer term energy usage could be. This method is a little more complicated when testing motors, variable speed motor drives, and computers.
The other solution is to use a power logger, like Fluke’s 1735 series power logger , to do a 30-day load study. This takes longer to complete but will provide you with an absolute understanding of your power consumption.
With even just one entry level Fluke power quality meter, you can pinpoint the areas in your electrical system that are causing the power factor discrepancies and immediately take steps to eliminate the performance issues and reduce utility charges while increasing your system’s capacity. | |