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TLE 9 – ELECTRICAL INSTALLATION & MAINTENANCE NC II ELECTRIC DISCHARGE LIGHTING SYSTEM FLUORESCENT LAMP Electric Discharge – current/ electricity that does not flow in a conductor. THEORIES / PRINCIPLE: A fluorescent lamp is a form of electric discharge lighting source. It consist of a glass tube containing mercury vapor at a low pressure and inert gases like argon and krypton. The interior is coated with phosphor, which glows or fluoresces when exposed to ultra violet light. Coating the inner surface of the glass tube with different phosphors make it possible to obtain light corresponding to the type of the phosphor coating. There are several types of electric discharge lamps which are classified according to the kind of electrode used. 1. Cold Cathode Lamp - requires high voltage in its operation. This lamp has electrode made of thin type iron. It is not pre- heated and does not require a starter for starting. It is operated by a special high voltage transformer. Examples of Cold Cathode lamps: Neon lamps and Mercury lamps 2. Hot Cathode Lamp – requires starter ( glow switch ) and is preheated during starting. It uses a ballast to produce high voltage to start the lamp into operation and to limit the flow of current. This fluorescent lamp which is commonly used for general lighting system is one of the hot cathode type. A fluorescent lamp fixture consist of several parts which are listed and describe below: 1. Fluorescent tube – is a circular or tubular tube containing mercury vapor and inert gas with phosphor coating inside. Types of fluorescent lamp : tubular & circular Wattage Rating ( Tubular ): 8 watts lamp & 10 watts lamp --- use 10 watts ballast 18 watts lamp & 20 watts lamp ----use 20 watts ballast 36 watts lamp , 40 watts lamp & 38 watts lamp ----- use 40 watts ballast 2. Ballast – is an induction coil which produces high voltage to start the lamp into operation. It also limits the flow of current during the operation of the lamp. It also consumes power which is about 10% – 20% of the power consumed by the lamp itself. Induce - process of increasing voltage. 3. Starter - is a glow switch that opened and closed the circuit so as to produce high voltage or inductive kick across the filament during the starting period. It has a bi – metallic element that when it feels heat, it will open. Two Types of Fluorescent Starter FS – 20 for 20 W fluorescent lamp & FS – 40 for 40 W fluorescent lamp 4. Lamp Holder & Starter Socket – are points of connection of the fluorescent tube and the starter. 5. Frame – is the metal housing of the whole fixture. PRINCIPLE OF OPERATION The first step in the ballast – starting sequence of a fluorescent lamp is to preheat the cathodes. The current heats the cathodes until they “boil off” clouds of electrons. Initially, the starter is at close position to allow complete circuit for current to flow. When the cathode had heated up, the starter opens. The magnetic field of the ballast collapses. This action generated an inductive voltage “kick” which strikes an arc across the lamp, causing it to light.

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TLE 9 ELECTRICAL INSTALLATION & MAINTENANCE NC IIELECTRIC DISCHARGE LIGHTING SYSTEMFLUORESCENT LAMP

Electric Discharge current/ electricity that does not flow in a conductor. THEORIES / PRINCIPLE: A fluorescent lamp is a form of electric discharge lighting source. It consist of a glass tube containing mercury vapor at a low pressure and inert gases like argon and krypton. The interior is coated with phosphor, which glows or fluoresces when exposed to ultra violet light. Coating the inner surface of the glass tube with different phosphors make it possible to obtain light corresponding to the type of the phosphor coating. There are several types of electric discharge lamps which are classified according to the kind of electrode used.

1. Cold Cathode Lamp - requires high voltage in its operation. This lamp has electrode made of thin type iron. It is not pre- heated and does not require a starter for starting. It is operated by a special high voltage transformer. Examples of Cold Cathode lamps: Neon lamps and Mercury lamps

2. Hot Cathode Lamp requires starter ( glow switch ) and is preheated during starting. It uses a ballast to produce high voltage to start the lamp into operation and to limit the flow of current. This fluorescent lamp which is commonly used for general lighting system is one of the hot cathode type.

A fluorescent lamp fixture consist of several parts which are listed and describe below:1. Fluorescent tube is a circular or tubular tube containing mercury vapor and inert gas with phosphor coating inside. Types of fluorescent lamp : tubular & circularWattage Rating ( Tubular ):8 watts lamp & 10 watts lamp --- use 10 watts ballast18 watts lamp & 20 watts lamp ----use 20 watts ballast36 watts lamp , 40 watts lamp & 38 watts lamp ----- use 40 watts ballast

2. Ballast is an induction coil which produces high voltage to start the lamp into operation. It also limits the flow of current during the operation of the lamp. It also consumes power which is about 10% 20% of the power consumed by the lamp itself.Induce -process of increasing voltage.

3. Starter - is a glow switch that opened and closed the circuit so as to produce high voltage or inductive kick across the filament during the starting period. It has a bi metallic element that when it feels heat, it will open.Two Types of Fluorescent StarterFS 20 for 20 W fluorescent lamp & FS 40 for 40 W fluorescent lamp

4. Lamp Holder & Starter Socket are points of connection of the fluorescent tube and the starter.

5. Frame is the metal housing of the whole fixture.PRINCIPLE OF OPERATIONThe first step in the ballast starting sequence of a fluorescent lamp is to preheat the cathodes. The current heats the cathodes until they boil off clouds of electrons. Initially, the starter is at close position to allow complete circuit for current to flow.When the cathode had heated up, the starter opens. The magnetic field of the ballast collapses. This action generated an inductive voltage kick which strikes an arc across the lamp, causing it to light. Characteristics of Fluorescent LightingAdvantages:1. Highly efficient supplies four times as much light as incandescent lamp of the same wattage.2. Available in types to supply variety of colors3. Produce cooler illumination. It is possible to keep a hand on the tube during normal operation.4. Produces distributed light which is less injurious to the eye.5. Expected life is up to seven times more than incandescent lamps.

Disadvantages:1. Initial cost is greater.2. Starts with flickering light.3. Operates at low power factor.

IDENTIFYING GOOD OR BAD FLUORESCENT STARTERINDICATORCAUSESREMARKS

No LightOpen circuitBad

Dim light / steadyShort circuitBad

Flickering light ConditionedGood

IDENTIFYING GOOD OR BAD BALLASTINDICATORCAUSESREMARKS

No LightOpen circuitBad

Normal LightShort circuitBad

Dimmed LightConditionedGood

IDENTIFYING GOOD OR BAD FLUORESCENT TUBEINDICATORCAUSESREMARKS

No deflectionOpen cathodeBad

Full deflectionShort circuitBad

30 ohms 50 ohmsConditionedGood

TROUBLESHOOTING CHART FOR FLUORESCENT LAMPSSYMPTOMSCAUSESREMEDIES

1. Flashing On & OFF- End of Life ( If old Lamp )- Possible fault of lamp holder

- Faulty starter- Low ballast rating

- Low circuit voltage - Loose contacts

- Replace lamp- Replace lamp holders. If blinking continues, investigate further- Replace starter- Check ballast and replace ballast if necessary- Check voltage and correct if possible- See that lamps are securely fitted and holders rigidly mounted

2. No Starting Effort or Slow Starting

- End of life- Defective starter- Incorrect wiring

- Low line voltage- Air leak in lamp - Low ballast rating- Open electrode circuit- Possible open circuit- Replace lamp- Replace starter- Check wiring and make proper connection- Check voltage and correct if possible- Replace lamp- Check ballast and replace- Replace lamp- Test lamp in other circuit

3. End of lamp remain lighted

- Faulty starter- Incorrect wiring- Low ballast rating- Replace starter- Make proper connections- Replace ballast

4. Flicker, swirl, flutter

- New lamps may flicker when first placed in service - End of life if old lamps- Defective starter- High voltage- Usually clears after short operation

- Replace lamp- Replace starter- Check voltage and correct if possible

5. End blackening dense at one end or both

- End of life- Defective starter- High or low voltage- Loose circuit

- Improper ballast - Replace lamp- Replace starter- Check voltage and correct if possible- See that lamps are securely fitted and holders rigidly mounted- Use approved ballast of correct rating

6. Decrease light output

- Low circuit voltage- Dust , dirt on lamps, fixtures, walls- Check voltage and correct if possible - Clean

7. Radio Interference

- radio too close to lamp- Move radio 9 10 ft. from lamp

8. Noise from ballast

- Slight hum is inherent- If objectionable, mount ballast in soft rubber- Replace ballast if too noisy