What Are the Advantages of power factor tester？

Power factor correction can be extremely beneficial, offering improvements in power management and power quality. Benefits include everything from reduced demand charges on your power system to increased load-carrying capabilities in your existing circuits and overall reduced power system losses. Below you'll find a list of five benefits in descending order of the potential financial impact on your utility bill.

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1. Avoid Power Factor Penalties

Most industrial processing facilities use many induction motors to drive their pumps, conveyors, and other machinery in the plant. These induction motors cause the power factor to be inherently low for most industrial facilities. Many electric utility companies assess a power factor penalty for a lower power factor (usually below 0.80 or 0.85). Some also incentive high power factor (above 0.95, for example). By adding power factor correction, you can eliminate the power factor penalty from your bill.

2. Reduced Demand Charges

Many electric utility companies charge for maximum metered demand based on either the highest registered demand in kilowatts (KW meter) or a percentage of the highest registered demand in KVA (KVA meter), whichever is greater. If the power factor is low, the percentage of the measured KVA will be significantly greater than the KW demand. Improving the power factor through power factor correction not only lowers the demand charge, but enhances industrial energy management, reducing your electricity bill.

3. Increased Load Carrying Capabilities in Existing Circuits

Loads drawing reactive power also demand reactive current. Installing power factor correction capacitors at the end of existing circuits near the inductive loads reduces the current carried by each circuit. The reduced current flow from improved power factor correction can increase load-carrying capabilities in existing circuits, saving the cost of upgrading the distribution network when extra capacity is required for additional machinery or equipment, saving your company thousands of dollars in unnecessary upgrade costs. In addition, the reduced current flow reduces resistive losses in the circuit.

4. Improved Voltage

A lower power factor causes a higher current flow for a given load. As the line current increases, the voltage drop in the conductor increases, resulting in a lower voltage at the equipment. With an improved power factor, the voltage drop in the conductor is reduced, improving the voltage of the equipment.

5. Reduced Power System Losses

Although the financial return from conductor loss reduction alone is insufficient to justify the installation of capacitors, it is sometimes an attractive additional benefit; especially in older plants with long feeders or in field pumping operations.

What is Power Factor Correction and why is it important?

You may not have heard of Power Factor or the ways it can be corrected but running your electrical equipment at the best power factor ratio can help keep your business costs down and help the environment.

What is power factor?

Power factor is a measure of how effectively you are using electricity. Various types of power are used to provide us with electrical energy. This power is split between something called Working Power and Reactive Power. Working power is used in all electrical appliances to create such things as heat, light and motion. This power is measured as kW or kilowatts. Reactive Power is used by inductive loads, such as motors, to generate and sustain a magnetic field to operate. The working power and reactive power of your equipment makes up your Apparent Power. Hope you are all still with me! Power Factor is the ratio of Working Power to Apparent Power.

All motors which come in the form of a machine, such as conveyors, mixers, compressors, lifts and escalator all have an efficiency rating known as a Power Factor. It is a measure of 'efficiency' and has values ranging from 0 to 1, where 1 is 100% efficient. A bad power factor ' is less than 0.95, which results in higher electrical current flowing than is necessary. A good power factor is greater than 0.95, so power is used more effectively. A 'perfect' Power Factor is 1.

Most motors operate at a much lower efficiency than 1 with some having a Power Factor as low as 0.50. For a typical uncorrected industrial supply, the power factor is around 0.80. This means it is 80% efficient and will consume 20% more power. So, you need more generators and a heavier distribution network, resulting in higher energy bills.

What is power factor correction?

The easiest way to improve Power Factor is to use Power factor correction capacitors in parallel with the connected motor or lighting circuits. These can be applied at the equipment, distribution board or at the origin of the installation. They improve the overall electrical efficiency of your electrical supply, so less electrical current is needed to achieve the same result.

An example of this could be a 1MVA transformer with a 0.75 Power Factor. This can only supply 750KW of load. Increasing this to a power factor of 0.95 can give an extra 200KW of load. It can also reduce the current flow and power loss in cables and transformers. Overall it can reduce the number of KWH units consumed. Using this example, a 200KVA saving in chargeable load saves £300 per month on a typical charge of £1.50 per KVA of maximum demand charge for supply. Power factor correction can also reduce Power Factor charges and climate levy charges.

What are the benefits of power factor correction?

There are numerus advantages to installing power factor correction devices to your electrical supply. They include:
' A reduction in electricity bills
' Increased load carrying capabilities in your existing circuits
' Reduction of I2R losses in transformers and distribution equipment
' overall reduced power system loses
' Extended equipment life
' Reduced electrical burden on cables and electrical components.

Does power factor correction save energy?

The benefits of power factor correction aren't just financial. there are also important environmental benefits. By being more energy efficient you will reduce your power consumption. This means less greenhouse gas emissions and a reduced carbon footprint.

How can Equiptest help me?

With our reputation for integrity and our high levels of customer care we can help you make your power supply as efficient as possible. Our experienced engineers will assess the demands placed on your supply and identify and correct areas where power has been lost.

We use a wide variety of products, some of which operate automatically, that compensate for varying electrical loads. This situation is common in today's manufacturing plants and offices and we are ideally placed to help you improve the way you utilise your electricity supply.

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Power Factor / Grading Capacitance Measurement

Measuring the power factor, or the dissipation factor, also known as the tangent delta (tan δ), provides effective means for verifying the integrity of the insulation condition of circuit breaker components. In particular, the insulation condition of dead tank high voltage breaker bushings should be verified with this measurement. On dead tank breakers this measurement method is used to verify the insulation condition of the bushings by detecting deterioration in capacitive layers. On life tank high voltages breakers this measurement method is used to evaluate the capacitance of grading capacitors. If the measurement is performed outside of mains frequency, interferences from nearby live station components can be filtered out and minimized. Measuring over a range of frequencies provides better insight into the insulation condition.

Why is Power Factor Important When Measuring Efficiency?

The Basics of Power Factor and Efficiency

Engineers using external power supplies (EPS) are no stranger to efficiency measurements. However, as their applications typically run on dc power, common mistakes can be made when measuring the power on the ac side of the power supply. These common pitfalls include incorrectly measuring or completely omitting power factor when calculating the power input to the supply, which results in incorrect efficiency measurements. In this blog post, we will review the basics of power factor and efficiency, then provide guidance on how to incorporate power factor when measuring ac-dc power supply efficiency.

Power Factor and Efficiency, a Review

Efficiency (η) is the ratio of output power to input power:

Equation 1: Efficiency

In the context of an External Power Supply (EPS) dealing with direct current, the output power is calculated by simply multiplying the output voltage by the output current by quickly providing the numerator to equation.

Calculating Output Power

Calculating the output power of an EPS, which is dc, is simply the output voltage multiplied by the output current:

Equation 2: Output Power

Equation 2 calculates the direct current (dc) output power (P_dc) of an Electric Power Supply (EPS) by multiplying the output voltage (V_dc) by the output current (I_dc), resulting in the power measured in watts (W).

Understanding Power Factor

A common mistake is to apply this same calculation to obtain the input power. This presents a problem because the volt-ampere product in ac circuits does not always equal the real power, and in fact, in the case of external adapters, the volt-ampere product will never equal the real power. In ac circuits, the volt-ampere product is equal to the apparent power (S), which is related to the real pow-er through a term called Power Factor (PF):

Equation 3: Apparent Power

Equation 3 computes the apparent power (S) in volt-amperes (VA) by multiplying the root mean square (rms) voltage (Vrms) with the rms current (Irms).

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Defining Power Factor

By definition, power factor is the ratio of real power to apparent power, where apparent power is the product of the rms voltage and rms current. Only when the power factor equals 1 does the volt-ampere product equal the real power:

Equation 4: Power Factor

Different Types of Power Factor

If power factor is considered when calculating the efficiency, it must be calculated correctly. Many engineers have to rewind all the way back to their early engineering classes to remember what power factor is and how to measure it. However, in school they of-ten focus on a linear case where both the voltage and current are pure sinusoids of equal frequency. In this case the power factor is simply the cosine of the phase difference between the voltage and current and is more accurately known as the displacement power factor:

Equation 5: Displacement Power Factor

Many engineers are familiar with the power triangle, shown in Figure 1, which visually represents the relationship of Equation 5. By definition, the cosine of θ is equal to the ratio of the adjacent side to the hypotenuse. In the power triangle this equals the ratio of real power to apparent power, which matches our definition in Equation 4. On the other hand, when it comes to non-linear systems, of which ac-dc power supplies are one example, this does not present the whole picture.

Figure 1: Power triangle for linear systems

The Role of Distortion Power Factor

What is missing is the distortion power factor, which adds a third dimension to the power triangle as shown in Figure 2. This point is critical because in power supplies the distortion factor is the major contributor to reducing power factor since the displacement factor tends to be close to unity.

Figure 2: Power triangle for non-linear systems

Total Harmonic Distortion

Fourier analysis shows that this non-linear current waveform can be broken down into a series of harmonic components of various magnitudes. These harmonics decrease the power factor, but are not accounted for in Equation 5. To calculate the distortion power factor, Total Harmonic Distortion (THD) is introduced. THD takes into account the current associated with each harmonic as high-lighted in the following equation:

Equation 6: Total Harmonic Distortion

Calculating the Distortion Power Factor

When the THD is equal to 0, the distortion power factor is equal to 1, which would be the case for a linear system:

Equation 7: Distortion Power Factor

The True Power Factor

The power factor picture is completed by multiplying the displacement power factor and distortion power factor, which results in the True Power Factor:

Equation 8: True Power Factor

Figure 3 shows the input current and voltage waveforms of a typical power supply. When compared to the sinusoidal voltage, the non-linear nature of the current can be clearly seen.

Figure 3: Scope showing current and voltage waveforms of a typical power supply

This is caused by the combination of a bridge rectifier and bulk-capacitor that create a high-voltage dc bus inside the supply. The rectifier is forward biased and only conducts current when the input voltage exceeds the voltage on the bulk-capacitor.

Measuring Power Factor

The best way to measure power factor is to use a power meter like the one shown in Figure 4 below. These devices will output the real power directly, so power factor does not need to be considered when calculating efficiency. In addition to the real power, these meters can measure power factor, THD, the current for each harmonic, and more. While low power external adapters do not have de-fined power factor or harmonic limits, higher power supplies do have specific regulatory limits on the harmonic content and power factor. Standards, such as EN -3-2 specify limits on harmonic current up to and including the 39th harmonic, for certain power levels. When measuring the harmonic current of a power supply, a power meter is essential.

Figure 4: WT210 Power Meter showing measurements corresponding to waveforms in Figure 3

Power Factor in Power Supplies

You may think that the impact of omitting the power factor will result in only a slight error and/or that the power factor of an external adapter cannot be that bad. In fact, without power factor correction, the power factor of an external adapter could easily be as low as 0.5 at a rated load. An adapter with a power factor of 0.5 will have an apparent power twice that of the real power, thus leading to incorrect results. Even if the power supply had a real efficiency of 100%, this measurement would only show 50%.

In addition to the general inclusion of power factor in efficiency calculations, it is important to note that the power factor is line and load dependent. Efficiency requirements, such as DoE Level VI, require the efficiency to be measured at several points (25%, 50%, 75%, and 100% load) at both high and low line voltages. If power factor is used in the calculation of real power, then it must be re-measured for each of these conditions.

Real World Example: The Impact of Power Factor

As a real-world example, take Figures 3 and 4, which were obtained from a 20 W external power supply operating at 10.8 W. With measurements obtained from the scope in Figure 3, we end up with a volt-ampere product of 22.5 VA. If we were to forget to include power factor, then using this number we would gather an efficiency figure of 48%:

Utilizing a power meter, like that shown in Figure 4, we see that the real input power is actually only 12.8 W, and using this value we end up with an efficiency of 84%, which is nearly twice what we obtained without factoring in the power factor:

Now if power factor was considered, but an oscilloscope and Equation 5 were used to calculate it (distortion factor omitted), a few problems present themselves. First, as shown in Figure 3, scopes can have trouble automatically calculating the phase difference. The scope used in Figure 3 calculated a phase angle of 72 degrees, which appears to be incorrect to the naked eye. When using scope cursors to manually measure the phase angle, we notice that we are attempting to measure the offset of two differently shaped waveforms and that the current waveform pulse is asymmetric.

So the question arises: where do we put the cursor, at the peak or at the center of the pulse? In either case the value ends up being a few degrees at most. Were we to use Equation 5 to calculate the displacement power factor with an angle of 5°, we end up with a value of 0.996. If we multiply our result of 22.5 VA gathered above by our calculated power factor, we find the result is nearly unchanged at 22.4 VA. This should confirm our earlier assertion that the displacement factor is close to unity and the distortion power factor is the dominant term in Equation 8. We can therefore see that the scope method is of no use to us and the only method that produced correct results was the use of a power meter.

Power Meters for Accurate Efficiency Testing

Decades of increasing regulation have made efficiency testing one of the most important factors in selecting and qualifying power supplies. Lack of experience in dealing with ac circuits can lead test engineers to omit or to incorrectly calculate the power factor, resulting in incorrect efficiency numbers. When testing external adapters, or any ac-dc power supply, the best method for calculating the real power input is through the use of a power meter. These devices not only measure real power directly but can measure the current associated with the individual harmonics and provide a complete picture of the power supply input.

Fundamentals , Testing & Failure Analysis

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