Saturday, February 8, 2014

Fluorescent Lamp and Bulbs nomenclature

Fluorescent Lamp Labeling

For Tube lights:-

There is certain nomenclature which is used while labelling tube lights.

The actual fluorescent tubes are identified by several letters and numbers and will look something like
'F40CW-T12' or 'FC12-T10'.
So, the typical labeling is of the form FSWWCCC-TDD (variations on this format are possible):

· F - Fluorescent lamp.

G means Germicidal shortwave UV lamp.

· S - Style - no letter indicates normal straight tube; C for Circline.

· WW - Nominal power in Watts. 4, 5, 8, 12, 15, 20, 30, 40, etc.

· CCC - Color.

W=White,

CW=Cool white,

WW=Warm white,

BL/BLB=Black light, etc.

· T - Tubular bulb.

· DD - Diameter of tube in of eighths of an inch. T8 is 1", T12 is 1.5", etc.

For the most common T12 (1.5 inch) tube, the wattage (except for newer energy saving types) is usually 5/6 of the length in inches. Thus, an F40-T12 tube is 48 inches long.

For Tungsten lamps:-

There are lamps (bulbs and LED who are available in different sizes and ratings in the market. There are most commonly used bulb sizes with Nomenclature starting with A and thereafter its size. Most commonly used are A15, A17, A19, A20, A21, A23 . These all sizes are multiple of 1/8th of inch. In Houses most commonly used size was of A19 having 100 W or 125 W rating.

Where A stands for Arbitrary.

There are other models designed according to shapes of bulbs are:-

(i)                 Bulged Reflector:-BR25, BR30, BR38, BR40

(ii)               Candle : C6, C7, C9, C11, C15

(iii)             Globe: G9, G11, G12, G16, G16.5, G19, G25, G30, G40

(iv)             Quartz Reflector Lamp: MR8, MR11, MR16, MR20

(v)               Parabolic Aluminized Reflector (PAR): PAR14, PAR16, PAR20, PAR30 Short or Long Neck

(vi)             Blown Reflector (R): R12, R14, R16, R20, R25, R30, R40)

(vii)           Twist:- CFL’s are known as Twist shaped bulbs.:T2 Coil, T3 Coil, T4 Coil
As stated above there are so many shapes and sizes available in the market but most commonly used are:-A-19, MR16, PAR38 and 40, R-20 , BR-30, CFL – Twister, G-25 and Candelabras

Now above most commonly used shapes and sizes are having following applications in various fields:-

·                     A-19 is most commonly used in houses. This shape is same as it is first discovered by Edison.

·                     MR-16 lamps are used in Kitchens, Architects and have aesthetic looks.

·                     CFL are most widely used and had replaced A-19 bulbs.

·                     G-25 are most widely used in bathrooms

·                     PAR30 and 40 are used in outdoor lighting. They are having higher wattage ratings.

·                     R-20 and BR-30 lights are used in houses and used as flood lights.

·                     Candelabras:- These are little lights and are used as accent lighting.

Fluorescent Lamp Basics

The fluorescent lamp was the first major advance to be a commercial success in small scale lighting since the tungsten incandescent bulb. Its greatly increased efficiency resulted in cool (temperature wise) brightly lit workplaces (offices and factories) as well as home kitchens and baths. The development of the mercury vapor high intensity discharge (HID) lamp actually predates the fluorescent (the latter being introduced commercially in 1938, four years after the HID). However, HID type lamps have only relatively recently become popular in small sizes for task lighting in the home and office; yard and security area lighting; and light source applications in overhead, computer, and video projectors.

Fluorescent lamps are a type of gas discharge tube similar to neon signs and mercury or sodium vapor street or yard lights. A pair of electrodes, one at each end - are sealed along with a drop of mercury and some inert gases (usually argon) at very low pressure inside a glass tube. The inside of the tube is coated with a phosphor which produces visible light when excited with ultra-violet (UV) radiation. The electrodes are in the form of filaments which for preheat and rapid or warm start fixtures are heated during the starting process to decrease the voltage requirements and remain hot during normal operation as a result of the gas discharge (bombardment by positive ions).

When the lamp is off, the mercury/gas mixture is non-conductive. When power is first applied, a high voltage (several hundred volts) is needed to initiate the discharge. However, once this takes place, a much lower voltage - usually under 100 V for tubes under 30 watts, 100 to 175 volts for 30 watts or more - is needed to maintain it.

The electric current passing through the low pressure gases emits quite a bit of UV (but not much visible light). The gas discharge's radiation is almost entirely mercury radiation, although the gas mixture is mostly inert gas and generally around something like 1 percent mercury vapor. The internal phosphor coating very efficiently converts most of the UV to visible light. The mix of the phosphor(s) is used to tailor the light spectrum to the intended application. Thus, there are cool white, warm white, colored, and black light fluorescent (long wave UV) lamps. There are also lamps intended for medical or industrial uses with a special envelope such as quartz that passes short wave UV radiation. Some have an uncoated envelope, and emit short-wave UV mercury radiation. Others have phosphors that convert shortwave UV to medium wave UV.

Fluorescent lamps are about 2 to 4 times as efficient as incandescent lamps at producing light at the wavelengths that are useful to humans. Thus, they run cooler for the same effective light output. The bulbs themselves also last a lot longer - 10,000 to 20,000 hours vs. 1000 hours for a typical incandescent. However, for certain types of ballasts, this is only achieved if the fluorescent lamp is left on for long periods of time without frequent on-off cycles.

Air Gap Values while designing Machine

Air Gap in Electrical Motors: A Necessary Evil

In the design of electrical Motos, the air gap is often referred to as a necessary evil. While it cannot be avoided, it must be minimized as much as possible. If there were no air gap, motors would not start. At the same time, too large a gap severely reduces performance.

Why Air Gap Matters in Motors

In electromagnetic devices, materials are chosen to offer low resistance (reluctance) to magnetic flux, which reduces the electrical energy required to establish the flux.

However, in rotating machines, an air gap is unavoidable between stator and rotor. Air has very high reluctance compared to iron, so:

A larger air gap requires higher magnetizing current.
More electrical energy is needed to produce the required flux.
It causes undesirable electrical losses.

This is why careful optimization of the air gap is crucial in machine design.

Rule of Thumb

Higher motor speed → Larger air gap.
Slower motor → Smaller air gap.

This compromise balances mechanical safety (too small a gap risks rotor-stator contact) and electrical efficiency (too large a gap reduces power factor and efficiency).

Why Air Gap Should Be Small

Let’s take the case of an induction motor:

When supply is given to the stator, flux is induced in the rotor.
The flux crosses the air gap, which has high reluctance.
For every unit length of flux path, the mmf requirement in the air gap is much higher than in iron.

👉 Therefore, magnetizing current depends heavily on the air gap size.

Impacts of larger air gap in induction motors:

Lower power factor.
Lower efficiency.
High no-load current (30–40% of full load current).

In contrast, transformers (no air gap) have much lower no-load current for the same rating.

Air Gap in Different Machines

Induction Motors → Air gap kept as small as possible (to reduce magnetizing current).
Synchronous & DC Machines → Larger air gaps are required.
- Here, the armature magnetic field distorts the main DC field (armature reaction).
- Larger gaps reduce this effect but sacrifice some efficiency.

This is why synchronous and DC machines have air gaps several times larger than induction motors.

The Design Contradiction

Mechanical Requirement → Larger air gap avoids rotor-stator collision and ensures mechanical safety.
Electrical Requirement → Smaller air gap reduces reluctance, improves efficiency, and lowers no-load current.

Thus, designers must always find an optimum compromise.

Formula for Air Gap Calculation

A practical formula used for estimating required air gap:

\text{Air gap (inches)} = 0.005 + 0.0003D + 0.001L + 0.003V

Where:

$D$ = Rotor outer diameter (inches)
$L$ = Core stack length (inches)
$V$ = Rotor peripheral velocity (thousand ft/min)
$V = D \times \frac{RPM}{12,000}$

⚡ Air gap must always be uniform. A non-uniform gap leads to vibrations, noise, and further losses.

Typical Values of Air Gap

For standard motors (0.75 kW – 750 kW): 0.2 mm to 5 mm.

This small but critical range directly impacts motor performance, efficiency, and reliability.

✅ Key Takeaway:
Air gap cannot be eliminated, but minimizing it within safe limits is the cornerstone of efficient motor design. It’s the balancing act between mechanical safety and electrical efficiency that makes the air gap a true necessary evil.

Precautions while working with Gas Discharge Lamps & Fixtures

Safely Working with Gas Discharge Lamps and Fixtures

Gas discharge lamps (fluorescent, HID, sodium, mercury vapor, neon, etc.) operate at very high voltages—sometimes up to 30,000 V during startup. Many fixtures are not isolated from the mains supply, making them potentially lethal if handled carelessly.

The golden rule:
👉 Always treat these fixtures as dangerous and handle them with proper respect.

Main Hazards

⚡ 1. Electric Shock

High voltage risks: Neon signs often use transformers or electronic ballasts producing up to 15,000 V.

General rule: Never probe a live fixture.

Safe troubleshooting: Most issues can be detected visually or with an ohmmeter/continuity tester when unplugged.

✅ Iron-ballast fixtures:

Generally inert when unplugged.

Small internal capacitors may exist (for RFI filtering), but they are usually harmless.

Still, always disconnect power before touching.

✅ Electronic-ballast fixtures:

Can retain a dangerous charge in internal capacitors even after switching off.

Always check for residual voltage across outputs before handling.

Treat troubleshooting like working with a switch-mode power supply.

⚠️ Pulse starters (HID lamps):

Can produce up to 30 kV during ignition.

30 kV can jump over an inch through air → keep clear.

☠️ 2. Hazardous Chemicals

High-pressure discharge lamps may contain:

Mercury (toxic heavy metal).

Sodium (reacts violently with water → produces explosive hydrogen gas).

Neon signs may contain toxic phosphor coatings.

👉 If a lamp breaks:

Avoid direct contact with the glass or chemicals.

Clean and dispose of fragments properly.

Do not allow metallic sodium to contact water.

🌞 3. Ultra-Violet (UV) Radiation

HID lamps generate intense UV, often the harmful UV-B type.

Normally, the outer glass envelope or phosphor coating blocks UV.

If the outer glass breaks:

The lamp may still operate temporarily, but will emit dangerous UV.

Exposure can cause eye and skin damage.

👉 Safety precaution:

Never operate a discharge lamp without its protective outer envelope.

If you must test it, use UV protective gear (gloves, glasses, shielding).

Practical Safety Tips

✔ Always unplug fixtures before inspection.
✔ Assume capacitors are charged—discharge them safely.
✔ Keep hands dry and tools insulated.
✔ Maintain safe clearance around high-voltage starters.
✔ Dispose of broken lamps according to hazardous waste rules.
✔ Use protective eyewear and gloves when handling.

Final Word

Gas discharge lamps are efficient and widely used, but their high voltages, toxic chemicals, and UV emissions make them hazardous if mishandled. Treat every fixture as live and dangerous until proven otherwise, and follow strict safety procedures to protect yourself.

Gas Discharge lamps Basics

Gas discharge lamp basics

The use of electrically excited gas discharges significantly predates the invention of the incandescent lamp. Physics labs of yesteryear as well as today have use of a variety of gas filled tubes used for numerous purposes involving light generation including spectroscopy, materials analysis, studies of gas dynamics, and laser pumping. Look through any scientific supply catalog and you will see many different types of gas filled tubes in all shapes and sizes.

Gas discharge lamps are used in virtually all areas of modern lighting technology including common fluorescent lighting for home and office - and LCD backlights for laptop computers, high intensity discharge lamps for very efficient area lighting, neon and other miniature indicator lamps, germicidal and tanning lamps, neon signs, photographic electronic flashes and strobes, arc lamps for industry and A/V projectors, and many more. Gas discharge automotive headlights are on the way - see the section: "HID automotive headlights".

Because of the unusual appearance of the light from gas discharge tubes, quacks and con artists also have used and are using this technology as part of expensive useless devices for everything from curing cancer to contacting the dead.

Unlike incandescent lamps, gas discharge lamps have no filament and do not produce light as a result of something solid getting hot (though heat may be a byproduct). Rather, the atoms or molecules of the gas inside a glass, quartz, or translucent ceramic tube, are ionized by an electric current through the gas or a radio frequency or microwave field in proximity to the tube. This results in the generation of light - usually either visible or ultraviolet (UV). The color depends on both the mixture of gasses or other materials inside the tube as well as the pressure and type and amount of the electric current or RF power. (At the present time, this document only deals with directly excited gas discharge lamps where an AC or DC electric current flows through the gas.)

Fluorescent lamps are a special class of gas discharge lamps where the electric current produces mostly invisible UV light which is turned into visible light by a special phosphor coating on the interior of the tube.

LUMENS Selection

How to Choose Lumens

Brightness (Lumens)
The brightness of a projector is measured in ANSI Lumens—a standard unit of light output. Choosing the right lumen rating depends on the room lighting, screen size, and audience size.

Lumens Categories

🔹 Less than 1000 Lumens

Use Case: Entry-level, budget projectors
Best For: Small, dark rooms only
Limitations:
- Requires a dark or dimly lit environment
- Image easily washed out by ambient light

🔹 1000 – 2000 Lumens

Use Case: Standard business or small classroom projectors
Best For: Conference rooms & classrooms with some light control
Performance:
- Works in rooms with dimmed lights
- Adequate brightness for medium-sized screens

🔹 2000 – 3000 Lumens

Use Case: High-performance portable/semi-portable projectors
Best For: Large classrooms & conference rooms
Performance:
- Handles moderate ambient light
- Supports larger audiences and bigger screens
- Image remains sharp and bright

🔹 More than 3000 Lumens

Use Case: Ultra-bright projectors for professional and large venues
Best For: Auditoriums, churches, concerts, nightclubs, and training halls
Performance:
- Works even with strong ambient light
- Produces vivid, clear images on very large screens
- Typically more expensive

✅ Quick Tip:

Home Theater (dark room) → 1000–1500 Lumens
Business/Classroom → 2000–3000 Lumens
Large Venues → 3000+ Lumens

The air gap in rotating machines: Necessary Evil

Air Gap in Rotating Machines: The Necessary Evil That Designers Can’t Ignore

Why the Air Gap Matters

The air gap—the tiny clearance between rotor and stator in a motor or generator—often gets overlooked in design discussions. Yet it is a critical parameter influencing efficiency, noise, power factor, and mechanical stability.

Too large? → Higher magnetizing current, poor power factor, increased losses.
Too small? → Risk of rotor–stator contact, unbalanced pull, mechanical instability.

That’s why experts call the air gap a “necessary evil”—it can’t be eliminated, only optimized.

What Makes Air Different

High reluctance: Air resists magnetic flux ~10× more than steel.
More MMF needed: Magnetizing current rises with air gap length.
Trade-off: Designers want the gap as small as possible electrically, but not so small that mechanical safety is compromised.

Special Demands in Motors & Generators

Unlike transformers, rotating machines must have a complete air gap to allow free rotor motion. Designers must also counteract:

Magnetic pull: Strong attraction between rotor and stator requires stiff shafts.
Eccentricity risk: Non-uniform gaps increase vibration, stray losses, and noise.
Noise control: Doubling the air gap can cut motor noise by ~10 dB.

Design Compromise

Slow-speed, low-hp machines → Smaller gap is preferred (better PF needed).
High-speed, large-hp machines → Larger gap tolerable (mechanical reliability matters more).

Empirical Formula (used in practice):

g (\text{inch}) = 0.005 + 0.0003D + 0.001L + 0.003V