The Power Factor(PF) is the measurement of the relationship between the AC source voltage and current. Power factor can range from 0 to 1.0, with 1.0 being ideal. In a purely resistive AC circuit, voltage and current waveforms are in phase, changing polarity at the same instant in each cycle, and all the power entering the load is consumed. However, when reactive loads are present in the circuit such as capacitors or inductors, energy storage in the loads results in a phase difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic fields, and then returned to the power grid a fraction of the period later. The non-productive power increases the current in the line, and cause lower power factor. Thus, a circuit with a lower power factor will use higher current to transfer a given quantity of real power than a circuit with higher power factor.

Besides Power Factor, we need to know what the Apparent Power is. When inductors and capacitors in the circuit, they dissipate zero power , yet the fact that they drop voltage and draw current gives the deceptive impression that they actually consume power which is called “reactive power.” The actual amount of power being used, or dissipated, in a circuit is called “True Power.” The combination of reactive power and true power is called apparent power, which is measured in the unit of Volt-Amps(VA).

Here is the relationship between Power Factor, True Power and Apparent Power:

Power Factor(PF)= True Power(W)/Apparent Power(VA) = W/VA

Power factor can be an important aspect to consider in an AC circuit, because any power factor less than 1 means that the circuit’s wiring has to carry more current than what would be necessary with zero reactance in the circuit to deliver the same amount of (true) power to the resistive load. However, poor power factor can be corrected which is called power factor correction(PFC). PFC can be done by adding another load to the circuit drawing an equal and opposite amount of reactive power, to cancel out the effects of the load’s inductive reactance. Usually the power factor of transformers on the market is 0.7-0.85, and 0.9-0.95 for electronic drivers with PFC function.

In lighting industry, Color Rendering Index (CRI) has been widely used for measuring the quality of light source. CRI values range from 1-100, with 100 rendering colors the best to natural sunlight. CRI is calculated from the differences in the chromaticity of eight CIT standard color samples (R1-R8), the smaller the average difference in chromaticity, the higher the CRI. However, new research indicates that the CRI value may not accurately describe how well LEDs render colors. For example, an LED can have a relatively high CRI but render red poorly.

The R9 value is one of the 14 pigment colors scientists have established to measure color rendition, and it produces strong, vibrant reds. It is important because strong reds are prevalent in skin tones, meat, fruit, and artwork.  LED with higher R9 values produce the most vivid colors. However R9 is not measured in CRI. Sometimes LED with high CRI value might have negative R9 value, which is not good for more accurate representation of the actual color. Whether in an art gallery, hospital, restaurant, or residential home, the color red is critical in order for the human eye to interpret pure colors.

Title 24 and JA8 is California's energy standard for new homes and commercial buildings, and it requires a 90+ CRI and R9 value of 50 or more as high quality, high efficacy light sources. So next time do not forget to ask about R9 value when you need high quality LEDs.

In the electrical appliance manufacturing industry, the IEC protection classes are used to differentiate between the protective-earth connection requirements of devices. Depending on how exactly the protection is provided, electrical appliances are put into five classes of equipment construction., Class I, II, III, 0 and 01. Of these the most important are Class I and Class II.

Class I

In Class I appliances, the protection is provided by a combination of basic insulation and the use of electrical earth. These appliances must have their chassis connected to electrical earth by an earth conductor  (colored yellow/green in most countries, green in the U.S., Canada and Japan).

To safeguard against electric shock from metal cased electrical appliances, the metal chassis or case or any exposed metal of appliances (other than double-insulated items) must incorporate a protective Earthing conductor connected to the Earth pin of an approved three pin plug incorporation an "Earth" terminal.

Class II

In a Class II appliance, the user is protected by at least two layers of insulation between the current carrying parts and any metal accessible to the user.

•Basic Insulation, and

•Supplementary Insulation

For this reason, Class II appliances are also known as Double Insulated appliances. They do not require an Earth connection. In Europe, a double insulated appliance must be labelled " Class II", "double insulated" or bear the double insulation symbol (a square inside another square). If the basic insulation or the supplementary insulation breaks down, it will not result in an electric shock risk.

Are Class I and Class II appliances just as safe?

Class I appliance, one of the layers of safety is provided by the earth connection. For this to be effective, the wiring in the building has to be inspected regularly to check that the Earth in the mains socket is correctly taken to the local earth potential. Class I appliances depend on the external wiring in the building to fully provide the 2 levels of protection.

Class appliances however always provide 2 levels of protection irrespective of the status of the wiring installation. Both layers of the protection are built into the design making Class II appliances a lot safer than Class I appliances.

Class 1, 2  and 3 circuits are classified as remote-control, signaling, and

power-limited circuits in the National Electrical Code (NEC).

Class 2 and 3 circuits - The NEC defines Class 2 in chapter 9 NEC provides the power limitations for the power sources: on for AC current and one for DC current. In general, a Class 2 circuit (operation at 24V with a power supply durable marked " Class 2" and not exceeding 100VA) is the type most commonly used.

The NEC defines a Class 2 circuit as that portion of the wiring system between the load side of Class 2 power source and the connected equipment. Due to its power limitations, a Class 2 circuit is considered safe from a fire initiation standpoint and provides acceptable protection from electrical shock.

Class 2 or Class II Power Supplies?

Class 2 - is a classification referring to the NEC - National Electric Code. to avoid potential cable overheating due to excessive currents and electric shock, the output of the power supply is limited to 60VDC or 100VA, (100W when used with an AC-DC power supply). You will often see 24V output DIN rail power supplies or LED drivers rated at 91W rather than 100W because if the power supply is overloaded, an tolerance in the over current protection has to be accounted for.

Class II - Refers to power supplies with either a double or reinforced insulation barrier between the input and the output. Class II supplies do not rely on an earth connection to protect against shock hazard. Many cell phone chargers and laptop power supplies are Class II. TDK-Lambda's DSP series also are Class II, having just a Line and Neutral AC input without a ground connection.

One advantage of Class II is better surge protection between input and ground and usually a lower earth leakage current.

Ultra-thin polyurethane film deposition provides an ingress protection rating of IP54 for all of our TivoTape™ products.  eXo Shield Protects the LEDs and electronics  from nominal moisture and dust, letting LEDs run cooler, thus living longer.  This results in a brighter fixture with no color shift due to dust and dirt, while coating remains clear and flexible.

HOW TO READ IP RATINGS

(TivoTape eXo Shield offers IP54 protection)

First Digit (intrusion protection)

1. No special protection.

2. Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter.

3. Protection against fingers or other object not greater than 80mm in length and 12mm in diameter.

4. Protection from entry by tools, wires etc, with a diameter of 2.5 mm or more.

5. Protection against solid bodies larger than 1mm (eg fine tools/small etc).

6. Protected against dust that may harm equipment.

7. Totally dust tight.

Second Digit (moisture protection)

1. No protection.

2. Protection against condensation

3. Protection against water droplets deflected up to 15° from vertical

4. Protected against spray up to 60° from vertical.

5. Protected against water spray from all directions.

6. Protection against low pressure water jets (all directions)

7. Protection against strong water jets and waves.

8. Protected against temporary immersion.

9. Protected against prolonged effects of immersion under pressure.

For indoor applications IP67 (outdoor rating) would be overkill

6. Protected against dust that may harm equipment.

7. Protection against strong water jets and waves.

If the indoor tape did not have eXo Shield it would be IP20

2. Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter.

0. Zero protection from water ingress.