Module 3 - Lamps and Lighting Technologies

Lamps

• GLS lamps provide general lighting service
• Tungsten filaments operate at 2500°C
• Bayonet-cap lamps have two bottom contacts fixed with two side pins
• Edison-screw lamps feature a center bottom contact and a screw thread as a neutral conductor

Lamp Efficacy

• Efficacy is a comparison between power input and light output
• Measured in lumens per watt (lm/W)

Voltage Effects on Lamps

• Increased voltage reduces lamp lifespan
• A 5% voltage increase can reduce lamp life by 50%
• A 1% voltage increase can raise lumens by 3.5%
• Energy suppliers may vary energy supply between +10% and -6%

Tungsten Halogen Lamps

• Quartz tubes filled with halogenated gas, typically iodine
• Operate at high temperatures
• Quartz tubes should not be handled directly as skin oils can cause opaque patches
• Must be installed level, within a ±4° range
• Output 100% lumen output
• The Halide regenerative cycle extends the bulb's lifespan

Halide Regenerative Cycle in Four Steps

• Current heating tungsten causes atoms to evaporate and travel to the quartz wall
• Tungsten, oxygen, and halogen atoms then react, creating tungsten oxyhalide
• Molecules then move to the tungsten filament where heat breaks them apart
• Tungsten atoms then return to the filament

Discharge Lighting

• Uses gas ionization to produce light
• Does not use a filament

Low Pressure Mercury Vapor Lamps

• Glass tubes filled with krypton or argon gas, plus mercury vapor
• Feature a phosphor coating inside the glass tube and oxide-coated cathodes at each end
• Cathodes made of tungsten filament

Low Pressure Mercury Lamps - Operation

• Voltage heats cathodes, causing them to emit electrons
• An arc is struck and maintained within the mercury vapor
• The low-pressure mercury arc produces mostly UV light and very low visible light
• The phosphor coating absorbs and converts the UV light into visible light

Lamp Efficacy

• Luman output for a given wattage is between 40 to 90 lm/W

Colour Rendering

• Describes a lamp's ability to show colors accurately
• Essential in jobs where true color is important, such as paint shops
• A full color range can make objects appear better or brighter

Colour Appearance

• Lamp's temperature can be described as hot, warm, or cold
• Measured in Kelvin (K)

Types of Fluorescent Lamps

• Includes UV tubes and Glowlux lamps
• Low-energy PL and compact fluorescent lamps replace incandescent lamps
• Available in shapes like tubes, twisted tubes, golf balls, butterflies, bullets, etc

Control Gear

• Discharge lighting needs higher starting voltage to overcome gas resistance
• Once the arc is sustained, gas resistance becomes negligible
• Current in the lamp must be limited to prevent damage
• Transformers or chokes restrict current

Glow Type Starters

• Circuits include a tube, choke, capacitor, and glow-type starter
• Capacitor improves power factor
• Starters are ‘can’ shaped with two internal open contacts in helium gas

Glow Starter Operation

• When turned on, internal contacts heat and bend, connecting the fluorescent tube's electrodes
• Current through the choke creates an intense magnetic field
• The starter's glow stops when contacts touch, then they cool and separate
• The normal running current is insufficient to operate the starter, so contacts stay open
• Choke limits current to prevent tube disintegration
• May flash due to not working the first time
• Disadvantages include flicker, poor cold starting, and shortened lifespan if switched off/on frequently

Semi-Resonant Circuits

• Use a special wound transformer instead of a choke
• Current runs through the primary coil, then the secondary coil, which is wound in the opposite direction
• Offer a high power factor and are easy to start at low temperatures

High Frequency Lamp Circuits

• Operate at 30,000 Hz, making flickering imperceptible
• Increase lamp efficacy, saving between 10%-30%
• Have first-time starting capabilities
• Noise-free
• Ballast shuts down automatically upon lamp failure
• Many HF ballasts work with standard fluorescent lamps
• Supply cables within the luminaire should not run near ballast terminal leads due to initial cost

Stroboscopic Effect

• Flickering lights cause disorientation or fits
• Tungsten filament lamps reduce the effect without complete elimination
• Adjacent fluorescents in a three-phase supply are 120° out of phase, reducing effects from alternating flickering
• High-frequency fluorescent lights reduce effects by ~60%
• Twin lamps on a lead-lag circuit counteract flicker

Lighting Circuit Wiring - Key Considerations

• Types of lamps used
• Number of lamps
• Number of locations for lamp controls
• Type of wiring system
• Environmental factors

Conduit and Trunking Wiring

• Uses PVC single core insulated cables (BS 6491X)
• Line conductor goes directly to the switch
• Loops switch to switch for all sub-circuits
• Neutral conductor runs to the first outlet, then loops through the rest
• The switch wire runs between the switch and the luminaires

Multicore Cable Wiring

• Uses sheathed multicore twin and circuit protective conductor (earth) BS 6242Y
• OR uses three core and circuit protective conductor (earth) BS 6243Y
• Method used to wire lighting: joint box (no longer acceptable for use under floor), loop in method and wiring at the switch method
• Circuits share the same design, but termination locations vary

Joint Box Wiring Method

• Usually, one cable runs to each wiring outlet
• Joint boxes under the floor should have accessible covers

Loop in ‘Three Plate’ Wiring Method

• Supply cable loops from the customer unit to each switch
• A 2-core cable runs between each ceiling rose and switch
• Each ceiling rose, except the last, connects three 2-core cables to three terminal sets
• All connections are made at the ceiling rose

Cable Colour

• The installation uses different colors for the line conductor at switches and strappers. Red before 2004, brown post-2004 must identify cores
• Cable sheathing should enter accessories by at least 10mm
• The CPC (earth) must have a green/yellow insulated sleeve where the sheathing is removed from a multicore cable

Light Circuit Switching

• Includes one-way and two-way switches

One Way Switch

• Has two terminals and one possible path for the current
• Placed along the phase wire

Two Way Switch

• Used to control lights from multiple locations, such as stairs
• Switch feed terminal is termed the common
• Strapper terminals are two lines connecting to another two-way switch
• The light turns on if both switches share a single route
• The light stays off if each switch shares alternating routes

Intermediate Switch

• Includes four terminals
• Phase connects to a strapper on the first two-way switch, then to the intermediate switch, then to another two-way switch; the last switch's common connects to the first switch's common, and the last switch's neutral connects to the first switch's second strapper

Ring Final Circuits

• Line, neutral, and CPC connect to the customer unit, loop at each socket outlet, and return to the customer unit
• Each socket outlet has dual connections to mains supply
• A 30A or 32A ring circuit serves a floor area not exceeding 100 m² in domestic installations
• Sockets should be distributed evenly when more than one ring circuit is installed in a property to balance load
• Fuses not exceeding 13A or circuit breakers not exceeding 16A should protect permanently connected equipment

Radial Circuits

• Radial circuits come to an end at the last socket

A3 Radial Circuits

• When installed in a domestic property, they use 2.5mm² copper cables and have 20A protection

• The maximum size is 50m²

Water Heater Circuits

• Use a 20A double pole switch
• Have a 15A fuse or 16A breaker
• Use heat-resistant flex (typically 1.5mm² 85° butyl)

Cooker and Showers

• Traditional 6mm PVC wiring but could need more power

Power Generation and Distribution

• The alternator's stator has three coils around its internal periphery
• Each winding is cut by magnetic flux lines produced electromagnetic rotor
• One end of each coil is earthed, the other connects to conductors
• Each identical winding has the same voltage across and generates the same current
• Known as balanced conditions or balanced 3-phase supply
• Each current is a sine wave oscillating and alternating direction
• A graph shows 120° intervals between each coil's rises and falls
• Phase displacement occurs due to the current production delay of each coil
• Line current is 3√[1.732] greater than phase current

Frequency

• Frequency is the number of complete cycles per second of alternating current
• Measured in hertz (Hz)
• UK supply is 50Hz, produced at 3000 rpm

Delta Connection

• Phase windings connect at each end to form a triangle
• Phase relationship V₁ = VPH and IL = IPH X √3
• VPH is voltage across the phase winding
• VL is voltage across the lines
• IL is current flowing from the lines
• IPH is phase current flowing through the windings

Star Connection

• One end of each winding joins to form a star point
• The star point connects to earth
• Conductors connect to non-star point winding ends
• A fourth connection links to the earthed star point, making the line neutral and maintaining potential at zero volts
• IPH is the current through phase windings
• IL is current out into the lines
• VL is line voltage, measured across two lines
• VPH is phase voltage through windings
• Phase relationship VL = VPH X √3 and IL = IPH